I've had this for a few years. When it works, it works great. About a year ago, it acted up (wouldn't power on), until I flipped the speaker selection switch on the rear panel up and down a few times. And all was good.
Now, it won't power up (no "power on" light on the front panel). There was no telltale POP, no smoke, nothing. It's as if it's plugged into a dead outlet. The power cord is good. I knew the switch and main fuse were still good, because when I flipped on the power switch, the lights in the room dimmed slightly as the caps in the amp drew power. The dual cooling fans are thermostatically controlled, so they don't kick on with power-up anyway.
I cracked the case open and tested the power cord, switch, and main fuse. All are good. I have a good ground to the chassis. I'm getting proper voltages off the test points on the power supply section of the PC board; it's conveniently labeled with proper voltages. I'm getting the proper lower operating voltages for the front end (channel strips, effects section, master volumes, and patch points) through the ribbon cable.
I checked all the ribbon cables and they're all good.
I inspected the board and components and there are no cooked resistors, no popped caps, no fried-bacon traces...everything looks pristine, other than a little fine dust from the airflow.
I'm at the limits of my abilities because I can troubleshoot tube amps, but not solid state stuff.
I went online to see if this power thing is an issue, and apparently it is. The PPM-series powered mixers appear to be less than reliable. Lovely.
Any advice is greatly appreciated. I thought I could troubleshoot this, but I may have to take it in for service...or toss it into the bay.
