Replacing Mallory CGS capacitors in an APT power amp - diyAudio
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Old 7th December 2014, 09:56 PM   #1
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Default Replacing Mallory CGS capacitors in an APT power amp


I have an APT power amp which I am refurbishing, and it has 2 Mallory 10000uf 75v electrolytic caps in the power supply.
I have measured both out of circuit with the neat Peak ESR 70 and both have Zero ESR, one has capacitance of 10,480uf and the other 11,780uf. Having tried to decipher the codes on the cans I think these were made in 1980, and as they are 30+ years old could/should be replaced.

Given thier size, there a couple of alternatives, some Nichicon 10k uf 80v and 100v @85c and another larger Nichicon 10k uf 80v @ 105c- however all of these are +/- 20% whereas the Cornell Dublier CGS series (which I am assuming is the descendant/replacement for the Mallory) is -10%/+75%.

so would I be better off the the CD CGS series or the Nichicon and does it matter?
and secondly would one be wise to add a (say) 1uf 250v decoupling film cap (say a panasonic) across these?

any assistance and guidance appreciated


btw photos attached
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Old 11th December 2014, 07:51 PM   #2
mlloyd1 is offline mlloyd1  United States
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Location: illinois
i'd used the higher temp rated parts and call it a day.
as for the extra bypass cap, i think you'd get more bag for the buck with a R-C snubber across the transformer secondaries or across the power supply rectifiers, but that's just me.

nice amp, btw. i used to have one years ago. lost it due to a lightning strike that caused a fire when i was out traveling for work.
does yours hisssss?

btw2: there's a thread here somewhere where one of the techs and original designer for the amp discuss it's performance, which was quite good for its day (and still is in a lot of ways).


Last edited by mlloyd1; 11th December 2014 at 07:54 PM.
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