Zenith ChromaColor II 19KC52 won't power up (long msg)

Hi,
I didn't find the answers I need in the archived posts. So here goes.

Zenith model SK1989W5
chassis 19KC52
Chroma Color II
Space Command
built October 1978

This was owned by my wife's uncle, given to us after getting married, around 12 years ago. We used it daily for about 12 years. Last week it would not power up. I don't have any schematics or service literature.

I found that the circuit breaker was tripped. Reset it, powered up, immediately popped again. Opened up the set, and followed the AC wires thru the circuit breaker to the power transformer, and what appears to be the Space Command power unit A-7550. After the power transformer, there is a rectifier board 9-122-04, followed by a can electrolytic cap and an oval AC cap (3.5uF 440V 60Hz).

1) Terminals of each capacitor don't seem to be shorted to GND
2) Power transformer input resistance is 3.8 ohms
3) Removed Space Command power module, apply power --> set does not power up, circuit breaker does not pop (I suppose it is because power does not get far with the module removed).
3) Installed Space Command, but kept disconnected from the Space Command the 4-wire card edge connector (wht/red, red, wht/vio, vio) that is wired to the the front panel Power switch. Apply power --> circuit breaker pops
4) Removed rectifier board 9-122-04 (figuring this would eliminate most/all DC supplies in the set). Apply power --> circuit breaker pops.

Any recommendations would be appreciated.