I just unearthed my father's old Nakamichi 500 from storage and went to put it through it's paces. Unfortunately, no mater where the switches and controls are set, it starts producing a loud tone and pegs both meters about 1 - 2 seconds after turning on the power switch. It is like it's generating some kind of feedback (very loud). Even when nothing is connected to it and all faders are down as low as they can go, it still generates a signal that pegs the meters. I have removed the pan, cover and front panel, but I hesitate to go further without knowing where to look. Any ideas about what could be causing this and how to debug the source?
