I finally got around to working on my 250.
One bank of power supply fets were blown as were a few output transistors.
I removed all power supply fets and replaced the 10 ohm resistors on the blown bank (they were all open).
All caps in the primary and secondary side were replaced as well.
With all the outputs removed and only two power supply FETs installed I was getting +/- 8V rails and one side of the power supply was getting really hot. A zener diode (12v zener) between the gate and ground in the power supply was shorted so I pulled both.
Now the amp produces +/-26.6V rails, but one side of the power supply still gets really hot. I only have one fet per side and they are not clamped to the heatsink. I swapped out a few fets from my parts bin, but it still gets hot. It's the one installed on the side that wasn't blown. The other fet stays cool to the touch (I replaced that one as well, no change).
MPSA56/06 were replaced as were the 10ohm resistors going to ground. I inspected for solder bridges and didn't see any. The toroid looks rather suspect, but all coils measure around 5 ohms and is consistent across all coils.
Should I install more fets per side and test it in the heatsink?
One bank of power supply fets were blown as were a few output transistors.
I removed all power supply fets and replaced the 10 ohm resistors on the blown bank (they were all open).
All caps in the primary and secondary side were replaced as well.
With all the outputs removed and only two power supply FETs installed I was getting +/- 8V rails and one side of the power supply was getting really hot. A zener diode (12v zener) between the gate and ground in the power supply was shorted so I pulled both.
Now the amp produces +/-26.6V rails, but one side of the power supply still gets really hot. I only have one fet per side and they are not clamped to the heatsink. I swapped out a few fets from my parts bin, but it still gets hot. It's the one installed on the side that wasn't blown. The other fet stays cool to the touch (I replaced that one as well, no change).
MPSA56/06 were replaced as were the 10ohm resistors going to ground. I inspected for solder bridges and didn't see any. The toroid looks rather suspect, but all coils measure around 5 ohms and is consistent across all coils.
Should I install more fets per side and test it in the heatsink?