[hsusmann]

Madmurdok,

I had to do a similar coil re-wind on a 60B last year.
Nice job! Also nice job on the tin box re-stuff.

Herb S.
Ithaca NY

[TV MAN]

Here are the pics of my electrolytic cap rebuild. I put some thought and time into this one, took some ideas that were mentioned, and this is what I came up with.

I showed the disassembly in an earlier post. I used a propane torch to heat the bolt. It came out after some gentle rocking and pulling. It did not damage the threaded area. I cleaned up the rubber gasket, then used a brass screw, soldered to it, then put together.
   
   
The outer can slipped over the base, and I used 3 little dabs of JB quick to attach. So far, I havent broken them off. I think I can heat and remove if I need to replace the cap sometime. I did have to make sure I had the metal cans lined up with the ground strap. I cleaned both and checked for continuity. It looks factory from over and under. I didnt have to change any wiring. Here is the finished product.
   

[morzh]

Tim,

Excellent. Neat idea with trhe bolt also.
Just watch when you tighten it so the whole thing does not twist.
BTW what cap is it that you used here to stuff it? I mean, type, year and mfr.

[TV MAN]

So far, things seem solid. The cap I used is a Solen Fast metalized polyprop 6.8mf, 630v. non polarized. It is made in France. Cost $4.50 from AES. PART # C-FS6D8-630. I did this on the reccomentation of another member (Greg I think). It is working fine.

[morzh]

Like I mentioned before, one of my caps in 90 was exactly the same, but the insulator disintegrated once I touched the nut when I was taking the cap out so I did not have the chance of trying to use a bolt.

[TV MAN]

I am still having a few remaining (and stubborn -irritating-time consuming-intermittent) issues that I am working out, but in general, the 70 is now playing. The worst, and biggest hangup is an intermittent volume issue, which I "think" I have traced back the the RF side of the volume control. I'm not 100% sure it is all the problem, but is definatly contributing to fluctuations in the volume. At this writing, I have both sides of the control bypassed with a series of fixed resistors and change the volume by the antenna. I am looking for a solution. It needs a control. Cleaning seems to help - for awhile.

[morzh]

Tim

Is yours the dissassemblable type (mine is not)? If yes that would solve all problems.
Although from the looks of it I am not sure it could be easily opened. Mine certainly could not - I sprayed Deoxit through rivets.

I guess if you really prove that it is the pot and no amount of cleaning without opening helps, maybe it would be worth trying to open it then. Could be tedious though.

[jerryhawthorne]

Tim, with the specs on the pots and if you can't get them working properly, it might be time to get in contact with Mark who assembles pots from new stock. He will need the resistance and taper.
Jerry

[morzh]

Not a bad idea, I did not know he does that. Good source for the future.

[jerryhawthorne]

Here is a link to his site.
Jerry
http://www.oldradioparts.net/controls.html

[TV MAN]

Thanks guys. I'm trying to contact him. This may be the solution I am looking for.

[morzh]

Just make sure you did isolate the problem 100%.
BTW you did check the integrity of that insulating centering washer between the pot and the chassis?

[Joeztech]

You might find a recent type variable control to temporarily connect into the circuit while having the old one completely disconnected and see if it solves the problem you are experiencing with it. Then you will know for sure if the problem is solved. Make sure the case of the control is grounded properly while doing this to eliminate hum and extraneous signal pickup though.

Joe

[TV MAN]

THE GREMLIN LIVES! There arent too many problems as irritating as a persistant intermittent that fixes itself, then breaks again. I recall the washer on the volume control as ok. Right now, I have the control bypassed with a series of fixed resistors, and it behaved for several days, then - it returned! I have been playing the radio almost daily by the bench while on another project. I had determined the problem is in the signal circuit, not the power supply. I have tapped, froze, flexed and checked to the point of stupidity. Anyway - I think I may have found the culprit, or at least, something that is contributing to the problem. The #4 trimmer on the tuning cap. It had been real touchy when aligning and crackeled a lot. I had tapped and messed with it, but finally I hit it a certain way with a plastic tool, and bingo! The volume started jumping and the crackeling started. It is way worse on the higher freq's, which is how I found it. I usually listen to a station at 800khz. It is also right beside that hot running 47 output tube.

I was suspicious of this before and removed the screws and cleaned, but didnt get it to act up since. Now, I can push on the washer on the side near the tube and sometimes get the crackeling sound and the volume jumps up or down. Sometimes not. I am not talking about pushing down in a way that will adjust the cap, as I have done this and know how it sounds. This sounds like a bad connection somehow. I had a lot of trouble when adjusting this one. Has anyone removed and cleaned this or replaced this part? Any thoughts?

[morzh]

Well, good, Tim. I never repaired one of those but them being simply a copper leaf and a piece of insulation you could see if you have some insulation problem. I am sure it can be replaced with a piece of mica from a donor cap or in my case there was some material, like mylar or something.