Hi. Good. This time I want to request your valuable help to restore a Sunn brand amplifier. It is the Concert Bass II. It turns out that I was abandoned and I want to restore it but I don't have the documentation. The problem is that after turning it on even if it has no signal at the entrance and with the minimum volume it makes background noises as if something was being cooked, which I don't know that could be causing it. They could be the power filters (2 x 3300mf at 50v) although the source voltage is stable at +36v-36v. Or maybe some output transistor. (It takes 4 2N3055) What do you think? I would appreciate if you share the diagram of this device to make more accurate measurements or advise me how to proceed to correct the fault and fix this equipment. I attach some photos. Thanks in advance and best regards. Atte: Volt Fierce.

Well as I comment above. Now there is only a slight background noise. I think that replacing the 3300mF / 50v filter capacitors will solve the problem related to the amplifier. Thanks in advance for the support. They are a great electronic community. Best regards.