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Upping caps Peavy M2600

Started by markorock37, March 02, 2013, 12:05:37 AM

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markorock37

I have a Peavey M2600 power amp on the bench right now with low output. Guessing the main caps are shot. They are 5000uf 55v. Having trouble finding these but I do have some 6800uf 80v will those be okay? Thanks.

Enzo

Two thoughts:

1.  Yes, those 5000uf/55v caps are not available, they were custom made for Peavey years ago, the factory sends out 4700uf/63v caps in their place now.  I am sure 6800uf would be fine too, and any voltage over the 55v would also be fine as long as the caps fit the space available inside the amp.  Modern "snap-in" caps, or even regular leaded ones, may not fit the pc board tracework.  You may have to drill a new hole or two for them.  Watch polarity and glue them down.

2.  And this is the more important one.  Why are you changing caps if the problem is low output?   If your filter caps are dried out, the amp will be full of hum, not reduced output.    I highly recommend finding out WHY the amp has the problem before swapping out a lot of parts.

WHich M2600 do you have?  The original 1982 version or the 1987 version?  The older one has a pull switch on each volume control, while the newer one has a DDT defeat switch between them.

Are both channels affected the same?    Check the power supplies.  Are both polarities of 42vDC close to that voltage and free of most ripple?  And are both 15v supplies up to voltage and clean?  The ICs won;t work right with a collapsed 15v rail.

On each driver card is a 14 pin IC and an smaller 8 pin IC.  The small IC is the DDT or compressor IC, and it can be removed during tests.  That will eliminate the compression action, and if that allows the output to return, we can find out why.  If it makes no difference, then that ain't it.

DrGonz78

#2
Well the problem is probably not the caps. I would suggest checking the amp further to figure out what is the real problem. Check all jacks that might shunt the audio output stage. Low output just does not make sense with filter caps being shot. Hum would make more sense here if it was the caps.

Does the schematic that I posted resemble the amp that you have??

Edit: Simulpost!! lol Sorry Enzo!
"A person who never made a mistake never tried anything new." -Albert Einstein

Enzo

No, the M2600 is older.

Here is the early version.  The two versions are really close, mainly different on the input board.

DrGonz78

Yeah well here is the 87 version of the amp if that proves to be any help at all...
"A person who never made a mistake never tried anything new." -Albert Einstein

Roly

Quote from: EnzoI highly recommend finding out WHY the amp has the problem before swapping out a lot of parts.

Quote from: DrGonz78Well the problem is probably not the caps. I would suggest checking the amp further to figure out what is the real problem.

First you locate the fault, then you take Berlin.

:dbtu:

An early check should be the DC supply voltages, +/-42V and +/-15V.
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

Sorry, the schematic link didn't attach to my post. At the time the forum was moving REAL slow.

markorock37

Thanks for clearing that up, I figured since it was 29 years old (it is an 84) that they were bad. I will get voltages today and go from there.

Enzo

They may be dried up and weak, and needing change, but that is not what is causing your problem,   So replacing them might well be a good idea, but only after we solve the immediate problem.

Steve Dalllman

I have a lot of old PV amps, and the main filter caps do have a limited life. I usually go 10,000 or 12,000uF. More capacitance yields better headroom. Since modern caps are generally smaller in size than the originals, one can go with higher value caps. I have replaced caps in Mark III, Mark IV bass amps, XR600, and M3000. All had nothing wrong with them other than filter caps.

FWIW, a bad filter cap in the XR600 caused DC to kill 6 old EV SRO speakers (not all at once.) It would intermittently spit DC which would freeze the speakers (overexcursion). Fine after the cap change.