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FDP Forum / Amp Mods, Repairs, and Projects / Filter cap voltage rating



Mar 6th, 2017 08:22 AM   Edit   Profile   Print Topic   Search Topic

I bought new F&T filter caps for my 5F6a and for th life of me, I can't find the info in the threads where I know I have seen it. The caps I bought are rated 20uF-500V. Does anyone know how much of a margin exists between the rated voltage and typical failure? The last thing I want to do is launch the power transformer but I would like it to be reliable.

I was checking the caps yesterday (now that I have a tester that can measure caps, resistors, ESR, etc) and when I opened the housing for the filter caps, I saw that the first node has two paralleled 40uF caps and the others are 20uF, giving it a total of 80uF on that node.

Specific to vintage amps, is everyone using 600V caps, or will the F&T caps work well over the long haul?




The last real bug hunter
Mar 16th, 2017 06:55 AM   Edit   Profile   Print Topic   Search Topic

I don't know the margin of failure, but about 10% over-voltage can be sustained for short periods. The first caps after the rectifier are not parallel, they are in series, which HALVES the capacitance but doubles the voltage rating. 100u @ 300v or better are good to use there. F & T caps are very good. The 600v caps I've seen are simply two stacked 300v (in series) wrapped in one package.

FDP Forum / Amp Mods, Repairs, and Projects / Filter cap voltage rating

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