Peavey IPR-1600DSP Pwr on issues

[Mars Amp Repair]

Hey folks,
I'm not certain the attached PDF will open. I had issues with it.
So, this amp has a very weird power on relay circuit. I'm actually not certain why they made it so weird. It has it's own power supply that is directly derived from the AC line, so be careful you're isolated. Use the negative side of the filter cap C1 as your negative meter lead.
This one just wouldn't trigger the relay on it. I had already bypassed the board to determine the rest of the amp was ok. I tried to understand what they're doing on this board almost to no avail until I realized the positive power for the relay is derived from the 20 LED's on the board that are in series!!
I was only getting about 6V to the relay to power it. The MOSFET 'grounds' the bottom side of the relay.
All of the blue LED's were illuminated, but about 4 of them have 10-30V voltage drops across them! Has anyone else ever seen that?
I jumped just one of the LED's that had 20V drop across it and the power relay clicked & all was well.
BTW, the square contact marked HW1 in the lower right corner of the schemo is merely the pad the MOSFET is mounted on, not an input to the pcb.
Crazy, huh.
Glen

[JP-Stereo]

Just replace the diodes that do not test like the other.
It's a first step...

[Mars Amp Repair]

Just replace the diodes that do not test like the other.
It's a first step...

The purpose of jumping one of the bad diodes was a troubleshooting technique in case other techs encountered this unusual issue. Of course I'll replace all of these diodes that are in series as they all may have experienced whatever caused the others to go bad. Just kinda standard practice to avoid reworks & inconvenience for the customer. g