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Electrolytic Capacitors - Printable Version

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Electrolytic Capacitors - Guest - 05-13-2008

I'm having trouble finding 12 mfd and 8 mfd capacitors rated at 600VDC.

Help.

Thanks,

Gary

- Chuck Schwark - 05-13-2008

12 and 8 uF are not standard values any more. Use 10uF. caps and you'll be ok. Electrolytics have a +/-20% value tolerance anyway.

Chuck

- exray - 05-13-2008

Whats a recommended source for 600 volters?

-Bill M

- Chuck Schwark - 05-13-2008

I think either Mouser or Digi-Key carry them.

Chuck

Electrolytic Capacitors - Guest - 05-13-2008

I can't find 600V 10mfd at either DigiKey or Mouser

- Chuck Schwark - 05-13-2008

Parts Express maybe? I know some house has them...

Anyone else remember who???

If no luck you may have to stack two 450 volt caps (900 volt rating then, but half the capacitance of series pair so double the cap values) to get what you need in voltage rating. Be sure to use equalising resistors across every stacked cap.

Two 20 uF/450 volt electrolytics, in series, equals one 10 uF/900 volt cap. Bridging each cap with a 100-150K, 1/2 watt resistor equalises the voltages across each cap.

Chuck

- Ron Ramirez - 05-13-2008

I don't remember who right now...LONG day at work...

Mojoman, what sort of radio do you have that requires a 600 volt electrolytic??? I'm frankly not familiar with any Philco that fits that description...not even the 37-690 or 38-690 sets.

- Guest - 05-14-2008

It's a 42-365. I thought the PS filter caps were 600 V. I'll check again, I may be wrong.

- Ron Ramirez - 05-14-2008

Okay. Here are the factory specs for the electrolytics used in Model 42-365:

(37) Dual, 8 and 8 uF, 475 volts (per 1946 replacement 40-3003) - Part No. 30-2476
(60) 12 uF, 400 volts - Part No. 30-2471

Now let's look at the circuit. The input filter (60) sees 320 volts across it according to the schematic. Given today's higher line voltages, and using modern, more sensitive multimeters that do not load down the circuit under test, that voltage may actually be around 350 or so.

Output filter (37A) shows 190 volts across it; you can count on 225 or so.

The extra electrolytic for the B+ line applied to the plates of the mixer and oscillator tubes shows 160 volts across it. In reality, that is probably in the neighborhood of 175.

Thus, armed with this information, it is safe to assume that 450 volt electrolytics will be just fine for this radio. In fact you could probably get by with 300 volt electrolytics for the two 8 uF units, but to simplify things, you may wish to go ahead and use 450 volts.

8 and 12 uF are no longer standard values. 10 uF will be fine as substitutes for all three.

- Guest - 05-15-2008

Ron,

Thanks for the detailed information. I will proceed accordingly.

- Doug Houston - 05-15-2008

RON: Here's one for ya. I have a Philco chassis that was in a office building PA system. It had been a custom built outfit, with an RCA-furnished manual motor board.The reeceiver chassis was a modified Philco 91 set, and this is where it got interesting. There was a power amplifier with this set that used 2-81 rectifiers, and 2-50 outputs!

Have you ever known of Philco to use Push-pull 50 outputs? I never have. I have all of those pieces as I bought them, years ago at AWA in Canandaigua. At that time, even the 81's and the 50's were there. I've never fired up the chassis.

- Ron Ramirez - 05-16-2008

Hi Doug

Your unit probably has an "INTERNATIONAL PHILCO" decal, yes? Those big modified Philco radios with external amplifiers and (sometimes) phonographs were a joint venture of Philco and IBM! These were produced for schools and industrial use.

This is mentioned in the History section of my website, with a couple of photos.

I've never heard of a Philco home radio that used a Type 50 or 81 tube.