Need some help repairing a Mega CD (model 1, JP)

Hi there!

I've been looking around online for any info on fixing a Mega CD unit that turns on as far as the BIOS screen and ejects the disc tray, but then becomes unresponsive (no logo, no music, just clouds in the background). The CD unit's LEDs flash on occasionally when I power on the system, but otherwise, remain off after that.

From what I've read so far, this sounds like one or more broken traces between the CPU and RAM of the CD unit. I've seen the schematics, but I'm unsure how to read them and match them up with my circuit board.

Just inspecting the circuit board, it doesn't look like any damage is obvious from leaking capacitors, and the capacitors themselves seem to be in alright shape, but there are random wires and a resistor that's soldered on the rear side of the main board and bridge board between the CD unit and the Mega Drive, so I think the previous owner may have already done some work on it, possibly already replaced the capacitors. So I'm guessing, again, the issue is a broken trace, but I need some help figuring out how to read the schematics.