You will need to try to isolate whatever components that you can from the incoming power and check them with an ohmmeter. You are looking for a source of low/no resistance. Within my unit, one of the diodes within the bridge rectifier went out and caused a similar issue. It looks like a tall, thin, black block with a hole through it and 4 leads.
Thanks. There is indeed a short in the bridge rectifier (KBU606.)
Ordered the replacement varistor and bridge rectifier for the IO board and already replaced the op amp on the control pod. I've spent $8.40 so far and I have 5 extra op amps and 3 extra varistors. Not bad.