Another technical casualty this weekend is my Peavey MP600 mixer amp. As soon as you turn it on, you get full volume mains hum.

Does anyone here have a circuit diagram of this little beast, so I can scope out the fault? Is it worth repairing?


Peavey MP600

Sounds like a simple power supply fault to me - probably one leg of a smoothing capacitor come unsoldered from the board. Often happens with big heavy caps, I have seen plenty of these faults on a certain well respected brand of guitar amplifier too. Best to remove them, clean the PCB holes up and resolder them, and use some silicon sealer to hold them on to the board at the base to give a bit more mechanical strength. Other bets could be one half of the bridge rectifier not working - you can soon asscertain that with a scope.

HTH

Jon.

Thanks Jon, that's roughly what I was thinking. I will find out next week when I take it apart.

If you ring up Peavey and speak to technical they'll usually post you a photocopy of the schematic!

As mentioned it's probably a main smoothing cap but also high current drain through the PSU can cause this symptom....eg shorted O/P transistor....in which case dont leave it humming for long will you..?

Peavey stuff is jolly well-built so usually worth TLC no matter how old.