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  •  » Want to be sure about a cap substitution in Fliptops kit

#1 2012-12-10 19:44:21

Redwood
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Registered: 2012-12-10
Posts: 19

Want to be sure about a cap substitution in Fliptops kit

Hey all, new member here attempting a rebuild of a distortion model V4. I can't find an exact schematic but the one numbered 591761 is very close, the main differences being some resistor and cap ID numbers are not the same on the PC boards even if the values appear correct in most cases.

This amp was redplating pretty badly before I got my hands on it so I've never even fired it up yet.  At least one 7027A power tube is smoked and there are a dozen or more various caps and resistors on the PC boards that are pretty ugly so I'm going through it part by part and replacing anything that looks or tests bad. 

I'm just replacing all the big caps on basic principal though so I ordered the cap kit from Fliptops.  My main question right now is regarding C305, an off-board electrolytic mounted to the chassis with the ground connected to the C304 40/40/40 can and the hot side connected to R41, a 10K 1/2 watt resistor.

The schematic calls out C305 as 20mF/450V.  What I find installed is a 20/20-450V wired in parallel for net 40mF.  The kit from Fliptops was supposed to include a 47mF-450V but they screwed up and sent me a 100mF-450V by mistake.

Question is, can I get away with the higher value here or do I need to hunt down the correct value, and beyond that, is the correct value the 20 in the schematic, the 40 currently installed, or the 47 Fliptops is selling?

Thanks in advance,
Redwood

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#2 2012-12-10 21:16:25

hangman
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From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: Want to be sure about a cap substitution in Fliptops kit

Where is c305?  I can't seem to find it.

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#3 2012-12-10 23:07:10

Redwood
Member
Registered: 2012-12-10
Posts: 19

Re: Want to be sure about a cap substitution in Fliptops kit

Thanks for the response.

C305 is hiding, that's for sure.  If you're looking at the same schematic I referred to it's in the top section close to the center, directly above the "12" part of 12DW7.

It's almost a moot point now, I just picked up a 47-500V axial cap that I'm going to go ahead and use, although I'd still like to understand the impact of increasing it from the 20 mF that was originally called out in the schematic.   I didn't mention in my original post, I actually have a quad of 33mF/450V caps that I am reluctant to break up, but when I spoke to Fliptops the guy actually told me not to go with less than 40mF, but he explanation for why wasn't clear to me.

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#4 2012-12-11 05:13:15

hangman
Banned
From: Seattle Washington
Registered: 2006-09-04
Posts: 1848

Re: Want to be sure about a cap substitution in Fliptops kit

How interesting,  I never noticed that hiding out in the schematic. 
I don't think you need to take it to 100uf,  but I doubt you would hear much of a difference.   It is really only being used to filter the supply for the mid eq amplifier.  I agree with Bruce though,  keep it at 40uf or above.

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