8uF 600V Primary Filter Cap - 1946 Masco -

[goangling]

I'm replacing 2 filter caps on my Masco MA-25P, they are each 8 uF, 600V.  Having a hard time finding that 600V cap without breaking the bank.  This has a 5U4 rectifier, and 6L6s - could I get away with 500V caps, or should I put 2, 16uF 500V in series?  The 8 uF can caps on this thing stand 4.5" high and look like the twin towers of Kuala Lumpur!

[PRR]

Two 22uFd 350V caps series, with 100K 2W in parallel with each cap, each place.

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Yes, it will soar to like 600V at turn-on before the 6L6es sag it down. E-caps go to 450 maybe 500V. e-Caps can be seriesed and the voltage almost adds, but you need to equalize the leakage.

350V caps in larger sizes are very common for large 230VAC DC supplies. I have not shopped for 16u-22u sizes but they should be around. 

[goangling]

OK, thanks - I ordered 22 uF 500V F&T caps (four of them).  I've had good results with the F&T previously.  Will going from 350V in your example up to 500V change value of balancing resistors?

[eleventeen]

Those 47K "balancing" resistors are going to run sort of on the warm side.


Assuming 500 "steady state" volts / 100K (the sum of 47K + 47K) you have .005 amps or 5 mils. .005 * .005 * 100,000 = 2.5 watts. Each of those R's has to dump 1.25 watts. Yeah, OK. Warm.


Go look at a Fender Twin Reverb p/s and you will see your supply with 220K balancing resistors. All you really need for the "balancing" action is a mil. If it's all the same to you, I'd would go with 100K or 150K resistors, if you haven't bought them yet. Same price, same function, run cooler.

[goangling]

OK,  Thanks for the replys -  I went with 22uF@450V in series, Used 100K - 2W resistors -  I'll let you know how it works out.  I attached a pic showing the capacitors in series and the vintage Solar 8 uF / 600V can cap.  Was pretty easy un-stuffing the can, was filled with a single large cardboard cap coated with black wax.