1959 Airline WG-5061A

[Phil Nelson]

Yes, with electrolytics it's usually OK to go up (sometimes quite a way up), but never down.

In a pinch, wiring two caps in parallel adds their capacitance together. To keep life simple, I normally do this with two caps rated for the same voltage. (If you use caps with unequal voltage, the voltage rating is the lower of the two.)

For example, you need one 150mfd/150v cap. Wire two 80mfd/160v caps in parallel and you have one 160mfd/160v.

<deleted dumb remark about equalizing resistors>

The article at http://antiqueradio.org/recap.htm has a little more info about combining caps to get particular values.

I find Mouser's filtering system a little confusing at times. If you are too specific when searching for a certain value, you may miss values a bit higher that would work fine.

Phil Nelson

[old_coot88]

Originally Posted by Phil Nelson

...Some people debate at great length whether you should also add parallel resistors to balance the load, but IMHO they are arguing over angels dancing on pinheads.

Phil, balancing (or equalizing) resistors are useful only when putting caps in series. oc

[Phil Nelson]

Parallel, series, who cares?

Sorry, I was typing too fast (and thinking too slowly). BTW, maybe someday I'll figure out why DuMont used two 80mfd caps in series in the RA-103 power supply. Perhaps it was just cheaper than way. And they did use equalizing resistors, so that's one argument in favor of the pro-equalizer party.

Phil

[old_coot88]

Nowadays it's probably far less common to have electrolytics in series than it was 'back in the day'. The balancing resistors were a simple safeguard against unequal leakage values in the two caps. It wouldn't take much leakage difference to throw a higher voltage across one cap than the other, potentially exceeding its voltage rating.

[wa2ise]

I've done caps in series, usually when what I have on hand doesn't have enough voltage, and as a bonus, the capacitence too big. One radio I restored needed 475V filter caps at 50uF, so I used a pair of 100uF at 250V caps in series, and I used 470K resistors across each one to be sure the voltage would divide evenly. The resistors also will bleed off the cap charge when turning the radio off, useful when working on the radio. Oh, the bleedoff isn't very fast, but 20 seconds it's down to safer levels.

Did this in an Admiral I restored as well, plenty of room under the chassis for the extra terminal strips too.