Open IF transformer? Test all those.
:Open IF transformer? Test all those.
:thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
:wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
:
Lewis
::how do i do this
:
:
:
:
:
:Try checking the local oscillator with a second radio.
:Lewis
:
:::how do i do this
::
::
::
::
::
::Try checking the local oscillator with a second radio.
::Lewis
::
:
Now- first of all, this is a good place to make a couple of points.
Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. It is also a good idea to stop and test the set after each component change. I am not an advocate of just replacing every cap. Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
OK- class over.
As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". There are a bunch of great suggestions there about checking out the oscillator.
Welcome to the club,
don't blow yourself up,
good luck,
and,
HAVE FUN!!
::::how do i do this
:::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
:::
:::
:::
:::
:::Try checking the local oscillator with a second radio.
:::Lewis
:::
::
:
:Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
:Now- first of all, this is a good place to make a couple of points.
:Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
:The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. It is also a good idea to stop and test the set after each component change. I am not an advocate of just replacing every cap. Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
:The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
:Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
:OK- class over.
:As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". There are a bunch of great suggestions there about checking out the oscillator.
:Welcome to the club,
:don't blow yourself up,
:good luck,
:and,
:HAVE FUN!!
:
:::::how do i do this
::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. If not, then you have an open coil, open resistor, or shorted cap. You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
Hope this helps some-
t.
::::
::::
::::
::::
::::Try checking the local oscillator with a second radio.
::::Lewis
::::
:::
::
::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
::Now- first of all, this is a good place to make a couple of points.
::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. It is also a good idea to stop and test the set after each component change. I am not an advocate of just replacing every cap. Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
::OK- class over.
::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". There are a bunch of great suggestions there about checking out the oscillator.
::Welcome to the club,
::don't blow yourself up,
::good luck,
::and,
::HAVE FUN!!
::
:
::::::how do i do this
:::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
:
:Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. If not, then you have an open coil, open resistor, or shorted cap. You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
:Hope this helps some-
:t.
:::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
:::::
:::::
:::::Try checking the local oscillator with a second radio.
:::::Lewis
:::::
::::
:::
:::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
:::Now- first of all, this is a good place to make a couple of points.
:::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
:::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. It is also a good idea to stop and test the set after each component change. I am not an advocate of just replacing every cap. Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
:::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
:::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
:::OK- class over.
:::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". There are a bunch of great suggestions there about checking out the oscillator.
:::Welcome to the club,
:::don't blow yourself up,
:::good luck,
:::and,
:::HAVE FUN!!
:::
::
:
If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. In any case you will need a signal generator in order to be sure that C7 is aligned properly.
On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
T.
Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
T.
:
:Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
:
:T.
:havenot got that far yet.after further testing found some res. way out of range
It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
T.
:
:It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
:i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
:T.
:
:
:It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
:where can i find a sig. gen.
:T.
:
The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. It is also a good idea to stop and test the set after each component change. I am not an advocate of just replacing every cap. Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. There are a bunch of great suggestions there about checking out the oscillator. If not, then you have an open coil, open resistor, or shorted cap. You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. In any case you will need a signal generator in order to be sure that C7 is aligned properly. If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. |
Find your strongest "static" source device for us. |
:
: : :  : : : :working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. : : :Sir Doug. . . . . : : :Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. : : :Here it is sequentially . . . now being all condensed: : : : : : :Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: : : : : :doug 02/05/2010 15:11 : : : :sears 6424 model no stations heard : : :i replaced caps and res. no voices : : : : :Warren 02/05/2010 16:38 : : : :Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? : : :Open IF transformer? Test all those. : : : : :doug 02/05/2010 18:33 : : : :thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. : : : : :Warren 02/05/2010 19:58 : : : :You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity : : : : :doug 02/05/2010 20:37 : : : ::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. : : : : :Warren 02/06/2010 01:58 : : : :The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. : : : : :Lewis L 02/06/2010 06:47 : : : :Try checking the local oscillator with a second radio. : : :Lewis : : : :doug 02/06/2010 07:44 : : : :how do i do this : : : : :Terry Decker 02/06/2010 11:09 : : : :Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. : : :Now- first of all, this is a good place to make a couple of points. : : :Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! : : :The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. : :It is also a good idea to stop and test the set after each component change. : : I am not an advocate of just replacing every cap. : : Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. : : :The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. : : :Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". : :Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. : :If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. : : :OK- class over. : : :As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". : :There are a bunch of great suggestions there about checking out the oscillator. : : :Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! : : : : :doug 02/06/2010 13:22 : : : :thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. : : : : :Terry Decker 02/06/2010 13:53 : : : :Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. : : If not, then you have an open coil, open resistor, or shorted cap. : :You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. : : This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. : :Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. : : :Hope this helps some- : : : : :Warren 02/06/2010 13:58 : : : :At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. : : : : :doug 02/06/2010 14:51 : : : :no opens : : :my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position : : : : :Thomas Dermody 02/06/2010 20:30 : : : :If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. : : :If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. : :Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. : : :If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. : : Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. : : :Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. : :Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. : :Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. : :Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. : :Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. : : :If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. : :For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. : : No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. : :Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. : : :If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. : :In any case you will need a signal generator in order to be sure that C7 is aligned properly. : : :On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. : : : : :Thomas Dermody 02/06/2010 20:35 : : : :Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. : : :Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. : : : : :doug 02/06/2010 22:56 : : : :have not got that far yet.after further testing found some res. way out of range : : : : :Thomas Dermody 02/07/2010 01:48 : : : :Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. : :If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. : : :It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. : : : : : :Posted by doug on 02/10/2010 08:23 : : : ::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. : : : : :Posted by doug on 02/15/2010 09:28 : : : : : :where can i find a sig. gen. : : : : : |
:
: : : : : : : : : : :Sir Doug. . . . . : : :BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. : : :First a couple of preliminary questions to zero in on the direction in which to initially proceed: : : :1 . . . You are not working in a metal building or down in a basement . . . are you ? : : :2 . . . Have you , in the past or at the present, EVER received a station on that radio ? : : :3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you : have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS : specs ? : : :4 . . . :yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position : : : :According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. : : :That would seem to be with the bandswitch being placed to its fully CCW position. : : :Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? : : :Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. : : :5. . . Preliminary Prep: : : :I want you to find the best generator and strongest source of damped wave oscillations that you can find. : : :Examples that I have found and have: : : :Dremel tool motor : : :Electric drill motor : : :Orbital and belt sanders (using universal AC/DC brushed motors) : : :Hair dryer, blowing cold air : : :Corded electric razor : : :Wifes hand mixer : : :Hand saber saw : : : : : :What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. : : :Then you move that static / inteference source around the loop to find its most responsive location. : : :That may require the volume up HIGH in case the device used is inherently acoustively noisy. : :Find your strongest "static" source device for us. : : : : :Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. : : :BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? : : : :Standing by for the above info's supplication . . . . . . : : : : :73's de Edd : : :  : |
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:: :: :: :: :: :: ::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. ::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. ::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :: ::Sir Doug. . . . . :: :: ::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. :: :: ::Here it is sequentially . . . now being all condensed: :: :: :: :: :: ::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: :: :: :: :: ::doug 02/05/2010 15:11 :: :: :: ::sears 6424 model no stations heard :: :: ::i replaced caps and res. no voices :: :: :: :: ::Warren 02/05/2010 16:38 :: :: :: ::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? :: :: ::Open IF transformer? Test all those. :: :: :: :: ::doug 02/05/2010 18:33 :: :: :: ::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. :: :: :: :: ::Warren 02/05/2010 19:58 :: :: :: ::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity :: :: :: :: ::doug 02/05/2010 20:37 :: :: :: :::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. :: :: :: :: ::Warren 02/06/2010 01:58 :: :: :: ::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. :: :: :: :: ::Lewis L 02/06/2010 06:47 :: :: :: ::Try checking the local oscillator with a second radio. :: :: ::Lewis :: :: :: ::doug 02/06/2010 07:44 :: :: :: ::how do i do this :: :: :: :: ::Terry Decker 02/06/2010 11:09 :: :: :: ::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. :: :: ::Now- first of all, this is a good place to make a couple of points. :: :: ::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! :: :: ::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. :: ::It is also a good idea to stop and test the set after each component change. :: :: I am not an advocate of just replacing every cap. :: :: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. :: :: ::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. :: :: ::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". :: ::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. :: ::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. :: :: ::OK- class over. :: :: ::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". :: ::There are a bunch of great suggestions there about checking out the oscillator. :: :: ::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! :: :: :: :: ::doug 02/06/2010 13:22 :: :: :: ::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. :: :: :: :: ::Terry Decker 02/06/2010 13:53 :: :: :: ::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. :: :: If not, then you have an open coil, open resistor, or shorted cap. :: ::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. :: :: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. :: ::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. :: :: ::Hope this helps some- :: :: :: :: ::Warren 02/06/2010 13:58 :: :: :: ::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. :: :: :: :: ::doug 02/06/2010 14:51 :: :: :: ::no opens :: :: ::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :: :: :: :: ::Thomas Dermody 02/06/2010 20:30 :: :: :: ::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. :: :: ::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. :: ::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. :: :: ::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. :: :: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. :: :: ::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. :: ::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. :: ::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. ::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. :: ::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. :: ::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. :: :: ::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. :: ::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. :: :: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. :: ::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. :: :: ::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. :: ::In any case you will need a signal generator in order to be sure that C7 is aligned properly. :: :: ::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. :: :: :: :: ::Thomas Dermody 02/06/2010 20:35 :: :: :: ::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. :: :: ::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. :: :: :: :: ::doug 02/06/2010 22:56 :: :: :: ::have not got that far yet.after further testing found some res. way out of range :: :: :: :: ::Thomas Dermody 02/07/2010 01:48 :: :: :: ::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. :: ::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. :: :: ::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. :: :: :: :: :: ::Posted by doug on 02/10/2010 08:23 :: :: :: :::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. :: :: :: :: ::Posted by doug on 02/15/2010 09:28 :: :: :: :: :: ::where can i find a sig. gen. :: :: :: :: :: |
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:: :: :: :: :: :: :: :: :: :: ::Sir Doug. . . . . :: :: ::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. :: :: ::First a couple of preliminary questions to zero in on the direction in which to initially proceed: :: :: ::1 . . . You are not working in a metal building or down in a basement . . . are you ? :: :: ::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? :: :: ::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you :: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS :: specs ? :: :: ::4 . . . ::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :: :: :: ::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. :: :: ::That would seem to be with the bandswitch being placed to its fully CCW position. :: :: ::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? :: :: ::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. :: :: ::5. . . Preliminary Prep: :: :: ::I want you to find the best generator and strongest source of damped wave oscillations that you can find. :: :: ::Examples that I have found and have: :: :: ::Dremel tool motor :: :: ::Electric drill motor :: :: ::Orbital and belt sanders (using universal AC/DC brushed motors) :: :: ::Hair dryer, blowing cold air :: :: ::Corded electric razor :: :: ::Wifes hand mixer :: :: ::Hand saber saw :: :: :: :: :: ::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. :: :: ::Then you move that static / inteference source around the loop to find its most responsive location. :: :: ::That may require the volume up HIGH in case the device used is inherently acoustively noisy. :: ::Find your strongest "static" source device for us. :: :: :: :: ::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. :: :: ::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? :: :: :: ::Standing by for the above info's supplication . . . . . . :: :: :: :: ::73's de Edd :: :: :: :: |
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::: ::: ::: ::: ::: ::: :::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2 :::Sir Doug. . . . . ::: ::: :::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::: ::: :::Here it is sequentially . . . now being all condensed: ::: ::: ::: ::: ::: :::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::: ::: ::: ::: :::doug 02/05/2010 15:11 ::: ::: ::: :::sears 6424 model no stations heard ::: ::: :::i replaced caps and res. no voices ::: ::: ::: ::: :::Warren 02/05/2010 16:38 ::: ::: ::: :::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::: ::: :::Open IF transformer? Test all those. ::: ::: ::: ::: :::doug 02/05/2010 18:33 ::: ::: ::: :::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::: ::: ::: ::: :::Warren 02/05/2010 19:58 ::: ::: ::: :::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::: ::: ::: ::: :::doug 02/05/2010 20:37 ::: ::: ::: ::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::: ::: ::: ::: :::Warren 02/06/2010 01:58 ::: ::: ::: :::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::: ::: ::: ::: :::Lewis L 02/06/2010 06:47 ::: ::: ::: :::Try checking the local oscillator with a second radio. ::: ::: :::Lewis ::: ::: ::: :::doug 02/06/2010 07:44 ::: ::: ::: :::how do i do this ::: ::: ::: ::: :::Terry Decker 02/06/2010 11:09 ::: ::: ::: :::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::: ::: :::Now- first of all, this is a good place to make a couple of points. ::: ::: :::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::: ::: :::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::: :::It is also a good idea to stop and test the set after each component change. ::: ::: I am not an advocate of just replacing every cap. ::: ::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::: ::: :::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::: ::: :::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::: :::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::: :::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::: ::: :::OK- class over. ::: ::: :::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::: :::There are a bunch of great suggestions there about checking out the oscillator. ::: ::: :::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::: ::: ::: ::: :::doug 02/06/2010 13:22 ::: ::: ::: :::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::: ::: ::: ::: :::Terry Decker 02/06/2010 13:53 ::: ::: ::: :::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::: ::: If not, then you have an open coil, open resistor, or shorted cap. ::: :::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::: ::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::: :::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::: ::: :::Hope this helps some- ::: ::: ::: ::: :::Warren 02/06/2010 13:58 ::: ::: ::: :::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::: ::: ::: ::: :::doug 02/06/2010 14:51 ::: ::: ::: :::no opens ::: ::: :::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::: ::: ::: ::: :::Thomas Dermody 02/06/2010 20:30 ::: ::: ::: :::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::: ::: :::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::: :::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::: ::: :::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::: ::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::: ::: :::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::: :::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::: :::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::: :::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::: :::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::: ::: :::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::: :::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::: ::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::: :::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::: ::: :::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::: :::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::: ::: :::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::: ::: ::: ::: :::Thomas Dermody 02/06/2010 20:35 ::: ::: ::: :::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::: ::: :::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::: ::: ::: ::: :::doug 02/06/2010 22:56 ::: ::: ::: :::have not got that far yet.after further testing found some res. way out of range ::: ::: ::: ::: :::Thomas Dermody 02/07/2010 01:48 ::: ::: ::: :::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::: :::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::: ::: :::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::: ::: ::: ::: ::: :::Posted by doug on 02/10/2010 08:23 ::: ::: ::: ::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::: ::: ::: ::: :::Posted by doug on 02/15/2010 09:28 ::: ::: ::: ::: ::: :::where can i find a sig. gen. ::: ::: ::: ::: ::: |
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::: ::: ::: ::: ::: ::: ::: ::: ::: ::: :::Sir Doug. . . . . ::: ::: :::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::: ::: :::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::: ::: :::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::: ::: :::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::: ::: :::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::: specs ? ::: ::: :::4 . . . :::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::: ::: ::: :::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::: ::: :::That would seem to be with the bandswitch being placed to its fully CCW position. ::: ::: :::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::: ::: :::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::: ::: :::5. . . Preliminary Prep: ::: ::: :::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::: ::: :::Examples that I have found and have: ::: ::: :::Dremel tool motor ::: ::: :::Electric drill motor ::: ::: :::Orbital and belt sanders (using universal AC/DC brushed motors) ::: ::: :::Hair dryer, blowing cold air ::: ::: :::Corded electric razor ::: ::: :::Wifes hand mixer ::: ::: :::Hand saber saw ::: ::: ::: ::: ::: :::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::: ::: :::Then you move that static / inteference source around the loop to find its most responsive location. ::: ::: :::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::: :::Find your strongest "static" source device for us. ::: ::: ::: ::: :::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::: ::: :::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::: ::: ::: :::Standing by for the above info's supplication . . . . . . ::: ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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:::: :::: :::: :::: :::: :::: ::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. ::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. ::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. ::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end ::::Sir Doug. . . . . :::: :::: ::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. :::: :::: ::::Here it is sequentially . . . now being all condensed: :::: :::: :::: :::: :::: ::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: :::: :::: :::: :::: ::::doug 02/05/2010 15:11 :::: :::: :::: ::::sears 6424 model no stations heard :::: :::: ::::i replaced caps and res. no voices :::: :::: :::: :::: ::::Warren 02/05/2010 16:38 :::: :::: :::: ::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? :::: :::: ::::Open IF transformer? Test all those. :::: :::: :::: :::: ::::doug 02/05/2010 18:33 :::: :::: :::: ::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. :::: :::: :::: :::: ::::Warren 02/05/2010 19:58 :::: :::: :::: ::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity :::: :::: :::: :::: ::::doug 02/05/2010 20:37 :::: :::: :::: :::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. :::: :::: :::: :::: ::::Warren 02/06/2010 01:58 :::: :::: :::: ::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. :::: :::: :::: :::: ::::Lewis L 02/06/2010 06:47 :::: :::: :::: ::::Try checking the local oscillator with a second radio. :::: :::: ::::Lewis :::: :::: :::: ::::doug 02/06/2010 07:44 :::: :::: :::: ::::how do i do this :::: :::: :::: :::: ::::Terry Decker 02/06/2010 11:09 :::: :::: :::: ::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. :::: :::: ::::Now- first of all, this is a good place to make a couple of points. :::: :::: ::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! :::: :::: ::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. :::: ::::It is also a good idea to stop and test the set after each component change. :::: :::: I am not an advocate of just replacing every cap. :::: :::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. :::: :::: ::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. :::: :::: ::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". :::: ::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. :::: ::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. :::: :::: ::::OK- class over. :::: :::: ::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". :::: ::::There are a bunch of great suggestions there about checking out the oscillator. :::: :::: ::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! :::: :::: :::: :::: ::::doug 02/06/2010 13:22 :::: :::: :::: ::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. :::: :::: :::: :::: ::::Terry Decker 02/06/2010 13:53 :::: :::: :::: ::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. :::: :::: If not, then you have an open coil, open resistor, or shorted cap. :::: ::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. :::: :::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. :::: ::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. :::: :::: ::::Hope this helps some- :::: :::: :::: :::: ::::Warren 02/06/2010 13:58 :::: :::: :::: ::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. :::: :::: :::: :::: ::::doug 02/06/2010 14:51 :::: :::: :::: ::::no opens :::: :::: ::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::: :::: :::: :::: ::::Thomas Dermody 02/06/2010 20:30 :::: :::: :::: ::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. :::: :::: ::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. :::: ::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. :::: :::: ::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. :::: :::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. :::: :::: ::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. :::: ::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. :::: ::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. ::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. :::: ::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. :::: ::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. :::: :::: ::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. :::: ::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. :::: :::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. :::: ::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. :::: :::: ::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. :::: ::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. :::: :::: ::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. :::: :::: :::: :::: ::::Thomas Dermody 02/06/2010 20:35 :::: :::: :::: ::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. :::: :::: ::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. :::: :::: :::: :::: ::::doug 02/06/2010 22:56 :::: :::: :::: ::::have not got that far yet.after further testing found some res. way out of range :::: :::: :::: :::: ::::Thomas Dermody 02/07/2010 01:48 :::: :::: :::: ::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. :::: ::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. :::: :::: ::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. :::: :::: :::: :::: :::: ::::Posted by doug on 02/10/2010 08:23 :::: :::: :::: :::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. :::: :::: :::: :::: ::::Posted by doug on 02/15/2010 09:28 :::: :::: :::: :::: :::: ::::where can i find a sig. gen. :::: :::: :::: :::: :::: |
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:::: :::: :::: :::: :::: :::: :::: :::: :::: :::: ::::Sir Doug. . . . . :::: :::: ::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. :::: :::: ::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: :::: :::: ::::1 . . . You are not working in a metal building or down in a basement . . . are you ? :::: :::: ::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? :::: :::: ::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you :::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS :::: specs ? :::: :::: ::::4 . . . ::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::: :::: :::: ::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. :::: :::: ::::That would seem to be with the bandswitch being placed to its fully CCW position. :::: :::: ::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? :::: :::: ::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. :::: :::: ::::5. . . Preliminary Prep: :::: :::: ::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. :::: :::: ::::Examples that I have found and have: :::: :::: ::::Dremel tool motor :::: :::: ::::Electric drill motor :::: :::: ::::Orbital and belt sanders (using universal AC/DC brushed motors) :::: :::: ::::Hair dryer, blowing cold air :::: :::: ::::Corded electric razor :::: :::: ::::Wifes hand mixer :::: :::: ::::Hand saber saw :::: :::: :::: :::: :::: ::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. :::: :::: ::::Then you move that static / inteference source around the loop to find its most responsive location. :::: :::: ::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. :::: ::::Find your strongest "static" source device for us. :::: :::: :::: :::: ::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. :::: :::: ::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? :::: :::: :::: ::::Standing by for the above info's supplication . . . . . . :::: :::: :::: :::: ::::73's de Edd :::: :::: :::: :::: |
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::::: ::::: ::::: ::::: ::::: ::::: :::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::Sir Doug. . . . . ::::: ::::: :::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::: ::::: :::::Here it is sequentially . . . now being all condensed: ::::: ::::: ::::: ::::: ::::: :::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::: ::::: ::::: ::::: :::::doug 02/05/2010 15:11 ::::: ::::: ::::: :::::sears 6424 model no stations heard ::::: ::::: :::::i replaced caps and res. no voices ::::: ::::: ::::: ::::: :::::Warren 02/05/2010 16:38 ::::: ::::: ::::: :::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::: ::::: :::::Open IF transformer? Test all those. ::::: ::::: ::::: ::::: :::::doug 02/05/2010 18:33 ::::: ::::: ::::: :::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::: ::::: ::::: ::::: :::::Warren 02/05/2010 19:58 ::::: ::::: ::::: :::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::: ::::: ::::: ::::: :::::doug 02/05/2010 20:37 ::::: ::::: ::::: ::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::: ::::: ::::: ::::: :::::Warren 02/06/2010 01:58 ::::: ::::: ::::: :::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::: ::::: ::::: ::::: :::::Lewis L 02/06/2010 06:47 ::::: ::::: ::::: :::::Try checking the local oscillator with a second radio. ::::: ::::: :::::Lewis ::::: ::::: ::::: :::::doug 02/06/2010 07:44 ::::: ::::: ::::: :::::how do i do this ::::: ::::: ::::: ::::: :::::Terry Decker 02/06/2010 11:09 ::::: ::::: ::::: :::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::: ::::: :::::Now- first of all, this is a good place to make a couple of points. ::::: ::::: :::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::: ::::: :::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::: :::::It is also a good idea to stop and test the set after each component change. ::::: ::::: I am not an advocate of just replacing every cap. ::::: ::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::: ::::: :::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::: ::::: :::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::: :::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::: :::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::: ::::: :::::OK- class over. ::::: ::::: :::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::: :::::There are a bunch of great suggestions there about checking out the oscillator. ::::: ::::: :::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::: ::::: ::::: ::::: :::::doug 02/06/2010 13:22 ::::: ::::: ::::: :::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::: ::::: ::::: ::::: :::::Terry Decker 02/06/2010 13:53 ::::: ::::: ::::: :::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::: ::::: If not, then you have an open coil, open resistor, or shorted cap. ::::: :::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::: ::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::: :::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::: ::::: :::::Hope this helps some- ::::: ::::: ::::: ::::: :::::Warren 02/06/2010 13:58 ::::: ::::: ::::: :::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::: ::::: ::::: ::::: :::::doug 02/06/2010 14:51 ::::: ::::: ::::: :::::no opens ::::: ::::: :::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::: ::::: ::::: ::::: :::::Thomas Dermody 02/06/2010 20:30 ::::: ::::: ::::: :::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::: ::::: :::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::: :::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::: ::::: :::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::: ::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::: ::::: :::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::: :::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::: :::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::: :::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::: :::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::: ::::: :::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::: :::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::: ::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::: :::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::: ::::: :::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::: :::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::: ::::: :::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::: ::::: ::::: ::::: :::::Thomas Dermody 02/06/2010 20:35 ::::: ::::: ::::: :::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::: ::::: :::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::: ::::: ::::: ::::: :::::doug 02/06/2010 22:56 ::::: ::::: ::::: :::::have not got that far yet.after further testing found some res. way out of range ::::: ::::: ::::: ::::: :::::Thomas Dermody 02/07/2010 01:48 ::::: ::::: ::::: :::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::: :::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::: ::::: :::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::: ::::: ::::: ::::: ::::: :::::Posted by doug on 02/10/2010 08:23 ::::: ::::: ::::: ::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::: ::::: ::::: ::::: :::::Posted by doug on 02/15/2010 09:28 ::::: ::::: ::::: ::::: ::::: :::::where can i find a sig. gen. ::::: ::::: ::::: ::::: ::::: |
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::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::Sir Doug. . . . . ::::: ::::: :::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::: ::::: :::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::: ::::: :::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::: ::::: :::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::: ::::: :::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::: specs ? ::::: ::::: :::::4 . . . :::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::: ::::: ::::: :::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::: ::::: :::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::: ::::: :::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::: ::::: :::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::: ::::: :::::5. . . Preliminary Prep: ::::: ::::: :::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::: ::::: :::::Examples that I have found and have: ::::: ::::: :::::Dremel tool motor ::::: ::::: :::::Electric drill motor ::::: ::::: :::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::: ::::: :::::Hair dryer, blowing cold air ::::: ::::: :::::Corded electric razor ::::: ::::: :::::Wifes hand mixer ::::: ::::: :::::Hand saber saw ::::: ::::: ::::: ::::: ::::: :::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::: ::::: :::::Then you move that static / inteference source around the loop to find its most responsive location. ::::: ::::: :::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::: :::::Find your strongest "static" source device for us. ::::: ::::: ::::: ::::: :::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::: ::::: :::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::: ::::: ::::: :::::Standing by for the above info's supplication . . . . . . ::::: ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: |
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:::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede.
::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help.
::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help.
::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end
::::::Sir Doug. . . . .
::::::
::::::
::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions.
::::::
::::::
::::::Here it is sequentially . . . now being all condensed:
::::::
::::::
::::::
::::::
::::::
::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin:
::::::
::::::
::::::
::::::
::::::doug 02/05/2010 15:11
::::::
::::::
::::::
::::::sears 6424 model no stations heard
::::::
::::::
::::::i replaced caps and res. no voices
::::::
::::::
::::::
::::::
::::::Warren 02/05/2010 16:38
::::::
::::::
::::::
::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil?
::::::
::::::
::::::Open IF transformer? Test all those.
::::::
::::::
::::::
::::::
::::::doug 02/05/2010 18:33
::::::
::::::
::::::
::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
::::::
::::::
::::::
::::::
::::::Warren 02/05/2010 19:58
::::::
::::::
::::::
::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity
::::::
::::::
::::::
::::::
::::::doug 02/05/2010 20:37
::::::
::::::
::::::
:::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
::::::
::::::
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::::::Warren 02/06/2010 01:58
::::::
::::::
::::::
::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end.
::::::
::::::
::::::
::::::
::::::Lewis L 02/06/2010 06:47
::::::
::::::
::::::
::::::Try checking the local oscillator with a second radio.
::::::
::::::
::::::Lewis
::::::
::::::
::::::
::::::doug 02/06/2010 07:44
::::::
::::::
::::::
::::::how do i do this
::::::
::::::
::::::
::::::
::::::Terry Decker 02/06/2010 11:09
::::::
::::::
::::::
::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
::::::
::::::
::::::Now- first of all, this is a good place to make a couple of points.
::::::
::::::
::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
::::::
::::::
::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph.
::::::
::::::It is also a good idea to stop and test the set after each component change.
::::::
:::::: I am not an advocate of just replacing every cap.
::::::
:::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
::::::
::::::
::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
::::::
::::::
::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester".
::::::
::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on.
::::::
::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
::::::
::::::
::::::OK- class over.
::::::
::::::
::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations".
::::::
::::::There are a bunch of great suggestions there about checking out the oscillator.
::::::
::::::
::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!!
::::::
::::::
::::::
::::::
::::::doug 02/06/2010 13:22
::::::
::::::
::::::
::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
::::::
::::::
::::::
::::::
::::::Terry Decker 02/06/2010 13:53
::::::
::::::
::::::
::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil.
::::::
:::::: If not, then you have an open coil, open resistor, or shorted cap.
::::::
::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted.
::::::
:::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough.
::::::
::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
::::::
::::::
::::::Hope this helps some-
::::::
::::::
::::::
::::::
::::::Warren 02/06/2010 13:58
::::::
::::::
::::::
::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere.
::::::
::::::
::::::
::::::
::::::doug 02/06/2010 14:51
::::::
::::::
::::::
::::::no opens
::::::
::::::
::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
::::::
::::::
::::::
::::::
::::::Thomas Dermody 02/06/2010 20:30
::::::
::::::
::::::
::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it.
::::::
::::::
::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output.
::::::
::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
::::::
::::::
::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch.
::::::
:::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
::::::
::::::
::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them.
::::::
::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work.
::::::
::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark.
::::::
::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark.
::::::
::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
::::::
::::::
::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands.
::::::
::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band.
::::::
:::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible.
::::::
::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
::::::
::::::
::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you.
::::::
::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly.
::::::
::::::
::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
::::::
::::::
::::::
::::::
::::::Thomas Dermody 02/06/2010 20:35
::::::
::::::
::::::
::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments.
::::::
::::::
::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
::::::
::::::
::::::
::::::
::::::doug 02/06/2010 22:56
::::::
::::::
::::::
::::::have not got that far yet.after further testing found some res. way out of range
::::::
::::::
::::::
::::::
::::::Thomas Dermody 02/07/2010 01:48
::::::
::::::
::::::
::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity.
::::::
::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet.
::::::
::::::
::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
::::::
::::::
::::::
::::::
::::::
::::::Posted by doug on 02/10/2010 08:23
::::::
::::::
::::::
:::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
::::::
::::::
::::::
::::::
::::::Posted by doug on 02/15/2010 09:28
::::::
::::::
::::::
::::::
::::::
::::::where can i find a sig. gen.
::::::
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::::::
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::::::
::::::Sir Doug. . . . .
::::::
::::::
::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such.
::::::
::::::
::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed:
::::::
::::::
::::::1 . . . You are not working in a metal building or down in a basement . . . are you ?
::::::
::::::
::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ?
::::::
::::::
::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you
:::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS
:::::: specs ?
::::::
::::::
::::::4 . . .
::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
::::::
::::::
::::::
::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially.
::::::
::::::
::::::That would seem to be with the bandswitch being placed to its fully CCW position.
::::::
::::::
::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ?
::::::
::::::
::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers.
::::::
::::::
::::::5. . . Preliminary Prep:
::::::
::::::
::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find.
::::::
::::::
::::::Examples that I have found and have:
::::::
::::::
::::::Dremel tool motor
::::::
::::::
::::::Electric drill motor
::::::
::::::
::::::Orbital and belt sanders (using universal AC/DC brushed motors)
::::::
::::::
::::::Hair dryer, blowing cold air
::::::
::::::
::::::Corded electric razor
::::::
::::::
::::::Wifes hand mixer
::::::
::::::
::::::Hand saber saw
::::::
::::::
::::::
::::::
::::::
::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band.
::::::
::::::
::::::Then you move that static / inteference source around the loop to find its most responsive location.
::::::
::::::
::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy.
::::::
::::::Find your strongest "static" source device for us.
::::::
::::::
::::::
::::::
::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning.
::::::
::::::
::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ?
::::::
::::::
::::::
::::::Standing by for the above info's supplication . . . . . .
::::::
::::::
::::::
::::::
::::::73's de Edd
::::::
::::::
::::::
::::::
::::::
::::::
::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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:::::
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:::
::
:
:
: :bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help http://img260.imageshack.us/img260/7910/fnlkilroylinewidthmarkeb.png> : : : : : : : :Sir Doug . . . . . . : : : :working in garage ,cinder walls. : : : :Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. : : :All of your voltages readings seem to be within range . . . nothing being grossly missing.. : : :Now lets use that working Rot-a-Mola 56A to get the Silvertone working. : : :PRELIMINARY: : : :Hooking-up of 2 AC/DC chassis. : : :We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. : : :This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. : : :A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. : : :Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. : : :Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. : : :The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. : : : What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. : : :To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. : : :That should now provide for no ground loops being involved in our onset of testing to now be started. : : :Tune in your Motorola to its best received station and tune spot on to it. : : :Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. : : :Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :on the next plug in cycle, as the power switches will no longer be used during testing. : : :Signal Injection: : : :You will be connecting a common test lead between the two sets using its two alligator clips at either end. : : :The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. : : :Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. : : :Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. : : :Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. : : :If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. : : :If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. : : :Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. : : :Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. : : :Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. : : :If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. : : :Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. : : : By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. : : :Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. : : : : : :73's de Edd : : : : |
:
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::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::Sir Doug. . . . . ::::::: ::::::: :::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::: ::::::: :::::::Here it is sequentially . . . now being all condensed: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::: ::::::: ::::::: ::::::: :::::::doug 02/05/2010 15:11 ::::::: ::::::: ::::::: :::::::sears 6424 model no stations heard ::::::: ::::::: :::::::i replaced caps and res. no voices ::::::: ::::::: ::::::: ::::::: :::::::Warren 02/05/2010 16:38 ::::::: ::::::: ::::::: :::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::: ::::::: :::::::Open IF transformer? Test all those. ::::::: ::::::: ::::::: ::::::: :::::::doug 02/05/2010 18:33 ::::::: ::::::: ::::::: :::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::: ::::::: ::::::: ::::::: :::::::Warren 02/05/2010 19:58 ::::::: ::::::: ::::::: :::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::: ::::::: ::::::: ::::::: :::::::doug 02/05/2010 20:37 ::::::: ::::::: ::::::: ::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::: ::::::: ::::::: ::::::: :::::::Warren 02/06/2010 01:58 ::::::: ::::::: ::::::: :::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::: ::::::: ::::::: ::::::: :::::::Lewis L 02/06/2010 06:47 ::::::: ::::::: ::::::: :::::::Try checking the local oscillator with a second radio. ::::::: ::::::: :::::::Lewis ::::::: ::::::: ::::::: :::::::doug 02/06/2010 07:44 ::::::: ::::::: ::::::: :::::::how do i do this ::::::: ::::::: ::::::: ::::::: :::::::Terry Decker 02/06/2010 11:09 ::::::: ::::::: ::::::: :::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::: ::::::: :::::::Now- first of all, this is a good place to make a couple of points. ::::::: ::::::: :::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::: ::::::: :::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::: :::::::It is also a good idea to stop and test the set after each component change. ::::::: ::::::: I am not an advocate of just replacing every cap. ::::::: ::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::: ::::::: :::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::: ::::::: :::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::: :::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::: :::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::: ::::::: :::::::OK- class over. ::::::: ::::::: :::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::: :::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::: ::::::: :::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::: ::::::: ::::::: ::::::: :::::::doug 02/06/2010 13:22 ::::::: ::::::: ::::::: :::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::: ::::::: ::::::: ::::::: :::::::Terry Decker 02/06/2010 13:53 ::::::: ::::::: ::::::: :::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::: ::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::: :::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::: ::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::: :::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::: ::::::: :::::::Hope this helps some- ::::::: ::::::: ::::::: ::::::: :::::::Warren 02/06/2010 13:58 ::::::: ::::::: ::::::: :::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::: ::::::: ::::::: ::::::: :::::::doug 02/06/2010 14:51 ::::::: ::::::: ::::::: :::::::no opens ::::::: ::::::: :::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::: ::::::: ::::::: ::::::: :::::::Thomas Dermody 02/06/2010 20:30 ::::::: ::::::: ::::::: :::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::: ::::::: :::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::: :::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::: ::::::: :::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::: ::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::: ::::::: :::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::: :::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::: :::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::: :::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::: :::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::: ::::::: :::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::: :::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::: ::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::: :::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::: ::::::: :::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::: :::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::: ::::::: :::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::: ::::::: ::::::: ::::::: :::::::Thomas Dermody 02/06/2010 20:35 ::::::: ::::::: ::::::: :::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::: ::::::: :::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::: ::::::: ::::::: ::::::: :::::::doug 02/06/2010 22:56 ::::::: ::::::: ::::::: :::::::have not got that far yet.after further testing found some res. way out of range ::::::: ::::::: ::::::: ::::::: :::::::Thomas Dermody 02/07/2010 01:48 ::::::: ::::::: ::::::: :::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::: :::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::: ::::::: :::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Posted by doug on 02/10/2010 08:23 ::::::: ::::::: ::::::: ::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::: ::::::: ::::::: ::::::: :::::::Posted by doug on 02/15/2010 09:28 ::::::: ::::::: ::::::: ::::::: ::::::: :::::::where can i find a sig. gen. ::::::: ::::::: ::::::: ::::::: ::::::: |
:::::::
::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug. . . . . ::::::: ::::::: :::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::: ::::::: :::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::: ::::::: :::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::: ::::::: :::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::: ::::::: :::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::: specs ? ::::::: ::::::: :::::::4 . . . :::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::: ::::::: ::::::: :::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::: ::::::: :::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::: ::::::: :::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::: ::::::: :::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::: ::::::: :::::::5. . . Preliminary Prep: ::::::: ::::::: :::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::: ::::::: :::::::Examples that I have found and have: ::::::: ::::::: :::::::Dremel tool motor ::::::: ::::::: :::::::Electric drill motor ::::::: ::::::: :::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::: ::::::: :::::::Hair dryer, blowing cold air ::::::: ::::::: :::::::Corded electric razor ::::::: ::::::: :::::::Wifes hand mixer ::::::: ::::::: :::::::Hand saber saw ::::::: ::::::: ::::::: ::::::: ::::::: :::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::: ::::::: :::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::: ::::::: :::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::: :::::::Find your strongest "static" source device for us. ::::::: ::::::: ::::::: ::::::: :::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::: ::::::: :::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::: ::::::: ::::::: :::::::Standing by for the above info's supplication . . . . . . ::::::: ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: |
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:::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
Sir Doug . . . . . .
::working in garage ,cinder walls.
::
::
::
::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation.
::
::
::All of your voltages readings seem to be within range . . . nothing being grossly missing..
::
::
::Now lets use that working Rot-a-Mola 56A to get the Silvertone working.
::
::
::PRELIMINARY:
::
::
::Hooking-up of 2 AC/DC chassis.
::
::
::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line.
::
::
::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket.
::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time.
::
::
::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that.
::
::
::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference.
::
::
::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it.
::
::
::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal.
::
::
:: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line.
::
::
::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one.
::
::
::That should now provide for no ground loops being involved in our onset of testing to now be started.
::
::
::Tune in your Motorola to its best received station and tune spot on to it.
::
::
::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position.
::
::
::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity
::on the next plug in cycle, as the power switches will no longer be used during testing.
::
::
::Signal Injection:
::
::
::You will be connecting a common test lead between the two sets using its two alligator clips at either end.
::
::
::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set.
::
::
::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube.
::
::
::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube.
::
::
::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now.
::
::
::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with.
::
::
::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance..
::
::
::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry.
::
::
::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now.
::
::
::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set.
::
::
::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer.
::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed.
::
::
::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer.
::
::
:: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own.
::
::
::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up.
::
::
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::
::
::73's de Edd
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::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede.
::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help.
::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help.
::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end
::::::::Sir Doug. . . . .
::::::::
::::::::
::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions.
::::::::
::::::::
::::::::Here it is sequentially . . . now being all condensed:
::::::::
::::::::
::::::::
::::::::
::::::::
::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin:
::::::::
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::::::::doug 02/05/2010 15:11
::::::::
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::::::::sears 6424 model no stations heard
::::::::
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::::::::i replaced caps and res. no voices
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::::::::
::::::::Warren 02/05/2010 16:38
::::::::
::::::::
::::::::
::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil?
::::::::
::::::::
::::::::Open IF transformer? Test all those.
::::::::
::::::::
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::::::::
::::::::doug 02/05/2010 18:33
::::::::
::::::::
::::::::
::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
::::::::
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::::::::Warren 02/05/2010 19:58
::::::::
::::::::
::::::::
::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity
::::::::
::::::::
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::::::::
::::::::doug 02/05/2010 20:37
::::::::
::::::::
::::::::
:::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
::::::::
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::::::::Warren 02/06/2010 01:58
::::::::
::::::::
::::::::
::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end.
::::::::
::::::::
::::::::
::::::::
::::::::Lewis L 02/06/2010 06:47
::::::::
::::::::
::::::::
::::::::Try checking the local oscillator with a second radio.
::::::::
::::::::
::::::::Lewis
::::::::
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::::::::
::::::::doug 02/06/2010 07:44
::::::::
::::::::
::::::::
::::::::how do i do this
::::::::
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::::::::
::::::::Terry Decker 02/06/2010 11:09
::::::::
::::::::
::::::::
::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
::::::::
::::::::
::::::::Now- first of all, this is a good place to make a couple of points.
::::::::
::::::::
::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
::::::::
::::::::
::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph.
::::::::
::::::::It is also a good idea to stop and test the set after each component change.
::::::::
:::::::: I am not an advocate of just replacing every cap.
::::::::
:::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
::::::::
::::::::
::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
::::::::
::::::::
::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester".
::::::::
::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on.
::::::::
::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
::::::::
::::::::
::::::::OK- class over.
::::::::
::::::::
::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations".
::::::::
::::::::There are a bunch of great suggestions there about checking out the oscillator.
::::::::
::::::::
::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!!
::::::::
::::::::
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::::::::
::::::::doug 02/06/2010 13:22
::::::::
::::::::
::::::::
::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
::::::::
::::::::
::::::::
::::::::
::::::::Terry Decker 02/06/2010 13:53
::::::::
::::::::
::::::::
::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil.
::::::::
:::::::: If not, then you have an open coil, open resistor, or shorted cap.
::::::::
::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted.
::::::::
:::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough.
::::::::
::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
::::::::
::::::::
::::::::Hope this helps some-
::::::::
::::::::
::::::::
::::::::
::::::::Warren 02/06/2010 13:58
::::::::
::::::::
::::::::
::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere.
::::::::
::::::::
::::::::
::::::::
::::::::doug 02/06/2010 14:51
::::::::
::::::::
::::::::
::::::::no opens
::::::::
::::::::
::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
::::::::
::::::::
::::::::
::::::::
::::::::Thomas Dermody 02/06/2010 20:30
::::::::
::::::::
::::::::
::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it.
::::::::
::::::::
::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output.
::::::::
::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
::::::::
::::::::
::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch.
::::::::
:::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
::::::::
::::::::
::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them.
::::::::
::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work.
::::::::
::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark.
::::::::
::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark.
::::::::
::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
::::::::
::::::::
::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands.
::::::::
::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band.
::::::::
:::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible.
::::::::
::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
::::::::
::::::::
::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you.
::::::::
::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly.
::::::::
::::::::
::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
::::::::
::::::::
::::::::
::::::::
::::::::Thomas Dermody 02/06/2010 20:35
::::::::
::::::::
::::::::
::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments.
::::::::
::::::::
::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
::::::::
::::::::
::::::::
::::::::
::::::::doug 02/06/2010 22:56
::::::::
::::::::
::::::::
::::::::have not got that far yet.after further testing found some res. way out of range
::::::::
::::::::
::::::::
::::::::
::::::::Thomas Dermody 02/07/2010 01:48
::::::::
::::::::
::::::::
::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity.
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::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet.
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::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
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::::::::Posted by doug on 02/10/2010 08:23
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:::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
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::::::::Posted by doug on 02/15/2010 09:28
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::::::::where can i find a sig. gen.
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::::::::Sir Doug. . . . .
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::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such.
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::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed:
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::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ?
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::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ?
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::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you
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::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
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::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially.
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::::::::That would seem to be with the bandswitch being placed to its fully CCW position.
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::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ?
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::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers.
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::::::::5. . . Preliminary Prep:
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::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find.
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::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band.
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::::::::Then you move that static / inteference source around the loop to find its most responsive location.
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::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy.
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::::::::Find your strongest "static" source device for us.
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::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning.
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::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ?
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::::::::Standing by for the above info's supplication . . . . . .
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::::::::73's de Edd
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::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: :thanks edd for all yourhelp. i have to work 12 hours a day till sunday night. then its back to radio land monday morning ,will give answeres to question then,again thanks for your help. : : : : : : : : :Sir Doug. . . . . . : : :Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. : : :In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. : : :Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? : : :In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. : : :Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? : : :That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. : : :It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. : : :There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. : : :We are interested in that GREEN-BLACK winding and its integrity. : : :No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? : : :One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. : : :In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. : : :Then you tune across the AM band to see if any more stations come in. : : :Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? : : :Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. : : :As it stands I am in line with the further possibility of the unit: : : :1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) : : :2 . . .Still a problem in the ANT input section : : :3 . . .A gross mistuning of C7 GREY osc padder. : : :BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. : : :Thassit . . . . Standing by for feed back . . . . : : :R.F. THUMBNAIL of area now of prime interest: : : : : :  : : : :73's de Edd : : : : |
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:Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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: : : : : : : : : : :Sir Doug . . . . . . : : : ::: :::working in garage ,cinder walls. ::: ::: ::: :::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::: ::: :::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::: ::: :::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::: ::: :::PRELIMINARY: ::: ::: :::Hooking-up of 2 AC/DC chassis. ::: ::: :::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::: ::: :::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::: ::: :::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::: ::: :::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::: ::: :::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::: ::: :::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::: ::: ::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::: ::: :::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::: ::: :::That should now provide for no ground loops being involved in our onset of testing to now be started. ::: ::: :::Tune in your Motorola to its best received station and tune spot on to it. ::: ::: :::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::: ::: :::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::on the next plug in cycle, as the power switches will no longer be used during testing. ::: ::: :::Signal Injection: ::: ::: :::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::: ::: :::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::: ::: :::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::: ::: :::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::: ::: :::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::: ::: :::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::: ::: :::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::: ::: :::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::: ::: :::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::: ::: :::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::: ::: :::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::: ::: :::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::: ::: ::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::: ::: :::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::: ::: ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::Sir Doug. . . . . ::::::::: ::::::::: :::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::: ::::::::: :::::::::Here it is sequentially . . . now being all condensed: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 15:11 ::::::::: ::::::::: ::::::::: :::::::::sears 6424 model no stations heard ::::::::: ::::::::: :::::::::i replaced caps and res. no voices ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/05/2010 16:38 ::::::::: ::::::::: ::::::::: :::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::: ::::::::: :::::::::Open IF transformer? Test all those. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 18:33 ::::::::: ::::::::: ::::::::: :::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/05/2010 19:58 ::::::::: ::::::::: ::::::::: :::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 20:37 ::::::::: ::::::::: ::::::::: ::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/06/2010 01:58 ::::::::: ::::::::: ::::::::: :::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Lewis L 02/06/2010 06:47 ::::::::: ::::::::: ::::::::: :::::::::Try checking the local oscillator with a second radio. ::::::::: ::::::::: :::::::::Lewis ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 07:44 ::::::::: ::::::::: ::::::::: :::::::::how do i do this ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Terry Decker 02/06/2010 11:09 ::::::::: ::::::::: ::::::::: :::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::: ::::::::: :::::::::Now- first of all, this is a good place to make a couple of points. ::::::::: ::::::::: :::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::: ::::::::: :::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::: :::::::::It is also a good idea to stop and test the set after each component change. ::::::::: ::::::::: I am not an advocate of just replacing every cap. ::::::::: ::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::: ::::::::: :::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::: ::::::::: :::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::: :::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::: :::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::: ::::::::: :::::::::OK- class over. ::::::::: ::::::::: :::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::: :::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::: ::::::::: :::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 13:22 ::::::::: ::::::::: ::::::::: :::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Terry Decker 02/06/2010 13:53 ::::::::: ::::::::: ::::::::: :::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::: ::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::: :::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::: ::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::: :::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::: ::::::::: :::::::::Hope this helps some- ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/06/2010 13:58 ::::::::: ::::::::: ::::::::: :::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 14:51 ::::::::: ::::::::: ::::::::: :::::::::no opens ::::::::: ::::::::: :::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/06/2010 20:30 ::::::::: ::::::::: ::::::::: :::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::: ::::::::: :::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::: :::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::: ::::::::: :::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::: ::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::: ::::::::: :::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::: :::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::: :::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::: :::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::: :::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::: ::::::::: :::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::: :::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::: ::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::: :::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::: ::::::::: :::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::: :::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::: ::::::::: :::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/06/2010 20:35 ::::::::: ::::::::: ::::::::: :::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::: ::::::::: :::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 22:56 ::::::::: ::::::::: ::::::::: :::::::::have not got that far yet.after further testing found some res. way out of range ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/07/2010 01:48 ::::::::: ::::::::: ::::::::: :::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::: :::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::: ::::::::: :::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Posted by doug on 02/10/2010 08:23 ::::::::: ::::::::: ::::::::: ::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Posted by doug on 02/15/2010 09:28 ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::where can i find a sig. gen. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: |
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sir Doug. . . . . ::::::::: ::::::::: :::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::: ::::::::: :::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::: ::::::::: :::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::: ::::::::: :::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::: ::::::::: :::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::: specs ? ::::::::: ::::::::: :::::::::4 . . . :::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::: ::::::::: ::::::::: :::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::: ::::::::: :::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::: ::::::::: :::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::: ::::::::: :::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::: ::::::::: :::::::::5. . . Preliminary Prep: ::::::::: ::::::::: :::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::: ::::::::: :::::::::Examples that I have found and have: ::::::::: ::::::::: :::::::::Dremel tool motor ::::::::: ::::::::: :::::::::Electric drill motor ::::::::: ::::::::: :::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::: ::::::::: :::::::::Hair dryer, blowing cold air ::::::::: ::::::::: :::::::::Corded electric razor ::::::::: ::::::::: :::::::::Wifes hand mixer ::::::::: ::::::::: :::::::::Hand saber saw ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::: ::::::::: :::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::: ::::::::: :::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::: :::::::::Find your strongest "static" source device for us. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::: ::::::::: :::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::: ::::::::: ::::::::: :::::::::Standing by for the above info's supplication . . . . . . ::::::::: ::::::::: ::::::::: ::::::::: :::::::::73's de Edd ::::::::: ::::::::: ::::::::: ::::::::: |
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:::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: : : : : :the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help : : : : :Sir Doug. . . . . . : : :Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. : : :In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. : : :Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? : : :In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. : : :Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? : : :That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. : : :It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. : : :There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. : : :We are interested in that GREEN-BLACK winding and its integrity. : : :No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? : : :One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. : : :In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. : : :Then you tune across the AM band to see if any more stations come in. : : :Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? : : :Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. : : :As it stands I am in line with the further possibility of the unit: : : :1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) : : :2 . . .Still a problem in the ANT input section : : :3 . . .A gross mistuning of C7 GREY osc padder. : : :BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. : : :Thassit . . . . Standing by for feed back . . . . : : :R.F. THUMBNAIL of area now of prime interest: : : : : : : : : :73's de Edd : : : : |
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:Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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: : : : : : : : : : :Sir Doug . . . . . . : : : ::: :::working in garage ,cinder walls. ::: ::: ::: :::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::: ::: :::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::: ::: :::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::: ::: :::PRELIMINARY: ::: ::: :::Hooking-up of 2 AC/DC chassis. ::: ::: :::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::: ::: :::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::: ::: :::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::: ::: :::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::: ::: :::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::: ::: :::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::: ::: ::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::: ::: :::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::: ::: :::That should now provide for no ground loops being involved in our onset of testing to now be started. ::: ::: :::Tune in your Motorola to its best received station and tune spot on to it. ::: ::: :::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::: ::: :::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::on the next plug in cycle, as the power switches will no longer be used during testing. ::: ::: :::Signal Injection: ::: ::: :::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::: ::: :::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::: ::: :::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::: ::: :::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::: ::: :::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::: ::: :::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::: ::: :::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::: ::: :::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::: ::: :::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::: ::: :::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::: ::: :::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::: ::: :::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::: ::: ::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::: ::: :::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::: ::: ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::Sir Doug. . . . . ::::::::: ::::::::: :::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::: ::::::::: :::::::::Here it is sequentially . . . now being all condensed: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 15:11 ::::::::: ::::::::: ::::::::: :::::::::sears 6424 model no stations heard ::::::::: ::::::::: :::::::::i replaced caps and res. no voices ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/05/2010 16:38 ::::::::: ::::::::: ::::::::: :::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::: ::::::::: :::::::::Open IF transformer? Test all those. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 18:33 ::::::::: ::::::::: ::::::::: :::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/05/2010 19:58 ::::::::: ::::::::: ::::::::: :::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/05/2010 20:37 ::::::::: ::::::::: ::::::::: ::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/06/2010 01:58 ::::::::: ::::::::: ::::::::: :::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Lewis L 02/06/2010 06:47 ::::::::: ::::::::: ::::::::: :::::::::Try checking the local oscillator with a second radio. ::::::::: ::::::::: :::::::::Lewis ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 07:44 ::::::::: ::::::::: ::::::::: :::::::::how do i do this ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Terry Decker 02/06/2010 11:09 ::::::::: ::::::::: ::::::::: :::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::: ::::::::: :::::::::Now- first of all, this is a good place to make a couple of points. ::::::::: ::::::::: :::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::: ::::::::: :::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::: :::::::::It is also a good idea to stop and test the set after each component change. ::::::::: ::::::::: I am not an advocate of just replacing every cap. ::::::::: ::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::: ::::::::: :::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::: ::::::::: :::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::: :::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::: :::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::: ::::::::: :::::::::OK- class over. ::::::::: ::::::::: :::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::: :::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::: ::::::::: :::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 13:22 ::::::::: ::::::::: ::::::::: :::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Terry Decker 02/06/2010 13:53 ::::::::: ::::::::: ::::::::: :::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::: ::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::: :::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::: ::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::: :::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::: ::::::::: :::::::::Hope this helps some- ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Warren 02/06/2010 13:58 ::::::::: ::::::::: ::::::::: :::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 14:51 ::::::::: ::::::::: ::::::::: :::::::::no opens ::::::::: ::::::::: :::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/06/2010 20:30 ::::::::: ::::::::: ::::::::: :::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::: ::::::::: :::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::: :::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::: ::::::::: :::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::: ::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::: ::::::::: :::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::: :::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::: :::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::: :::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::: :::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::: ::::::::: :::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::: :::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::: ::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::: :::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::: ::::::::: :::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::: :::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::: ::::::::: :::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/06/2010 20:35 ::::::::: ::::::::: ::::::::: :::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::: ::::::::: :::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::doug 02/06/2010 22:56 ::::::::: ::::::::: ::::::::: :::::::::have not got that far yet.after further testing found some res. way out of range ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Thomas Dermody 02/07/2010 01:48 ::::::::: ::::::::: ::::::::: :::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::: :::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::: ::::::::: :::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Posted by doug on 02/10/2010 08:23 ::::::::: ::::::::: ::::::::: ::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Posted by doug on 02/15/2010 09:28 ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::where can i find a sig. gen. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: |
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sir Doug. . . . . ::::::::: ::::::::: :::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::: ::::::::: :::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::: ::::::::: :::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::: ::::::::: :::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::: ::::::::: :::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::: specs ? ::::::::: ::::::::: :::::::::4 . . . :::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::: ::::::::: ::::::::: :::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::: ::::::::: :::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::: ::::::::: :::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::: ::::::::: :::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::: ::::::::: :::::::::5. . . Preliminary Prep: ::::::::: ::::::::: :::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::: ::::::::: :::::::::Examples that I have found and have: ::::::::: ::::::::: :::::::::Dremel tool motor ::::::::: ::::::::: :::::::::Electric drill motor ::::::::: ::::::::: :::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::: ::::::::: :::::::::Hair dryer, blowing cold air ::::::::: ::::::::: :::::::::Corded electric razor ::::::::: ::::::::: :::::::::Wifes hand mixer ::::::::: ::::::::: :::::::::Hand saber saw ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::: ::::::::: :::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::: ::::::::: :::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::: :::::::::Find your strongest "static" source device for us. ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::: ::::::::: :::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::: ::::::::: ::::::::: :::::::::Standing by for the above info's supplication . . . . . . ::::::::: ::::::::: ::::::::: ::::::::: :::::::::73's de Edd ::::::::: ::::::::: ::::::::: ::::::::: |
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:::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. |
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::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help
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::Sir Doug. . . . . .
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::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!.
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::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception.
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::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ?
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::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times.
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::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ?
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::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna.
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::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB.
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::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up.
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::We are interested in that GREEN-BLACK winding and its integrity.
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::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ?
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::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function.
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::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie.
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::Then you tune across the AM band to see if any more stations come in.
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::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.?
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::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed.
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::As it stands I am in line with the further possibility of the unit:
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::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.)
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::2 . . .Still a problem in the ANT input section
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::3 . . .A gross mistuning of C7 GREY osc padder.
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::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?.
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::Thassit . . . . Standing by for feed back . . . .
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::R.F. THUMBNAIL of area now of prime interest:
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::73's de Edd
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::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::Sir Doug . . . . . .
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::::working in garage ,cinder walls.
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::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation.
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::::All of your voltages readings seem to be within range . . . nothing being grossly missing..
::::
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::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working.
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::::PRELIMINARY:
::::
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::::Hooking-up of 2 AC/DC chassis.
::::
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::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line.
::::
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::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket.
::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time.
::::
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::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that.
::::
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::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference.
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::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it.
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::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal.
::::
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:::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line.
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::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one.
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::::That should now provide for no ground loops being involved in our onset of testing to now be started.
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::::Tune in your Motorola to its best received station and tune spot on to it.
::::
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::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position.
::::
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::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity
::::on the next plug in cycle, as the power switches will no longer be used during testing.
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::::Signal Injection:
::::
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::::You will be connecting a common test lead between the two sets using its two alligator clips at either end.
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::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set.
::::
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::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube.
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::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube.
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::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now.
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::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with.
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::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance..
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::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry.
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::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now.
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::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set.
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::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer.
::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed.
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::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer.
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:::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own.
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::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up.
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::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede.
::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help.
::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help.
::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end
::::::::::Sir Doug. . . . .
::::::::::
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::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions.
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::::::::::Here it is sequentially . . . now being all condensed:
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::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin:
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::::::::::doug 02/05/2010 15:11
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::::::::::sears 6424 model no stations heard
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::::::::::i replaced caps and res. no voices
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::::::::::Warren 02/05/2010 16:38
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::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil?
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::::::::::Open IF transformer? Test all those.
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::::::::::doug 02/05/2010 18:33
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::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
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::::::::::Warren 02/05/2010 19:58
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::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity
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::::::::::doug 02/05/2010 20:37
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:::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
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::::::::::Warren 02/06/2010 01:58
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::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end.
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::::::::::Lewis L 02/06/2010 06:47
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::::::::::Try checking the local oscillator with a second radio.
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::::::::::Lewis
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::::::::::doug 02/06/2010 07:44
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::::::::::how do i do this
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::::::::::Terry Decker 02/06/2010 11:09
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::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
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::::::::::Now- first of all, this is a good place to make a couple of points.
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::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
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::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph.
::::::::::
::::::::::It is also a good idea to stop and test the set after each component change.
::::::::::
:::::::::: I am not an advocate of just replacing every cap.
::::::::::
:::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
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::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
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::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester".
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::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on.
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::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
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::::::::::OK- class over.
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::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations".
::::::::::
::::::::::There are a bunch of great suggestions there about checking out the oscillator.
::::::::::
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::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!!
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::::::::::doug 02/06/2010 13:22
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::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
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::::::::::Terry Decker 02/06/2010 13:53
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::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil.
::::::::::
:::::::::: If not, then you have an open coil, open resistor, or shorted cap.
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::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted.
::::::::::
:::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough.
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::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
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::::::::::Hope this helps some-
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::::::::::Warren 02/06/2010 13:58
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::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere.
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::::::::::doug 02/06/2010 14:51
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::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
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::::::::::Thomas Dermody 02/06/2010 20:30
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::::::::::
::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it.
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::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output.
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::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
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::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch.
::::::::::
:::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
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::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them.
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::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work.
::::::::::
::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark.
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::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark.
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::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
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::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands.
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::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band.
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:::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible.
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::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
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::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you.
::::::::::
::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly.
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::::::::::
::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
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::::::::::Thomas Dermody 02/06/2010 20:35
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::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments.
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::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
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::::::::::doug 02/06/2010 22:56
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::::::::::have not got that far yet.after further testing found some res. way out of range
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::::::::::Thomas Dermody 02/07/2010 01:48
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::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity.
::::::::::
::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet.
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::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
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::::::::::Posted by doug on 02/10/2010 08:23
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:::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
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::::::::::Posted by doug on 02/15/2010 09:28
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::::::::::where can i find a sig. gen.
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::::::::::Sir Doug. . . . .
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::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such.
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::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed:
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::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ?
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::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ?
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::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you
:::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS
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::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
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::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially.
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::::::::::That would seem to be with the bandswitch being placed to its fully CCW position.
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::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ?
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::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers.
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::::::::::5. . . Preliminary Prep:
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::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find.
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::::::::::Examples that I have found and have:
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::::::::::Hair dryer, blowing cold air
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::::::::::Corded electric razor
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::::::::::Wifes hand mixer
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::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band.
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::::::::::Then you move that static / inteference source around the loop to find its most responsive location.
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::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy.
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::::::::::Find your strongest "static" source device for us.
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::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning.
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::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ?
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::::::::::Standing by for the above info's supplication . . . . . .
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::::::::::73's de Edd
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::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: : : : : : : : : : :Sir Doug. . . . . . : : : :With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. : : :Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. : : :Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. : : :Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. : : :With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? : : :Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. : : :Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . : : : :Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. : : :Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. : : :Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. : : :Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. : : : :C7 Padder location: : : :  : : :Standing by for your procedural evaluation and any feedback . . . : :good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) : : : :73's de Edd : : : : |
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::: ::: ::: ::: ::: :::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help ::: ::: ::: ::: :::Sir Doug. . . . . . ::: ::: :::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. ::: ::: :::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. ::: ::: :::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? ::: ::: :::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. ::: ::: :::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? ::: ::: :::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. ::: ::: :::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. ::: ::: :::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. ::: ::: :::We are interested in that GREEN-BLACK winding and its integrity. ::: ::: :::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? ::: ::: :::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. ::: ::: :::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. ::: ::: :::Then you tune across the AM band to see if any more stations come in. ::: ::: :::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? ::: ::: :::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. ::: ::: :::As it stands I am in line with the further possibility of the unit: ::: ::: :::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) ::: ::: :::2 . . .Still a problem in the ANT input section ::: ::: :::3 . . .A gross mistuning of C7 GREY osc padder. ::: ::: :::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. ::: ::: :::Thassit . . . . Standing by for feed back . . . . ::: ::: :::R.F. THUMBNAIL of area now of prime interest: ::: ::: ::: ::: ::: ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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:::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::: ::: ::: ::: ::: ::: ::: ::: ::: ::: :::Sir Doug . . . . . . ::: ::: ::: ::::: :::::working in garage ,cinder walls. ::::: ::::: ::::: :::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::::: ::::: :::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::::: ::::: :::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::::: ::::: :::::PRELIMINARY: ::::: ::::: :::::Hooking-up of 2 AC/DC chassis. ::::: ::::: :::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::::: ::::: :::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::::: ::::: :::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::::: ::::: :::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::::: ::::: :::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::::: ::::: :::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::::: ::::: ::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::::: ::::: :::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::::: ::::: :::::That should now provide for no ground loops being involved in our onset of testing to now be started. ::::: ::::: :::::Tune in your Motorola to its best received station and tune spot on to it. ::::: ::::: :::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::::: ::::: :::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::::on the next plug in cycle, as the power switches will no longer be used during testing. ::::: ::::: :::::Signal Injection: ::::: ::::: :::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::::: ::::: :::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::::: ::::: :::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::::: ::::: :::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::::: ::::: :::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::::: ::::: :::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::::: ::::: :::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::::: ::::: :::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::::: ::::: :::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::::: ::::: :::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::::: ::::: :::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::::: ::::: :::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::::: ::::: ::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::::: ::::: :::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::::: ::::: ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: |
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::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::::Sir Doug. . . . . ::::::::::: ::::::::::: :::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::::: ::::::::::: :::::::::::Here it is sequentially . . . now being all condensed: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/05/2010 15:11 ::::::::::: ::::::::::: ::::::::::: :::::::::::sears 6424 model no stations heard ::::::::::: ::::::::::: :::::::::::i replaced caps and res. no voices ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Warren 02/05/2010 16:38 ::::::::::: ::::::::::: ::::::::::: :::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::::: ::::::::::: :::::::::::Open IF transformer? Test all those. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/05/2010 18:33 ::::::::::: ::::::::::: ::::::::::: :::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Warren 02/05/2010 19:58 ::::::::::: ::::::::::: ::::::::::: :::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/05/2010 20:37 ::::::::::: ::::::::::: ::::::::::: ::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Warren 02/06/2010 01:58 ::::::::::: ::::::::::: ::::::::::: :::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Lewis L 02/06/2010 06:47 ::::::::::: ::::::::::: ::::::::::: :::::::::::Try checking the local oscillator with a second radio. ::::::::::: ::::::::::: :::::::::::Lewis ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/06/2010 07:44 ::::::::::: ::::::::::: ::::::::::: :::::::::::how do i do this ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Terry Decker 02/06/2010 11:09 ::::::::::: ::::::::::: ::::::::::: :::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::::: ::::::::::: :::::::::::Now- first of all, this is a good place to make a couple of points. ::::::::::: ::::::::::: :::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::::: ::::::::::: :::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::::: :::::::::::It is also a good idea to stop and test the set after each component change. ::::::::::: ::::::::::: I am not an advocate of just replacing every cap. ::::::::::: ::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::::: ::::::::::: :::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::::: ::::::::::: :::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::::: :::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::::: :::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::::: ::::::::::: :::::::::::OK- class over. ::::::::::: ::::::::::: :::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::::: :::::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::::: ::::::::::: :::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/06/2010 13:22 ::::::::::: ::::::::::: ::::::::::: :::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Terry Decker 02/06/2010 13:53 ::::::::::: ::::::::::: ::::::::::: :::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::::: ::::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::::: :::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::::: ::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::::: :::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::::: ::::::::::: :::::::::::Hope this helps some- ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Warren 02/06/2010 13:58 ::::::::::: ::::::::::: ::::::::::: :::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/06/2010 14:51 ::::::::::: ::::::::::: ::::::::::: :::::::::::no opens ::::::::::: ::::::::::: :::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Thomas Dermody 02/06/2010 20:30 ::::::::::: ::::::::::: ::::::::::: :::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::::: ::::::::::: :::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::::: :::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::::: ::::::::::: :::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::::: ::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::::: ::::::::::: :::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::::: :::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::::: :::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::::: :::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::::: :::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::::: ::::::::::: :::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::::: :::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::::: ::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::::: :::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::::: ::::::::::: :::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::::: :::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::::: ::::::::::: :::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Thomas Dermody 02/06/2010 20:35 ::::::::::: ::::::::::: ::::::::::: :::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::::: ::::::::::: :::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::doug 02/06/2010 22:56 ::::::::::: ::::::::::: ::::::::::: :::::::::::have not got that far yet.after further testing found some res. way out of range ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Thomas Dermody 02/07/2010 01:48 ::::::::::: ::::::::::: ::::::::::: :::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::::: :::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::::: ::::::::::: :::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Posted by doug on 02/10/2010 08:23 ::::::::::: ::::::::::: ::::::::::: ::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Posted by doug on 02/15/2010 09:28 ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::where can i find a sig. gen. ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: |
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::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Sir Doug. . . . . ::::::::::: ::::::::::: :::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::::: ::::::::::: :::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::::: ::::::::::: :::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::::: ::::::::::: :::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::::: ::::::::::: :::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::::: specs ? ::::::::::: ::::::::::: :::::::::::4 . . . :::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::: ::::::::::: ::::::::::: :::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::::: ::::::::::: :::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::::: ::::::::::: :::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::::: ::::::::::: :::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::::: ::::::::::: :::::::::::5. . . Preliminary Prep: ::::::::::: ::::::::::: :::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::::: ::::::::::: :::::::::::Examples that I have found and have: ::::::::::: ::::::::::: :::::::::::Dremel tool motor ::::::::::: ::::::::::: :::::::::::Electric drill motor ::::::::::: ::::::::::: :::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::::: ::::::::::: :::::::::::Hair dryer, blowing cold air ::::::::::: ::::::::::: :::::::::::Corded electric razor ::::::::::: ::::::::::: :::::::::::Wifes hand mixer ::::::::::: ::::::::::: :::::::::::Hand saber saw ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::::: ::::::::::: :::::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::::: ::::::::::: :::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::::: :::::::::::Find your strongest "static" source device for us. ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::::: ::::::::::: :::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::::: ::::::::::: ::::::::::: :::::::::::Standing by for the above info's supplication . . . . . . ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::73's de Edd ::::::::::: ::::::::::: ::::::::::: ::::::::::: |
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:::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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:: :: :: :: :: :: :: :: :: :: ::Sir Doug. . . . . . :: :: :: ::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. :: :: ::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. :: :: ::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. :: :: ::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. :: :: ::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? :: :: ::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. :: :: ::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . :: :: :: ::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. :: :: ::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. :: :: ::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. :: :: ::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. :: :: :: ::C7 Padder location: :: :: :: :: :: ::Standing by for your procedural evaluation and any feedback . . . :: ::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) :: :: :: ::73's de Edd :: :: :: :: |
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:::: :::: :::: :::: :::: ::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help :::: :::: :::: :::: ::::Sir Doug. . . . . . :::: :::: ::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. :::: :::: ::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. :::: :::: ::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? :::: :::: ::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. :::: :::: ::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? :::: :::: ::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. :::: :::: ::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. :::: :::: ::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. :::: :::: ::::We are interested in that GREEN-BLACK winding and its integrity. :::: :::: ::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? :::: :::: ::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. :::: :::: ::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. :::: :::: ::::Then you tune across the AM band to see if any more stations come in. :::: :::: ::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? :::: :::: ::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. :::: :::: ::::As it stands I am in line with the further possibility of the unit: :::: :::: ::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) :::: :::: ::::2 . . .Still a problem in the ANT input section :::: :::: ::::3 . . .A gross mistuning of C7 GREY osc padder. :::: :::: ::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. :::: :::: ::::Thassit . . . . Standing by for feed back . . . . :::: :::: ::::R.F. THUMBNAIL of area now of prime interest: :::: :::: :::: :::: :::: :::: :::: :::: ::::73's de Edd :::: :::: :::: :::: |
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::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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:::: :::: :::: :::: :::: :::: :::: :::: :::: :::: ::::Sir Doug . . . . . . :::: :::: :::: :::::: ::::::working in garage ,cinder walls. :::::: :::::: :::::: ::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. :::::: :::::: ::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. :::::: :::::: ::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. :::::: :::::: ::::::PRELIMINARY: :::::: :::::: ::::::Hooking-up of 2 AC/DC chassis. :::::: :::::: ::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. :::::: :::::: ::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. ::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. :::::: :::::: ::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. :::::: :::::: ::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. :::::: :::::: ::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. :::::: :::::: ::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. :::::: :::::: :::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. :::::: :::::: ::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. :::::: :::::: ::::::That should now provide for no ground loops being involved in our onset of testing to now be started. :::::: :::::: ::::::Tune in your Motorola to its best received station and tune spot on to it. :::::: :::::: ::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. :::::: :::::: ::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity ::::::on the next plug in cycle, as the power switches will no longer be used during testing. :::::: :::::: ::::::Signal Injection: :::::: :::::: ::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. :::::: :::::: ::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. :::::: :::::: ::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. :::::: :::::: ::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. :::::: :::::: ::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. :::::: :::::: ::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. :::::: :::::: ::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. :::::: :::::: ::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. :::::: :::::: ::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. :::::: :::::: ::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. :::::: :::::: ::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. ::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. :::::: :::::: ::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. :::::: :::::: :::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. :::::: :::::: ::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. :::::: :::::: :::::: :::::: :::::: ::::::73's de Edd :::::: :::::: :::::: :::::: |
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:::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. ::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. ::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. ::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end ::::::::::::Sir Doug. . . . . :::::::::::: :::::::::::: ::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. :::::::::::: :::::::::::: ::::::::::::Here it is sequentially . . . now being all condensed: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/05/2010 15:11 :::::::::::: :::::::::::: :::::::::::: ::::::::::::sears 6424 model no stations heard :::::::::::: :::::::::::: ::::::::::::i replaced caps and res. no voices :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Warren 02/05/2010 16:38 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? :::::::::::: :::::::::::: ::::::::::::Open IF transformer? Test all those. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/05/2010 18:33 :::::::::::: :::::::::::: :::::::::::: ::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Warren 02/05/2010 19:58 :::::::::::: :::::::::::: :::::::::::: ::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/05/2010 20:37 :::::::::::: :::::::::::: :::::::::::: :::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Warren 02/06/2010 01:58 :::::::::::: :::::::::::: :::::::::::: ::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Lewis L 02/06/2010 06:47 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Try checking the local oscillator with a second radio. :::::::::::: :::::::::::: ::::::::::::Lewis :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/06/2010 07:44 :::::::::::: :::::::::::: :::::::::::: ::::::::::::how do i do this :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Terry Decker 02/06/2010 11:09 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. :::::::::::: :::::::::::: ::::::::::::Now- first of all, this is a good place to make a couple of points. :::::::::::: :::::::::::: ::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! :::::::::::: :::::::::::: ::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. :::::::::::: ::::::::::::It is also a good idea to stop and test the set after each component change. :::::::::::: :::::::::::: I am not an advocate of just replacing every cap. :::::::::::: :::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. :::::::::::: :::::::::::: ::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. :::::::::::: :::::::::::: ::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". :::::::::::: ::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. :::::::::::: ::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. :::::::::::: :::::::::::: ::::::::::::OK- class over. :::::::::::: :::::::::::: ::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". :::::::::::: ::::::::::::There are a bunch of great suggestions there about checking out the oscillator. :::::::::::: :::::::::::: ::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/06/2010 13:22 :::::::::::: :::::::::::: :::::::::::: ::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Terry Decker 02/06/2010 13:53 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. :::::::::::: :::::::::::: If not, then you have an open coil, open resistor, or shorted cap. :::::::::::: ::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. :::::::::::: :::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. :::::::::::: ::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. :::::::::::: :::::::::::: ::::::::::::Hope this helps some- :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Warren 02/06/2010 13:58 :::::::::::: :::::::::::: :::::::::::: ::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/06/2010 14:51 :::::::::::: :::::::::::: :::::::::::: ::::::::::::no opens :::::::::::: :::::::::::: ::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Thomas Dermody 02/06/2010 20:30 :::::::::::: :::::::::::: :::::::::::: ::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. :::::::::::: :::::::::::: ::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. :::::::::::: ::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. :::::::::::: :::::::::::: ::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. :::::::::::: :::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. :::::::::::: :::::::::::: ::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. :::::::::::: ::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. :::::::::::: ::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. ::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. :::::::::::: ::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. :::::::::::: ::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. :::::::::::: :::::::::::: ::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. :::::::::::: ::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. :::::::::::: :::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. :::::::::::: ::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. :::::::::::: :::::::::::: ::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. :::::::::::: ::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. :::::::::::: :::::::::::: ::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Thomas Dermody 02/06/2010 20:35 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. :::::::::::: :::::::::::: ::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::doug 02/06/2010 22:56 :::::::::::: :::::::::::: :::::::::::: ::::::::::::have not got that far yet.after further testing found some res. way out of range :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Thomas Dermody 02/07/2010 01:48 :::::::::::: :::::::::::: :::::::::::: ::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. :::::::::::: ::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. :::::::::::: :::::::::::: ::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Posted by doug on 02/10/2010 08:23 :::::::::::: :::::::::::: :::::::::::: :::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Posted by doug on 02/15/2010 09:28 :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::where can i find a sig. gen. :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: |
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:::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Sir Doug. . . . . :::::::::::: :::::::::::: ::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. :::::::::::: :::::::::::: ::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: :::::::::::: :::::::::::: ::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? :::::::::::: :::::::::::: ::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? :::::::::::: :::::::::::: ::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you :::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS :::::::::::: specs ? :::::::::::: :::::::::::: ::::::::::::4 . . . ::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::::::::::: :::::::::::: :::::::::::: ::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. :::::::::::: :::::::::::: ::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. :::::::::::: :::::::::::: ::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? :::::::::::: :::::::::::: ::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. :::::::::::: :::::::::::: ::::::::::::5. . . Preliminary Prep: :::::::::::: :::::::::::: ::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. :::::::::::: :::::::::::: ::::::::::::Examples that I have found and have: :::::::::::: :::::::::::: ::::::::::::Dremel tool motor :::::::::::: :::::::::::: ::::::::::::Electric drill motor :::::::::::: :::::::::::: ::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) :::::::::::: :::::::::::: ::::::::::::Hair dryer, blowing cold air :::::::::::: :::::::::::: ::::::::::::Corded electric razor :::::::::::: :::::::::::: ::::::::::::Wifes hand mixer :::::::::::: :::::::::::: ::::::::::::Hand saber saw :::::::::::: :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. :::::::::::: :::::::::::: ::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. :::::::::::: :::::::::::: ::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. :::::::::::: ::::::::::::Find your strongest "static" source device for us. :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. :::::::::::: :::::::::::: ::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? :::::::::::: :::::::::::: :::::::::::: ::::::::::::Standing by for the above info's supplication . . . . . . :::::::::::: :::::::::::: :::::::::::: :::::::::::: ::::::::::::73's de Edd :::::::::::: :::::::::::: :::::::::::: :::::::::::: |
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::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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::: :::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL ::: ::: ::: ::: ::: ::: ::: ::: :::Sir Doug. . . . . . ::: ::: ::: :::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. ::: ::: :::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. ::: ::: :::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. ::: ::: :::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. ::: ::: :::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? ::: ::: :::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. ::: ::: :::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . ::: ::: ::: :::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. ::: ::: :::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. ::: ::: :::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. ::: ::: :::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. ::: ::: ::: :::C7 Padder location: ::: ::: ::: ::: ::: :::Standing by for your procedural evaluation and any feedback . . . ::: :::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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::::: ::::: ::::: ::::: ::::: :::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help ::::: ::::: ::::: ::::: :::::Sir Doug. . . . . . ::::: ::::: :::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. ::::: ::::: :::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. ::::: ::::: :::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? ::::: ::::: :::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. ::::: ::::: :::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? ::::: ::::: :::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. ::::: ::::: :::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. ::::: ::::: :::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. ::::: ::::: :::::We are interested in that GREEN-BLACK winding and its integrity. ::::: ::::: :::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? ::::: ::::: :::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. ::::: ::::: :::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. ::::: ::::: :::::Then you tune across the AM band to see if any more stations come in. ::::: ::::: :::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? ::::: ::::: :::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. ::::: ::::: :::::As it stands I am in line with the further possibility of the unit: ::::: ::::: :::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) ::::: ::::: :::::2 . . .Still a problem in the ANT input section ::::: ::::: :::::3 . . .A gross mistuning of C7 GREY osc padder. ::::: ::::: :::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. ::::: ::::: :::::Thassit . . . . Standing by for feed back . . . . ::::: ::::: :::::R.F. THUMBNAIL of area now of prime interest: ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: |
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:::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::Sir Doug . . . . . . ::::: ::::: ::::: ::::::: :::::::working in garage ,cinder walls. ::::::: ::::::: ::::::: :::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::::::: ::::::: :::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::::::: ::::::: :::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::::::: ::::::: :::::::PRELIMINARY: ::::::: ::::::: :::::::Hooking-up of 2 AC/DC chassis. ::::::: ::::::: :::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::::::: ::::::: :::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::::::: ::::::: :::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::::::: ::::::: :::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::::::: ::::::: :::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::::::: ::::::: :::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::::::: ::::::: ::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::::::: ::::::: :::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::::::: ::::::: :::::::That should now provide for no ground loops being involved in our onset of testing to now be started. ::::::: ::::::: :::::::Tune in your Motorola to its best received station and tune spot on to it. ::::::: ::::::: :::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::::::: ::::::: :::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::::::on the next plug in cycle, as the power switches will no longer be used during testing. ::::::: ::::::: :::::::Signal Injection: ::::::: ::::::: :::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::::::: ::::::: :::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::::::: ::::::: :::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::::::: ::::::: :::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::::::: ::::::: :::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::::::: ::::::: :::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::::::: ::::::: :::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::::::: ::::::: :::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::::::: ::::::: :::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::::::: ::::::: :::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::::::: ::::::: :::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::::::: ::::::: :::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::::::: ::::::: ::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::::::: ::::::: :::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::::::: ::::::: ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: |
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::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::::::Sir Doug. . . . . ::::::::::::: ::::::::::::: :::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::::::: ::::::::::::: :::::::::::::Here it is sequentially . . . now being all condensed: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/05/2010 15:11 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::sears 6424 model no stations heard ::::::::::::: ::::::::::::: :::::::::::::i replaced caps and res. no voices ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Warren 02/05/2010 16:38 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::::::: ::::::::::::: :::::::::::::Open IF transformer? Test all those. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/05/2010 18:33 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Warren 02/05/2010 19:58 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/05/2010 20:37 ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Warren 02/06/2010 01:58 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Lewis L 02/06/2010 06:47 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Try checking the local oscillator with a second radio. ::::::::::::: ::::::::::::: :::::::::::::Lewis ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/06/2010 07:44 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::how do i do this ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Terry Decker 02/06/2010 11:09 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::::::: ::::::::::::: :::::::::::::Now- first of all, this is a good place to make a couple of points. ::::::::::::: ::::::::::::: :::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::::::: ::::::::::::: :::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::::::: :::::::::::::It is also a good idea to stop and test the set after each component change. ::::::::::::: ::::::::::::: I am not an advocate of just replacing every cap. ::::::::::::: ::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::::::: ::::::::::::: :::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::::::: ::::::::::::: :::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::::::: :::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::::::: :::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::::::: ::::::::::::: :::::::::::::OK- class over. ::::::::::::: ::::::::::::: :::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::::::: :::::::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::::::: ::::::::::::: :::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/06/2010 13:22 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Terry Decker 02/06/2010 13:53 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::::::: ::::::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::::::: :::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::::::: ::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::::::: :::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::::::: ::::::::::::: :::::::::::::Hope this helps some- ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Warren 02/06/2010 13:58 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/06/2010 14:51 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::no opens ::::::::::::: ::::::::::::: :::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Thomas Dermody 02/06/2010 20:30 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::::::: ::::::::::::: :::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::::::: :::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::::::: ::::::::::::: :::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::::::: ::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::::::: ::::::::::::: :::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::::::: :::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::::::: :::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::::::: :::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::::::: :::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::::::: ::::::::::::: :::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::::::: :::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::::::: ::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::::::: :::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::::::: ::::::::::::: :::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::::::: :::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::::::: ::::::::::::: :::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Thomas Dermody 02/06/2010 20:35 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::::::: ::::::::::::: :::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::doug 02/06/2010 22:56 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::have not got that far yet.after further testing found some res. way out of range ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Thomas Dermody 02/07/2010 01:48 ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::::::: :::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::::::: ::::::::::::: :::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Posted by doug on 02/10/2010 08:23 ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Posted by doug on 02/15/2010 09:28 ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::where can i find a sig. gen. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: |
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::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Sir Doug. . . . . ::::::::::::: ::::::::::::: :::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::::::: ::::::::::::: :::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::::::: ::::::::::::: :::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::::::: ::::::::::::: :::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::::::: ::::::::::::: :::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::::::: specs ? ::::::::::::: ::::::::::::: :::::::::::::4 . . . :::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::::::: ::::::::::::: :::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::::::: ::::::::::::: :::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::::::: ::::::::::::: :::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::::::: ::::::::::::: :::::::::::::5. . . Preliminary Prep: ::::::::::::: ::::::::::::: :::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::::::: ::::::::::::: :::::::::::::Examples that I have found and have: ::::::::::::: ::::::::::::: :::::::::::::Dremel tool motor ::::::::::::: ::::::::::::: :::::::::::::Electric drill motor ::::::::::::: ::::::::::::: :::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::::::: ::::::::::::: :::::::::::::Hair dryer, blowing cold air ::::::::::::: ::::::::::::: :::::::::::::Corded electric razor ::::::::::::: ::::::::::::: :::::::::::::Wifes hand mixer ::::::::::::: ::::::::::::: :::::::::::::Hand saber saw ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::::::: ::::::::::::: :::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::::::: ::::::::::::: :::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::::::: :::::::::::::Find your strongest "static" source device for us. ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::::::: ::::::::::::: :::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::Standing by for the above info's supplication . . . . . . ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: :::::::::::::73's de Edd ::::::::::::: ::::::::::::: ::::::::::::: ::::::::::::: |
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:::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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::::my new signal generator will be hereon the3/15
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::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL
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::::Sir Doug. . . . . .
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::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located.
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::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station.
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::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale.
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::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial.
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::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ?
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::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C.
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::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola .
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::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position.
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::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position.
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::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception.
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::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band.
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::::C7 Padder location:
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::::Standing by for your procedural evaluation and any feedback . . .
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::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really)
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::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help
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::::::Sir Doug. . . . . .
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::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!.
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::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception.
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::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ?
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::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times.
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::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ?
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::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna.
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::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB.
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::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up.
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::::::We are interested in that GREEN-BLACK winding and its integrity.
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::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ?
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::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function.
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::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie.
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::::::Then you tune across the AM band to see if any more stations come in.
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::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.?
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::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed.
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::::::As it stands I am in line with the further possibility of the unit:
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::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.)
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::::::2 . . .Still a problem in the ANT input section
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::::::3 . . .A gross mistuning of C7 GREY osc padder.
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::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?.
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::::::Thassit . . . . Standing by for feed back . . . .
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::::::R.F. THUMBNAIL of area now of prime interest:
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::::::73's de Edd
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::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::::Sir Doug . . . . . .
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::::::::working in garage ,cinder walls.
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::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation.
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::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing..
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::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working.
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::::::::PRELIMINARY:
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::::::::Hooking-up of 2 AC/DC chassis.
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::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line.
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::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket.
::::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time.
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::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that.
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::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference.
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::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it.
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::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal.
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:::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line.
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::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one.
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::::::::That should now provide for no ground loops being involved in our onset of testing to now be started.
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::::::::Tune in your Motorola to its best received station and tune spot on to it.
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::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position.
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::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity
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::::::::Signal Injection:
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::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end.
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::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set.
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::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube.
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::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube.
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::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now.
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::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with.
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::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance..
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::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry.
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::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now.
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::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set.
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::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer.
::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed.
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::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer.
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:::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own.
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::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up.
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::::::::73's de Edd
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::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede.
::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help.
::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help.
::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end
::::::::::::::Sir Doug. . . . .
::::::::::::::
::::::::::::::
::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions.
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::::::::::::::Here it is sequentially . . . now being all condensed:
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::::::::::::::
::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin:
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::::::::::::::doug 02/05/2010 15:11
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::::::::::::::sears 6424 model no stations heard
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::::::::::::::i replaced caps and res. no voices
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::::::::::::::Warren 02/05/2010 16:38
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::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil?
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::::::::::::::Open IF transformer? Test all those.
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::::::::::::::doug 02/05/2010 18:33
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::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
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::::::::::::::Warren 02/05/2010 19:58
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::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity
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::::::::::::::doug 02/05/2010 20:37
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:::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
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::::::::::::::Warren 02/06/2010 01:58
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::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end.
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::::::::::::::Lewis L 02/06/2010 06:47
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::::::::::::::Try checking the local oscillator with a second radio.
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::::::::::::::Lewis
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::::::::::::::doug 02/06/2010 07:44
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::::::::::::::how do i do this
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::::::::::::::Terry Decker 02/06/2010 11:09
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::::::::::::::
::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
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::::::::::::::
::::::::::::::Now- first of all, this is a good place to make a couple of points.
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::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
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::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph.
::::::::::::::
::::::::::::::It is also a good idea to stop and test the set after each component change.
::::::::::::::
:::::::::::::: I am not an advocate of just replacing every cap.
::::::::::::::
:::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
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::::::::::::::
::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
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::::::::::::::
::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester".
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::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on.
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::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
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::::::::::::::OK- class over.
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::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations".
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::::::::::::::There are a bunch of great suggestions there about checking out the oscillator.
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::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!!
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::::::::::::::doug 02/06/2010 13:22
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::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
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::::::::::::::Terry Decker 02/06/2010 13:53
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::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil.
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:::::::::::::: If not, then you have an open coil, open resistor, or shorted cap.
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::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted.
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:::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough.
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::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
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::::::::::::::Hope this helps some-
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::::::::::::::Warren 02/06/2010 13:58
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::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere.
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::::::::::::::doug 02/06/2010 14:51
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::::::::::::::no opens
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::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
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::::::::::::::Thomas Dermody 02/06/2010 20:30
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::::::::::::::
::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it.
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::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output.
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::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
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::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch.
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:::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
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::::::::::::::
::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them.
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::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work.
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::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark.
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::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark.
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::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
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::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands.
::::::::::::::
::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band.
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:::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible.
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::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
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::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you.
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::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly.
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::::::::::::::
::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
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::::::::::::::Thomas Dermody 02/06/2010 20:35
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::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments.
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::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
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::::::::::::::doug 02/06/2010 22:56
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::::::::::::::have not got that far yet.after further testing found some res. way out of range
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::::::::::::::Thomas Dermody 02/07/2010 01:48
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::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity.
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::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet.
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::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
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::::::::::::::Posted by doug on 02/10/2010 08:23
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:::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
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::::::::::::::Posted by doug on 02/15/2010 09:28
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::::::::::::::where can i find a sig. gen.
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::::::::::::::Sir Doug. . . . .
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::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such.
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::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed:
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::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ?
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::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ?
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::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you
:::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS
:::::::::::::: specs ?
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::::::::::::::4 . . .
::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
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::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially.
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::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position.
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::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ?
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::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers.
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::::::::::::::5. . . Preliminary Prep:
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::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find.
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::::::::::::::Examples that I have found and have:
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::::::::::::::Dremel tool motor
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::::::::::::::Electric drill motor
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::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors)
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::::::::::::::Hair dryer, blowing cold air
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::::::::::::::Corded electric razor
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::::::::::::::Wifes hand mixer
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::::::::::::::Hand saber saw
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::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band.
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::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location.
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::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy.
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::::::::::::::Find your strongest "static" source device for us.
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::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning.
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::::::::::::::
::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ?
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::::::::::::::Standing by for the above info's supplication . . . . . .
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::::::::::::::73's de Edd
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::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: :thanks edd for getting back with me. i have to work 4 days at 12 hours each day. will get back on the radio on monday,will let you know what happens then .again thank you for your help,i am learning : : : : : : : : :Sir Doug . . . . . . : : :Been VEWY- VEWY . .BIZZZZY with clients on this end, not just ignoring you. : : :It looks like that the antenna section of the tuning condenser, on the BCB, that its coil windings are isolated with capacitors or at least a 2 meg + resistor in one situation in series with them. : : :Now, on the oscillator section, looks it is also completely capacitively isolated form the osc coil winding. : : :Soooo . . . do an ohms test between the stators and the common rotor, whilst SLOWLY moving the tuning condenser thru its range. : : :Naturally the more the condenser swings towards the lower frequency, the more the intermeshing of the rotor and stator plates, and the greater the potential becomes for a short. : : :Usually its the outside plates that are mechanically subjective to getting ever so slightly bent inward and out of place the easiest, but certainly, ALL are suspect. : : :Will be back with more on the Loopey-Doopey later as that currently seems to be my highest suspicion, IF not being so simple as the tuning consenser plates touching and/or dragging on down band frequency tuning. : : : : : :73's de Edd : : : : |
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:::::my new signal generator will be hereon the3/15
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::::: :::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::Sir Doug. . . . . . ::::: ::::: ::::: :::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. ::::: ::::: :::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. ::::: ::::: :::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. ::::: ::::: :::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. ::::: ::::: :::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? ::::: ::::: :::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. ::::: ::::: :::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . ::::: ::::: ::::: :::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. ::::: ::::: :::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. ::::: ::::: :::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. ::::: ::::: :::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. ::::: ::::: ::::: :::::C7 Padder location: ::::: ::::: ::::: ::::: ::::: :::::Standing by for your procedural evaluation and any feedback . . . ::::: :::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: |
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::::::: ::::::: ::::::: ::::::: ::::::: :::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug. . . . . . ::::::: ::::::: :::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. ::::::: ::::::: :::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. ::::::: ::::::: :::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? ::::::: ::::::: :::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. ::::::: ::::::: :::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? ::::::: ::::::: :::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. ::::::: ::::::: :::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. ::::::: ::::::: :::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. ::::::: ::::::: :::::::We are interested in that GREEN-BLACK winding and its integrity. ::::::: ::::::: :::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? ::::::: ::::::: :::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. ::::::: ::::::: :::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. ::::::: ::::::: :::::::Then you tune across the AM band to see if any more stations come in. ::::::: ::::::: :::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? ::::::: ::::::: :::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. ::::::: ::::::: :::::::As it stands I am in line with the further possibility of the unit: ::::::: ::::::: :::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) ::::::: ::::::: :::::::2 . . .Still a problem in the ANT input section ::::::: ::::::: :::::::3 . . .A gross mistuning of C7 GREY osc padder. ::::::: ::::::: :::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. ::::::: ::::::: :::::::Thassit . . . . Standing by for feed back . . . . ::::::: ::::::: :::::::R.F. THUMBNAIL of area now of prime interest: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: |
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:::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug . . . . . . ::::::: ::::::: ::::::: ::::::::: :::::::::working in garage ,cinder walls. ::::::::: ::::::::: ::::::::: :::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::::::::: ::::::::: :::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::::::::: ::::::::: :::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::::::::: ::::::::: :::::::::PRELIMINARY: ::::::::: ::::::::: :::::::::Hooking-up of 2 AC/DC chassis. ::::::::: ::::::::: :::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::::::::: ::::::::: :::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::::::::: ::::::::: :::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::::::::: ::::::::: :::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::::::::: ::::::::: :::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::::::::: ::::::::: :::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::::::::: ::::::::: ::::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::::::::: ::::::::: :::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::::::::: ::::::::: :::::::::That should now provide for no ground loops being involved in our onset of testing to now be started. ::::::::: ::::::::: :::::::::Tune in your Motorola to its best received station and tune spot on to it. ::::::::: ::::::::: :::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::::::::: ::::::::: :::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::::::::on the next plug in cycle, as the power switches will no longer be used during testing. ::::::::: ::::::::: :::::::::Signal Injection: ::::::::: ::::::::: :::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::::::::: ::::::::: :::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::::::::: ::::::::: :::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::::::::: ::::::::: :::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::::::::: ::::::::: :::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::::::::: ::::::::: :::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::::::::: ::::::::: :::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::::::::: ::::::::: :::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::::::::: ::::::::: :::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::::::::: ::::::::: :::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::::::::: ::::::::: :::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::::::::: ::::::::: :::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::::::::: ::::::::: ::::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::::::::: ::::::::: :::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::73's de Edd ::::::::: ::::::::: ::::::::: ::::::::: |
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::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::::::::Sir Doug. . . . . ::::::::::::::: ::::::::::::::: :::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::::::::: ::::::::::::::: :::::::::::::::Here it is sequentially . . . now being all condensed: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 15:11 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::sears 6424 model no stations heard ::::::::::::::: ::::::::::::::: :::::::::::::::i replaced caps and res. no voices ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/05/2010 16:38 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::::::::: ::::::::::::::: :::::::::::::::Open IF transformer? Test all those. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 18:33 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/05/2010 19:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 20:37 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/06/2010 01:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Lewis L 02/06/2010 06:47 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Try checking the local oscillator with a second radio. ::::::::::::::: ::::::::::::::: :::::::::::::::Lewis ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 07:44 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::how do i do this ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Terry Decker 02/06/2010 11:09 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::::::::: ::::::::::::::: :::::::::::::::Now- first of all, this is a good place to make a couple of points. ::::::::::::::: ::::::::::::::: :::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::::::::: ::::::::::::::: :::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::::::::: :::::::::::::::It is also a good idea to stop and test the set after each component change. ::::::::::::::: ::::::::::::::: I am not an advocate of just replacing every cap. ::::::::::::::: ::::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::::::::: ::::::::::::::: :::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::::::::: ::::::::::::::: :::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::::::::: :::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::::::::: :::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::::::::: ::::::::::::::: :::::::::::::::OK- class over. ::::::::::::::: ::::::::::::::: :::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::::::::: :::::::::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::::::::: ::::::::::::::: :::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 13:22 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Terry Decker 02/06/2010 13:53 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::::::::: ::::::::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::::::::: :::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::::::::: ::::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::::::::: :::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::::::::: ::::::::::::::: :::::::::::::::Hope this helps some- ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/06/2010 13:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 14:51 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::no opens ::::::::::::::: ::::::::::::::: :::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/06/2010 20:30 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::::::::: ::::::::::::::: :::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::::::::: :::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::::::::: ::::::::::::::: :::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::::::::: ::::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::::::::: ::::::::::::::: :::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::::::::: :::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::::::::: :::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::::::::: :::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::::::::: :::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::::::::: ::::::::::::::: :::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::::::::: :::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::::::::: ::::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::::::::: :::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::::::::: ::::::::::::::: :::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::::::::: :::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::::::::: ::::::::::::::: :::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/06/2010 20:35 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::::::::: ::::::::::::::: :::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 22:56 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::have not got that far yet.after further testing found some res. way out of range ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/07/2010 01:48 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::::::::: :::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::::::::: ::::::::::::::: :::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Posted by doug on 02/10/2010 08:23 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Posted by doug on 02/15/2010 09:28 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::where can i find a sig. gen. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: |
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::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Sir Doug. . . . . ::::::::::::::: ::::::::::::::: :::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::::::::: ::::::::::::::: :::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::::::::: ::::::::::::::: :::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::::::::: ::::::::::::::: :::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::::::::: ::::::::::::::: :::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::::::::: specs ? ::::::::::::::: ::::::::::::::: :::::::::::::::4 . . . :::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::::::::: ::::::::::::::: :::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::::::::: ::::::::::::::: :::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::::::::: ::::::::::::::: :::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::::::::: ::::::::::::::: :::::::::::::::5. . . Preliminary Prep: ::::::::::::::: ::::::::::::::: :::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::::::::: ::::::::::::::: :::::::::::::::Examples that I have found and have: ::::::::::::::: ::::::::::::::: :::::::::::::::Dremel tool motor ::::::::::::::: ::::::::::::::: :::::::::::::::Electric drill motor ::::::::::::::: ::::::::::::::: :::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::::::::: ::::::::::::::: :::::::::::::::Hair dryer, blowing cold air ::::::::::::::: ::::::::::::::: :::::::::::::::Corded electric razor ::::::::::::::: ::::::::::::::: :::::::::::::::Wifes hand mixer ::::::::::::::: ::::::::::::::: :::::::::::::::Hand saber saw ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::::::::: ::::::::::::::: :::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::::::::: ::::::::::::::: :::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::::::::: :::::::::::::::Find your strongest "static" source device for us. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::::::::: ::::::::::::::: :::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Standing by for the above info's supplication . . . . . . ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::73's de Edd ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: |
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:::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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:: ::thanks edd for getting back with me. i have to work 4 days at 12 hours each day. will get back on the radio on monday,will let you know what happens then .again thank you for your help,i am learning :: :: :: ::HEY EDD,I,M BACK. WORKED ON RADIO ALL DAY, GOING OVER WHAT YOU HAVE SAID.HAVE NOW FIGURED OUT THE WAY MY RF GEN. WORKS.I HOOKED UP RF TO BLACK TO CHASSIS ,RED WIRE TO WIRE FROM GRID CAP OF 6U7 TO TI.I PICK UP SIGNAL AT 6.9KHZ.IF I ADJUST C7 AND MOVE POINTER TO 4.5KHZ CANNOT FIND SIGNAL.DO I ADJUST T1 TO FIND SIGNAL,IF SO WHICH SCREW,THE ONE CLOSEST TO6U5(EYE)OR THE ONE FARTHEST FROM IT. :: :: :: ::Sir Doug . . . . . . :: :: ::Been VEWY- VEWY . .BIZZZZY with clients on this end, not just ignoring you. :: :: ::It looks like that the antenna section of the tuning condenser, on the BCB, that its coil windings are isolated with capacitors or at least a 2 meg + resistor in one situation in series with them. :: :: ::Now, on the oscillator section, looks it is also completely capacitively isolated form the osc coil winding. :: :: ::Soooo . . . do an ohms test between the stators and the common rotor, whilst SLOWLY moving the tuning condenser thru its range. :: :: ::Naturally the more the condenser swings towards the lower frequency, the more the intermeshing of the rotor and stator plates, and the greater the potential becomes for a short. :: :: ::Usually its the outside plates that are mechanically subjective to getting ever so slightly bent inward and out of place the easiest, but certainly, ALL are suspect. :: :: ::Will be back with more on the Loopey-Doopey later as that currently seems to be my highest suspicion, IF not being so simple as the tuning consenser plates touching and/or dragging on down band frequency tuning. :: :: :: :: :: ::73's de Edd :: :: :: :: |
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:::::: ::::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL :::::: :::::: :::::: :::::: :::::: :::::: :::::: :::::: ::::::Sir Doug. . . . . . :::::: :::::: :::::: ::::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. :::::: :::::: ::::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. :::::: :::::: ::::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. :::::: :::::: ::::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. :::::: :::::: ::::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? :::::: :::::: ::::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. :::::: :::::: ::::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . :::::: :::::: :::::: ::::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. :::::: :::::: ::::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. :::::: :::::: ::::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. :::::: :::::: ::::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. :::::: :::::: :::::: ::::::C7 Padder location: :::::: :::::: :::::: :::::: :::::: ::::::Standing by for your procedural evaluation and any feedback . . . :::::: ::::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) :::::: :::::: :::::: ::::::73's de Edd :::::: :::::: :::::: :::::: |
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:::::::: :::::::: :::::::: :::::::: :::::::: ::::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help :::::::: :::::::: :::::::: :::::::: ::::::::Sir Doug. . . . . . :::::::: :::::::: ::::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. :::::::: :::::::: ::::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. :::::::: :::::::: ::::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? :::::::: :::::::: ::::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. :::::::: :::::::: ::::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? :::::::: :::::::: ::::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. :::::::: :::::::: ::::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. :::::::: :::::::: ::::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. :::::::: :::::::: ::::::::We are interested in that GREEN-BLACK winding and its integrity. :::::::: :::::::: ::::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? :::::::: :::::::: ::::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. :::::::: :::::::: ::::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. :::::::: :::::::: ::::::::Then you tune across the AM band to see if any more stations come in. :::::::: :::::::: ::::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? :::::::: :::::::: ::::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. :::::::: :::::::: ::::::::As it stands I am in line with the further possibility of the unit: :::::::: :::::::: ::::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) :::::::: :::::::: ::::::::2 . . .Still a problem in the ANT input section :::::::: :::::::: ::::::::3 . . .A gross mistuning of C7 GREY osc padder. :::::::: :::::::: ::::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. :::::::: :::::::: ::::::::Thassit . . . . Standing by for feed back . . . . :::::::: :::::::: ::::::::R.F. THUMBNAIL of area now of prime interest: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: ::::::::73's de Edd :::::::: :::::::: :::::::: :::::::: |
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::::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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:::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: :::::::: ::::::::Sir Doug . . . . . . :::::::: :::::::: :::::::: :::::::::: ::::::::::working in garage ,cinder walls. :::::::::: :::::::::: :::::::::: ::::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. :::::::::: :::::::::: ::::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. :::::::::: :::::::::: ::::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. :::::::::: :::::::::: ::::::::::PRELIMINARY: :::::::::: :::::::::: ::::::::::Hooking-up of 2 AC/DC chassis. :::::::::: :::::::::: ::::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. :::::::::: :::::::::: ::::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. ::::::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. :::::::::: :::::::::: ::::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. :::::::::: :::::::::: ::::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. :::::::::: :::::::::: ::::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. :::::::::: :::::::::: ::::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. :::::::::: :::::::::: :::::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. :::::::::: :::::::::: ::::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. :::::::::: :::::::::: ::::::::::That should now provide for no ground loops being involved in our onset of testing to now be started. :::::::::: :::::::::: ::::::::::Tune in your Motorola to its best received station and tune spot on to it. :::::::::: :::::::::: ::::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. :::::::::: :::::::::: ::::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity ::::::::::on the next plug in cycle, as the power switches will no longer be used during testing. :::::::::: :::::::::: ::::::::::Signal Injection: :::::::::: :::::::::: ::::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. :::::::::: :::::::::: ::::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. :::::::::: :::::::::: ::::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. :::::::::: :::::::::: ::::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. :::::::::: :::::::::: ::::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. :::::::::: :::::::::: ::::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. :::::::::: :::::::::: ::::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. :::::::::: :::::::::: ::::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. :::::::::: :::::::::: ::::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. :::::::::: :::::::::: ::::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. :::::::::: :::::::::: ::::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. ::::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. :::::::::: :::::::::: ::::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. :::::::::: :::::::::: :::::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. :::::::::: :::::::::: ::::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. :::::::::: :::::::::: :::::::::: :::::::::: :::::::::: ::::::::::73's de Edd :::::::::: :::::::::: :::::::::: :::::::::: |
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:::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. ::::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. ::::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. ::::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end ::::::::::::::::Sir Doug. . . . . :::::::::::::::: :::::::::::::::: ::::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. :::::::::::::::: :::::::::::::::: ::::::::::::::::Here it is sequentially . . . now being all condensed: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/05/2010 15:11 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::sears 6424 model no stations heard :::::::::::::::: :::::::::::::::: ::::::::::::::::i replaced caps and res. no voices :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Warren 02/05/2010 16:38 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? :::::::::::::::: :::::::::::::::: ::::::::::::::::Open IF transformer? Test all those. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/05/2010 18:33 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Warren 02/05/2010 19:58 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/05/2010 20:37 :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Warren 02/06/2010 01:58 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Lewis L 02/06/2010 06:47 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Try checking the local oscillator with a second radio. :::::::::::::::: :::::::::::::::: ::::::::::::::::Lewis :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/06/2010 07:44 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::how do i do this :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Terry Decker 02/06/2010 11:09 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. :::::::::::::::: :::::::::::::::: ::::::::::::::::Now- first of all, this is a good place to make a couple of points. :::::::::::::::: :::::::::::::::: ::::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! :::::::::::::::: :::::::::::::::: ::::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. :::::::::::::::: ::::::::::::::::It is also a good idea to stop and test the set after each component change. :::::::::::::::: :::::::::::::::: I am not an advocate of just replacing every cap. :::::::::::::::: :::::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. :::::::::::::::: :::::::::::::::: ::::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. :::::::::::::::: :::::::::::::::: ::::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". :::::::::::::::: ::::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. :::::::::::::::: ::::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. :::::::::::::::: :::::::::::::::: ::::::::::::::::OK- class over. :::::::::::::::: :::::::::::::::: ::::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". :::::::::::::::: ::::::::::::::::There are a bunch of great suggestions there about checking out the oscillator. :::::::::::::::: :::::::::::::::: ::::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/06/2010 13:22 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Terry Decker 02/06/2010 13:53 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. :::::::::::::::: :::::::::::::::: If not, then you have an open coil, open resistor, or shorted cap. :::::::::::::::: ::::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. :::::::::::::::: :::::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. :::::::::::::::: ::::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. :::::::::::::::: :::::::::::::::: ::::::::::::::::Hope this helps some- :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Warren 02/06/2010 13:58 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/06/2010 14:51 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::no opens :::::::::::::::: :::::::::::::::: ::::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Thomas Dermody 02/06/2010 20:30 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. :::::::::::::::: :::::::::::::::: ::::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. :::::::::::::::: ::::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. :::::::::::::::: :::::::::::::::: ::::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. :::::::::::::::: :::::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. :::::::::::::::: :::::::::::::::: ::::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. :::::::::::::::: ::::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. :::::::::::::::: ::::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. ::::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. :::::::::::::::: ::::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. :::::::::::::::: ::::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. :::::::::::::::: :::::::::::::::: ::::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. :::::::::::::::: ::::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. :::::::::::::::: :::::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. :::::::::::::::: ::::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. :::::::::::::::: :::::::::::::::: ::::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. :::::::::::::::: ::::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. :::::::::::::::: :::::::::::::::: ::::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Thomas Dermody 02/06/2010 20:35 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. :::::::::::::::: :::::::::::::::: ::::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::doug 02/06/2010 22:56 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::have not got that far yet.after further testing found some res. way out of range :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Thomas Dermody 02/07/2010 01:48 :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. :::::::::::::::: ::::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. :::::::::::::::: :::::::::::::::: ::::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Posted by doug on 02/10/2010 08:23 :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Posted by doug on 02/15/2010 09:28 :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::where can i find a sig. gen. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: |
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:::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Sir Doug. . . . . :::::::::::::::: :::::::::::::::: ::::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. :::::::::::::::: :::::::::::::::: ::::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: :::::::::::::::: :::::::::::::::: ::::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? :::::::::::::::: :::::::::::::::: ::::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? :::::::::::::::: :::::::::::::::: ::::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you :::::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS :::::::::::::::: specs ? :::::::::::::::: :::::::::::::::: ::::::::::::::::4 . . . ::::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. :::::::::::::::: :::::::::::::::: ::::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. :::::::::::::::: :::::::::::::::: ::::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? :::::::::::::::: :::::::::::::::: ::::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. :::::::::::::::: :::::::::::::::: ::::::::::::::::5. . . Preliminary Prep: :::::::::::::::: :::::::::::::::: ::::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. :::::::::::::::: :::::::::::::::: ::::::::::::::::Examples that I have found and have: :::::::::::::::: :::::::::::::::: ::::::::::::::::Dremel tool motor :::::::::::::::: :::::::::::::::: ::::::::::::::::Electric drill motor :::::::::::::::: :::::::::::::::: ::::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) :::::::::::::::: :::::::::::::::: ::::::::::::::::Hair dryer, blowing cold air :::::::::::::::: :::::::::::::::: ::::::::::::::::Corded electric razor :::::::::::::::: :::::::::::::::: ::::::::::::::::Wifes hand mixer :::::::::::::::: :::::::::::::::: ::::::::::::::::Hand saber saw :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. :::::::::::::::: :::::::::::::::: ::::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. :::::::::::::::: :::::::::::::::: ::::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. :::::::::::::::: ::::::::::::::::Find your strongest "static" source device for us. :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. :::::::::::::::: :::::::::::::::: ::::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::Standing by for the above info's supplication . . . . . . :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: ::::::::::::::::73's de Edd :::::::::::::::: :::::::::::::::: :::::::::::::::: :::::::::::::::: |
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::::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: : : : : : :edd,have been going over what i have been told.seems now ,upper and lower stations and shortwave are coming in but very faintly.have to turn volume up all the way to hear faintly. still have not figured out rf gen. completely.i can find signal but cannot seem to adjust it to get down to 455,i pick it up at 600,need help to adjust. will be off sat. all day ,would like to work on radio. : : : :Sir Doug . . . . . . : : :Been VEWY- VEWY . .BIZZZZY with clients on this end, not just ignoring you. : : :It looks like that the antenna section of the tuning condenser, on the BCB, that its coil windings are isolated with capacitors or at least a 2 meg + resistor in one situation in series with them. : : :Now, on the oscillator section, looks it is also completely capacitively isolated form the osc coil winding. : : :Soooo . . . do an ohms test between the stators and the common rotor, whilst SLOWLY moving the tuning condenser thru its range. : : :Naturally the more the condenser swings towards the lower frequency, the more the intermeshing of the rotor and stator plates, and the greater the potential becomes for a short. : : :Usually its the outside plates that are mechanically subjective to getting ever so slightly bent inward and out of place the easiest, but certainly, ALL are suspect. : : :Will be back with more on the Loopey-Doopey later as that currently seems to be my highest suspicion, IF not being so simple as the tuning consenser plates touching and/or dragging on down band frequency tuning. : : : : : :73's de Edd : : : : |
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::::: :::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL ::::: ::::: ::::: ::::: ::::: ::::: ::::: ::::: :::::Sir Doug. . . . . . ::::: ::::: ::::: :::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. ::::: ::::: :::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. ::::: ::::: :::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. ::::: ::::: :::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. ::::: ::::: :::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? ::::: ::::: :::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. ::::: ::::: :::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . ::::: ::::: ::::: :::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. ::::: ::::: :::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. ::::: ::::: :::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. ::::: ::::: :::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. ::::: ::::: ::::: :::::C7 Padder location: ::::: ::::: ::::: ::::: ::::: :::::Standing by for your procedural evaluation and any feedback . . . ::::: :::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) ::::: ::::: ::::: :::::73's de Edd ::::: ::::: ::::: ::::: |
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::::::: ::::::: ::::::: ::::::: ::::::: :::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug. . . . . . ::::::: ::::::: :::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. ::::::: ::::::: :::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. ::::::: ::::::: :::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? ::::::: ::::::: :::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. ::::::: ::::::: :::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? ::::::: ::::::: :::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. ::::::: ::::::: :::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. ::::::: ::::::: :::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. ::::::: ::::::: :::::::We are interested in that GREEN-BLACK winding and its integrity. ::::::: ::::::: :::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? ::::::: ::::::: :::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. ::::::: ::::::: :::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. ::::::: ::::::: :::::::Then you tune across the AM band to see if any more stations come in. ::::::: ::::::: :::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? ::::::: ::::::: :::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. ::::::: ::::::: :::::::As it stands I am in line with the further possibility of the unit: ::::::: ::::::: :::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) ::::::: ::::::: :::::::2 . . .Still a problem in the ANT input section ::::::: ::::::: :::::::3 . . .A gross mistuning of C7 GREY osc padder. ::::::: ::::::: :::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. ::::::: ::::::: :::::::Thassit . . . . Standing by for feed back . . . . ::::::: ::::::: :::::::R.F. THUMBNAIL of area now of prime interest: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: |
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:::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug . . . . . . ::::::: ::::::: ::::::: ::::::::: :::::::::working in garage ,cinder walls. ::::::::: ::::::::: ::::::::: :::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::::::::: ::::::::: :::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::::::::: ::::::::: :::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::::::::: ::::::::: :::::::::PRELIMINARY: ::::::::: ::::::::: :::::::::Hooking-up of 2 AC/DC chassis. ::::::::: ::::::::: :::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::::::::: ::::::::: :::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::::::::: ::::::::: :::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::::::::: ::::::::: :::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::::::::: ::::::::: :::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::::::::: ::::::::: :::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::::::::: ::::::::: ::::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::::::::: ::::::::: :::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::::::::: ::::::::: :::::::::That should now provide for no ground loops being involved in our onset of testing to now be started. ::::::::: ::::::::: :::::::::Tune in your Motorola to its best received station and tune spot on to it. ::::::::: ::::::::: :::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::::::::: ::::::::: :::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::::::::on the next plug in cycle, as the power switches will no longer be used during testing. ::::::::: ::::::::: :::::::::Signal Injection: ::::::::: ::::::::: :::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::::::::: ::::::::: :::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::::::::: ::::::::: :::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::::::::: ::::::::: :::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::::::::: ::::::::: :::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::::::::: ::::::::: :::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::::::::: ::::::::: :::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::::::::: ::::::::: :::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::::::::: ::::::::: :::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::::::::: ::::::::: :::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::::::::: ::::::::: :::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::::::::: ::::::::: :::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::::::::: ::::::::: ::::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::::::::: ::::::::: :::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::73's de Edd ::::::::: ::::::::: ::::::::: ::::::::: |
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::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::::::::Sir Doug. . . . . ::::::::::::::: ::::::::::::::: :::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::::::::: ::::::::::::::: :::::::::::::::Here it is sequentially . . . now being all condensed: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 15:11 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::sears 6424 model no stations heard ::::::::::::::: ::::::::::::::: :::::::::::::::i replaced caps and res. no voices ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/05/2010 16:38 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::::::::: ::::::::::::::: :::::::::::::::Open IF transformer? Test all those. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 18:33 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/05/2010 19:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/05/2010 20:37 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/06/2010 01:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Lewis L 02/06/2010 06:47 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Try checking the local oscillator with a second radio. ::::::::::::::: ::::::::::::::: :::::::::::::::Lewis ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 07:44 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::how do i do this ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Terry Decker 02/06/2010 11:09 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::::::::: ::::::::::::::: :::::::::::::::Now- first of all, this is a good place to make a couple of points. ::::::::::::::: ::::::::::::::: :::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::::::::: ::::::::::::::: :::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::::::::: :::::::::::::::It is also a good idea to stop and test the set after each component change. ::::::::::::::: ::::::::::::::: I am not an advocate of just replacing every cap. ::::::::::::::: ::::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::::::::: ::::::::::::::: :::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::::::::: ::::::::::::::: :::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::::::::: :::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::::::::: :::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::::::::: ::::::::::::::: :::::::::::::::OK- class over. ::::::::::::::: ::::::::::::::: :::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::::::::: :::::::::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::::::::: ::::::::::::::: :::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 13:22 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Terry Decker 02/06/2010 13:53 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::::::::: ::::::::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::::::::: :::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::::::::: ::::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::::::::: :::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::::::::: ::::::::::::::: :::::::::::::::Hope this helps some- ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Warren 02/06/2010 13:58 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 14:51 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::no opens ::::::::::::::: ::::::::::::::: :::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/06/2010 20:30 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::::::::: ::::::::::::::: :::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::::::::: :::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::::::::: ::::::::::::::: :::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::::::::: ::::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::::::::: ::::::::::::::: :::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::::::::: :::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::::::::: :::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::::::::: :::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::::::::: :::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::::::::: ::::::::::::::: :::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::::::::: :::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::::::::: ::::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::::::::: :::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::::::::: ::::::::::::::: :::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::::::::: :::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::::::::: ::::::::::::::: :::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/06/2010 20:35 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::::::::: ::::::::::::::: :::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::doug 02/06/2010 22:56 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::have not got that far yet.after further testing found some res. way out of range ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Thomas Dermody 02/07/2010 01:48 ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::::::::: :::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::::::::: ::::::::::::::: :::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Posted by doug on 02/10/2010 08:23 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Posted by doug on 02/15/2010 09:28 ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::where can i find a sig. gen. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: |
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::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Sir Doug. . . . . ::::::::::::::: ::::::::::::::: :::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::::::::: ::::::::::::::: :::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::::::::: ::::::::::::::: :::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::::::::: ::::::::::::::: :::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::::::::: ::::::::::::::: :::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::::::::: specs ? ::::::::::::::: ::::::::::::::: :::::::::::::::4 . . . :::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::::::::: ::::::::::::::: :::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::::::::: ::::::::::::::: :::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::::::::: ::::::::::::::: :::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::::::::: ::::::::::::::: :::::::::::::::5. . . Preliminary Prep: ::::::::::::::: ::::::::::::::: :::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::::::::: ::::::::::::::: :::::::::::::::Examples that I have found and have: ::::::::::::::: ::::::::::::::: :::::::::::::::Dremel tool motor ::::::::::::::: ::::::::::::::: :::::::::::::::Electric drill motor ::::::::::::::: ::::::::::::::: :::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::::::::: ::::::::::::::: :::::::::::::::Hair dryer, blowing cold air ::::::::::::::: ::::::::::::::: :::::::::::::::Corded electric razor ::::::::::::::: ::::::::::::::: :::::::::::::::Wifes hand mixer ::::::::::::::: ::::::::::::::: :::::::::::::::Hand saber saw ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::::::::: ::::::::::::::: :::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::::::::: ::::::::::::::: :::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::::::::: :::::::::::::::Find your strongest "static" source device for us. ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::::::::: ::::::::::::::: :::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::Standing by for the above info's supplication . . . . . . ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: :::::::::::::::73's de Edd ::::::::::::::: ::::::::::::::: ::::::::::::::: ::::::::::::::: |
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:::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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::edd,have been going over what i have been told.seems now ,upper and lower stations and shortwave are coming in but very faintly.have to turn volume up all the way to hear faintly. still have not figured out rf gen. completely.i can find signal but cannot seem to adjust it to get down to 455,i pick it up at 600,need help to adjust. will be off sat. all day ,would like to work on radio.
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::Sir Doug . . . . . .
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::Been VEWY- VEWY . .BIZZZZY with clients on this end, not just ignoring you.
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::It looks like that the antenna section of the tuning condenser, on the BCB, that its coil windings are isolated with capacitors or at least a 2 meg + resistor in one situation in series with them.
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::Now, on the oscillator section, looks it is also completely capacitively isolated form the osc coil winding.
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::Soooo . . . do an ohms test between the stators and the common rotor, whilst SLOWLY moving the tuning condenser thru its range.
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::Naturally the more the condenser swings towards the lower frequency, the more the intermeshing of the rotor and stator plates, and the greater the potential becomes for a short.
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::Usually its the outside plates that are mechanically subjective to getting ever so slightly bent inward and out of place the easiest, but certainly, ALL are suspect.
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::Will be back with more on the Loopey-Doopey later as that currently seems to be my highest suspicion, IF not being so simple as the tuning consenser plates touching and/or dragging on down band frequency tuning.
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::73's de Edd
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::::::my new signal generator will be hereon the3/15
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::::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL
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::::::Sir Doug. . . . . .
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::::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located.
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::::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station.
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::::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale.
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::::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial.
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::::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ?
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::::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C.
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::::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola .
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::::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position.
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::::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position.
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::::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception.
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::::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band.
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::::::Standing by for your procedural evaluation and any feedback . . .
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::::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really)
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::::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help
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::::::::Sir Doug. . . . . .
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::::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!.
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::::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception.
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::::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ?
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::::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times.
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::::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ?
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::::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna.
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::::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB.
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::::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up.
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::::::::We are interested in that GREEN-BLACK winding and its integrity.
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::::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ?
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::::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function.
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::::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie.
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::::::::Then you tune across the AM band to see if any more stations come in.
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::::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.?
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::::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed.
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::::::::As it stands I am in line with the further possibility of the unit:
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::::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.)
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::::::::2 . . .Still a problem in the ANT input section
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::::::::3 . . .A gross mistuning of C7 GREY osc padder.
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::::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?.
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::::::::Thassit . . . . Standing by for feed back . . . .
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::::::::R.F. THUMBNAIL of area now of prime interest:
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::::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::::::Sir Doug . . . . . .
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::::::::::working in garage ,cinder walls.
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::::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation.
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::::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing..
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::::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working.
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::::::::::PRELIMINARY:
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::::::::::Hooking-up of 2 AC/DC chassis.
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::::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line.
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::::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket.
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::::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that.
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::::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference.
::::::::::
::::::::::
::::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it.
::::::::::
::::::::::
::::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal.
::::::::::
::::::::::
:::::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line.
::::::::::
::::::::::
::::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one.
::::::::::
::::::::::
::::::::::That should now provide for no ground loops being involved in our onset of testing to now be started.
::::::::::
::::::::::
::::::::::Tune in your Motorola to its best received station and tune spot on to it.
::::::::::
::::::::::
::::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position.
::::::::::
::::::::::
::::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity
::::::::::on the next plug in cycle, as the power switches will no longer be used during testing.
::::::::::
::::::::::
::::::::::Signal Injection:
::::::::::
::::::::::
::::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end.
::::::::::
::::::::::
::::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set.
::::::::::
::::::::::
::::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube.
::::::::::
::::::::::
::::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube.
::::::::::
::::::::::
::::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now.
::::::::::
::::::::::
::::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with.
::::::::::
::::::::::
::::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance..
::::::::::
::::::::::
::::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry.
::::::::::
::::::::::
::::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now.
::::::::::
::::::::::
::::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set.
::::::::::
::::::::::
::::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer.
::::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed.
::::::::::
::::::::::
::::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer.
::::::::::
::::::::::
:::::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own.
::::::::::
::::::::::
::::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up.
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::
::::::::::73's de Edd
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::::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede.
::::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help.
::::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help.
::::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end
::::::::::::::::Sir Doug. . . . .
::::::::::::::::
::::::::::::::::
::::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions.
::::::::::::::::
::::::::::::::::
::::::::::::::::Here it is sequentially . . . now being all condensed:
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin:
::::::::::::::::
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::::::::::::::::
::::::::::::::::doug 02/05/2010 15:11
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::sears 6424 model no stations heard
::::::::::::::::
::::::::::::::::
::::::::::::::::i replaced caps and res. no voices
::::::::::::::::
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::::::::::::::::
::::::::::::::::Warren 02/05/2010 16:38
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil?
::::::::::::::::
::::::::::::::::
::::::::::::::::Open IF transformer? Test all those.
::::::::::::::::
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::::::::::::::::doug 02/05/2010 18:33
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::::::::::::::::
::::::::::::::::
::::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer.
::::::::::::::::
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::::::::::::::::
::::::::::::::::Warren 02/05/2010 19:58
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::doug 02/05/2010 20:37
::::::::::::::::
::::::::::::::::
::::::::::::::::
:::::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum.
::::::::::::::::
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::::::::::::::::Warren 02/06/2010 01:58
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end.
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Lewis L 02/06/2010 06:47
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Try checking the local oscillator with a second radio.
::::::::::::::::
::::::::::::::::
::::::::::::::::Lewis
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::::::::::::::::doug 02/06/2010 07:44
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::how do i do this
::::::::::::::::
::::::::::::::::
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::::::::::::::::
::::::::::::::::Terry Decker 02/06/2010 11:09
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found.
::::::::::::::::
::::::::::::::::
::::::::::::::::Now- first of all, this is a good place to make a couple of points.
::::::::::::::::
::::::::::::::::
::::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!!
::::::::::::::::
::::::::::::::::
::::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph.
::::::::::::::::
::::::::::::::::It is also a good idea to stop and test the set after each component change.
::::::::::::::::
:::::::::::::::: I am not an advocate of just replacing every cap.
::::::::::::::::
:::::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc.
::::::::::::::::
::::::::::::::::
::::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops.
::::::::::::::::
::::::::::::::::
::::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester".
::::::::::::::::
::::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on.
::::::::::::::::
::::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply.
::::::::::::::::
::::::::::::::::
::::::::::::::::OK- class over.
::::::::::::::::
::::::::::::::::
::::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations".
::::::::::::::::
::::::::::::::::There are a bunch of great suggestions there about checking out the oscillator.
::::::::::::::::
::::::::::::::::
::::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!!
::::::::::::::::
::::::::::::::::
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::::::::::::::::
::::::::::::::::doug 02/06/2010 13:22
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now.
::::::::::::::::
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::::::::::::::::
::::::::::::::::Terry Decker 02/06/2010 13:53
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil.
::::::::::::::::
:::::::::::::::: If not, then you have an open coil, open resistor, or shorted cap.
::::::::::::::::
::::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted.
::::::::::::::::
:::::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough.
::::::::::::::::
::::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have.
::::::::::::::::
::::::::::::::::
::::::::::::::::Hope this helps some-
::::::::::::::::
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::::::::::::::::
::::::::::::::::
::::::::::::::::Warren 02/06/2010 13:58
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere.
::::::::::::::::
::::::::::::::::
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::::::::::::::::
::::::::::::::::doug 02/06/2010 14:51
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::no opens
::::::::::::::::
::::::::::::::::
::::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Thomas Dermody 02/06/2010 20:30
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it.
::::::::::::::::
::::::::::::::::
::::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output.
::::::::::::::::
::::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement.
::::::::::::::::
::::::::::::::::
::::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch.
::::::::::::::::
:::::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position.
::::::::::::::::
::::::::::::::::
::::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them.
::::::::::::::::
::::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work.
::::::::::::::::
::::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained.
::::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark.
::::::::::::::::
::::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark.
::::::::::::::::
::::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark.
::::::::::::::::
::::::::::::::::
::::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands.
::::::::::::::::
::::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band.
::::::::::::::::
:::::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible.
::::::::::::::::
::::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band.
::::::::::::::::
::::::::::::::::
::::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you.
::::::::::::::::
::::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly.
::::::::::::::::
::::::::::::::::
::::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band.
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Thomas Dermody 02/06/2010 20:35
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments.
::::::::::::::::
::::::::::::::::
::::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory.
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::::::::::::::::
::::::::::::::::doug 02/06/2010 22:56
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::have not got that far yet.after further testing found some res. way out of range
::::::::::::::::
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::::::::::::::::
::::::::::::::::
::::::::::::::::Thomas Dermody 02/07/2010 01:48
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity.
::::::::::::::::
::::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet.
::::::::::::::::
::::::::::::::::
::::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator.
::::::::::::::::
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::::::::::::::::
::::::::::::::::Posted by doug on 02/10/2010 08:23
::::::::::::::::
::::::::::::::::
::::::::::::::::
:::::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help.
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::::::::::::::::Posted by doug on 02/15/2010 09:28
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::where can i find a sig. gen.
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::::::::::::::::
::::::::::::::::Sir Doug. . . . .
::::::::::::::::
::::::::::::::::
::::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such.
::::::::::::::::
::::::::::::::::
::::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed:
::::::::::::::::
::::::::::::::::
::::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ?
::::::::::::::::
::::::::::::::::
::::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ?
::::::::::::::::
::::::::::::::::
::::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you
:::::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS
:::::::::::::::: specs ?
::::::::::::::::
::::::::::::::::
::::::::::::::::4 . . .
::::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially.
::::::::::::::::
::::::::::::::::
::::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position.
::::::::::::::::
::::::::::::::::
::::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ?
::::::::::::::::
::::::::::::::::
::::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers.
::::::::::::::::
::::::::::::::::
::::::::::::::::5. . . Preliminary Prep:
::::::::::::::::
::::::::::::::::
::::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find.
::::::::::::::::
::::::::::::::::
::::::::::::::::Examples that I have found and have:
::::::::::::::::
::::::::::::::::
::::::::::::::::Dremel tool motor
::::::::::::::::
::::::::::::::::
::::::::::::::::Electric drill motor
::::::::::::::::
::::::::::::::::
::::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors)
::::::::::::::::
::::::::::::::::
::::::::::::::::Hair dryer, blowing cold air
::::::::::::::::
::::::::::::::::
::::::::::::::::Corded electric razor
::::::::::::::::
::::::::::::::::
::::::::::::::::Wifes hand mixer
::::::::::::::::
::::::::::::::::
::::::::::::::::Hand saber saw
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band.
::::::::::::::::
::::::::::::::::
::::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location.
::::::::::::::::
::::::::::::::::
::::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy.
::::::::::::::::
::::::::::::::::Find your strongest "static" source device for us.
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning.
::::::::::::::::
::::::::::::::::
::::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ?
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::Standing by for the above info's supplication . . . . . .
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::
::::::::::::::::73's de Edd
::::::::::::::::
::::::::::::::::
::::::::::::::::
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::::::::::::::::
::::::::::::::::
::::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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: : : : : : :hey edd,glad to hear from ya.have been working on radio,found the ant. had not been picking up lower sta.found problem to be in the ant.replaced ant.with another one of similar turns and hook ups.wired it to the sears.have got great reception on all sta.,will try short wave after dark. again thank you and your pals for all your paintence with this beginer. am now going to start on a kadette model 1194.so look forward to hearing from me again,also my new signal generator is load star 100khz-150mhz model#4160b.again thanks i could not have done this without your help and others. : : : :Sir Doug . . . . . . : : : ::edd,have been going over what i have been told.seems now ,upper and lower stations and shortwave are coming in but very faintly.have to turn volume up all the way to hear faintly. : : : :OK without my ability to have an hands on trial of the radio. I am statring to wonder now about the fault being in the RF portion or possibly the audio / speaker portion. : : :To answer the RF aspect lets go back to that "gold standard" in the respect of the second Motorola set of yours. If you tune across the BC band with the Motorola and take a received station count as well as the strongest received stations . . . ???? . . . . . Does your Sears set now compare in its capability of picking up the same amount of stations and signal strengths ? : : :Orrrrr . . . it could be that your sensitivity now might be in the same order as the Motorola . .BUT . . a lower volume might be attributable to deficiency in the Sears trailing audio section. : : :That could be answered with your new RF signal generator . . . Submit brand and model please . . .if you will set it for modulated RF output and inject a 455 kHZ signal into the 1st grid cap of the 6K8 mixer tube and bring up the RF output from the generator, you should then almost be able to shake the speaker out of the cabinet as you bring up the volume control. : : : :still have not figured out rf gen. completely.i can find signal but cannot seem to adjust it to get down to 455,i pick it up at 600,need help to adjust. : : : :You now seem to have got your 600 and 455 khz referencing down pat now and are no longer referring to them as small sub decimal variants of a Mhz. The 455 IF signal should PUNCH right on thru the receiver from a 1st grid cap of the 6K8 mixer insertion point with irrespective positioning of the tuning condensers tuned setting. That is with the sole exception of the 2 (x) 455 = 910 Khz (second harmonic) position, and the 3 ( x ) 455 =1365 Khx (third harmonic)positions where the signal will be enhanced a bit at setting at those select tuned positions. : : :I usually leave my tuning condenser fully unmeshed while aligning the 455 IF strip. : : :Now back to the injection of a 600 khz signal input, that then should ONLY come in at that 600 setting on the tuning condenser dial setting (with subtle exception of that 600 signal second harmonic also coming in weaker at 1200 Khz) . : : :The same should be the case if using a 1400 kHZ signal input if you are evaluating the RF aspect up at the high end of the band. : : : :will be off sat. all day ,would like to work on radio. : : : :Ahhhh . .sooooo . .most honnable apologies . . . for delaying a response so far into your Saturday . . : :. : : : : :73's de Edd : : : : |
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::: ::: ::: ::: ::: ::: :::edd,have been going over what i have been told.seems now ,upper and lower stations and shortwave are coming in but very faintly.have to turn volume up all the way to hear faintly. still have not figured out rf gen. completely.i can find signal but cannot seem to adjust it to get down to 455,i pick it up at 600,need help to adjust. will be off sat. all day ,would like to work on radio. ::: ::: ::: :::Sir Doug . . . . . . ::: ::: :::Been VEWY- VEWY . .BIZZZZY with clients on this end, not just ignoring you. ::: ::: :::It looks like that the antenna section of the tuning condenser, on the BCB, that its coil windings are isolated with capacitors or at least a 2 meg + resistor in one situation in series with them. ::: ::: :::Now, on the oscillator section, looks it is also completely capacitively isolated form the osc coil winding. ::: ::: :::Soooo . . . do an ohms test between the stators and the common rotor, whilst SLOWLY moving the tuning condenser thru its range. ::: ::: :::Naturally the more the condenser swings towards the lower frequency, the more the intermeshing of the rotor and stator plates, and the greater the potential becomes for a short. ::: ::: :::Usually its the outside plates that are mechanically subjective to getting ever so slightly bent inward and out of place the easiest, but certainly, ALL are suspect. ::: ::: :::Will be back with more on the Loopey-Doopey later as that currently seems to be my highest suspicion, IF not being so simple as the tuning consenser plates touching and/or dragging on down band frequency tuning. ::: ::: ::: ::: ::: :::73's de Edd ::: ::: ::: ::: |
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::::::: :::::::SIG.GEN.CAME UPS TODAY.EVERYTHING ALIGNED .NO STATIONS AFTER 900AM-590AM,THINKING I MIGHT HAVE A SHORT AT LOWER FREQ. NO SOUND AT ALL ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Sir Doug. . . . . . ::::::: ::::::: ::::::: :::::::With your current mentioned situation of WEKY 1340 coming in at ~1420 on the dial scale, lets initially move to the bottom of the chassis and look over to the rear corner where the C6--- BCB Osc and C1--- BCB ANT trimmer capacitors are located. ::::::: ::::::: :::::::Tune the set right onto the WEKY station and then and then position the dial pointer just to the left of the station. ::::::: ::::::: :::::::Trimming the C6 osc adjustment should then let you progressively use C6 and use a repeated left movement of the dial tuner positioning to "walk" the tuning down to ~ its then proper calibration locale. ::::::: ::::::: :::::::Typically, the sets C1 BCB ANT trimmer capacitor is normally set for optimum reception signal strength of an ~1400 Khz station on the dial. ::::::: ::::::: :::::::With only the WEKY 1340 coming in, along with your 2nd station professed to be at 1190 ?. . . wonder if it actually might be WDFB at 1170 or WCBR at 1110 Khz ? ::::::: ::::::: :::::::Lets now try another exploratory procedure. that will now require going back to the post where I queried you on your electrically noisiest type of appliance, of which I listed several. You should have ascertained that, by evaluating on the normally operating Motorola, as well as its degree of damped wave interfernce . . . aka . . . S ..T.. A .. T..I .. C. ::::::: ::::::: :::::::Now you want to bring that device up to your Sears loop antenna, and optimally position it, and KEEP it in that mechanical position, but you will probably see it not being as strongly received, as was done on the Motorola . ::::::: ::::::: ::::::: :::::::Now lets try three adjustments, first will be tuning the Sears up close to the 1400 dial scale positioning and peak C1 adjustment for maximum level of static received. Then, Sharpie mark the C6 trimmer screw slots positioning, and then just check the possibility of re-touching the previously set C6 to see if any STRONGER noise peaking will occur. Leave it at the noisiest reception position. ::::::: ::::::: :::::::Finally move down to the C7 osc padder, which pictorally shows it to be a bit deeper in towards the center of bottom chassis, as the C6 trimmer to the rear of the chassis is shown and being laterally in line with it , but more towards center chassis position. ::::::: ::::::: :::::::Swing the Sears tuning condenser down towards a 600-700 Khz position and then tune C7 for max static noise reception. ::::::: ::::::: :::::::Finally, shut down the static source and then see how the SEARS radio is now picking up stations all across the BC band. ::::::: ::::::: ::::::: :::::::C7 Padder location: ::::::: ::::::: ::::::: ::::::: ::::::: :::::::Standing by for your procedural evaluation and any feedback . . . ::::::: :::::::good morning edd. i did your above info,on the lower sta. 600-700 i dont get any sta. only motor boating. now if i place my finger on the grid cap of 6u7,the 650 lex.,ky sta. comes in good ,but only at low voice rec.take my finger off goes back to motor boating.also if i touch any part of frame the sound gets louder on 1340 and at 650(690 really) ::::::: ::::::: ::::::: :::::::73's de Edd ::::::: ::::::: ::::::: ::::::: |
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::the radio comes in at 1420am on my sears,the station is 1340am in richmond,ky.also1190am comes in at 1210.the antenna gets stronger,with 5 jumpers hooked to either green or yellow on antenna.my speaker came with three yellow wires on antenna unhooked and in box with radio.tuning eye moves closer together on local sta. but does not close.the only time it closes is on lower bands at motor boating sounds.i cannot get to c7 it is inside the frame with no outside screw hole.thanks again edd for your help ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sir Doug. . . . . . ::::::::: ::::::::: :::::::::Well . . . .Great shades of Tennessee Ernie Ford . . .with all thet , 'lil pea picker dialogue . . .!. ::::::::: ::::::::: :::::::::In a look-see at that string of quick posts, in between , I see that you had placed one info bit down at the very bottom end of a post that I did not see until just now, where you respond as to the set now having short wave reception. ::::::::: ::::::::: :::::::::Any chance that the reception is now enhanced by your having the 455 IF's in the ball park now ? ::::::::: ::::::::: :::::::::In my locale, SW reception is ONLY in the late afternoon, midnite or AM thru daybreak listening times. ::::::::: ::::::::: :::::::::Am I corect in the respect that the Sears radio is now able to bring in that sole BCB station on its own now, and does it tune in on the dial scale at approximately the proper dial scale logging position ? ::::::::: ::::::::: :::::::::That is sounding like a very frontal Rf section problem now. With specific attention to that AM broadcast loop antenna. ::::::::: ::::::::: :::::::::It consists of a larger inductive section for the AM receive functioning in conjunction with the AM section of the tuning condenser, along with but a mere single turn or so of inductive coupling on that ANTENNA terminal to the YELLOW wire winding for coupling in to its GREEN-BLACK winding for the BCB. ::::::::: ::::::::: :::::::::There is a supplemental routing down to the SW and POL band antenna coils with their input winding links being also fed in series as is being shown with my YELLOW mark-up. ::::::::: ::::::::: :::::::::We are interested in that GREEN-BLACK winding and its integrity. ::::::::: ::::::::: :::::::::No chance that that loop antenna has a problem, or that the three wires might have been transposed on a prior repair ? ::::::::: ::::::::: :::::::::One should be able to visually ascertain the LARGER NUMBER OF TURNS on the loop as being the winding that is ending up at the common cold sides of the other ant coils and the top side of that winding ending up at the "A" terminal of the band switches ANT coil switching function. ::::::::: ::::::::: :::::::::In order to hop up the available received AM signal level, lets connect up a short . .5 ft or so . . of vertically strung out hook-up wire or 4 or so cascaded jumper clips and connect to wherever it is easiest for you to get to my mark up of the GREEN buss feeding between the loop antenna winding and the Grid cap of the 6K8 toobie. ::::::::: ::::::::: :::::::::Then you tune across the AM band to see if any more stations come in. ::::::::: ::::::::: :::::::::Back when you tuned in the STRONG ? local station . . . or a local one a mile away . . . was it strong enough now to make your tuning eye respond, or did it close on any of those short wave stations you mentioned.? ::::::::: ::::::::: :::::::::Give me response to all of my questions . .for analysis sake . . even if cramped at a 1 WPM posting speed. ::::::::: ::::::::: :::::::::As it stands I am in line with the further possibility of the unit: ::::::::: ::::::::: :::::::::1 . . . Merely TRF'ing that strong stations signal thru . . so that is WHY I asked for its correctness of reception in perspective to the sets dial scale logging. (Even though you earlier confirmed OSC activity on the ajunct Motorola receiver.) ::::::::: ::::::::: :::::::::2 . . .Still a problem in the ANT input section ::::::::: ::::::::: :::::::::3 . . .A gross mistuning of C7 GREY osc padder. ::::::::: ::::::::: :::::::::BTW what is the call sign of that "powerhouse" station . . . or a mile away local . . .that youy ARE picking up ?. ::::::::: ::::::::: :::::::::Thassit . . . . Standing by for feed back . . . . ::::::::: ::::::::: :::::::::R.F. THUMBNAIL of area now of prime interest: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::73's de Edd ::::::::: ::::::::: ::::::::: ::::::::: |
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:::::::::Bless your pe-picking heart i finally got some voices out of this wonderful radio,but theres allways a but,ican only pick up the local station i tuned with thanks so much for helping this beginer .now i need more help
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::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: ::::::::: :::::::::Sir Doug . . . . . . ::::::::: ::::::::: ::::::::: ::::::::::: :::::::::::working in garage ,cinder walls. ::::::::::: ::::::::::: ::::::::::: :::::::::::Just wanted to be sure that you were not working in a RF dead / attenuated area. The performance of the 56A should have confirmed that situation. ::::::::::: ::::::::::: :::::::::::All of your voltages readings seem to be within range . . . nothing being grossly missing.. ::::::::::: ::::::::::: :::::::::::Now lets use that working Rot-a-Mola 56A to get the Silvertone working. ::::::::::: ::::::::::: :::::::::::PRELIMINARY: ::::::::::: ::::::::::: :::::::::::Hooking-up of 2 AC/DC chassis. ::::::::::: ::::::::::: :::::::::::We will need both of them as naked chassis' and laid out onto an insulated work area, and since they both are AC-DC, it will be necessary to get them plugged in with common groundings of both sets chassis being the same as well as having the combined chassis pair then going to the cold side of the AC line. ::::::::::: ::::::::::: :::::::::::This can be well served by the plugging of them into a 3 connection (using only 2 of them) extension cord and then taking note of the blade positioning when plugging into the AC line wall / bench socket. :::::::::::Then the power switches will not be used, just unplug the extension cord end , and replug using the same polarity every time. ::::::::::: ::::::::::: :::::::::::A tape marker at the wall outlet and near one blade of the extension cord plug will confirm that. ::::::::::: ::::::::::: :::::::::::Initially run an AC voltage check between chassis using a DVM . . .a battery powered meter is preferred, due to its AC line isolation . . .check between the two chassis and reverse one sets AC plug into the shared ext cord socket IF there is a large voltage difference. ::::::::::: ::::::::::: :::::::::::Now see if the chassis are now connected to the cold side of the AC line by taking an AC voltage reading with one meter probe into the round ground lug of the wall AC outlet that does not have the extension cord plugged into it. ::::::::::: ::::::::::: :::::::::::The other metering lead goes to one chassis and then to the other chassis to see if the AC voltage present is minimal. ::::::::::: ::::::::::: ::::::::::: What we want now,is that the chassis' will be commonly connected, and the pair will then have both their chassis' connected to the cold side of the AC line. ::::::::::: ::::::::::: :::::::::::To make a final safety confirmation take 2 test leads with their jumper clips and make a few seconds temp connection of a 5-10 K resistor between the 2 chassis . No sparkee sparkee ? If an AC voltage reading across the resistor reveals no significant voltage, that now confirms that any prior, smaller residual voltage reading was merely a stray STATIC voltage, and not a significantly hefty DYNAMIC one. ::::::::::: ::::::::::: :::::::::::That should now provide for no ground loops being involved in our onset of testing to now be started. ::::::::::: ::::::::::: :::::::::::Tune in your Motorola to its best received station and tune spot on to it. ::::::::::: ::::::::::: :::::::::::Also, now warm up the Silvertone and set its tuning condenser to its max unmeshed position. ::::::::::: ::::::::::: :::::::::::Now you can unplug the extension cord from the power source and possibly tape mark up its required polarity :::::::::::on the next plug in cycle, as the power switches will no longer be used during testing. ::::::::::: ::::::::::: :::::::::::Signal Injection: ::::::::::: ::::::::::: :::::::::::You will be connecting a common test lead between the two sets using its two alligator clips at either end. ::::::::::: ::::::::::: :::::::::::The 1st connection clip end will be going to the plate of the I.F. amplifier tube at its tube socket pin of the Motorola, and its other end will be going alternatively to two differnet places on the Sears set. ::::::::::: ::::::::::: :::::::::::Initially, let's go to the to the 1st grid of the I.F. amplifier of the Sears, and we do NOT want to clip on directly to the 1st grid of the tube. ::::::::::: ::::::::::: :::::::::::Instead, we want to loosely couple in by merely clipping across the INSULATED wire that is between that Sears 1st IF transformer and is going to the 1st grid of the IF amp tube. ::::::::::: ::::::::::: :::::::::::Time now to confirm that the Motorola is pumping out audio, then drop its volume down to THEN be able to hear if the same program is now coming through your Sears set, with ITS volume turned up now. ::::::::::: ::::::::::: :::::::::::If now heard only feebly, then peak up your two tuning adjustments to the 2nd IF transformer for the most sound, since you now have a 455 reference signal to work with. ::::::::::: ::::::::::: :::::::::::If by chance there is no sound you might need a bit heavier coupling than the very small area of the clip is now providing you via "gimmick" capacitance.. ::::::::::: ::::::::::: :::::::::::Unplug the extension cord for power down and then eyeball the length of insulated wire u are clipped onto and see if you can get a small length of alum-i-ninny-yum-yum foil and tightly encircle the insulated wire , one wrap, for the length that the wilre will permit you, with out shorting out to any circuitry. ::::::::::: ::::::::::: :::::::::::Then you reaffix the clip to the center of the alum foil wrap, presenting you with much more coupling capacitance now. ::::::::::: ::::::::::: :::::::::::Plug in the set and try again, hopefully, hearing the first music that you have EVER heard on that set. ::::::::::: ::::::::::: :::::::::::If successful this attempt, you can trim in the 2nd IF transformer adjustments this time and then power down and move the clip that you are injecting the IF signal with, forward in the RF portion of the set to the wire that is feeding to the top grid cap of the 6K8 mixer. :::::::::::IF that grid wire is NOT SHIELDED, if shielded, just move to the insulated GREEN wire associated with your loop antenna and use the same manner or degree of capacitance coupling in at that point, re-confirm that your Sears has its tuning condenser fully unmeshed. ::::::::::: ::::::::::: :::::::::::Power up the set and confirm aa much stronger signal now, or/and and then touch up the 2 tuning adjustments associated with your 1st IF transformer. ::::::::::: ::::::::::: ::::::::::: By this time if all IF adjustments have been made you can unclip the injection signal over at the Motorola and tune the Sears across the BC band to see if that unit can now fly on its own. ::::::::::: ::::::::::: :::::::::::Best to stop now at this end and wait for feed back or hear of any snags that might need to be cleared up. ::::::::::: ::::::::::: ::::::::::: ::::::::::: ::::::::::: :::::::::::73's de Edd ::::::::::: ::::::::::: ::::::::::: ::::::::::: |
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::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::working in garage ,cinder walls.bought this radio not working.confirm osc.with a motorala 56a,it is tubede. :::::::::::::::::supply voltages:25l6 pin p 83v.25l6pin s 88v.6u7 pin s 84v. 6u7 pin p 84v. 6f5 pin p 47v. 6k8 pin gs 86v. 6k8 pin ph 84v. 6u5 pin t 88v. 25z6 pin k 88v. help. :::::::::::::::::after trying ,i finally have a motorboat sound at 1400.have a whinning sound at 650.help. :::::::::::::::::on my print c1 is 1400kc and c6 is 650kc i dont know the settings on these for adj. also t1 and t2.i adjusted ti both screws out 2turns,adjusted t2 out 2turnseach screw. this stopped the motor boat at high end and whine at low end :::::::::::::::::Sir Doug. . . . . ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Just now tuned in to this topic and had to process it a bit before being able to fathom all of its individual portions. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Here it is sequentially . . . now being all condensed: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Sears 6426 Thread . . . Short of Dupes and Then Chronologically Arranged from its Origin: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/05/2010 15:11 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::sears 6424 model no stations heard ::::::::::::::::: ::::::::::::::::: :::::::::::::::::i replaced caps and res. no voices ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Warren 02/05/2010 16:38 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Open field coil? Open speaker? Open audio output transformer? Open antenna Coil? Open oscillator coil? ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Open IF transformer? Test all those. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/05/2010 18:33 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::thanks for your response,i am a beginer at trouble shooting. the tube6u7g has 99volts at p.but 0volts at .si am guessing that this is the outputfor the i.f. transformer. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Warren 02/05/2010 19:58 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::You may be looking at the pin base wrong. The point "S" is supplied from the B+. then goes through the IF coil, then to "P" .. Check this IF coil for continuity ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/05/2010 20:37 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::::wire not soldered,now have voltage atp,s. stillno voices.center leg of volume control to touch does increase sound. volume control does adjust hum. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Warren 02/06/2010 01:58 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::The audio section seems to be working if you get that buzz. Check and clean the band switch. The loop antenna does need to be connected too. Check for any shorting gangs in the tuner. This is the most simple to look for now. Post again any results and voltage testing on the front end. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Lewis L 02/06/2010 06:47 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Try checking the local oscillator with a second radio. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Lewis ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/06/2010 07:44 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::how do i do this ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Terry Decker 02/06/2010 11:09 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Hi Doug- Welcome to a hobby where the members addle their brains with the smell of 60 year old solder, but a nicer group can't be found. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Now- first of all, this is a good place to make a couple of points. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Whenever you remove a set from it's case with a speaker attached-PUT A PIECE OF CARDBOARD OVER IT!! ::::::::::::::::: ::::::::::::::::: :::::::::::::::::The second most important thing is to document EVERY thing you do. I write it out, make a drawing and, when applicable, take a photograph. ::::::::::::::::: :::::::::::::::::It is also a good idea to stop and test the set after each component change. ::::::::::::::::: ::::::::::::::::: I am not an advocate of just replacing every cap. ::::::::::::::::: ::::::::::::::::: Sure, that might wind up being the case, but in the meantime you might have a cold solder joint, accidently switch a lead, etc. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::The best way to quickly isolate a problem is with a "buzz" test. Simply put the tip of a screwdriver at the plate of each tube, starting with the detector. Gradually move forward until the buzz stops. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Do you have an isolation transformer? If you don't you might want to make a "Light bulb tester". ::::::::::::::::: :::::::::::::::::Simply wire a light socket in series with an extension cord. Plug in the radio and turn it on. ::::::::::::::::: :::::::::::::::::If the bulb glows dimly, proceed- if it comes on very bright STOP! You have some problem in the power supply. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::OK- class over. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::As to your fix. It might well be a problem with the oscillator. Refer to my thread about "Crackling problem solved but can't receive stations". ::::::::::::::::: :::::::::::::::::There are a bunch of great suggestions there about checking out the oscillator. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Welcome to the club,don't blow yourself up,good luck,and,HAVE FUN!! ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/06/2010 13:22 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::thanks terry.the old radio trick worked.ihear the whine out the good radio.where do i go now. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Terry Decker 02/06/2010 13:53 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Good, it seems that the oscillator is working. Check the voltages around the tube. I'm not looking at the schematic, but you should have around 100 VDC on each leg of the primary of the 1st IF coil. ::::::::::::::::: ::::::::::::::::: If not, then you have an open coil, open resistor, or shorted cap. ::::::::::::::::: :::::::::::::::::You said you replaced the caps, but there should be a cap to ground from the AVC line,(check at bottom leg of 2nd coil of 1st IF)which could be shorted. ::::::::::::::::: ::::::::::::::::: This is all rough stuff, and other members can dial you in much better than me. Your problem could also be alignment, which I hope you didn't mess with yet. Unless you replace something in the IF path, the alignment should be close enough. ::::::::::::::::: :::::::::::::::::Some people can't resist messing with the cans, though, when they don't get stations. It would be nice to know what test equipment you have. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Hope this helps some- ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Warren 02/06/2010 13:58 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::At this point go through all of the antenna coils in the broadcast position (A) with an ohm meter. Follow the schematic. You may find an open somewhere. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/06/2010 14:51 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::no opens ::::::::::::::::: ::::::::::::::::: :::::::::::::::::my schematic shows voltages,ichecked them at these points.all ok.ihave a fluke model 87 tester,jackson model 112 condenser tester,model 606 dyna jet tube tester.yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Thomas Dermody 02/06/2010 20:30 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::If someone did mess with the set's alignment, you will need to realign it. It is best to test the alignment to be sure that it is not the cause of your problem, and if it is the cause, to correct it. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::If you own a signal generator, you should inject a 455KC signal at the antenna, or at the G terminal of the 6K8. Adjust the trimmers of the IF transformers for maximum output. ::::::::::::::::: :::::::::::::::::Each time a trimmer is adjusted for maximum output, the RF output of the signal generator should be reduced to a level that is barely audible. Repeat until there is no improvement. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::If you do not own a signal generator, set the radio to the broadcast position. You will know which position this is by looking at the oscillator segments of the switch. ::::::::::::::::: ::::::::::::::::: Both of these should have a jumper between two terminals. The outer terminal of these two is used for the broadcast position. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Hope that noone adjusted C7. Be sure that the dial pointer stops at the stop marks on the dial (if any), or an equal distance from the stop marks, if it won't stop on them. ::::::::::::::::: :::::::::::::::::Tune to a strong station at the low end of the dial. Line up the dial pointer to the station's appropriate mark. Adjust the IF transformer capacitor trimmer screws snug, and count the number of turns you turned them in so that you may set them back if this procedure doesn't work. ::::::::::::::::: :::::::::::::::::Turn each one out one turn. Then try turning each one out two turns. Work in this range until you hear something, and then adjust the trimmers all so that maximum gain is obtained. :::::::::::::::::If this works for you, go to the high end of the dial and adjust C6 so that stations at that end line up with the appropriate frequency markings. Go back to the low end and readjust the IF trimmer caps so that the station you were working with is again on its appropriate mark. ::::::::::::::::: :::::::::::::::::Repeat for both ends until stations line up properly. Once you have both ends lining up properly, find a distant station at the low end and peak the IF trimmers for maximum sensitivity at its designated frequency mark. ::::::::::::::::: :::::::::::::::::Find a distant station at the high end of the dial and adjust the antenna trimmer cap for maximum sensitivity at its designated frequency mark. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::If this procedure works for you, you may check the oscillator and antenna trimmer caps for the police and short wave bands. ::::::::::::::::: :::::::::::::::::For the police band, the same oscillator coil and oscillator trimmers is/are used as is used for the broadcast band. ::::::::::::::::: ::::::::::::::::: No adjustment should be made to these trimmers for the police band. Only the antenna trimmer should be adjusted. Adjust it so that a distant station at the high end of the police band comes in accurately and as strongly as possible. ::::::::::::::::: :::::::::::::::::Also, though the short wave band has its own oscillator coil, no oscillator trimmer adjustment is provided. The only adjustment you can make here is to adjust the antenna trimmer for this band so that a distant station comes in as strongly and accurately as possible on the high end of this band. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::If this procedure doesn't work for you, I recommend obtaining a signal generator so that you may more accurately analyze your set. ...Though if your set is functioning properly, this procedure should work for you. ::::::::::::::::: :::::::::::::::::In any case you will need a signal generator in order to be sure that C7 is aligned properly. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::On a side note, you may wonder why your radio uses the same oscillator coil and associated capacitors for both the broadcast and police bands. What happens is that for both band the oscillator tunes through the same range of frequencies. These frequencies are 455KC above all frequencies tuned in by the broadcast band antenna coil, and are 455KC below all of the frequencies tuned in by the police band antenna coil. The difference is used as the IF for the broadcast band, and the sum is used for the police band. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Thomas Dermody 02/06/2010 20:35 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Regarding IF transformer adjustment, you may adjust the trimmers even 3 or 4 turns out, but usually adjustment is found around 1 or 2 turns. Once you are finished, the trimmers will all have slightly different adjustments. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Also, you can fine tune the oscillator for the short wave band by moving wiring and components associated with this circuit. However, it is best to leave them all where they were put at the factory. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::doug 02/06/2010 22:56 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::have not got that far yet.after further testing found some res. way out of range ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Thomas Dermody 02/07/2010 01:48 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Repairing those should help. Definitely make sure that all resistors and capacitors are in good order, as well as the coils that you've already checked for continuity. ::::::::::::::::: :::::::::::::::::If you can test your tubes, do that as well. If you have not checked the resistors in your tube tester (as well as any capacitors--they shouldn't leak at all), you shouldn't rely on its readings yet. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::It is best to have all of the obvious in good working order before checking alignment, especially if you don't own a signal generator. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Posted by doug on 02/10/2010 08:23 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::::i have not been able to work on my radio due to working. i will be off thursday. so be ready for more dumb questions,and thanks to all of you for your help. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Posted by doug on 02/15/2010 09:28 ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::where can i find a sig. gen. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: |
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::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Sir Doug. . . . . ::::::::::::::::: ::::::::::::::::: :::::::::::::::::BEFORE springing for a signal generator JUST yet, I might be able to steer you on diagnosis with out the need of such. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::First a couple of preliminary questions to zero in on the direction in which to initially proceed: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::1 . . . You are not working in a metal building or down in a basement . . . are you ? ::::::::::::::::: ::::::::::::::::: :::::::::::::::::2 . . . Have you , in the past or at the present, EVER received a station on that radio ? ::::::::::::::::: ::::::::::::::::: :::::::::::::::::3 . . .Is the other radio which you were utilizing to confirm local oscillator of the Sears set, a TUBED radio also , OR do you ::::::::::::::::: have another TUBE radio to use . . . as well as supplying a model and brand . . . so that I can additionally research ITS ::::::::::::::::: specs ? ::::::::::::::::: ::::::::::::::::: :::::::::::::::::4 . . . :::::::::::::::::yes the dummy messed with the alignment.also the cabinet is missing the decals so i really dont know the am,police or shortwave band switch position ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::According to the schematic, the receiver is shown in its Broadcast Band position, which is SOLELY which we should be working with initially. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::That would seem to be with the bandswitch being placed to its fully CCW position. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Now, does this mean that you sequentially diddled every adjustment on the unit or just a select few and was that in a helter skelter manner or did you at least attempt to return each adjustment to its original position as close as possible before moving to another ? ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Also the adjustments that you touched, HOPEFULLY, just the 2 internal sets of trimmer capacitor adjustments on the top of each of the IF transformers. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::5. . . Preliminary Prep: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::I want you to find the best generator and strongest source of damped wave oscillations that you can find. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Examples that I have found and have: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Dremel tool motor ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Electric drill motor ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Orbital and belt sanders (using universal AC/DC brushed motors) ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Hair dryer, blowing cold air ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Corded electric razor ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Wifes hand mixer ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Hand saber saw ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::What you would then be doing is bringing a unit up to near the loop antenna of that WORKING receiver which you have and placing the radio tuning OFF of receiving any stations up at the high end of the band. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Then you move that static / inteference source around the loop to find its most responsive location. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::That may require the volume up HIGH in case the device used is inherently acoustively noisy. ::::::::::::::::: :::::::::::::::::Find your strongest "static" source device for us. ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Finally, on the good aspects . . . at least the power supply and audio section from the volume control back thru the speaker is functioning. ::::::::::::::::: ::::::::::::::::: :::::::::::::::::BTW, did I ever see where you confirmed the presence of supply voltage thru to each of the screen grids and plates of the frontal RF stages when being metered right at the tube socket pins of those tubes ? ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::Standing by for the above info's supplication . . . . . . ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: :::::::::::::::::73's de Edd ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: ::::::::::::::::: |
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:::::::::::::::::okay with your alls help,i have good voltages.also can listen to shortwave very well,but noooo am stations,waiting for help.will be waiting
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:no opens