Here's the happy update:
When working on the suggested repairs, I remembered a bit of what had been going on last time. The reason the resistors looked so crazy is that I had transplanted them from another board in frustration after realizing I didn't have the right ribbon cable connectors for the pcb 
- I decided to solder brand new resistors everywhere (without the frustration this time), checking for a good resistance reading between cable pin and cartridge connector pin as I went. I had also previously checked continuity between all of the other pins, to be sure.
The result: everything works in my Sony! Thanks so very much, Alexey!
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