Peavey Centurion Mark III - no sound but BZZZ when turned on

[christobean]

i just recieved a Peavey bass head from my friends dad, and really want to bring it back to life.  i will try to keep this post as clean as possible to try to make it easier for anyone who has anything to help.

Peavey Centurion Mark III Series 260C
Bass amp head
120 W @ 4 ohms
produced in 1979

when turned on and plugged in there is no instrument sound...only a loud buzz, a lot like a 60 cycle hum.

nothing seems to be fried, and there are no burned parts or any obviously defective pieces inside.

however,
there are three prongs that seem like there was something between them, that is no longer present.



i cannot find a schematic online anywhere of this amp, so i cant see where these three prongs come into play, but i have a feeling they are the root of the problem.


any and all help/comments/suggestions welcome and greatly appreciated..i really want to get this head up and running.

[George Giblet]

The simple answer is: I've fixed a similar amplifer with the same problem before.  There are two axial 1000uF 35V caps on the power amplifier board.  Just replace them.

Rather than assume this fault you could spend more time narrowing  down the problem to see if it's the power amp or the preamp.  A simple thing to do is to put a jack into the "pwr in" socket and see if the buzz goes away.  Indicating possibily a preamp issue, or broken wire between the pre and power boards.    IIRC the 1000uF affect both power and preamp but, with this fault,  the degree of buzz from the power amp alone be be low and make you think it's OK.

[christobean]

ok thanks, i will try this and report back.