[morzh]

After having attached the line cord, I checked the switch and the volume pot again. That is, I did check the switch before. Intermittent. But it's the pot that is bad. Even after restoring the wiper to rheostat contact with Fafer lube, the rheostat itself is over 3M at the nominal of 350K.
I think, a call to Mark Oppat is going to happen.

[Arran]

Mike;
So if you check the resistance from end to end the volume pot reads 3 meg Ohm? I could see 1 meg maybe, if someone had changed the control, but something weird is going on, it would be more normal for the resistive element to wear out, which would men that the wiper would not make contact. If it were my set I would investigate, but then again I've had to clean out a lot of controls in farm battery radios so I'm not too concerned about breaking something.
Happy Christmas
Arran

[morzh]

Arran

The control is original. The wiper is some sort of round brass plate, that probably just digs into the carbon every time it's turned. And, yes, end-to-end is between 2M and 3M. Right at the leads. I will have to check the wiper contact again after yesterday's F5 bath dries up but this is not expected to change the rheostat's value.

I will see if I have a stash of suitable values parts; likelyh not; the values would be from 250K to 500K or so.

[morzh]

After having ordered the pot from eBay (cheap enough, $10 or so and free shipping) I realized I have a small box in my organizer labelled "potentiometers" where I found 3 pots, two of which fit the application, and one of which was fully functional.
The "D" on the shaft is a bit deeper so will have to be padded when the knob is installed. The ground was provided separately (on 60s the lower lead is grounded to the case and the chassis).
I gave it a profilactic F5 injection.

   
   


Now I am almost ready to power up. After inspecting the coils.

[morzh]

Remembered that I wanted to clean the tuning cap.
At the same time the rust spots are better accessible without the cap in.
Washed it in hot soapy water.

Before
   

After
   
   



When I blew some air at it, small mica flakes started coming out. Never had mica disintegrating before. Guess I buy some mica sheets and replace it, if needed.

[jrblasde]

I was unaware that these air tuning capacitors contained any mica. Are the individual stator and rotor plates coated in mica?

[morzh]

No. The padders on the side, small caps in parallel to each section, contain mica.
Those two brass screw/nuts on the side.

[jrblasde]

The trimmer caps, that’s right. Somehow I didn’t consider those.

[morzh]

Yep. I ordered some mica pieces for TO-type transistor heatsink mounts; should come tomorrow. Not expensive and will likely last me 'till my demise, whether it will take 20 years or 1 year.

[jrblasde]

Let’s hope for 20. We need your expertise! Surely your family hopes for 20 as well.

[morzh]

I hope that they hope

[morzh]

Reassembled the tuning cap, it works fine, the gear works fine, and the padders also work fine. No short, nice capacitance change, so I think I will use it the way it is now.

I received a volume pot, but will stash it for the future projects, and also the mica sheets will be reserved for those just in case situations.