I’ve updated the schematic for the power supply. Made a few corrections and rearranged a few things.
Still haven’t figured out why the outputs are behaving like they’re shorted out. Putting a my DMM across the output terminals gives me about 148Ω, which seemed on the low side to me.
A quick check of the SCR shows that it seems to be ok. I think I’ll check the pass transistors next. Looks like they should be easy enough to remove for a quick test. I should probably check the big filter caps too, although I wouldn’t expect those to be bad.
In the process of troubleshooting, I’ve removed the 6 pin connector and large capacitor (1.4 mF) associated with it. I’m planning on replacing them with Powerpole connectors. Three of them will fit nicely in the space occupied by the 6 pin connector. Just need to figure out how to secure them in place.