I have a problem that I bet the experts here can help me with. I have restored an RCA610V2 and it works great on AM. FM calibrations are all done per the alignment procedures and the stations that it receives, sounds great. The problem is that the dial is way too high in frequencies. 88 is way below the dial and 106 about in the middle of the dial. I have completely rebuilt the V1 section even with putting in a new tube socket. Same trouble. The L3 oscillator adjustments work but it makes the scale worse, i.e., when the shaft is screwed all the way in, the middle of the dial scale is actually tuning the radio to 115 MHz! Screwing the shaft out lowers the frequency but all the way in doesn't adjust it in either. The middle of the dial is then pulling in 106Mhz. Weird. The radio works, and seems to have the proper spread (or close to it) but I can't get 106 to move up to 106 where it belongs. Any help would be greatly appreciated. Thanks! Dean
: I have a problem that I bet the experts here can help me with. I have restored an RCA610V2 and it works great on AM. FM calibrations are all done per the alignment procedures and the stations that it receives, sounds great. The problem is that the dial is way too high in frequencies. 88 is way below the dial and 106 about in the middle of the dial. I have completely rebuilt the V1 section even with putting in a new tube socket. Same trouble. The L3 oscillator adjustments work but it makes the scale worse, i.e., when the shaft is screwed all the way in, the middle of the dial scale is actually tuning the radio to 115 MHz! Screwing the shaft out lowers the frequency but all the way in doesn't adjust it in either. The middle of the dial is then pulling in 106Mhz. Weird. The radio works, and seems to have the proper spread (or close to it) but I can't get 106 to move up to 106 where it belongs. Any help would be greatly appreciated. Thanks! Dean
Welll, sure looks like a local oscillator problem. Try the old "use a good radio tuned 10.7 mHz higher than the bad radio" trick and make sure. Without a crystal, the oscilattor frequency is determined by coils and capacitors, so you must have one of those out of tolerence.
Lewis
:: I have a problem that I bet the experts here can help me with. I have restored an RCA610V2 and it works great on AM. FM calibrations are all done per the alignment procedures and the stations that it receives, sounds great. The problem is that the dial is way too high in frequencies. 88 is way below the dial and 106 about in the middle of the dial. I have completely rebuilt the V1 section even with putting in a new tube socket. Same trouble. The L3 oscillator adjustments work but it makes the scale worse, i.e., when the shaft is screwed all the way in, the middle of the dial scale is actually tuning the radio to 115 MHz! Screwing the shaft out lowers the frequency but all the way in doesn't adjust it in either. The middle of the dial is then pulling in 106Mhz. Weird. The radio works, and seems to have the proper spread (or close to it) but I can't get 106 to move up to 106 where it belongs. Any help would be greatly appreciated. Thanks! Dean
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:Welll, sure looks like a local oscillator problem. Try the old "use a good radio tuned 10.7 mHz higher than the bad radio" trick and make sure. Without a crystal, the oscilattor frequency is determined by coils and capacitors, so you must have one of those out of tolerence.
:Lewis
Hi Lewis,
Yeah you would think so, but I have totally rebuilt the thing, new caps and resistors. This one has me stumped. Gotta be something obvious but I am just not seeing it. Will keep looking. Thanks for the reply.
Dean
It's a miracle. . . . IT'S A MIRACLE. . . . that they got that design off the air, using a 6BE6 at FM frequencies.
With your info of the FM tracking error that you are experiencing, consult the thumbnail that I have made up on that unit at the bottom and you will see that the tandem mechanical ganging of the variable tuning condensers RF and oscillator sections are specified as the magenta boxed C51 and C53 respectively with their companion capacitive corrective trimmer capacitors being C52 and C52.
I also make reference to the SM osc grid coupling capacitor with its yellow box and the [A] designator, hopefully you have not replaced that unit.
Also I am assuming that the IF strip is tuned to 10.7 or else has not been touched.
Now in getting our alignment corrected, such that your dial scale logging will be in accordance. The main thing that we will be interested in will be just the oscillator adjustments aspects initially, an RF alignment (L2-C52) error would be affective in the respect of knocking down the reception sensitivity of the receiver.
With your having mentioned that the 88 aspect being waaaay too low and the referenced 106 and 115 being waaaay too low in frequency. That is telling us that your C54 trimmer capacitor is set with too much compensative capacitance being added, and the L3's compensating agent. . . .its slug …is not decreasing the effective inductance of L3.. . . . local oscillator coil. . . .enough.
Now mind you that when you get through with this mass produced consumer product, of its questionable aging, yet, don't expect to be getting an 88.010--------100.050--------107.010 Mhz dial scale tracking accuracy and resolution.
Lets start with that C54 trimmer adjustment initially and tune the radio right to the high frequency edge of that received 88 signal and trim in C54 until its resultant frequency shift makes the unit be tuned right on to "88†then tune off to the high side again and do the same procedure repetitively until you find out how close that you can get to having "88†come in at "88†dial scale logging position. IF you then find that that is not possible with C54 then you will have to additionally move over to L3 's inductive adjustment and use it to additionally correct with, by having its tuning being such that it is decreasing the inductive value present in the combos tuning action.
COMPREHENSIVELY:
Your sets oscillator can tune to a frequency with a certain value of capacitance being used in conjunction with a certain value of inductance to result in the desired resonant frequency of that local oscillator circuit.
Both of those values can be shifted..e.g. you can up the capacitance a bit and decrease the inductance a bit and still end up with that same resonating frequency, or just its converse.
Sooooo what you seem to have ended up in your oscillator alignment of your receiver is a capacitive and inductive elements, BOTH of which, are set for being too large in value.
I'm going to stop here for feedback, in case you experience a roadblock. . .
Thumbnail Schematic Referencing:
73's de Edd
ADDENDA. . . Correcting text:
corrective trimmer capacitors being C52 and C54.
73's de Edd
Thanks so much for your help with this problem. I knew I would find an expert here.
Please continue, I am not lost.
Dean
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:ADDENDA. . . Correcting text:
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:corrective trimmer capacitors being C52 and C54.
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:73's de Edd
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When I adjust L3 and C54 for the proper setting of 88 MHz, 106 sits about 99Mhz. I can hear station very well and the sound is great. I can adjust the low end but no matter where I place L3 and C54, there is not enough "spread" in the dial. Everything from 88 to 108 is shrunk down between 88 and about 101 with 88 being where it should be on the dial. Hope this helps.
Dean
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:ADDENDA. . . Correcting text:
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:corrective trimmer capacitors being C52 and C54.
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:73's de Edd
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OH-TAY !. . . .U-back. . . .now since I don’t know what that ‘completely rebuilt’ aspect involved in the FM tuner section, what with lead dress and stray capacitance factors being involved at those frequencies, I believe that I will pull an ostrich and stick my head down deeeep in the sand at this point / perspective in time.
Also tell me if the L3 osc coil is as mechanically solid as a rock, or is it somewhat loose such that coil turns can be compressed / knifed. Not to worry about that yet, tho.
Also, at AM frequencies our adjustable slugs in cores are typically powdered iron – ferrites, however, on FM, the small frequency shifting needed and acquired, is usually accomplished by that core being non ferrous like a brass slug or in newer times, alumminuminuniyum.
Remember, on this end you are dealing with someone that is deaf, blind and dumb. . . but I do feel pretty good.
Now,is it possible to confirm which is the situation on your units core construction, if viewable?
Now, with your latest data, looks like you are going to be flitting from one end of the dial scale to the other repetitively in order to check out your compensatory adjustments.
Its. . . . .SHOWTIME :
If you are now able to get 88 coming in as 88 , but with 108 coming in at ~ 98, you are still compressed up too much so that will now require you to take that high band station reference and tune off just to the right of it and you then adjust C54 until the station peaks on it .
Now you swing back to 88 and see that it hasn’t walked off excessively ?, then you run back up to the high side reference station and walk it on upwards a bit with a refined C54 adjustment. Getting the hang of it now ? You will now be basically using L3 osc adjustment for the setting of the LOW BAND station and the C54 trimmer for the HIGH BAND station, and the high band station position should gradually spread out to eventually be in congruence with your dial scale logging.
Remember me telling you that we could get a frequency with two SHIFTING values of inductance and capacitance, well the situation here is that we have that variable tuning condenser pair, ( but currently we are now totally ignoring the ANT section….as that could get real mind boggggling, you know ?)
And in looking at the specs they don’t give the values of the FM variable sections, so I am just thinking that variable osc section of the capacitor might be 7 decimal5575 pf value, when swung completely open for its being tuning to the VEWY-VEWY high end of the FM band and at a 35 decimal 9964 pf value, as it is completely closed, when being tuned to the VEWY-VEWY low end of the FM band. Hey I can see that now, but we need compensation of that variable tuning condenser to make up for manufacturing, construction, component variables SO they shunt the osc tuning capacitor with that C54 trimmer capacitor which they tell me is 2.5 thru 10 pf.
Soooooo now if I have that tuning capacitor swung ALL the way open and am looking for that 108 station, IF that shunting trimmer is adding in too much shunt capacitance,(to the BOTH of them, being in parallel) we can’t get DOWN to that minimum value that is needed and we NEVAH going to get that high band station tuned in right , it will be located lower on the dial scale.
Go to the mountain. . .and . . .CHECK it out now. . . . .
‘scuse pleeze any typos…. as I ripped this off at a blazing ~135wpm at the 11th hour and didn’t fully proof it.
73's de Edd
Thanks for getting back to me.
Lets see if I can answer a few questions for you. First, completely rebuilt is just that. All components in the oscillator stage (even the tube socket and the tube) are new except for the two variable inductors L3 and L1/L2. Both of the coils have their windings in exactly the same spot as when made. I have added a little service cement around the coil L1 to hold the two turns of fine wire in place as they were comming loose with age. The coils have not slipped up or down on the forms and I have another completely separate chassis here for parts if I need it and have compared the coils between the two. They are in identical size, shape and position on the forms. All capacitors are new micas laid out in exactly the same positions as the originals, as are the resistors in that section. The core in the L3 coil is a brassish material, as is the one in the spare chassis. The slug in the L1/L2 coil is powdered iron as is the one in the spare chassis.
When adjusting the coil L3 and cap C54, C54 really does not do anything as far as moving the stations anywhere. As you listen to a station, turn the cap, the station does move just slightly but never off of the frequency set by L3, and the main tuning capacitor. In fact, you can completely turn the cap 360 degrees around and you NEVER loose the station you are listening to. It is NOT spreading out the stations, or the distance between them. The only thing that IS happening is that with L3, I move the entire range up or down the dial scale but can't get any spread whatsoever out of any of the adjustments. As far as the specs of the caps goes, according to the schematic I have, C54 is 2.5 to 13pf and C53 is 7 to 19pf if the blurred print here is correct. The only component I have NOT installed new is the trimmer C54. I say new here as I only have the spare one on the spare chassis. It is still the original and I was considering taking the one off the spare chassis to see what happens. I did do a test by disconnecting the end of that cap that connects to ground and just let it float to see what it did to the range. IT CHANGED ABSOLUTELY NOTHING. The range and set frequencies were the same with or without the cap installed! I have considered to try a different tube, maybe a substitute like a 6BY6 or 6CS6 to see if interelement capacitances may differ and see at least some improvement. Have not done that though.
Hope this info helps you. Let me know what you think! Thanks again for your help. Dean
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:OH-TAY !. . . .U-back. . . .now since I don’t know what that ‘completely rebuilt’ aspect involved in the FM tuner section, what with lead dress and stray capacitance factors being involved at those frequencies, I believe that I will pull an ostrich and stick my head down deeeep in the sand at this point / perspective in time.
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:Also tell me if the L3 osc coil is as mechanically solid as a rock, or is it somewhat loose such that coil turns can be compressed / knifed. Not to worry about that yet, tho.
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:Also, at AM frequencies our adjustable slugs in cores are typically powdered iron – ferrites, however, on FM, the small frequency shifting needed and acquired, is usually accomplished by that core being non ferrous like a brass slug or in newer times, alumminuminuniyum.
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:Remember, on this end you are dealing with someone that is deaf, blind and dumb. . . but I do feel pretty good.
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:Now,is it possible to confirm which is the situation on your units core construction, if viewable?
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:Now, with your latest data, looks like you are going to be flitting from one end of the dial scale to the other repetitively in order to check out your compensatory adjustments.
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:Its. . . . .SHOWTIME :
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:If you are now able to get 88 coming in as 88 , but with 108 coming in at ~ 98, you are still compressed up too much so that will now require you to take that high band station reference and tune off just to the right of it and you then adjust C54 until the station peaks on it .
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:Now you swing back to 88 and see that it hasn’t walked off excessively ?, then you run back up to the high side reference station and walk it on upwards a bit with a refined C54 adjustment. Getting the hang of it now ? You will now be basically using L3 osc adjustment for the setting of the LOW BAND station and the C54 trimmer for the HIGH BAND station, and the high band station position should gradually spread out to eventually be in congruence with your dial scale logging.
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:Remember me telling you that we could get a frequency with two SHIFTING values of inductance and capacitance, well the situation here is that we have that variable tuning condenser pair, ( but currently we are now totally ignoring the ANT section….as that could get real mind boggggling, you know ?)
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:And in looking at the specs they don’t give the values of the FM variable sections, so I am just thinking that variable osc section of the capacitor might be 7 decimal5575 pf value, when swung completely open for its being tuning to the VEWY-VEWY high end of the FM band and at a 35 decimal 9964 pf value, as it is completely closed, when being tuned to the VEWY-VEWY low end of the FM band. Hey I can see that now, but we need compensation of that variable tuning condenser to make up for manufacturing, construction, component variables SO they shunt the osc tuning capacitor with that C54 trimmer capacitor which they tell me is 2.5 thru 10 pf.
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:Soooooo now if I have that tuning capacitor swung ALL the way open and am looking for that 108 station, IF that shunting trimmer is adding in too much shunt capacitance,(to the BOTH of them, being in parallel) we can’t get DOWN to that minimum value that is needed and we NEVAH going to get that high band station tuned in right , it will be located lower on the dial scale.
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:Go to the mountain. . .and . . .CHECK it out now. . . . .
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:‘scuse pleeze any typos…. as I ripped this off at a blazing ~135wpm at the 11th hour and didn’t fully proof it.
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:73's de Edd
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In the immortal words of Tony the Tiger. . . .GREEEEEEEEEEAAAAAATTTT feedback coverage !
I pulled a photo of that sets chassis top and was wanting to inspect around the tuner, but only limited definition was permissible, however I do think that I might make out on my photo referencing below that the L3 coil below chassis and its shaft sticking up is a ~4-40 threaded brass screw thread [Red Arrow Reference] with a standard cross cut slot formed into its end for acceptance of an alignment tool.
AND NOW, the real point of interest is that C54 trimmer capacitor, [Blue Arrow Reference] which I had in the back of my mind was a common leaf trimmer with its mica sheet and leaf. BUT am I making out a CRL type of rotary trimmer capacitor that will make a 360 degree rotation with the capacitance shift occurring within 180 degrees of rotation, then it repeats.
And I am still dead set on the suspicion of you having too much capacitance in the OSC circuit, but can not decrease that value. . . . . so I am wondering what might be the possibility of that trimmer capacitor innards, having a charge of WD-40 /or/ oil inside of it ? The capacitive dielectric constant of air in the variable C53 is 1.0059, whereas when we look at the possibilities of those modes of trimmer constructions, mica would have been 6, but if that is a ceramic, as it certanly appears to me now, that would be exhibiting a 76 constant, BUT if having a film of oil present, tack on another additional boost of + 46 for the oil. Capacitance sure shoots up, doesn’t it, and we seem to have too much of it, and can’t get it down. GOTS Milk ?. . . .oops, I mean degreaser ? for that trimmer .
Top Chassis View:
73's de Edd
I will probably give it a try this weekend as must attend to other duties for now..........no time for playing! Darn!
Anyway Edd, I thank you so much for the help and sharing of your knowledge. It is much appreciated. I will let you know what we find.
Sincerely,
Dean
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:In the immortal words of Tony the Tiger. . . .GREEEEEEEEEEAAAAAATTTT feedback coverage !
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:I pulled a photo of that sets chassis top and was wanting to inspect around the tuner, but only limited definition was permissible, however I do think that I might make out on my photo referencing below that the L3 coil below chassis and its shaft sticking up is a ~4-40 threaded brass screw thread [Red Arrow Reference] with a standard cross cut slot formed into its end for acceptance of an alignment tool.
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:AND NOW, the real point of interest is that C54 trimmer capacitor, [Blue Arrow Reference] which I had in the back of my mind was a common leaf trimmer with its mica sheet and leaf. BUT am I making out a CRL type of rotary trimmer capacitor that will make a 360 degree rotation with the capacitance shift occurring within 180 degrees of rotation, then it repeats.
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:And I am still dead set on the suspicion of you having too much capacitance in the OSC circuit, but can not decrease that value. . . . . so I am wondering what might be the possibility of that trimmer capacitor innards, having a charge of WD-40 /or/ oil inside of it ? The capacitive dielectric constant of air in the variable C53 is 1.0059, whereas when we look at the possibilities of those modes of trimmer constructions, mica would have been 6, but if that is a ceramic, as it certanly appears to me now, that would be exhibiting a 76 constant, BUT if having a film of oil present, tack on another additional boost of + 46 for the oil. Capacitance sure shoots up, doesn’t it, and we seem to have too much of it, and can’t get it down. GOTS Milk ?. . . .oops, I mean degreaser ? for that trimmer .
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:73's de Edd
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At composing time, I have not received your comeback for the last queries , plus, at the last time, I did not have the text of the previous
reply to consult details on one statement, and that was:
"I did do a test by disconnecting the end of that cap that connects to ground and just let it float to see what it did to the range. IT CHANGED ABSOLUTELY NOTHING. The range and set frequencies were the same with or without the cap installed!"
Now if you came back with the confirmation that the C54 trimmer capacitor is of the CRL design of a rotary ceramic trimmer capacitor, AND if
that trimmer cap is mounted to the variable condenser with any rivets or twist tabs. I believe that what happened was that the bottom of the
trimmer capacitor was additionally making a ground connection, so even though you floated the "official" ground soldering terminal, there was
still a ground connection being made with the mounting mechanics of the cap. Therefore the cap was still in the circuit.
Now, if you will repeat the procedure, this time lift the "hot" wiring terminal lug of the C54 trimmer that connects to the osc variable tuning condensers terminal.
73's de Edd
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OK I will try it. The cap is just held on with 2 tiny screws. An easy removal.
Will let you know! Cross your fingers!
Dean
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:At composing time, I have not received your comeback for the last queries , plus, at the last time, I did not have the text of the previous
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:reply to consult details on one statement, and that was:
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: "I did do a test by disconnecting the end of that cap that connects to ground and just let it float to see what it did to the range. IT CHANGED ABSOLUTELY NOTHING. The range and set frequencies were the same with or without the cap installed!"
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:Now if you came back with the confirmation that the C54 trimmer capacitor is of the CRL design of a rotary ceramic trimmer capacitor, AND if
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:that trimmer cap is mounted to the variable condenser with any rivets or twist tabs. I believe that what happened was that the bottom of the
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:trimmer capacitor was additionally making a ground connection, so even though you floated the "official" ground soldering terminal, there was
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:still a ground connection being made with the mounting mechanics of the cap. Therefore the cap was still in the circuit.
:Now, if you will repeat the procedure, this time lift the "hot" wiring terminal lug of the C54 trimmer that connects to the osc variable tuning condensers terminal.
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:ZUJ'ing
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:73's de Edd
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