[TenTec] 9420 power supply

[Tom Macon]

I have a Hercules II amp with the 9420 power supply that's having problems.  
1. When the amp is switched on, the Overload light comes on immediately.
2. When trying to run the tranceiver (Omni VI) from the 9420, there is a loud relay buzz from the 9420 followed by something tripping out.  This happens regardless of whether the amp is plugged into the 9420.

The first problem appears to be voltage spike from the 9420 that trips the overvoltage circuit in the amp.  I've been able to capture a 20v spike at turn-on but can't determine which of the four supplies is causing it.

The second problem occurs with either the Omni or a resistive load plugged into the transceiver connector.  Evidently something trips because when the buzzing stops (after a couple of seconds), the output voltage is about 0.62v.

It's very difficult to troubleshoot the 9420 because of limited access to it's internals and it can't be run in a partially disassembled state because many of the cables are too short.  I'm hoping someone is familiar with the beast will have suggestions to help me zero in on the problem(s) - they will be greatly appreciated!

Tom Macon, K9BTQ