Hello Everyone, last night and early this morning was spent recapping my Zenith 10S690 Radio and after I finished recapping it and struggling for about an hour trying to get the chassis back into the cabinet (I was having a hard time getting the chassis screw holes to line up with the cabinet holes for the screws to go into to secure the chassis to the cabinet).

I plugged in the radio and turned it on to test out my work and sure enough my volume control wasn't working right, instead of raising and lowering the volume like its supposed to it instead acts like a tone control, and my tone control switches don't work except for the one marked "Normal".

I was trying to be careful to observe where each capacitor went when I was removing the old ones and installing the new ones and only replacing one capacitor at a time.

I've looked over the schematic for this radio and I can't seem to figure out what could be causing this issue, the radio was working fine prior to the recap (just had an intermittent AVC circuit that was more than likely due to a leaky AVC Bypass Cap).

Any ideas as to what might be causing my problem?

The schematic for this radio is posted below.

Any help with this matter would be appreciated.

An open at the ground end of the volume control would cause the problem you describe. Either an open at the end of the resistive element, or at the external ground connection. Hopefully the latter.

An open at the ground end of the volume control would cause the problem you describe. Either an open at the end of the resistive element, or at the external ground connection. Hopefully the latter.

Ground end of the volume control? There's no ground connection indicated on the schematic for the volume control pot, and the volume control pot isn't connected to ground anywhere according to the schematic, there's a reference to ground on the tone control keyboard itself but not not on the volume control pot.

Ground end of the volume control? There's no ground connection indicated on the schematic for the volume control pot, and the volume control pot isn't connected to ground anywhere according to the schematic, there's a reference to ground on the tone control keyboard itself but not not on the volume control pot.


:scratch2: I think ol Levi here could use some schematic reading lessons , the side of the volume control pot at resistor R12 is at B- potential , which is a HELL of a lot closer to "ground" than it is to B+ , that's for sure .

Old coot 88 knows his stuff , so don't be SO quick to jump on people trying to help you especially when you don't appear to have a clue as to how that circuit actually works ...... :sigh:

:scratch2: I think ol Levi here could use some schematic reading lessons , the side of the volume control pot at resistor R12 is at B- potential , which is a HELL of a lot closer to "ground" than it is to B+ , that's for sure .

Old coot 88 knows his stuff , so don't be SO quick to jump on people trying to help you especially when you don't appear to have a clue as to how that circuit actually works ...... :sigh:

When I said that I was thinking of an actual chassis ground connection and yes I do know how to read a schematic but like I said, when he said "ground connection" I was thinking he meant a physical chassis ground connection, not B- connection.

Also how would of that ground connection of just suddenly broke when it was working just fine previously?

All I touched in this radio was the capacitors I never touched any of the wiring.

When I said that I was thinking of an actual chassis ground connection and yes I do know how to read a schematic but like I said, when he said "ground connection" I was thinking he meant a physical chassis ground connection, not B- connection.

Also how would of that ground connection of just suddenly broke when it was working just fine previously?

All I touched in this radio was the capacitors I never touched any of the wiring.

;) Ok , so we've got the "ground" and "B-" thing worked out , great .

Now , just know that while you didn't purposefully touch any wiring that doesn't mean a wire couldn't have got bumped or nudged as you were changing your capacitors . Your best troubleshooting clue that you've given us here is that the volume control worked before you changed the capacitors , that in itself is telling you to check the installation of those new caps very carefully , it's all too easy to make a mistake and sometimes it's not easy to spot a mistake we have ourselves made (a great reason for having at least one electronics savvy friend who might spot something you've missed) ...

;) Ok , so we've got the "ground" and "B-" thing worked out , great .

Now , just know that while you didn't purposefully touch any wiring that doesn't mean a wire couldn't have got bumped or nudged as you were changing your capacitors . Your best troubleshooting clue that you've given us here is that the volume control worked before you changed the capacitors , that in itself is telling you to check the installation of those new caps very carefully , it's all too easy to make a mistake and sometimes it's not easy to spot a mistake we have ourselves made (a great reason for having at least one electronics savvy friend who might spot something you've missed) ...

Thanks, I'll probably monkey around with it more tomorrow as I spent most of the evening at the doctor's office because I accidentally cut my right pointer finger knuckle on a 1907 GE Pancake Fan Blade when I was trying to turn it off after demonstrating it to a friend of mine, and wound up with 2 stitches in my finger and a tetnus shot.

Thanks, I'll probably monkey around with it more tomorrow as I spent most of the evening at the doctor's office because I accidentally cut my right pointer finger knuckle on a 1907 GE Pancake Fan Blade when I was trying to turn it off after demonstrating it to a friend of mine, and wound up with 2 stitches in my finger and a tetnus shot.

Man that sucks , and I can totally sympathize with you . One of my other hobbies is RC planes and 10 or so years ago I almost lost a finger to a hungry propeller , by my luck it was a carbon fiber prop that disintegrated when it hit my finger after slicing what looked like a shark's gills into it , and it took about 5 hours for them to fish out all the carbon fiber chunks and sew up the mess (had like 4 different sets of X rays till they were satisfied they got all the propeller chunks out) .

Just for the heck of it , post up a few closeup pics of some of the caps you replaced , who knows something may look familiar (or unfamiliar) enough to spot the problem

Sorry, I shoulda been more specific. 'Ground end' simply means the lowest potential or no-signal end. In this case, there's a 40 ohm resistor (R22) from there to chassis ground. See if there's 40 ohms from the low end lug of the control to chassis.

(R22 may be physically distant from the control since it's part of the negative bias supply circuit.)

Sorry, I shoulda been more specific. 'Ground end' simply means the lowest potential or no-signal end. In this case, there's a 40 ohm resistor (R22) from there to chassis ground. See if there's 40 ohms from the low end lug of the control to chassis.

(R22 may be physically distant from the control since it's part of the negative bias supply circuit.)

The Candohm is still good, it measures a little high but still within tolerance, I'm getting about 53 Ohms there at the 40 Ohm section and about 215 Ohms at the 200 ohm section.

I have some pictures of the radio underside showing the capacitors I changed, there was one little spot that looked like it could of been from a component that was cut out at some point in time but there wasn't anything near by that matched it so I chalked it up to maybe a sloppy part placement job from the factory.

See pictures below.

And yes there's 53 Ohms on the low side of the volume control pot to the chassis, so that means that the negative side of the volume control pot is fine it seems.

... so that means that the negative side of the volume control pot is fine it seems.
Not necessarily. There could still be an open in the resistive element itself. If you float the negative lug (disconnect everything from it), see whether the element measures called-for resistance, or if it's open.

Not necessarily. There could still be an open in the resistive element itself. If you float the negative lug (disconnect everything from it), see whether the element measures called-for resistance, or if it's open.

yikes that's going to be a pain in the butt to do, as there's like several things hooked up to that volume control pot that will need to be disconnected as there are 5 lugs on that volume control pot and all 5 lugs have something hooked to them... :yikes:

Disconnect only what's going to the negative (low end) lug. Measure from that lug to the wiper lug, and rotate the control stop-to-stop. The meter should show a smoothly-changing ohms value, from very low to very high. (The wiper is the middle lug between the bottom and top-end lugs.)

Or does the meter show open circuit (infinite resistance) thru the full range of rotation?

Disconnect only what's going to the negative (low end) lug. Measure from that lug to the wiper lug, and rotate the control stop-to-stop. The meter should show a smoothly-changing ohms value, from very low to very high. (The wiper is the middle lug between the bottom and top-end lugs.)

Or does the meter show open circuit (infinite resistance) thru the full range of rotation?

Well I figured out what it was, a piece of capacitor lead wire got down into the volume control pot and was shorting it out, so I flushed it out with some contact cleaner and now the volume control pot seems to be working fine now.

The biggest give away was that the volume control pot wasn't measuring open but it was being rather difficult to turn so I took some contact cleaner and sprayed it into the volume control pot and sure enough that piece of capacitor lead wire flew right out of the pot and it now rotates perfectly.

OK I got the volume control issue fixed but now I've got a new problem, I'm not getting any stations in on any of the bands on this radio, and it was working just fine before I worked on the volume control issue.

It seems like this radio is developing one problem after another... :sigh:

I guess I should of just left it alone seeing as it was working fine before I replaced the capacitors in it.

I don't think I've ever repaired a radio that was this touchy before.

Do you get any noise when turning the bandswitch, or is it silent?

Do you get any noise when turning the bandswitch, or is it silent?

All I get is the electrical sound of the band switch making contact at each position and when I tune through the tuning dial all I get is a hissing noise across the dial.

I disconnected the B- Wire Lead from the volume control like you told me to when I was testing the continuity of the volume control and I also disconnected a capacitor that went to that terminal as well, but I reconnected them just like they were originally and I wouldn't think that disturbing the B- connection to the volume control pot would mess with the radio's reception capabilities.

The aforementioned disconnecting of the wires from the negative terminal of the volume control pot was the only thing I disturbed in the radio this time around, so I'm kind of confused as to what could of happened to make the radio lose reception.

Check that there is plate voltage on the 6A8 and 6K7 (pin 3 of both tubes).

Also check screen grid voltage on both tubes (pin 4 of both).

Check that there is plate voltage on the 6A8 and 6K7 (pin 3 of both tubes).

Also check screen grid voltage on both tubes (pin 4 of both).

Geez this radio is turning out to be a pain in the butt, because I have to put the radio in the cabinet to test it (the antenna is in the cabinet and the radio won't work without that antenna attached to it) and the speaker is too big for me to take out of the cabinet and plop it on my bench next to the radio, so I have to keep removing and installing the radio from the cabinet to do all of these tests. :sigh:

So what are you thinking may have happened if you don't mind me asking?

Also I rechecked the radio and it is indeed dead silent except for the popping noise it makes when changing the band switch, there is absolutely nothing on the radio reception wise when tuning through the dial not even a little bit of static or hiss.

I also checked all of the tubes and they all tested fine (they are all the original Zenith branded Tubes to this radio except for the 6A8 tube and the 5Y4 Rectifier tube which are RCA and GE Branded tubes respectively.)

Do you have a spare 6A8 to try for a sub? If not, try wiggling the 7G7, 6A8 and 6K7 in their sockets (with power on, volume high). Also try tapping them to check for intermittents.

This is a dumb question, but is there any chance the 6A8 and 6K7 coulda got interchanged?

Some 40s Zeniths would go stone deaf if the wave magnet wasn't connected. Don't forget to connect it for your tests.

:scratch2: What tube is the parallel caps shown in this picture connected to ? If it's anything "front end" related (RF amp /osc / or mixer) and it's in a grid circuit , the parallel caps may have thrown the circuit out of alignment ?

:scratch2: What tube is the parallel caps shown in this picture connected to ? If it's anything "front end" related (RF amp /osc / or mixer) and it's in a grid circuit , the parallel caps may have thrown the circuit out of alignment ?

those are the coupling cap for the 6V6s (the original was a .05 MFD but the closest I had at the time that I replaced that was 2 .033 MFD caps which I paralleled to make a .06 MFD cap.

So nothing to do with the front end.

Do you have a spare 6A8 to try for a sub? If not, try wiggling the 7G7, 6A8 and 6K7 in their sockets (with power on, volume high). Also try tapping them to check for intermittents.

This is a dumb question, but is there any chance the 6A8 and 6K7 coulda got interchanged?

I never touched any of the tubes when I was recapping this radio or when I undid the B- wiring from the negative leg of the volume control.

The only time I touched the tubes was to test them in my tube tester to make sure there weren't any dead ones, but I disconnected them one at a time so that there wasn't a chance for them to be put into the wrong socket.

I don't have any spare 6A8 tubes unfortunatly, and the weird thing is that the original owner of this radio replaced the original 6A8G tube with a metal 6A8 tube so because of that they ended up throwing out the original tube shield that went in that spot and unfortunately the metal 6A8 tube doesn't fit into the tube socket very tightly like the original 6A8G did so I have a feeling that the replacement 6A8 tube may not be making very good contact with the tube socket because the tube pins don't seat all the way into the tube socket.

I also checked the 7G7 tube and the pins looked kind of crusty looking but I wasn't sure if that would of caused the issue I was having or not (I know Loctal tubes are notorius for making bad contact between the tube pins and the socket).

Some 40s Zeniths would go stone deaf if the wave magnet wasn't connected. Don't forget to connect it for your tests.

I know, I double checked to make sure the connection was good between the wavemagnet and the radio chassis and it still seems unresponive.

OK so now I'm getting some static sounds out of the tuner at the spots where the stations would be coming in at but still no audio or reception.

I tried wiggling the tubes you suggested I wiggle (the 6A7 and the 7G7 tube) and it didn't make much difference.

So another question, can having the chassis not being completely tightened down to the cabinet cause reception issues?

... can having the chassis not being completely tightened down to the cabinet cause reception issues?
Can't think of any reason how/why it should. Question- is there any way the cabinet can be laid on its side, and the chassis slid back far enough to take voltage readings in the RF and IF areas? Or is this a large floor-standing console?

(Back in the day, this was a common accessability practice in TV service, even with console sets. It was usually done with the heavy end of the chassis down.)

Can't think of any reason how/why it should. Question- is there any way the cabinet can be laid on its side, and the chassis slid back far enough to take voltage readings in the RF and IF areas? Or is this a large floor-standing console?

(Back in the day, this was a common accessability practice in TV service, even with console sets. It was usually done with the heavy end of the chassis down.)

This is a large Phono/Radio Console it's kind of hard to tip it on its side.

This is a long shot, but.... in post# 10, fourth photo, near the center of the shot, there is a 330K (orange-orange-yellow) resistor. To its left is a yellow capacitor labeled 333K 630V. A bare lead from the resistor looks to be lying directly across a bare lead from the capacitor when you blow up the image 300%. It may just be the camera angle, but would be worth checking.

This is a long shot, but.... in post# 10, fourth photo, near the center of the shot, there is a 330K (orange-orange-yellow) resistor. To its left is a yellow capacitor labeled 333K 630V. A bare lead from the resistor looks to be lying directly across a bare lead from the capacitor when you blow up the image 300%. It may just be the camera angle, but would be worth checking.

I think that's an illusion, because the resistor you're referring to isn't actually touching that capacitor because it's about a 1/4" higher than the capacitor.

Well. I'll try and take the chassis out of the cabinet again and attempt to get the speaker out of the cabinet to put it on my bench and see if I can get some voltage measurements, the only reason why I didn't want to monkey around with taking it out of the cabinet is because with my cut on my knuckle it's hard to unscrew the screws without hitting my knuckle against the cabinet.

OK. so question, what is this coil for?
See picture attached below.

I'm asking because when I was cleaning out my volume control pot earlier with the contact cleaner I accidentally got a bunch of contact cleaner on this coil assembly and I'm wondering if me getting contact cleaner on this coil assembly might of messed something up with the radio's reception.

This is the only other thing I could think of that might of been messing things up.

Thoughts?

OK, so I don't know what I did to it, but now the tuner is working again. :scratch2:

OK well, I tried it out again now that I got the tuner working again, and the volume control quit working again and it started working like a tone control knob again.

I double checked EVERYTHING and there isn't anything wired up wrong and the volume control pot isn't open, so it seems like I'm chasing down some sort of weird electrical phantom in this radio... :sigh:

Any other ideas as to what could be causing my volume control issues?

OK so the only thing I can think of is that one of the capacitors that is attached to the negative end of the volume control pot might of went bad or were faulty, in the physical radio itself there are 2 capacitors that are going off of the volume control pot negative leg, which is weird because looking at the schematic there's only one capacitor coming off the Negative leg, which is C14 unless I'm missing something... :scratch2:

In the actual radio chassis, there's a mica capacitor that's going between the negative leg of the volume control pot and one of the taps on the volume control pot, which that mica capacitor isn't marked on the schematic (at least not that I can see of anyways) there's 2 capacitors marked on the schematic in that area that seem like they might fit the description of a mica capacitor value wise but the way they are drawn on the schematic they don't seem to connect from the tap of the volume control to the negative leg of the volume control pot, C12, which is a 350 pF capacitor is one possibility, the other is C9 which is a 25 pF capacitor, but like I said none of those capacitors appear to have a physical connection with the volume control pot negative lead and the tap on the schematic.

When you had the bottom lug of the control disconnected, did you actually verify with an ohmmeter that the element isn't open?

When you had the bottom lug of the control disconnected, did you actually verify with an ohmmeter that the element isn't open?

yes I did, it didn't measure O. L. which usually means its open, it actually gave a value of 2.5 Meg like the schematic said it should of, as for whether or not I could get a smooth up or down movement of the numbers when rotating the knob, I couldn't get it to do that because I couldn't hold the meter probes onto the terminals and turn the knob at the same time, I tried to use an alligator clip to hold one of the meter probes onto one of the terminals while I held the other one in place with my left hand and turned the knob with my right hand but the alligator clip kept coming loose and the negative lead of the probe kept falling off the negative terminal of the volume control pot so then I couldn't get any sort of readings, one way or the other.

Well, since it showed the called-for 2.5 meg, it ain't open. Since turning the control affects the tone, does it change the volume at all? And what is the actual volume level? Is it full volume, or partial, or... ? For the heck of it, try disconnecting those two tone taps. That way, the control becomes just a plain potentiometer with no junk hanging off it.

Well, since it showed the called-for 2.5 meg, it ain't open. Since turning the control affects the tone, does it change the volume at all? And what is the actual volume level? Is it full volume, or partial, or... ? For the heck of it, try disconnecting those two tone taps. That way, the control becomes just a plain potentiometer with no junk hanging off it.

The volume level is between 1/8 and 1/4 volume level, and the volume control knob doesn't affect the volume at all, all it does is affect the tone and that's it, and the weird thing is that the tone control push buttons don't do anything to the radio except for the one marked "Normal" the rest of the tone control push-buttons don't do anything to the audio on the radio.

I'm wondering if one of my capacitors that I installed in the tone control/volume control circuit wasn't faulty or defective from the factory.

Have you done any signal injection testing to isolate the problem to a single stage yet? ISTR you recently bought RF generators (and they presumably have audio generator functionality too).

Inject audio (put a .1uF in series with your generator to protect it from DC) on the audio side of the detector if the set passes audio test the IF/RF system ( injecting IF frequency from the detector to every grid and plate back to the antenna) if it doesn't pass audio then trouble shoot the audio system by moving audio injection point to every grid and plate between the detector and speaker. If you know where the buck stops in the signal chain then you have isolated the problem to the components associated with 1-2 tubes....that is a heck of a lot easier than guessing where it is out of the entire radio.

Have you done any signal injection testing to isolate the problem to a single stage yet? ISTR you recently bought RF generators (and they presumably have audio generator functionality too).

Inject audio (put a .1uF in series with your generator to protect it from DC) on the audio side of the detector if the set passes audio test the IF/RF system ( injecting IF frequency from the detector to every grid and plate back to the antenna) if it doesn't pass audio then trouble shoot the audio system by moving audio injection point to every grid and plate between the detector and speaker. If you know where the buck stops in the signal chain then you have isolated the problem to the components associated with 1-2 tubes....that is a heck of a lot easier than guessing where it is out of the entire radio.

I got it to receive radio signals again, it was the Phono/Radio Switch that was causing the problems, I got switched to phono mode rather than radio mode.

The main thing causing problems right now is the volume control still giving me troubles, and signal injection isn't going to help me troubleshoot a malfunctioning volume control pot.

I'm still wondering if it isn't something with the capacitors I installed in the volume/tone control circuit.

I really wish I would of taken a picture of the underside of this radio before I worked on it so I could of seen how things were wired up originally so I could make sure I didn't accidentally install a capacitor in the wrong spot.

does anyone have a picture of the underside of this radio that they could post so I can make sure I didn't accidentally install a capacitor in the wrong spot?

OK I got the volume control issue fixed but now I've got a new problem, I'm not getting any stations in on any of the bands on this radio, and it was working just fine before I worked on the volume control issue.

It seems like this radio is developing one problem after another... :sigh:

I guess I should of just left it alone seeing as it was working fine before I replaced the capacitors in it.

I don't think I've ever repaired a radio that was this touchy before.

After working on these old relics for well over 60 years, I learned from my mistakes. For one thing, I never "shotgun" the project. I replace components in stages. Taking out the chassis and speaker and putting it on the bench to check or find out what the real cause is. If the set works, so much the better!
Then do the electrolytics and audio coupling caps.

After working on these old relics for well over 60 years, I learned from my mistakes. For one thing, I never "shotgun" the project. I replace components in stages. Taking out the chassis and speaker and putting it on the bench to check or find out what the real cause is. If the set works, so much the better!
Then do the electrolytics and audio coupling caps.

That's probably what I should of done with this set, because it was working for the most part, except for the AVC circuit which was acting wonky, it would make distant stations that would come it pretty clear at night fade in and out audio wise which were otherwise coming in really well, and the schematic for this radio didn't have the AVC circuit marked very well.

So that's why I just decided to replace all of the paper caps in this radio because I wasn't sure which caps were part of the AVC circuit in this radio (the AVC Bypass Cap).

Also I know for a fact that this radio's orginal Filter caps are still good in this radio because a.) the radio has no 60 Hz Hum whatsoever, and b.) I just got a nasty jolt from it when I was trying to take the chassis out of the cabinet even after the radio had been unplugged for more than a half hour.

Also the interesting thing is that this radio was bone stock original, there were no capacitors replaced underneath the chassis, it still had all of the original Zenith Capacitors underneath the chassis when I got this thing and it was working like new with the original caps still in place and the capacitors didn't show any signs of having any wax dripping from them in fact about 99% of the original capacitors underneath still had their factory molding marks in the wax on the sides of the capacitors yet.

This radio has all of its original Zenith tubes in it yet except for the 6A8 and the 5Y4 rectifier tube which are the only non-Zenith re-placements in the radio.

Besides the water marks on the top of the cabinet that is presumably from a plant being set on top for years, this Radio was like brand new, almost like it was mostly a display unit for most of its life.
I'm thinking maybe once the family got a TV in the 1950s the Radio just became a display piece, which might explain why it was such a low hours set.

OK so looking at the picture posted below, was there something attached at the point circled in the picture, something like a capacitor perhaps?


https://lh3.googleusercontent.com/gWxPNKX-Mx4RPxUX8RF3pT0io5-2aWkUVfwGiB3Iq9R56xSOGtp2WihkkhvDzD0G839QsAyySqr2F b2__TrJ7f-lDUCOvgmoujR8JQQGY3R6n1Z7PBzm7Xou1cU-DNqPLDamglPYppSqbMs_RnMOd1_6O0-4GyuV0AH8BDtSop4evfw-1OsQMypyYgvHfX2CnHE0P4pYjGtVp_GGN9_xu7gXuXWByod7o-oyFCpzokPddILZJ3s11OnjAkWNEEID0ONrP__ukviMDaHDZb1u c93yHWR0EZtIR0cGd1962Lt8EweMhCv4KYGU7yBt7znPwJJPtZ zukR6wsFnjCY-HILlLB2IwMwMitaokwOaQYpazdfAwWLL5x2RladXy86m0_klXB ZLYrh2BJHtZE5xISDeHWs73RDbqbMS45oVSKfV8DDBpHILEbBR fUXwZxmn3dVUSmUJE7aFijBsc_KvT5XbhXqaQ3zLzNfSb7zhJs JJUaWoKuSKF_I05yYhl17bT2pA4ZSojU23zv-lwVtvdGk2B2lgPyvi1MqKUnQHfiKcTDDQlxJlek8ijxMyK-F0VwMjf8MH6LaSfwp3WJIixJhProT1QBeu6eRWbsdJ5xUQzgfj PjDD8Kk-gno_danILSsB6yVMr_IpTNB5J8HIUS092YooVdYzaGD1ABTZNB 6YH0vaXLUfT8Va2d6m8tA=w434-h937-no?authuser=0

I'm wondering because maybe I had accidentally wired a capacitor in the wrong spot and that's what's causing my volume and tone control problems.

OK so I figured out why my volume control isn't working, I forgot to install C11, the only problem is that I don't have that part, because I forgot to order it, because I accidentally ordered two .0022 MFD capacitors rather than a .0022 MFD and a .022MFD capacitor. weird thing is that I didn't even get that second .0022 MFD capacitor in my order, so I didn't even have that capacitor to begin with.
I have lots of .2 MFD Capacitors but I don't think that would work in that spot when it calls for a .02 MFD.

I do have a .01 MFD Capacitor I wonder if that might work in the place of C11?

To borrow the words of Homor Simpson: Doh! :twak::withstpd:

'Oly 'ell old chap!! :eek::grnbounce:yikes::banana: That's the main coupling cap from the detector TO the volume control. The audio that's getting through is residual bleed past the volume control. Value's not critical. A .01 will work fine with possibly a slight reduction of the bass.

'Oly 'ell old chap!! :eek::grnbounce:yikes::banana: That's the main coupling cap from the detector TO the volume control. The audio that's getting through is residual bleed past the volume control. Value's not critical. A .01 will work fine with possibly a slight reduction of the bass.

OK, thanks! I'll put one in there right away! :thmbsp: :music: :yes:

I got a .01 MFD put in and its working now! :music::thmbsp::D

I'm not really noticing much of a difference in the bass on this radio with the .01 MFD vs. .02 MFD because this thing had really annoyingly low rattley bass previously and I think the .01 has actually toned the bass down to a much more tolerable level so that the speaker isn't rattling my radio's cabinet anymore.

OK well I think it was a little too early to celebrate, because the volume control started acting up again all the sudden, it was working perfectly but then all the sudden the volume got loud and the tone controls quit working again and the volume control is acting like a tone control again, so something must of happened to the capacitor I just stuck in there, which is weird because it was a brand new polypropolene capacitor that was never used so I wouldn't of thought that it would of shorted out or failed open suddenly... :sigh:

I'm kind of getting tired of having to take this radio apart over and over again just to keep chasing down problems that keep cropping up one after another like this, they really didn't make this radio servicer friendly seeing as you have to go through the front and the back to remove the chassis screws and the knobs on the front are a pain in the butt to remove as well and the preset panel is also a pain to remove.

I can see why they didn't make this particular model of radio for very long.

...all the sudden the volume got loud and the tone controls quit working again and the volume control is acting like a tone control again...
By "got loud", you mean it went to full volume and you can't turn it down? If so, that suggests the bottom lug of the control has lost its ground connection (or rather its connection to R22).

By "got loud", you mean it went to full volume and you can't turn it down? If so, that suggests the bottom lug of the control has lost its ground connection (or rather its connection to R22).

No, more like it went to quarter volume and I can't turn the volume down or up anymore because the volume control just acts like a tone control again like it did before when that detector coupling cap was out of the circuit and the tone control pushbuttons aren't functioning anymore excecpt the one marked "normal" (which I'm assuming the "normal" button bypasses the tone control circuit all together).

And like I said it was working fine for about 15 minutes then it suddently quit working again.

I don't know if this is a clue or not as to what may have happened but when I first turned on the radio (after I installed the .01 MFD cap into that spot that was missing the cap for the volume control) there was a smell of melting solder like maybe something might of gotten hot enough to melt some solder, but I'm wondering if something in that detector to volume control coupling circtui got hot enough to melt the solder on that coupling cap I installed and made that capacitor come loose?
If so what would of gotten that hot in that circuit to melt the solder on that capacitor and cause it to come loose?

There's nothing associated with that circuit that should draw any current to speak of, let alone enough to melt solder. Anyhow, check for solid continuity (zero ohms) from C11 to where it connects to the IF can, and to the 1 meg resistor (R11).

From the other side of C11, check for continuity to the top lug of the vol control.

There's gotta be an open on one side or the other of C11.

Doubtful, but maybe the cap itself has gone open(?)

There's nothing associated with that circuit that should draw any current to speak of, let alone enough to melt solder. Anyhow, check for solid continuity (zero ohms) from C11 to where it connects to the IF can, and to the 1 meg resistor (R11).

From the other side of C11, check for continuity to the top lug of the vol control.

There's gotta be an open on one side or the other of C11.

Doubtful, but maybe the cap itself has gone open(?)

Well I kind of lied about that capacitor being unused, (actually it was more like I forgot) it was used as a DC Blocking cap for my Signal Generator, but I wouldn't think that that would cause the capacitor to fail prematurely, if that's actually what happened here...:scratch2:

I have a .047 MFD capacitor, would that be ok in that spot if it turns out that the .01 capacitor did end up going bad?

It'd work, but with excessive bass.

But by all means, first check continuity as suggested, from C11 to where it enters the IF can, and to resistor R22. And from the other end of C11 to the top of the vol control.

Measure from right where the leads exit the capacitor body

It'd work, but with excessive bass.

But by all means, first check continuity as suggested, from C11 to where it enters the IF can, and to resistor R22. And from the other end of C11 to the top of the vol control.

Measure from right where the leads exit the capacitor body

OK so everything checks out, according to what you said it should check out, nothing is measuring open from what I can see anyways.

I don't know if this would cause a problem or not but one of the wires coming out of one of the IF cans has crumbling rubber insulation and it does have some exposed wire although it's not touching anything.

Not sure what O.L. means. But if you suspect the capacitor, just parallel your .0033 and .0047. That'll make .008 which will give a tad less bass than the .01. Be sure and test the caps first.:)

Not sure what O.L. means. But if you suspect the capacitor, just parallel your .0033 and .0047. That'll make .008 which will give a tad less bass than the .01. Be sure and test the caps first.:)

O. L. is overload or out of range according to my manual for my digital multimeter.

Going between the side of the capacitor that attaches to the side going into the IF can and R22 I get 2.5 Meg, and then from the same side of the capacitor to the lower volume control lug (B- lug) I get the same reading 2.5 Meg, and then from that side of the cap going to the IF can to the top lug on the volume control I get 0.3 Ohms.

Just need to verify solid continuity (zero ohms) as indicated by the red lines in the shetch:

Just need to verify solid continuity (zero ohms) as indicated by the red lines in the shetch:

Well if you mean using the continuity test to see if it beeps when the test leads touch the connection, then no there isn't any continuity. I traced back to the B- source which was the filter can negative, and I get continuity up until where C13 attaches to R13 after that I don't get a beep from my continuity checker until I get to one side of C11 which gives me continuity between it and the upper Volume control lug.
Which I'm assuming is what you wanted to know.

... I don't get a beep...until I get to one side of C11 which gives me continuity between it and the upper Volume control lug.
OK good. Now put the checker from the other side of the cap to where the signal lead exits the can. If it's got crumbly insulation, it should be easy to make contact. Or use a pin to stick thru the insulation. The checker should show continuity.

If it does, this suggests C11 is bad. Try the paralleled .0033/.0047 caps for C11.

OK good. Now put the checker from the other side of the cap to where the signal lead exits the can. If it's got crumbly insulation, it should be easy to make contact. Or use a pin to stick thru the insulation. The checker should show continuity.

If it does, this suggests C11 is bad. Try the paralleled .0033/.0047 caps for C11.

Well I didn't get continuity at that point that you told me to check, so I guess that means the capacitor is fine?
I'll still try the .0033 and the .0047 together to see what happens there,
also I'm trying to replace the old crumbling wire coming out of the IF can with some new wire.

I also have a question about how to go about putting that small cardboard spacer back into place on the bottom of the IF coil that helps keep the IF coil centered in the IF can, because it came loose at some point in its life and when I took the can apart it fell out and it looked like it was held into place with a dollop of wax of the same varity that they used to insulate the rest of the IF coil with, is that just everyday parafin wax or did they have something added to it to make sure it didn't harden right away so that they could brush it on to the bottom of the IF can spacer?

I would like to put that spacer back on and make it look as original as possible seeing as this is such a low hours set and is such a perfect candidate for restoration.

Hey, since this is a phono/radio rig, have you cleaned the phono/radio switch with Deoxit or similar? Jeez, I shoulda thought of that before. Senior moment.:bash:

Hey, since this is a phono/radio rig, have you cleaned the phono/radio switch with Deoxit or similar? Jeez, I shoulda thought of that before. Senior moment.:bash:

No, I haven't, I thought about it but haven't yet, but maybe, I should of tried that first.

I still am going to fix the wire for the IF can because it had crumbling wire insulation to the point that it had exposed wire.

Now that you've isolated which side of C11 the break is at, it's 99% gotta be in the switch.

On that cardboard spacer thingy, maybe a dab of 5 minute epoxy(?).

Now that you've isolated which side of C11 the break is at, it's 99% gotta be in the switch.

On that cardboard spacer thingy, maybe a dab of 5 minute epoxy(?).

OK so I got the IF Can rewired and I cleaned the Radio/Phono mode switch and I put the radio back together and Its completely dead again, no reception whatsoever, and I made sure I wired the new wire in at the right spots and everything and I can't get any signal out of the radio whatsoever, not even a bit of static, the only noise it will make is the popping noise of the tone control switches being pressed and that's it.

I even tried fiddling with the phono/radio switch and its still not responding.

Any ideas as to what may have happened?

If you had the coil assembly completely out of the can to work on it, how many wires did you have to disconnect/reconnect?

If you had the coil assembly completely out of the can to work on it, how many wires did you have to disconnect/reconnect?

I just disconnected 2 wires and that was it, the wire that attached the IF can to the 1 Meg resistor and the grid cap wire which I had to disconnect to get the coil out of the can.

When I disconnected the grid cap lead I just went ahead and replaced the wire because the old grid cap wire was starting to disintegrate, and I tried to make sure the 2 wires connected back to where they were supposed to go by doing the wires one at a time.

So I don't know, the only thing I can think of is that maybe I accidentally disconnected one of the coil wires that went to one of the two terminals I removed the wires from.

Yikes.:eek: That's the wrong IF can if it has a grid cap lead coming out the top. It's the first IF. Probably a fine coil wire got broke.

All this while, I assumed we were talkin' about the second IF can, the one that has the detected audio lead coming out the bottom. Never assume. Lesson learned. :nerd:

Edit:
If you find a broken wire in the 1st IF can, here's a handy-dandy way of stripping hair-fine wire that doesn't involve mechanical scraping. It really works. Scroll down to post# 26 - http://videokarma.org/showthread.php?t=257295&page=2

Yikes.:eek: That's the wrong IF can if it has a grid cap lead coming out the top. It's the first IF. Probably a fine coil wire got broke.

All this while, I assumed we were talkin' about the second IF can, the one that has the detected audio lead coming out the bottom. Never assume. Lesson learned. :nerd:

Edit:
If you find a broken wire in the 1st IF can, here's a handy-dandy way of stripping hair-fine wire that doesn't involve mechanical scraping. It really works. Scroll down to post# 26 - http://videokarma.org/showthread.php?t=257295&page=2

Ah yes, asprin trick, I think I read about that on here before, but unfortunately I don't have any on me right now.

And I didn't realize you were talking about the other IF can, because the only wire lead I saw going to that area was coming from the IF can with the Grid Cap, I didn't see the wire coming from the IF can without the Grid Cap.

And I didn't realize you were talking about the other IF can, because the only wire lead I saw going to that area was coming from the IF can with the Grid Cap, I didn't see the wire coming from the IF can without the Grid Cap.

R11 and C2 form the AVC filtering. Take a look at the schematic and you will see that each end of R11 goes to a separate IF can.

Deleted bad info. Disregard sketch, correction shown in post# 83

Deleted bad info. Disregard sketch, correction shown in post# 83.

R11 and C2 form the AVC filtering. Take a look at the schematic and you will see that each end of R11 goes to a separate IF can.

OK, well it was kind of hard to see that in the actual radio chassis because of how they had it wired up.

When you get the newest problem fixed and ready to revisit the original problem, the open is almost certain to be in the radio/phono switch, per the attached sketch. To verify, put a jumper across it and see if the audio is restored and the vol control works correctly.

OK, well I'm kind of wondering if it isn't the radio/phono mode switch that's causing my problems because it cuts in and out when I flip between modes (when it was functioning before this latest problem occured.)

OK well I was able to verify that the wiring in the IF can was fine, and that the problem definitely most likely lies in the Phono/Radio switch.

So now to try and figure out how to fix that issue...:sigh:

R11 and C2 form the AVC filtering. Take a look at the schematic and you will see that each end of R11 goes to a separate IF can.

Actually I think the schematic is wrong, because in the radio itself both IF cans go to only ONE SIDE of R11, and I didn't touch that wiring except to replace the old dry rotted wire from the 1st IF can and I just wired that wire back to where it was previously, and I didn't touch the wiring to the 2nd IF Transformer because the wiring was fine in it.

Have you tried Deoxit'ing the switch yet?

When you get the newest problem fixed and ready to revisit the original problem, the open is almost certain to be in the radio/phono switch, per the attached sketch. To verify, put a jumper across it and see if the audio is restored and the vol control works correctly.

How do I jumper the Switch? Because I think I definitely have it narrowed down to the switch being faulty, because with the volume control knob turned up completely I figured out that the radio is actually working but with barely any audio.
And when I try to monkey with the mode switch I can't get it to do anything.

Have you tried Deoxit'ing the switch yet?

Yes I have, 3 times and it hasn't made a difference, if anything its made it worse.

To jumper the switch, just trace the wiring. Trace it from where the signal wire exits the 2nd IF can and goes to the switch. And trace from C11 to the switch. Put the jumper across the appropriate two lugs.

If perchance you don't plan on using the phono, just leave the jumper in place.

To jumper the switch, just trace the wiring. Trace it from where the signal wire exits the 2nd IF can and goes to the switch. And trace from C11 to the switch. Put the jumper across the appropriate two lugs.

If perchance you don't plan on using the phono, just leave the jumper in place.

OK, thanks, I'm assuming the lugs I'm jumping are on the switch itself?

I think it is definitely the switch because I'm not getting anything out of radio when I touch the Grid Cap of the 6F5G Audio Amp tube unless I jiggle the switch several times, and even then the hum from touching the grid cap of the 6F5G tube goes away after awhile.

To jumper the switch, just trace the wiring. Trace it from where the signal wire exits the 2nd IF can and goes to the switch. And trace from C11 to the switch. Put the jumper across the appropriate two lugs.

If perchance you don't plan on using the phono, just leave the jumper in place.

I think I could probably find a replacement switch over at Mouser or Digikey.

Its just a standard 6 Lug SPDT Switch.

In fact here it is on Mouser. https://www.mouser.com/ProductDetail/Switchcraft/46203MRX?qs=iwvYsH9bSFa6UvWT6%2FVdLw%3D%3D

Dude, I gotta apologize. Been giving you bad info. Come to find the switching is done on the downstream side of C11, not on the upstream as in previous sketch.

Thus to jumper the switch, the wires you would trace would be:

1.) from the top lug of volume control to the switch.

2.) from the downstream side of C11 to the switch.

Jumper would go on the appropriate two lugs of the switch.

Damn, sorry for the screwup

Dude, I gotta apologize. Been giving you bad info. Come to find the switching is done on the downstream side of C11, not on the upstream as in previous sketch.

Thus to jumper the switch, the wires you would trace would be:

1.) from the top lug of volume control to the switch.

2.) from the downstream side of C11 to the switch.

Jumper would go on the appropriate two lugs of the switch.

Damn, sorry for the screwup

Its ok, so I'll just jump the switch that way.

Turns out there's an obscure little subnote to the main schematic, showing the radio/phono switching diagram. It's difficult to decipher, but shows the switch as DPDT (double pole/double throw), with the second section switching B+ on/off to the mixer stage.

I would seriously de-consider replacing the switch as that could turn into a real can of worms.

Turns out there's an obscure little subnote to the main schematic, showing the radio/phono switching diagram. It's difficult to decipher, but shows the switch as DPDT (double pole/double throw), with the second section switching B+ on/off to the mixer stage.

I would seriously de-consider replacing the switch as that could turn into a real can of worms.

Well I really wanted to use the record player on this thing, as it has a nice modern VM 1200 series record changer installed in it.

Right now, can you put a record on and play it without any intermittency when you wiggle the switch?

Well I really wanted to use the record player on this thing, as it has a nice modern VM 1200 series record changer installed in it.
It seems like the radio from h*ll. Its hard to believe that you had so much grief with it. You should replace the switch with a decent toggle switch, mounted on the back of the chassis. Easy to get at a bigger hardware store.

Right now, can you put a record on and play it without any intermittency when you wiggle the switch?

I don't know as I currently don't have the record player hooked up right now because I'm trying to fix the drawer glides because the original drawer glides were bad.

It seems like the radio from h*ll. Its hard to believe that you had so much grief with it. You should replace the switch with a decent toggle switch, mounted on the back of the chassis. Easy to get at a bigger hardware store.

I was thinking the same thing, this thing seems like its possessed.

The switch on the back won't look as complete as having the switch in the front like it originally had. I think I found a switch over at mouser that might work in place of the original.

Actually I think the schematic is wrong, because in the radio itself both IF cans go to only ONE SIDE of R11, and I didn't touch that wiring except to replace the old dry rotted wire from the 1st IF can and I just wired that wire back to where it was previously, and I didn't touch the wiring to the 2nd IF Transformer because the wiring was fine in it.

I don't think the schematic is wrong. You'd better retrace your wiring and verify where both ends of R11 terminate.

I don't think the schematic is wrong. You'd better retrace your wiring and verify where both ends of R11 terminate.

I did, and only one end of R11 terminates to both IF Cans.

Riders is known for making mistakes in their service data, so I wouldn't put it past them to accidentally misdraw the schematics.

I did, and only one end of R11 terminates to both IF Cans.

Riders is known for making mistakes in their service data, so I wouldn't put it past them to accidentally misdraw the schematics.

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

After finally deciphering the switching subnote below the main schematic, and correctly drawing it (finally:sing: in post# 83), R11 is not relevant to the discussion since it's not involved in the switch circuit.

The second gang of the switch is used for switching mixer (6A8) screen grid voltage on/off as shown:

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

Perhaps that second “IF can” is actually the antenna coil?

The schematic appears to be correct, from my understanding of the typical AVC circuit design.
jr

Perhaps that second “IF can” is actually the antenna coil?


Now there's a real possibility. :D

Fine if the radio works like that, but the Riders schematic makes sense as shown. The right end of R11 has audio present and the left end becomes the filtered AVC voltage that would normally be feeding the grids of the RF and 6K7 IF amp.

Either that or my set was a Friday special and was miswired from the factory but wasn't caught by Quality Control because it still worked that way...

Either that or my set was a Friday special and was miswired from the factory but wasn't caught by Quality Control because it still worked that way...

I'm more leaning towards this. ;)
Perhaps that second “IF can” is actually the antenna coil?

I'm more leaning towards this. ;)

It would explain why this thing is acting up like it is.

I'm more leaning towards this. ;)

I would wire it per the schematic. You stated there was an issue with the AVC not working properly.

I would wire it per the schematic. You stated there was an issue with the AVC not working properly.

Yeah. The audio would fade in and out even though there wasn't anything wrong with the signal.

I was thinking it was a problem with the AVC bypass cap being leaky but if you would of seen the condition of the original capacitors in this radio and the fact that it had almost all of it's original tubes in it yet, I'm beginning to wonder if this radio was a low hours set because of that wiring issue and AVC problem.

Any update on jumping those two switch contacts per old_coot88 directions? Undoubtedly you have two short lengths of wire, resistor clippings, anything?

Any update on jumping those two switch contacts per old_coot88 directions? Undoubtedly you have two short lengths of wire, resistor clippings, anything?

Not yet, been kind of busy the last couple of days.

Plus, I've been kind of taking a break on working on the radio part to try and work on the record player drawer trying to figure out how best to make some modern euro style drawer glides work with the record player drawer since the original drawer glides were broken and they were a custom job for this unit.

How many “IF cans” do you see on the radio chassis?
What does the other end of r-11 appear to be connected to?



jr

How many “IF cans” do you see on the radio chassis?
What does the other end of r-11 appear to be connected to?



jr

There's 2 IF cans and a 3rd can that looks like it should be an IF can but it doesn't have any trimmer caps on top like the actual IF cans do, it appears to be just a coil of some sort inside and that's it, no trimmer caps on the bottom either, maybe the RF Coil?

The other side of R11 from what I could see looked like it attached to the tone control panel/circuit somewhere.

Well I had a tree fall through the roof of my house and so I won't be able to work on my radio for a while until they get the roof and everything fixed, because the side of the house that the tree hit was the side of the house where my workshop was at. :sigh::tears:

It happened to us. Expensive and time-consuming. I hope you're repairs are all done soon.

It happened to us. Expensive and time-consuming. I hope you're repairs are all done soon.

I hope so too. Because I previously had my workshop redone because of mold issues last year and that took all but half a year to get done. :sigh:

I hope so too. Because I previously had my workshop redone because of mold issues last year and that took all but half a year to get done. :sigh:
We really had strange weather patterns in the Midwest this early summer. Heavy winds, excess rain in many areas, power outages and really oppressive heat. :thumbsdn:

We really had strange weather patterns in the Midwest this early summer. Heavy winds, excess rain in many areas, power outages and really oppressive heat. :thumbsdn:

The thing is, this tree fell because of termite damage not because of a storm...:scratch2:

The tree fell in two parts so far, the first section fell on the neighbor's house (it was actually their tree) and the second part fell on my house.