[morzh]

Now I think it is ready.

I had some braided wire, so I used the braid instead of the broken one, connecting the tuning cap to the chassis.
   

All assembled:

   

I also forgot I still ahd the cap from the volume pot wiper not installed. At the same time I remembered I did not check the AVC resistor, which turned out to be over 6M vs 2M required; it also got replaced.

All done now.

   


Possibly will try power-up tonight.

[morzh]

Sure'nuff.

Before I plugged it in, I decided to see the continuity.
After not seeing it, I remembered I put a cap in series, so I switched to the capacitance meter. Still no luck.
So I eventually did what I needed to do before: check the power switch.
See the first line.

Will have to open it and try to fix.That is, I could power up without it, but will have to do it anyway, so why not now.

The fun copntinues...

[Arran]

Mike;
  I looked at the schematic for that set, what an odd duck. Why would they use two filter chokes, and a field coil speaker, it almost defeats the economic advantage in building an AC/DC set over an AC one? I have a Kadette radio from the same era, 1936, and the only choke is in the field coil speaker. James Skinner must have been taking time off when this design was approved. 
  By the way, I think that the two shaft bushings may have been a phenolic material, possibly to isolate the control shafts from the chassis, otherwise they likely would have pressed a brass bushing in each hole, and called it done.
Regards
Arran

[morzh]

Arran

Yes, odd.
This said, one of the choke (the 2200 ohm one) quit, and it was working with overload (it is a 10mA choke that potentially saw 12-13mA current).
They might've wanted to really filter the output stage power to possibly diminish hum (I am yet to find out what it is) and so they used a separate LC with a lower DCR/higher current capacity choke, but they might've also wanted to decouple the output from the RF/OSC stage, so they used two.

Talking about odd: using the battery for the 1st Audio bias, how'bout it?

And yes, the bushing is, I think, a phenolic-impregnated fiber. So my nylon one should work just fine.

[Arran]

Those bias cells are an odd idea, but they are (unfortunately) quite common in Canadian Rogers, and Canadian Marconi sets, most of those use two of the wretched things. I could be wrong but I think the 37-604C may have been the only Philco model to actually use a Mallory bias cell, I don't think that even their battery operated radios did, they had "C" batteries sometimes, but not under the chassis. I have a Canadian Stewart Warner 6 volt set that uses a pair of them, in series, under the chassis, which is a little more understandable since the set uses battery tubes, so directly heated cathodes/filaments but I could never wrap my head around why an AC operated radio should incorporate bias cells when there were plenty of competing makes and models that never used them. In the case of Rogers built sets, my 10-60, a 1935-36 model does not have bias cells, they used cathode resistors, and bypass caps instead, those silly bias cells really seem like the answer to a question that nobody was bothering to ask. Even the question of patent royalty avoidance doesn't make sense since all companies in Canada belonged to a patent pool, which is why you occasionally see a Philco model with a factory installed RCA jack.
Regards
Arran

[morzh]

So, I took Deoxit D, lifted the cardboard dust cover from the pot, and, having located some openings, sprayed a little of it in.
I tried to keep the pot upright, so the cleaner does not go to the pot section.
Within a couple of minutes I had good contact in closed position.
Then I dripped some F5 to the shaft, in hope it penetrates to the rheostat and worked it a bit.
Will let it dry first.

[MrFixr55]

I used WD40 (gulp) to clean several toggle power switches for RCA Radiola 16, 17, 18 and 60 sets. However, this is before I bought the DeOxIt D and R5 Fader Lube when I got into restoring Audio mixers and PA systems.

I have an RCA 6BT that use 4 of those Mallory bias cells in the IF (-2V) and Convertor (-4V) AVC circuits (As if the bias developed by the AVC circuit was not enough). My 5BT uses 2 cells (2V on both the IF and Converter grids through the AVC circuit). Seems to work fine with the cells bypassed, but I am in a local area with plenty of stations and I run the radio on a power supply so I am not toasting B Batteries. The Bias for the Audio is an entirely different story. The bias voltage is there from 5 AA alkalines.

[morzh]

R5 is not Fader Lube. R5 was power booster for original contact cleaner.

F5 is the Fader lube.

[MrFixr55]

(Insert Homer Simpson "DOPF" Here.)

When all fails, look at the can. Took the Ron Ramirez advice, red Caig DeOxIt BAD for pots, green DeOxit GOOD for pots. The contact cleaner (Dunno the Caig product code, I am too lazy to go to the shop now) is red. The F5 can is green and states that it is for pots and faders. Both products are excellent.

[morzh]

Yep. F5 is green, D5 is Red.


Red is Bad.
Green is Clean.

[morzh]

So, I put the wires back to the power switch, plugged it in, slowly increasing the Variac output...nothing. No DC, not even AC.
Eventually, after 5 minutes, I remembered that some plugs, if fully inserted into my Variac (bought new, but, well...Chinese) do not make contact, so I pulled it back a little bit.
Briefly saw the AC, then checked the DC voltages on the caps, then I pretty much rotated the tuning cap and pulled in the local station.


Here's the video.

https://www.youtube.com/shorts/PcZLxpJqnr4

It's a start.