Rev E Using large can type capacitors question

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Rev E Using large can type capacitors question

Postby atwageman » Sun Mar 30, 2014 8:40 am

I've got 4 of these large can type capacitors. 250uf @ 500v. Thinking of using them in place of C9, C10, C11, and C12. Would using 250uf instead of the default 120uf cause any issues?

I'm gonna do this build on a larger then normal chassis, so mounting the caps I have to the chassis is not a problem as far as space is concerned. I think it would look kind of cool with the power supply caps up on top with the tubes and transformers.

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Re: Rev E Using large can type capacitors question

Postby TomMcNally » Sun Mar 30, 2014 10:03 am

They'll work fine. You really could just use three, as C-10 and C-11 are already in parallel, for the equivalent of 240 MFD.

Tip - mount the ugly metal clamp under the chassis with the only the capacitor showing on top, it will look much nicer.

... tom
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Re: Rev E Using large can type capacitors question

Postby atwageman » Sun Mar 30, 2014 10:10 am

TomMcNally wrote:They'll work fine. You really could just use three, as C-10 and C-11 are already in parallel, for the equivalent of 240 MFD.

Tip - mount the ugly metal clamp under the chassis with the only the capacitor showing on top, it will look much nicer.

... tom


I was planning on mounting the clamps under the chassis. I've seen others paint the clamps to match the color of the chassis, but its still ugly in my opinion.
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Re: Rev E Using large can type capacitors question

Postby paart » Sun Mar 30, 2014 8:35 pm

A 250 microfarad cap in the input cap position is getting “up there”. I imagine the inrush limiter will contain the heavy “turn on” current surge, but there’s also a possibility that over time, problems could arise. One issue with inrush limiters, is that if the AC power is removed, then quickly returned, as often happens during power “glitches” (thunderstorms) the limiter may not have time to cool and increase in resistance. I’d consider changing the rectifiers from 1 Amp to 3 Amp (ultrafast) devices. Be certain to use a “slow-blow” line fuse, and, if you have a Variac, I’d bring up the AC voltage slowly a few times, until you are certain everything is functioning properly. Be careful when working on the amp; larger caps will take longer to discharge through the bleeder resistors.
I’m an advocate of increased power supply energy storage, but caution is necessary.
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