I've recently got this error: 304-Keyboard or System Unit Error when booting my Compaq Prolinea. I've tested the keyboard on another computer and it's fine. I don't have another PS/2 keyboard to test, but the keyboard does briefly flash its lights when the computer first powers up, but then has no power.
Most people/sites online say that the original troubleshooting was to test the keyboard, then replace the system board. Obviously, I can no longer replace the system board, so I'm looking for a way to diagnose this problem and/or fix it. I've got a multi-meter and beginner-to-intermediate solder skills, but I don't know where to start, and I can't find any type of schematic for this old computer.
There was an old barrel battery (next to the PS/2 ports) that looked like it may have started leaking, but I removed it, and I couldn't find any obvious damage to the board.