Peavey 5150 volume issue

  • Thread starter Thread starter dainbramage
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dainbramage

dainbramage

Well-known member
I'm considering buying a Peavey 5150 tube amp from a friend. The only problem is that after having played for about 20 minutes (it varies) or so the volume decreases dramatically and stays like that until it has cooled off. The tubes were replaced recently and it did not solve the problem.

What could be wrong with this amp?
 
I'm not sure whether or not it has seen a lot of road gigs but it was fine when my friend bought it, and have only played about 6-7 gigs with it since then. It has been standing in the basement most of the time.

A cracked circuit board or a cold solder joint. That sounds expensive, Is it?
 
Could also be a blown or soon to blow transformer. Those are not too hard to install, and as they heat up sometimes they start to crap out and the volume drops. I know a number of 5150 that have had to replace the transformer (it's the big heavy part that makes the heads a pain to carry).

Also, was it biased properly when the tubes were swapped?

Have you checked simple things like loose tubes, wrong tubes, loose input/output jacks, any obvious/visible problems, tried the head with a different cab?

Finally, it could need to be recapped depending on how old it is (capacitors wear out and need to be replaced). Unlikely but this could cause volume drop when warmed up.

Start with the simplest and move forward...loose/wrong tubes, different cab, biasing, transformer swap, recapping. Could be a number of other things, but those are my best guesses.
 
If the tubes are way off bias it can exhibit this exact symptom. the amp should be biased and have a complete going over before you purchase.
 
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