As mentioned, fuse was blown on battery board. There was also battery corrosion. Reflowed solder on corroded solder joints, used fiberglass scratch pen to expose traces next to the absent fuse solder pads, and used a wire fragment/solder blob to bridge the gap for testing. It worked. Now need fuses. Overscratch area was covered with clear nail varnish (not visible but it’s there). Someday I’ll get myself some proper solder resist and a UV light.
Three items of note:
(1) the power connector (red/black wire connecting battery board to main board) disconnects by LIFTING the connector out of the socket, not by pulling horizontally.
(2) the D-pad left button didn’t work well. I blasted the rubber pad and external d-pad button with contact cleaner (even though there is no electrical connection involved with these items). There was hardly any dirt, so I didn’t think it would work. Holy shit was I wrong.
(3) the blue power LEDs don’t light. No idea if my board work broke the LEDs or if it happened when the fuse blew.