Sounds like an old TRF, and you'll need an external long wire antenna firstly.
marv
:Please help. Picked up a Sears & Roebuck radio out of a barn that has five number 27 tubes, two 45 tubes, and a number 80 tube. After much elbow grease to make it presentable and research I find it is considered a SEARS model 52 and Factory Model 95. I have replaced some badly aged wire, power cord, and swapped some 27 tubes with tested 227 tubes. I also swapped out three badly dryed out paper caps. I did my best to get there values off of a found schematic off of your site. I believe one was .00025 off of the detector tube and the others were .1. Hard to read on schematic so please correct me if I am wrong. I slowly add power and I get all tubes lite and the large transformer gives a slight humm. I get no humm or radio stations as I turn through the scale. I read somewhere to test your audio to r2 the 1st amp tube. I do and I get snappy static sounds an the speaker like your supposed to. I believe that means my audio is good. I am used to working with the easy American Five setup and this is new to me. Esp the high voltage which adds to the element of fun. What am I missing on this set? Usually by now my radios work. Where do I even start? No Electrolitics right? Any common tips or not so obviouse parts needed for these really old sets? Any voltages On a specific tube I got to have? can I send a Freq signal in a specific part and back trace? yep, stuck. Looks good but no radio. Going to risk my life tonight and get some voltages off of the 27 tubes to see if voltage match up. Any help is appreciated and will to send pics if necessary. Confident in my work so far just seems no signal is getting the amp tubes. Thanks for any help. You have a great site and can't count how many broken radios this site has helped me with. Thanks for the time and look forward on learning even more. Joe
:Sounds like an old TRF, and you'll need an external long wire antenna firstly.
:
:marv
:
::Please help. Picked up a Sears & Roebuck radio out of a barn that has five number 27 tubes, two 45 tubes, and a number 80 tube. After much elbow grease to make it presentable and research I find it is considered a SEARS model 52 and Factory Model 95. I have replaced some badly aged wire, power cord, and swapped some 27 tubes with tested 227 tubes. I also swapped out three badly dryed out paper caps. I did my best to get there values off of a found schematic off of your site. I believe one was .00025 off of the detector tube and the others were .1. Hard to read on schematic so please correct me if I am wrong. I slowly add power and I get all tubes lite and the large transformer gives a slight humm. I get no humm or radio stations as I turn through the scale. I read somewhere to test your audio to r2 the 1st amp tube. I do and I get snappy static sounds an the speaker like your supposed to. I believe that means my audio is good. I am used to working with the easy American Five setup and this is new to me. Esp the high voltage which adds to the element of fun. What am I missing on this set? Usually by now my radios work. Where do I even start? No Electrolitics right? Any common tips or not so obviouse parts needed for these really old sets? Any voltages On a specific tube I got to have? can I send a Freq signal in a specific part and back trace? yep, stuck. Looks good but no radio. Going to risk my life tonight and get some voltages off of the 27 tubes to see if voltage match up. Any help is appreciated and will to send pics if necessary. Confident in my work so far just seems no signal is getting the amp tubes. Thanks for any help. You have a great site and can't count how many broken radios this site has helped me with. Thanks for the time and look forward on learning even more. Joe
::Joe,
::Sounds like an old TRF, and you'll need an external long wire antenna firstly.
::
::marv
::
:::Please help. Picked up a Sears & Roebuck radio out of a barn that has five number 27 tubes, two 45 tubes, and a number 80 tube. After much elbow grease to make it presentable and research I find it is considered a SEARS model 52 and Factory Model 95. I have replaced some badly aged wire, power cord, and swapped some 27 tubes with tested 227 tubes. I also swapped out three badly dryed out paper caps. I did my best to get there values off of a found schematic off of your site. I believe one was .00025 off of the detector tube and the others were .1. Hard to read on schematic so please correct me if I am wrong. I slowly add power and I get all tubes lite and the large transformer gives a slight humm. I get no humm or radio stations as I turn through the scale. I read somewhere to test your audio to r2 the 1st amp tube. I do and I get snappy static sounds an the speaker like your supposed to. I believe that means my audio is good. I am used to working with the easy American Five setup and this is new to me. Esp the high voltage which adds to the element of fun. What am I missing on this set? Usually by now my radios work. Where do I even start? No Electrolitics right? Any common tips or not so obviouse parts needed for these really old sets? Any voltages On a specific tube I got to have? can I send a Freq signal in a specific part and back trace? yep, stuck. Looks good but no radio. Going to risk my life tonight and get some voltages off of the 27 tubes to see if voltage match up. Any help is appreciated and will to send pics if necessary. Confident in my work so far just seems no signal is getting the amp tubes. Thanks for any help. You have a great site and can't count how many broken radios this site has helped me with. Thanks for the time and look forward on learning even more. Joe
Paper capacitors do not dry out. They start to leak with age. If you test your capacitors with an ohmmeter, the meter needle should swing up just a little (might not be noticable with capacitors smaller than .001 MFD), and then go back down to exactly where it started. If there is any leakage at all, the capacitor should be replaced. In power supply circuits, leakage of ten million ohms or higher is acceptable.
The capacitors in your power supply are paper capacitors. If they have no leakage, you can continue to use them. Otherwise you may replace them with electrolytics, if you wish. You may use 10 MFD electrolytics. Make sure that your electroltyics have their negative side facing any wiring that goes to the center tap of the high voltage transformer winding, and their positive side facing any wiring that goes to the rectifier cathode.
Your radio does not have a built in speaker. You must connect an external speaker according to the schematic (perhaps the schematic doesn't show the speaker??). I'm not sure what impedance you should use, but an output transformer is definitely necessary on the speaker you decide to use. Using the ends of a transformer primary designed for push-pull 2A3 or 45 use should work well.
If you replace all faulty capacitors and resistors, and the set still won't work, you may have some faulty transformers. If you have faulty transformers, do not worry. They can be replaced, and there are temporary fixes that work quite well, too.
Thomas
Thank you for your time and knowledge. Learning alot and haven fun. Joe
:http://www.nostalgiaair.org/PagesByModel/238/M0017238.pdf
:
:Paper capacitors do not dry out. They start to leak with age. If you test your capacitors with an ohmmeter, the meter needle should swing up just a little (might not be noticable with capacitors smaller than .001 MFD), and then go back down to exactly where it started. If there is any leakage at all, the capacitor should be replaced. In power supply circuits, leakage of ten million ohms or higher is acceptable.
:
:The capacitors in your power supply are paper capacitors. If they have no leakage, you can continue to use them. Otherwise you may replace them with electrolytics, if you wish. You may use 10 MFD electrolytics. Make sure that your electroltyics have their negative side facing any wiring that goes to the center tap of the high voltage transformer winding, and their positive side facing any wiring that goes to the rectifier cathode.
:
:Your radio does not have a built in speaker. You must connect an external speaker according to the schematic (perhaps the schematic doesn't show the speaker??). I'm not sure what impedance you should use, but an output transformer is definitely necessary on the speaker you decide to use. Using the ends of a transformer primary designed for push-pull 2A3 or 45 use should work well.
:
:If you replace all faulty capacitors and resistors, and the set still won't work, you may have some faulty transformers. If you have faulty transformers, do not worry. They can be replaced, and there are temporary fixes that work quite well, too.
:
:Thomas
As for capacitors, they don't physically leak, so you can't tell if they're leaky by looking at them. They leak electricity when they become bad. An ohmmeter is all you need to check for leakage. It is necessary to disconnect at least one lead of each capacitor you test. The best test for a capacitor is under a high voltage (below the maximum it is rated for). This will reveal arcing. For a really reliable repair, however, it is probably best to just replace all capacitors. Since you are new to all of this, though, it is best, for now, that you just find the leaky ones, and replace them. Once you get the radio working, you may replace the remaining capacitors if you wish. If you aren't looking for a real thorough restoration at this point, and you have some capacitors in large tar filled cans, you may simply disconnect them and wire in modern units under the chassis in their places (electrically). Later on you may tackle melting tar out of the cans and fitting new units inside, etc.
Thomas
:Resistors should be 1/4 watt for any found in the RF and audio circuits. Resistors in the power supply should usually be 1 watt, unless you find the originals to be larger. You shouldn't replace resistors unless they have drifted higher, or are open. If you want to replace a resistor, tell us which one you are replacing, and we can give you an approximate wattage.
:
:As for capacitors, they don't physically leak, so you can't tell if they're leaky by looking at them. They leak electricity when they become bad. An ohmmeter is all you need to check for leakage. It is necessary to disconnect at least one lead of each capacitor you test. The best test for a capacitor is under a high voltage (below the maximum it is rated for). This will reveal arcing. For a really reliable repair, however, it is probably best to just replace all capacitors. Since you are new to all of this, though, it is best, for now, that you just find the leaky ones, and replace them. Once you get the radio working, you may replace the remaining capacitors if you wish. If you aren't looking for a real thorough restoration at this point, and you have some capacitors in large tar filled cans, you may simply disconnect them and wire in modern units under the chassis in their places (electrically). Later on you may tackle melting tar out of the cans and fitting new units inside, etc.
:
:Thomas
You can solder in a temporary jumper on the phono plug until you are confident with the radio.
Those are 0.1uF caps. Don't think the caps are preventing the radio from working since the plate voltages are about right.
Can you tell which transformer the orange log resistor is located?
Richard
I am going to do alot more trouble shouting tonight. Have a new plan of attack. Thanks for the help. will let you know if I get it working or not.
:Hi, Won't find a Sam's photo fax for a radio that old!
:
:You can solder in a temporary jumper on the phono plug until you are confident with the radio.
:
:Those are 0.1uF caps. Don't think the caps are preventing the radio from working since the plate voltages are about right.
:
:Can you tell which transformer the orange log resistor is located?
:
:Richard
:
:Good idea with temp jumper. Thanks for the definite cap size. The orange resistor is in some round about way connected to the large power transformer. It is in that section and is connected to the Dark Green resistor. What would be the rating on a completely orange large log reistor? 33000?
:I am going to do alot more trouble shouting tonight. Have a new plan of attack. Thanks for the help. will let you know if I get it working or not.
::Hi, Won't find a Sam's photo fax for a radio that old!
::
::You can solder in a temporary jumper on the phono plug until you are confident with the radio.
::
::Those are 0.1uF caps. Don't think the caps are preventing the radio from working since the plate voltages are about right.
::
::Can you tell which transformer the orange log resistor is located?
::
::Richard
::
: Hi napijoe's, I thought you meant "trouble shooting" but after looking over your posts, trouble shouting is most likely what your doing. PL
:
:
:
::Good idea with temp jumper. Thanks for the definite cap size. The orange resistor is in some round about way connected to the large power transformer. It is in that section and is connected to the Dark Green resistor. What would be the rating on a completely orange large log reistor? 33000?
::I am going to do alot more trouble shouting tonight. Have a new plan of attack. Thanks for the help. will let you know if I get it working or not.
:::Hi, Won't find a Sam's photo fax for a radio that old!
:::
:::You can solder in a temporary jumper on the phono plug until you are confident with the radio.
:::
:::Those are 0.1uF caps. Don't think the caps are preventing the radio from working since the plate voltages are about right.
:::
:::Can you tell which transformer the orange log resistor is located?
:::
:::Richard
:::
So I am back to the melting grounding orange resistor.
THe original is over tolerance according to the schematic. It should be 750 ohms and it measures 1.2K ohms. IT is orange and looks like a beat up linken log. There are also three others that look simular in the power supply. The check out ok. I remember someone saying they should be 1 watt. They are kind of big for resisters. Are we sure they are one watt? There is a giant metal box that is a resistor. That checked out ok at 300 ohms, thank god. Must be oil filled. I swapped to elect caps to make sure they are not causing my problem. ANyway, Going to replace one resistor at a time to see if it solves my problem. Lke I said, the orange resistor, 750 ohms, is my troublimg resistor and is over its rating and is my first to go. What would be a good guess on its wattage. Thank you for all your time. If anyone needs or wants pictures of radio I will more than happy to email them out. Cool old radio out of a barn. Joe
:Resistors should be 1/4 watt for any found in the RF and audio circuits. Resistors in the power supply should usually be 1 watt, unless you find the originals to be larger. You shouldn't replace resistors unless they have drifted higher, or are open. If you want to replace a resistor, tell us which one you are replacing, and we can give you an approximate wattage.
:
:As for capacitors, they don't physically leak, so you can't tell if they're leaky by looking at them. They leak electricity when they become bad. An ohmmeter is all you need to check for leakage. It is necessary to disconnect at least one lead of each capacitor you test. The best test for a capacitor is under a high voltage (below the maximum it is rated for). This will reveal arcing. For a really reliable repair, however, it is probably best to just replace all capacitors. Since you are new to all of this, though, it is best, for now, that you just find the leaky ones, and replace them. Once you get the radio working, you may replace the remaining capacitors if you wish. If you aren't looking for a real thorough restoration at this point, and you have some capacitors in large tar filled cans, you may simply disconnect them and wire in modern units under the chassis in their places (electrically). Later on you may tackle melting tar out of the cans and fitting new units inside, etc.
:
:Thomas
Verify the bias of the 45 tubes. Schematic seems to show 40V on the control grids which would be backwards. Expect 0V on the control grids, 40V on the cathodes.
Richard
I disconnected the speaker leads off of the dual 45 tubes. The radio stayed on without even warming the resistor. Reconnected the speaker and the resistor got hot.
Checked my speaker wire and it is fine. Then I ohmed out the speaker transformer. I don't know what to expect so I need some help here. Four wires comming off of transformer. One pair of yellow wires, the other pair red wire black wire. The black & read wire was 2.5K. The Yellow pair 276 ohms.
NOW IS WHERE GET CONFUSED AND START TO TROUBLE SHOUT AGAIN.(neighbors must hate me because my garage door is always wide open) BIG QUESTION = These coils of wire are seperate coils right? Wrong?
I ohmed out wires between pairs to see if they were open. NOPE I "ass"umed wrong. I get resistance between all wires. THIS IS BAD RIGHT?
black W & Yellow1 = 2.6K
Black W. & Yellow2 = 2.6K
Red & yellow1 = 148
red & yellow2 = 127
This why my resistor is shorting out guys right?
No speaker on schematic so no help there. Any help is greatly appreciated. Joe
Hi,
:Verify the bias of the 45 tubes. Schematic seems to show 40V on the control grids which would be backwards. Expect 0V on the control grids, 40V on the cathodes.
:
:Richard
:Who made this radio for Sears? I had a Crosley of about the same vintage that was doing exactly what yours is - even melted the ceramic coating on a power resistor. I found out (in my case) that the interstage transformer between the 1st AF stage and the output was shorted to ground. Once I replaced the transformer, the problem was solved. Also, there really should be no resistance like you report between the primary and secondary of the speaker transformer.
So I am back to the melting grounding orange resistor.
THe original is over tolerance according to the schematic. It should be 750 ohms and it measures 1.2K ohms. IT is orange and looks like a beat up linken log. There are also three others that look simular in the power supply. The check out ok. I remember someone saying they should be 1 watt. They are kind of big for resisters. Are we sure they are one watt? There is a giant metal box that is a resistor. That checked out ok at 300 ohms, thank god. Must be oil filled. I swapped to elect caps to make sure they are not causing my problem. ANyway, Going to replace one resistor at a time to see if it solves my problem. Lke I said, the orange resistor, 750 ohms, is my troublimg resistor and is over its rating and is my first to go. What would be a good guess on its wattage. Thank you for all your time. If anyone needs or wants pictures of radio I will more than happy to email them out. Cool old radio out of a barn. Joe
:Thank you for the reply. I just had a break through with the speaker. It is a "Operadio" speaker which has its own special setup. DOES anyone have working knowledge of this type of speaker and which terminal should be connected where? Or any known problem to look for?
::Who made this radio for Sears? I had a Crosley of about the same vintage that was doing exactly what yours is - even melted the ceramic coating on a power resistor. I found out (in my case) that the interstage transformer between the 1st AF stage and the output was shorted to ground. Once I replaced the transformer, the problem was solved. Also, there really should be no resistance like you report between the primary and secondary of the speaker transformer.
Get 2.1 watts on the 750 ohm resistor but better double that to a 5 watt as a general rule of thumb. Wattage is based on the 40 volts on the schematic then applying ohm's law (E^2/R, 40*40/750=2.1).
Make those grid and cathode voltage checks on the 45 tubes.
Richard
:
:Get 2.1 watts on the 750 ohm resistor but better double that to a 5 watt as a general rule of thumb. Wattage is based on the 40 volts on the schematic then applying ohm's law (E^2/R, 40*40/750=2.1).
:
:Make those grid and cathode voltage checks on the 45 tubes.
:
:Richard
Richard
If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
I hope this helps
MRO
:Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:
:Richard
The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
SO we changed the pink 1000ohm resistor out. but no change. what gives?
WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
:
:If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
:I hope this helps
:
:
:
:MRO
:
:
::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
::
::Richard
What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
Radiodoc
*************
:Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
:The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
:The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
:Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
:SO we changed the pink 1000ohm resistor out. but no change. what gives?
:WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
:The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
::
::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
::I hope this helps
::
::
::
::MRO
::
::
:::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:::
:::Richard
:Napijoe,
:
:What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
:
:Radiodoc
:*************
:
:
::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
::SO we changed the pink 1000ohm resistor out. but no change. what gives?
::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
:::
:::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
:::I hope this helps
:::
:::
:::
:::MRO
:::
:::
::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
::::
::::Richard
The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
Radiodoc
***********
:I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
::Napijoe,
::
::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
::
::Radiodoc
::*************
::
::
:::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
:::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
:::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
:::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
:::SO we changed the pink 1000ohm resistor out. but no change. what gives?
:::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
:::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
::::
::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
::::I hope this helps
::::
::::
::::
::::MRO
::::
::::
:::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:::::
:::::Richard
Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
Napijoe
:Napijoe,
:
:The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
:
:Radiodoc
:***********
:
::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
:::Napijoe,
:::
:::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
:::
:::Radiodoc
:::*************
:::
:::
::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
:::::
:::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
:::::I hope this helps
:::::
:::::
:::::
:::::MRO
:::::
:::::
::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
::::::
::::::Richard
I am not familiar with that type of speaker. There are others on here who may. Some speakers operated directly from the currents flowing thru its coil. The speaker didn't have an output transformer as such with a primary and secondary. Leave the speaker hooked up. I just wanted to eliminate the remote possibility of a short in the power transformer. Another thing you can try if you haven't already done is to disconnect the driver transformer leads from the 45 grids and tack in a couple of 470K resistors from each grid to ground/chassis in case there may be a short between the driver transformer primary and secondary.
Radiodoc
*************
:Radiodoc,
:Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
: Napijoe
::Napijoe,
::
::The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
::
::Radiodoc
::***********
::
:::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
::::Napijoe,
::::
::::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
::::
::::Radiodoc
::::*************
::::
::::
:::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
:::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
:::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
:::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
:::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
:::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
:::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
::::::
::::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
::::::I hope this helps
::::::
::::::
::::::
::::::MRO
::::::
::::::
:::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:::::::
:::::::Richard
I have the 470K resistors connected already. Didnt do much. I consulted with an older gentlemen who has a pretty good working knowledge of circuits. I was hoping you could read the following and tell me if you agree with the idea or not.
He took a look at the schematic and said remove the 27 tube next to the 45s (believe it is the Det tube) and turn the radio on. See if the resistor gets hot. He believes something is either causing the 45 tubes to drive high or a 45 tube is shorted inside. If you remove the tube it will stop any signal form the left side of the radio to the 45s to drive. Then the problem would be on the left side of the radio. If the resistor still gets hot without the 27 det tube in place he assumes a 45 tube may have a grid touching off inside. He did not believe it was the massiver powertransformer because we are getting the 2.6V and voltage in general. The speaker he dismissed as working.
So I tried that trick of removing the 27 tube. The resistor got hot. So, my question to you is do you agree with this logic?
I had the 45s tested and the tester said they where good. Do you agree tube testers can make mistakes with 45 tubes? esp shorts?
FUn fun fun. PLease let me know what you think. Right now we are looking for another pair of 45 tubes on ebay. Hoping this does the trick.
:Napijoe,
:
:I am not familiar with that type of speaker. There are others on here who may. Some speakers operated directly from the currents flowing thru its coil. The speaker didn't have an output transformer as such with a primary and secondary. Leave the speaker hooked up. I just wanted to eliminate the remote possibility of a short in the power transformer. Another thing you can try if you haven't already done is to disconnect the driver transformer leads from the 45 grids and tack in a couple of 470K resistors from each grid to ground/chassis in case there may be a short between the driver transformer primary and secondary.
:
:Radiodoc
:*************
:
::Radiodoc,
::Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
:: Napijoe
:::Napijoe,
:::
:::The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
:::
:::Radiodoc
:::***********
:::
::::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
:::::Napijoe,
:::::
:::::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
:::::
:::::Radiodoc
:::::*************
:::::
:::::
::::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
::::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
::::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
::::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
::::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
::::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
::::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
:::::::
:::::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
:::::::I hope this helps
:::::::
:::::::
:::::::
:::::::MRO
:::::::
:::::::
::::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
::::::::
::::::::Richard
Try only one 45 tube at a time and see if the resistor gets hot. If only one tube causes the resistor to get hot, then that tube is probably defective. If both tubes individually cause the resistor to get hot, then disconnect both transformer leads from the grids leaving the resistors in place and try again with the tubes one at a time. With the transformer leads disconnected, this should rule out a primary to secondary short in the transformer.
Radiodoc
**************
:Radiodoc,
:
:I have the 470K resistors connected already. Didnt do much. I consulted with an older gentlemen who has a pretty good working knowledge of circuits. I was hoping you could read the following and tell me if you agree with the idea or not.
:He took a look at the schematic and said remove the 27 tube next to the 45s (believe it is the Det tube) and turn the radio on. See if the resistor gets hot. He believes something is either causing the 45 tubes to drive high or a 45 tube is shorted inside. If you remove the tube it will stop any signal form the left side of the radio to the 45s to drive. Then the problem would be on the left side of the radio. If the resistor still gets hot without the 27 det tube in place he assumes a 45 tube may have a grid touching off inside. He did not believe it was the massiver powertransformer because we are getting the 2.6V and voltage in general. The speaker he dismissed as working.
:So I tried that trick of removing the 27 tube. The resistor got hot. So, my question to you is do you agree with this logic?
:I had the 45s tested and the tester said they where good. Do you agree tube testers can make mistakes with 45 tubes? esp shorts?
:FUn fun fun. PLease let me know what you think. Right now we are looking for another pair of 45 tubes on ebay. Hoping this does the trick.
::Napijoe,
::
::I am not familiar with that type of speaker. There are others on here who may. Some speakers operated directly from the currents flowing thru its coil. The speaker didn't have an output transformer as such with a primary and secondary. Leave the speaker hooked up. I just wanted to eliminate the remote possibility of a short in the power transformer. Another thing you can try if you haven't already done is to disconnect the driver transformer leads from the 45 grids and tack in a couple of 470K resistors from each grid to ground/chassis in case there may be a short between the driver transformer primary and secondary.
::
::Radiodoc
::*************
::
:::Radiodoc,
:::Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
::: Napijoe
::::Napijoe,
::::
::::The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
::::
::::Radiodoc
::::***********
::::
:::::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
::::::Napijoe,
::::::
::::::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
::::::
::::::Radiodoc
::::::*************
::::::
::::::
:::::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
:::::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
:::::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
:::::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
:::::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
:::::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
:::::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
::::::::
::::::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
::::::::I hope this helps
::::::::
::::::::
::::::::
::::::::MRO
::::::::
::::::::
:::::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:::::::::
:::::::::Richard
This is certainly one looooong, back and forth thread and I'm now coming in on it at the very end, but with you consulting the units
attached thumbnail schematic markup.
Confirm that the resistor in question that is heating up ...and that is HEAVY on the , if it took on a glow.... is the 750
ohm unit that completes the filament center tap counterpoise to ground and that I have highlighted in yellow. I certainly hope that extreme degree of overload has not damaged components in that loop !
That particular resistor is establishing the circuit equivalency of a cathode resistor, should the circuit have been designed using a cathodic type of tube.
The first topic that I would want to get on to would be the speaker. I have shown its windings in a markup to the bottom left
corner of the marked up schema as interpreted with your given information.
Now, in going by your info supplied, I perceive of the unit having two center tapped windings with one being of a high impedance (Z), and the other being of a low to medium Z.
I am somewhat confused by the referencing of them by the fact that they are both assigned as being yellow1 and yellow2.....e.g. four yellow wires being involved. BUT if those are OLD yellow cotton wires, you would be lucky in differentiating even that , regardless of any other trace marker placed on the wire
BUT you did give enough info in respect to the common Black-W wire referencing assignment as being the center tap of the highest Z winding .
That would then leave the Red as being the center tap of the lowest Z winding.
Here forth, I will refer between the two separate speaker windings as the [Black-W, hi Z winding], or the [Red, low Z winding], since they both seem to have like yellow color coded extreme outer leads.
Now what I would want to confirm would be the resistance from end to end of [Black-W, hi Z winding] as having an ~5,200 ohm reading, since it was ~2600 from center tap to each outer end.
Next confirm that the resistance from end to end of [Red, low Z winding] as having an ~275 ohm reading, since it was ~148 and 127 ohms from center tap to each outer end. ( I was certainly expecting those to be closer balanced, but it may be of minor consequence in the end.)
Now here is the real kicker, with all speaker leads floating, I certainly hope that when you take a resistance reading from the Black-W winding center tap to the Red winding center tap that you are measuring an open circuit, with there being no connection between the two windings.
If that is correct then we would want to confirm that the manner in which you hooked up that speaker to the radio was for the main B+ that comes up from the power supply filter choke [Red lined markup on the schema] to feed to the speaker is connected to the center Black-W wire of the [Black-W, hi Z winding] and that windings companion outside "yellow" wires each went to a plate of the '45's.That would make the B+ power loop having at its start on the red line referencing at the filter choke and then flow on up to the dual '45 plates and thermionic conduction would complete their circuit down to the filaments there they would flow down the green marked up loop and then out to the 750 ohm power resistor to ground.
If the above is the way that you had the [Black-W, hi Z winding] connected, then I would want
to know in what manner you had the [Red, low Z winding] portion of the speaker connected into the radio ?
Can't quite go any further with out feedback at this point, but I might ask if you have plugged in a set of high Z headphones, had the '45's unplugged out of circuit, and tried out the receivers front end in that headphone receiving mode to confirm successful AM reception, since your AF power output section is currently overstressed.
In the interim, before exchanging data, if you found that you had connected the speakers Hi Z winding , other than which I mentioned you might connect it as described, with the low Z winding being disregarded at the present time, and then do a short power up to confirm that the current consumption now is way more in line and with the resistor not being a problem. If so,
take a voltage check across that 750 ohm resistor with DVM DC negative metering probe to chassis ground and the + metering probe to the resistors high end. Write down its voltage and polarity for feedback. Then move up to the ‘45’s and place DVM DC metering negative probe to one of the filament pins…(to remain there for both ensuing readings) …. and take a voltage check on the first…(and sole!)…grid of EACH tube and record their voltages and polarities.
Aside:
Your description of the simple antenna sounds a bit deficient so I would be relying upon a looooong hank of wire for an antenna , until I picked up that first station, then you could see how much that you could cut back on the antenna requirement, unless you have a real powerhouse AM station nearby.
Also I can assume that the unit has had
replacement of the filters in the magenta boxed area..particularly the AF output relevant bypassing filter that is double boxed ?
Aside…deux:
By your garage door being up, and I am assuming that the referencing to the neighbors, was in respect to infrequent
outbursts / comments from your “troubleshouting” results . With occasional %#+$&### and *$@*&$...... drifting clearly thru the still night air in the wee-wee hours.
Ref marked-up schema:
73's de Edd
:Napijoe,
:
:Try only one 45 tube at a time and see if the resistor gets hot. If only one tube causes the resistor to get hot, then that tube is probably defective. If both tubes individually cause the resistor to get hot, then disconnect both transformer leads from the grids leaving the resistors in place and try again with the tubes one at a time. With the transformer leads disconnected, this should rule out a primary to secondary short in the transformer.
:
:Radiodoc
:**************
:
::Radiodoc,
::
::I have the 470K resistors connected already. Didnt do much. I consulted with an older gentlemen who has a pretty good working knowledge of circuits. I was hoping you could read the following and tell me if you agree with the idea or not.
::He took a look at the schematic and said remove the 27 tube next to the 45s (believe it is the Det tube) and turn the radio on. See if the resistor gets hot. He believes something is either causing the 45 tubes to drive high or a 45 tube is shorted inside. If you remove the tube it will stop any signal form the left side of the radio to the 45s to drive. Then the problem would be on the left side of the radio. If the resistor still gets hot without the 27 det tube in place he assumes a 45 tube may have a grid touching off inside. He did not believe it was the massiver powertransformer because we are getting the 2.6V and voltage in general. The speaker he dismissed as working.
::So I tried that trick of removing the 27 tube. The resistor got hot. So, my question to you is do you agree with this logic?
::I had the 45s tested and the tester said they where good. Do you agree tube testers can make mistakes with 45 tubes? esp shorts?
::FUn fun fun. PLease let me know what you think. Right now we are looking for another pair of 45 tubes on ebay. Hoping this does the trick.
:::Napijoe,
:::
:::I am not familiar with that type of speaker. There are others on here who may. Some speakers operated directly from the currents flowing thru its coil. The speaker didn't have an output transformer as such with a primary and secondary. Leave the speaker hooked up. I just wanted to eliminate the remote possibility of a short in the power transformer. Another thing you can try if you haven't already done is to disconnect the driver transformer leads from the 45 grids and tack in a couple of 470K resistors from each grid to ground/chassis in case there may be a short between the driver transformer primary and secondary.
:::
:::Radiodoc
:::*************
:::
::::Radiodoc,
::::Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
:::: Napijoe
:::::Napijoe,
:::::
:::::The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
:::::
:::::Radiodoc
:::::***********
:::::
::::::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
:::::::Napijoe,
:::::::
:::::::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
:::::::
:::::::Radiodoc
:::::::*************
:::::::
:::::::
::::::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
::::::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
::::::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
::::::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
::::::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
::::::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
::::::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
:::::::::
:::::::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
:::::::::I hope this helps
:::::::::
:::::::::
:::::::::
:::::::::MRO
:::::::::
:::::::::
::::::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
::::::::::
::::::::::Richard
:
:
:
:
:This is certainly one looooong, back and forth thread and I'm now coming in on it at the very end, but with you consulting the units
:attached thumbnail schematic markup.
:
:Confirm that the resistor in question that is heating up ...and that is HEAVY on the , if it took on a glow.... is the 750
:ohm unit that completes the filament center tap counterpoise to ground and that I have highlighted in yellow. I certainly hope that extreme degree of overload has not damaged components in that loop !
:
:That particular resistor is establishing the circuit equivalency of a cathode resistor, should the circuit have been designed using a cathodic type of tube.
:
:
:The first topic that I would want to get on to would be the speaker. I have shown its windings in a markup to the bottom left
:corner of the marked up schema as interpreted with your given information.
:Now, in going by your info supplied, I perceive of the unit having two center tapped windings with one being of a high impedance (Z), and the other being of a low to medium Z.
:
:I am somewhat confused by the referencing of them by the fact that they are both assigned as being yellow1 and yellow2.....e.g. four yellow wires being involved. BUT if those are OLD yellow cotton wires, you would be lucky in differentiating even that , regardless of any other trace marker placed on the wire
:
:BUT you did give enough info in respect to the common Black-W wire referencing assignment as being the center tap of the highest Z winding .
:
:That would then leave the Red as being the center tap of the lowest Z winding.
:
:Here forth, I will refer between the two separate speaker windings as the [Black-W, hi Z winding], or the [Red, low Z winding], since they both seem to have like yellow color coded extreme outer leads.
:
:Now what I would want to confirm would be the resistance from end to end of [Black-W, hi Z winding] as having an ~5,200 ohm reading, since it was ~2600 from center tap to each outer end.
:
:
:Next confirm that the resistance from end to end of [Red, low Z winding] as having an ~275 ohm reading, since it was ~148 and 127 ohms from center tap to each outer end. ( I was certainly expecting those to be closer balanced, but it may be of minor consequence in the end.)
:
:Now here is the real kicker, with all speaker leads floating, I certainly hope that when you take a resistance reading from the Black-W winding center tap to the Red winding center tap that you are measuring an open circuit, with there being no connection between the two windings.
:
:If that is correct then we would want to confirm that the manner in which you hooked up that speaker to the radio was for the main B+ that comes up from the power supply filter choke [Red lined markup on the schema] to feed to the speaker is connected to the center Black-W wire of the [Black-W, hi Z winding] and that windings companion outside "yellow" wires each went to a plate of the '45's.That would make the B+ power loop having at its start on the red line referencing at the filter choke and then flow on up to the dual '45 plates and thermionic conduction would complete their circuit down to the filaments there they would flow down the green marked up loop and then out to the 750 ohm power resistor to ground.
:
:If the above is the way that you had the [Black-W, hi Z winding] connected, then I would want
:to know in what manner you had the [Red, low Z winding] portion of the speaker connected into the radio ?
:
:Can't quite go any further with out feedback at this point, but I might ask if you have plugged in a set of high Z headphones, had the '45's unplugged out of circuit, and tried out the receivers front end in that headphone receiving mode to confirm successful AM reception, since your AF power output section is currently overstressed.
:
:
:
:In the interim, before exchanging data, if you found that you had connected the speakers Hi Z winding , other than which I mentioned you might connect it as described, with the low Z winding being disregarded at the present time, and then do a short power up to confirm that the current consumption now is way more in line and with the resistor not being a problem. If so,
:take a voltage check across that 750 ohm resistor with DVM DC negative metering probe to chassis ground and the + metering probe to the resistors high end. Write down its voltage and polarity for feedback. Then move up to the ‘45’s and place DVM DC metering negative probe to one of the filament pins…(to remain there for both ensuing readings) …. and take a voltage check on the first…(and sole!)…grid of EACH tube and record their voltages and polarities.
:
:
:
:
:Aside:
:
:Your description of the simple antenna sounds a bit deficient so I would be relying upon a looooong hank of wire for an antenna , until I picked up that first station, then you could see how much that you could cut back on the antenna requirement, unless you have a real powerhouse AM station nearby.
:
:Also I can assume that the unit has had
:replacement of the filters in the magenta boxed area..particularly the AF output relevant bypassing filter that is double boxed ?
:
:
:
:
:Aside…deux:
:
:By your garage door being up, and I am assuming that the referencing to the neighbors, was in respect to infrequent
:outbursts / comments from your “troubleshouting” results . With occasional %#+$&### and *$@*&$...... drifting clearly thru the still night air in the wee-wee hours.
:
:
:Ref marked-up schema:
:
:
:
:
:
:73's de Edd
:
:
:
:
:
:
:
:
::Napijoe,
::
::Try only one 45 tube at a time and see if the resistor gets hot. If only one tube causes the resistor to get hot, then that tube is probably defective. If both tubes individually cause the resistor to get hot, then disconnect both transformer leads from the grids leaving the resistors in place and try again with the tubes one at a time. With the transformer leads disconnected, this should rule out a primary to secondary short in the transformer.
::
::Radiodoc
::**************
::
:::Radiodoc,
:::
:::I have the 470K resistors connected already. Didnt do much. I consulted with an older gentlemen who has a pretty good working knowledge of circuits. I was hoping you could read the following and tell me if you agree with the idea or not.
:::He took a look at the schematic and said remove the 27 tube next to the 45s (believe it is the Det tube) and turn the radio on. See if the resistor gets hot. He believes something is either causing the 45 tubes to drive high or a 45 tube is shorted inside. If you remove the tube it will stop any signal form the left side of the radio to the 45s to drive. Then the problem would be on the left side of the radio. If the resistor still gets hot without the 27 det tube in place he assumes a 45 tube may have a grid touching off inside. He did not believe it was the massiver powertransformer because we are getting the 2.6V and voltage in general. The speaker he dismissed as working.
:::So I tried that trick of removing the 27 tube. The resistor got hot. So, my question to you is do you agree with this logic?
:::I had the 45s tested and the tester said they where good. Do you agree tube testers can make mistakes with 45 tubes? esp shorts?
:::FUn fun fun. PLease let me know what you think. Right now we are looking for another pair of 45 tubes on ebay. Hoping this does the trick.
::::Napijoe,
::::
::::I am not familiar with that type of speaker. There are others on here who may. Some speakers operated directly from the currents flowing thru its coil. The speaker didn't have an output transformer as such with a primary and secondary. Leave the speaker hooked up. I just wanted to eliminate the remote possibility of a short in the power transformer. Another thing you can try if you haven't already done is to disconnect the driver transformer leads from the 45 grids and tack in a couple of 470K resistors from each grid to ground/chassis in case there may be a short between the driver transformer primary and secondary.
::::
::::Radiodoc
::::*************
::::
:::::Radiodoc,
:::::Thank you for your help. Would a short in the speaker transformer cause the 45s to do this? This radio has a Operadio speaker which is an odd setup. Are you familiar with this type of speaker and what I should check for on it? Had some help figuring it out once before but there is always the chance we assumed wrong on something. Thank you for your help. Will try the resistor trick tonight. SHould I leave the speaker disconnected or connected while on?
::::: Napijoe
::::::Napijoe,
::::::
::::::The 93 volts DC is definitely way too high. Using Ohms Law that would make the current thru the 45s at somewhere around 124 milliamps instead of around 30 milliamps as stated on the schematic. Also the dissipation of the 750 Ohm resistor would be around 12 Watts. You may try removing the two 45s and place a 50K 5W or so resistor from B+ to ground/chassis/B- and turn the radio on and see if you have voltage on the 750 Ohm resistor. The 45s are definitely drawing too much current.
::::::
::::::Radiodoc
::::::***********
::::::
:::::::I am getting 93V across the 750 ohm resistors. I am getting 2.6V to the heaters of the 45s. O VOLTS off of pin the transformer is connected to and 300 V off of the plates. Everything else is also high. Almost all the plates of the 27 tubes are 209V. Supposed to be 115V. The 27 tube that has 44V off its plate is 0V. I am getting 2.6 V off of the orange and white wires. Im out of stuff to check. I swapped most of the resistors and all the caps. Do we think the massive power transformer is overdriving leg to the blue wire to the 45 Tubes? or is something in the 27 tubes causing the 45 tubes to overdrive? I did the before mentioned trick with the 470K ohm resistors to ground off of the 45s. Didnt make a difference. This thing sounds so close to working.
::::::::Napijoe,
::::::::
::::::::What is the voltage measured across the 750 Ohm resistor? It should be around 23 volts or so.
::::::::
::::::::Radiodoc
::::::::*************
::::::::
::::::::
:::::::::Once again I am working on the Sears & Roebuck radio from hell. Actually made alot of headway last night. I had to put the project on hold till I got the tubes back from testing. Thank you Larry for the help. All the tubes I have are good I am told. SOO...please help. This set has five number 27 tubes, two 45 tubes, and a number 80 tube. It is a SEARS model 52 and Factory Model 95 and the schematic is on this great and wonderful site under resources. My problem still is the 750ohm resistor heating up hot and no radio stations. It is connected to the 45 tube heaters. Something is over working the resistor but what?
:::::::::The speaker is a radiopera speaker which has been checked and is not shown on the diagram. 100% sure it is not causing the problem.
:::::::::The 45 tubes tested good and the heater wires have been replaced. I get the correct 2.6V on them.
:::::::::Supposed to be getting 115V on the plates of the 27 tubes. I AM Getting more like 200 to 250V. It seems like the 27 tubes are getting to much voltage.
:::::::::SO we changed the pink 1000ohm resistor out. but no change. what gives?
:::::::::WE also took apart the smaller transformer next to the 45 tubes and it checked out ok. It has a ground and is not shorted. Is there a way to check a transformer like that?
:::::::::The schematic calls for a 500 ohm and a 10000 ohm resistor in series to ground. For a antenna I have this red tube with copper wire spun around it with a little yellow ball in the middle of it. Is this the proper antenna? It is connected to the antenna and gnd terminal. Any gurus out there that can tell me I am gettingsuch a high voltage on my tubes? I get a low hum and all the tubes work. No stations yet and the resister is getting hot. Thank you everyone for the help so far. I refuse to give up now.
::::::::::
::::::::::If the audio interstage transformer which feeds the audio signal to each of the grids on the 45's opens up the grids will not be at the right voltage and the 45 tubes will draw too much current. This excessive current may be what is causing the resistor to run hot. I did not look at the other postings or the schematic so I am shooting from the hip so to speak. On some radios they install 470k ohm resistors from the grid to ground on the 45 tubes. These resistors don't affect the audio and prevent the grid voltage from floating around if the transformer opens up.
::::::::::I hope this helps
::::::::::
::::::::::
::::::::::
::::::::::MRO
::::::::::
::::::::::
:::::::::::Joe, Not sure how to go about testing a tube with a DVM out of circuit and besides wouldn't be very viable method IMHO. Really calls for a tube tester. Besides should be able to determine a lot from the radio itself. Schematic is showing 200V on the plates, 40V on the cathodes, and 0V on the control grids. Should be able to make these basic DC voltage checks in circuit. May want to try removing one 45 tube at a time to see if there is any change. Guessing that a wire going the plate circuit is somehow shorting to the cathode side. May need to try disconnecting transformer wires here and there. Good luck!
:::::::::::
:::::::::::Richard