Threshold 4000 - difference between output boards PC0S3 and PC0S1a

[Eric M]

I have several Threshold 4000 amps. Most have the PC0S1a output boards with the pcFE1B front end board.
I have one with a PC0S3 output board and the pcCFE 379 front end board.
The output boards are similar using the same A6 and A8 output devices. The FEB are entirely different.
The PC0S3 output board uses 4 wires to connect to the pcCFE 379 unlike the others that use 5 wires.

Anyone know anything about the PC0S3 and pcCFE 379? The serial of the amp is # F7908513. I'm guessing they are a newer design? Maybe?
Any schematics available, especially for the FEB pcCFE 379? I've got the output board figured out but both FEBs need work or rebuild.

Thanks,
Eric M.

 

[gary s]

Maybe Jon Soderberg at Vintage Amp Repair can answer those questions for you. He is always helpful when it comes to anything Threshold related.