If only I had hair to pull....
So, I ordered a new Rottendog power supply board. After replacing the board, the GI worked. However, nothing else does.
Jim was very helpful on the phone, and I seriously doubt that his product caused the problem.
Here's what happened. At first, the game booted and played but no sound. Then it booted but didn't play. The display said "one ball missing". After turning the power on and off again, the GI lit, but nothing else. No boot, no display's, no sound.
The MPU blanking LED never comes on, while the +5 stays lit all the time, and the PIA comes on, stays on for much longer than normal (a few minutes) then sometimes goes off, but comes back on, sometimes flickers.