Dear all, I join this forum because I have a Sunfire in repair and there is something I do not grasp in the schematic I downloaded from the Carver website. This thread was very helpfull and all that could be bad was bad : the powerstage transistors, some FETs, the 4 biassing diodes and of course the 2 jumpers JP1 and JP2. The glass fuses were OK ... https://www.ecoustics.com/electronics/forum/home-audio/618938.html After replacing the lot, the "+ down-convertor" does not work. For testing the low-voltage part, I disconnected the small transformer from the big powertrafo secondairy. That way, there is no danger blowing it all up again. My question : How is the circuit for the + down-convertor FETs powered (Opto U1, Q8&Q9) ? I see the diode D5 giving +13V as powersupply but where can it source current to ? The "ground" circuit is connected to the sources of the FETs Q22/23/24 and at that point the voltage will most of the time be higer than +13 V . . . Has anybody reverce-engineered that part of the system ? Anyway, if I measure the voltage over zener Z3, I get next to nothing (0.3V) altough the +13 V is OK.