Check that the power supply outputs 12V from the power connector.
Check if there is a shorted CXD90061GG behind the Southbridge IC. This may indicate that the IC itself is faulty.
Plug your desktop power supply into the 12V input pin. If you do not have a 300mA boot sequence, completely remove the BIOS chip from the motherboard for 10-20 minutes, resolder it, and try again. If the problem persists, reprogram the BIOS using the digital version (this will render the CD-ROM version incompatible with the BROM version).
