Status: Successfully repaired on October 29, 2021
In for repair was a Capcom CPS3 arcade board that had a Marqs HDMI mod installed by a prior technician. The board would no longer boot up.
First, I tried removing the HDMI mod board installation. The board booted up successfully and worked fine without it, so the mod was definitely the culprit.
I carefully redid the mod board installation, running fresh wiring for all the connections.
Unfortunately with the mod board reinstalled, the CPS3 once again wouldn’t start up. I started to suspect the mod board itself had catastrophically failed when I luckily noticed a small solder bridge across two pins on the mod board.
That was it! Removing the solder bridge restored full functionality and the board and HDMI mod now functioned properly.