X68000 Pro won't boot

[sigourneyanderson]

Hi,

I have acquired an X68000 Pro with a failed PSU. I have built a replacement loom to convert ATX to the X68000 power loom, I am getting power to the board and getting a red light but will not go any further. I have built a small circuit using a 74LS04 chip and seeing power at the board on the brown wire at the connector on the board.

I have tested all the pins and seeing 0V at the brown wire and +5v at the orange standby power. When I depress the power switch I am seeing -12v at the brown wire and +5v at the standby but nothing else across the rest of the connector. I have tested the power supply to ensure that I have no faults with that, and powers up a PC with no issues at all, so can rule out an issue with the new psu.

I have tried searching far and wide for a board schematic for the motherboard so I can try and start troubleshooting further but unable to find one anywhere for this model.

I have checked all the caps on the board to ensure that they are all within in spec, and none have failed.

I would be very grateful if anyone is able to provide some pointers or assistance to why my unit is not powering up.

Thanks for the help in advance.