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/gW...-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.

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.

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(?)

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

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.:)

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:

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.

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:

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(?).

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?

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

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.

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.

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

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:

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?

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.

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.