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Capacitor voltages - Printable Version

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Capacitor voltages - fossilexpress - 07-26-2013

Planning on a total recap of a 40-190. Some of the capacitors have already been replaced, don't know if correctly. I went to the list of replacement parts, and with the exception of two "Electolytic cond." (Parts #58 and #61), the voltages are not given. They generally read something like "Tubular cond. (.05 mfd)".
Based on a previous thread, should I just get all of these as 600 volts?
BTW. Will also be replacing all of the resistors, as recommended.

Thanks - Roy

RE: Capacitor voltages - Raleigh - 07-26-2013

The capacitors will have the voltages printed on the side of the body. Generally, radio restorers use 630 volt caps for almost everything, so the original voltage isn't very important. Suppliers to the old radio hobby generally stock this voltage in non-electrolytic caps, and 450 volts in electrolytic caps.

The only reason to use lower voltage caps would be size, but modern 630 volt caps are so much smaller than old paper caps in any voltage that you shouldn't ever need to buy voltages lower than 630.

There are a few places that Philco used 1000 volt capacitors. You should check caps in the final output circuit to see if they have 1000 volts printed on the side before you order capacitors. There may be 2 of them in the 40-190 , possibly #52 and #55. It should be easy to find capacitors with greater than 1000 volt ratings in either the poly or ceramic styles.

I buy most of my caps from justradios.com. They have everything I need for tube radios. I usually use the yellow axial poly type, but some people like the orange drops (or dips.) Just Radios also has capacitors in the old pre-WWII capacitance values, like 20 uF instead of 22 uF and so forth. Not that this matters much, but I still like to use original values.

RE: Capacitor voltages - fossilexpress - 07-26-2013

Thanks. I did notice that one of the replacement caps that the previous owner put in (but did not solder!) was a 1000 V. Will check. AGain - this group is wonderfully helpful.

RE: Capacitor voltages - Raleigh - 07-26-2013

It may not be necessary to replace all resistors. Many old resistors stay very close to their original values, but many others drift high. If you have an ohmmeter, you can measure them and reject any that are too far out of spec.

"Too far out or spec" is a matter of opinion. Many restorers keep anything within 20% of spec, but I am a little pickier. If a resistor is outside of 10%, I'll usually replace it. If it is a 5% part and out of spec I'll replace it with a 5% resistor. I mostly buy 5% resistors, but I have made exceptions on occasion to use 10% parts to replace 10% or greater parts.

RE: Capacitor voltages - codefox1 - 07-28-2013

Agree, don't have to replace all carbon resistors, but as they age they do drift, and become unreliable in other ways, as in temperature sensitive and porous, or noisy. Well, if the set is not too complicated and difficult to work on, a couple of dollars in nw resistors is worthwhile and easy enough to do whilst replacing the capacitors. Long term reliability and performance improved if done. I do this almost all the time now.

RE: Capacitor voltages - fossilexpress - 08-01-2013

Two things: went back and checked the replaced cap. it was 1600 V. Can I assume this is overkill and I can use a 1000? There is an original 1000 v elsewhere on the circuit. Second: how do I determine positive and negative on the two electrolytics? They are both in a can, but I think they are single units. I was going to cut the wires and just put in two new ones, leaving the cans in place. I looked at the schematic, but it seems like a non-standard way of representing a capacitor. So is the center of the can positive or negative?

RE: Capacitor voltages - BrendaAnnD - 08-01-2013

Can center is positive.

RE: Capacitor voltages - fossilexpress - 08-01-2013

Thanks!

RE: Capacitor voltages - morzh - 08-02-2013

If we are to trust the sch the voltage across 61 is 270V and across 58 - 185V.

Now granted that is working loaded voltage and it can go up to 40% up if unloaded, and this is why we want some margin on the WV plus the margin for derating, so where it is 270V I would use 450V cap, sure. 600V will take all the questions out.
1000V? Total overkill. 1600V? More overkill.