When I power the amp up the Drain on the low side of the output section slowly starts gaining voltage. This is without a single fet anywhere in the amp. Also the pin on the ps driver card that activates the relays alway has power. Even when I don't have any wires hooked up to it. It's holding onto what ever the b+ was at indefinitely.
The low-side drain is connected to the output filter inductor and the speaker terminal. Do you see the same rising voltage on those points?
No. After I didn't see it there i realized it's actually the the drain of the high side. My mistake. Its Directly connected to the of the + rectifiers. How are the rectifiers seeing any power without any fets in?
Either they could have been charged from when the amp was operating or it could be voltage due to dielectric absorption.
When I do put power supply fets in I get b+ on the 2 outside legs that should have nothing on them. I have the output card in but no 21844s chips in.
This amp will just change behavior out of nowhere. All of a sudden 1 of the 6 ps sections won't produce a clean square wave out of the fets. The signal going in is clean. The signal out looks like a jagged triangle wave. It's not the fets. I've swapped them out 2 times. I pulled the rectifiers without any change. I don't get it. The signal in is good. The same fets work in other sections.
If you have the 12v supply voltage on the secondary windings, one of the transformers could be shorted from the primary to the secondary.
Is the duty cycle of the square wave drive from the PS driver IC at 50% (as high as it can go) when you see the jagged drain signal on the PS FETs? Or is the duty cycle well below 50%?
Is the duty cycle of the square wave drive from the PS driver IC at 50% (as high as it can go) when you see the jagged drain signal on the PS FETs? Or is the duty cycle well below 50%?