Thread Tascam M-320B Hum - no Signal to Amp

Hello and Good Day!

The Problem:

Tascam M-320B Console will turn on, but only admits a "loud 60Mkz hum" (or some freq. in that area) in the headphone set connected to console, but no sound is admitted to amp from the console other than "AM/FM" interference. And when I say there is a loud hum in the headphones, that also means there is no control over that hum, even with all connected equipment turned off or disconnected.

I think that there must be two power supplies: One that turns the board on and the other that powers the signal to the amp, which would explain why the board turns on and meters indicate signal when audio signal is present, but no signal is getting to the amp. I haven't opened the unit up yet and I don't have a service manual, so I'm just guessing.

This is the second time this has happened in two days. The first time, I turned the unit off for an hour or so,
fired it up again and it was fine for the rest of the session. I thought it was a "city power surge" or something, no other equipment seemed to be affected. When it happened the second time the next day, the "hum" remained and no signal is getting to the amp.

I've owned this Tascam M-320B Audio Console for some 15+ plus years without incident. Some would say
money well spent and I would agree. It may very well be time to look for another mixing board. However if
this unit can be fixed, doing the work myself, all things considered, this would probably be the best option right now.

Taei