I'm working on an old Peavey power amp that's working but has a significant buzz in the audio at the speaker. It's a 200H 100 watt audio amp made by Peavey in 1979. It's supposed to have +42V on one side and -42V on the other, the +42 is there, but the minus voltage is -26V, no blown fuses and the circuit works except for the noise. I've replaced the output power transistors Nte130's (4) and nothing else is heating up including the transistors. The power supply filter caps seem to be OK as I've pulled them and checked them OK. I think there's a part shorted but don't know where to continue, I'm stuck. Any help would be appreciated...Dale