Hello,
A few things to try,
1) Connect a multimeter across pins 14 (+V) and 7 (0V) of one of the 74 series TTL devices and measure the voltage. It should be within 5% of 5 or 3.3V (not sure what the logic is).
2) Clean the A1200 CPU slot with isopropyl alcohol and use contact cleaner on the accelerator slot.
3) Check the voltage output of the LT1585 3.3V converter.
That's all I can think off for the moment.
