Neg Out on the board jumpers to -reg, -reg leaves to other various places to provide ground references. That board doesn't look well soldered, so I would start there, but otherwise follow the black wires back from Neg Out until you don't see that 1K resistance, then start resoldering where the black wires land until that goes away.
If you have 0 ohms at -reg, then you know you're down to soldering issues on that board.
