Carver PM 1200 Protection light on, amp works!

[screamersusa]

I am working on a Carver PM1200 for a friend.
The protection light is on yet the amp works. I did notice that it drops the positive powersupply rail to the output on turn off.
Got the service manual from musicparts.com but it does not have theory or calibration instructions and this amp design looks really bizzare. Can't figure it out.
Thanks

 

[anatech]

Check to make sure all the supply rail commutators are working. There are three voltages, the outputs should have the lowest voltages equally on the collectors. Each channel is independant of the other as far as rail voltage selection is concerned. Also check you don't have a bad supply cap (check the ripple when the amp is running).

-Chris