Tell me about these power section caps (1972 SL)

cooljuk

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I see some original amps have two .2uF 1kv caps on the far right of the board, next to the diodes. These are some additional filtering of the rectified AC, right? Looking at vintage amp photos and schematics, not all amps have them, though.

The one I'm restoring has had them clipped out (I can see the nubs right at the otherwise undisturbed turrets). Do I want to replace them? Seems I could go either way and stay "vintage correct." Is this a "cleaner sound / stiffer amp" situation like the main filters? I'm not easily finding modern .2uF caps rated over 630v.

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Also, while we're talking power section caps... Am I correct in thinking this .05uF 1kv cap, which is connected to the primary and the polarity switch (USA import model amp) is the equivalent of the "death cap" in 60's Fender amps? What's the common practice, here? Replace, disconnect, or rock on and let it be?
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neikeel

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The 0.22uF 1000v caps are snubbers to minimise switching noise from the rectifier diodes. I do not believe they add or detract much in the way of tone. RS do 0.22uF 1000 (or maybe 1500v rated ones but they are big and yellow!).

Yes that cap is the polarity (aka death cap) you should ideally disconnect it (if original appearance is original to you then just desolder it). If not please sell it to me as I need one for a 60s JMP50 restoration where it is used as and anti-pop cap on the HT switch.
 

cooljuk

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Ok, thanks. I'll look for the RS and see about the size.

I'm a looks guy for some projects, also, and this amp is mostly original (and the rest is getting put back that way) so I'll keep the .05 death cap and just disconnect it. I will keep you in mind as I am sourcing parts, though, and if I come across another I'll point you to it.

Hoping I can find some original Hunts or Erie .2uF caps for the snubbers and just restuff them with something modern that will fit inside.
 

neikeel

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Thanks for the link, bit too big (0.05 to 0.02 would work).
I had a bunch of the blue/cream Dubiliers but gave them away. I do have the RS ones but they will stick out like a sore thumb in there.
 

Seanxk

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I don't know what it is with that type of Hunts caps but I've seen more bad ones than good ( black or brown ), I think it's a heat or moisture issue, they seem to suffer/crack badly.

Saying that my 69 50w still has its death cap and has no screen grid R's either and it still rocks.
 


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