it's California amplifier!

i turn it on 10 minutes,the noise occur(example: ziii....ziiii....ziiii),mixed with audio signal!

then i turn off the amplifier,and turn on again,it run correctly and no noise occur anymore!

next time,that status replace

i don't know why,please help me!

 

Post a schematic and I can take a look.

 

it's have 2 micro board,1 echo board,1 music board,1 master board and 1 power board

the schematic is very big and i haven't convert it to PC image,but i think the Power board is very simple and it not damaged because it still run and can play music

i has replace coupling capacitor,but no effect.

i think the power contact has problem,it's old and can be damaged