The PHILCO Phorum

Hi -

I am about to restore a 40-120 and I found the schematic on nostalgia air .com

I am trying to build an order for the replacement capacitors and hit a bump.

The schematic gives me the uf ratings for each capacitor, but it doesn't list voltages like most schematics.

I know for most caps I can use their 640V replacements, but for the electrolytic caps, I would like to be close to the original voltage ratings.

Can anyone please tell me what voltage ratings the e-caps should be?

Or - does anyone have a 40-120 schematic that has the voltages listed for the caps?

I appreciate any help you can provide.

Many thanks,

John

Since it is a series strung set (no power transformer) the B+ comes directly from the line voltage. Probably what was in there were 150v
electrolytics but I would go with 250v or 350v new ones. 350v is probably
overkill but I would err on the side of higher voltage rating rather
than 150v. Lifetime ratings for electyolytic caps depend on temperature
and how close to the rated voltage rating you are running them.

Try to get 105 degree C rated caps also.

Herb S.
Ithaca NY

Thanks - I will order the 350V.

Also, if your wondering about a certain cap, you can usually look at the cap itself. It should say the voltage rating on it.

I think you will be just fine with 150V caps considering you are working at about 85 - 95V.
If the price difference is low, then by all means buy 105C 350V caps.

I would emphasize temp rating vs voltage.

The schematic here http://www.a1radio.com/Schematics/Philco%2040-120.pdf shows 120v across the first electrolytic. If the rectifier heats up any faster than the rest of the circuit, it will be higher than that. I wouldn't use 150v.

I agree, I'd go with 250v if available.

Herb

Regarding the feedback:

RE: Philco 40-120 Restoration
The schematic here http://www.a1radio.com/Schematics/Philco%2040-120.pdf shows 120v across the first electrolytic.

That's likely due to my immaturity at reading schematics adequately. As an IT programmer by training I like viewing everything as a "system" and I can roughly follow the circuit, but still working on the mechanics of completely comprehending the schematic.

Thanks for all the feedback!

Secondary question: is it OK if I use a 22uf instead of a 20uf, given I am pushing up the rated voltage on the e-cap?

Yes it is OK to use a 22uf.