A logic probe (LP) would be a good tool to invest in. You can pick these up for around $20USD plus postage... You can use the LP to verify there is activity on data lines to see if there is some sort of information flowing at the display driver board.

Your problem sounds like an issue with communications between the MPU and the Display Driver Board. You say the game works normally but the display is only cycling the Reset state. However there is no Watchdog Reset function on the Display Driver board - and here one would want the logic probe to check that:

A) you have a stable High on the output of U15A (pin 3) and after that that pin 37 of U9 (68B09E - CPU) is High. this indicates that RESET is stable and not active.

B) if both circuits in A) are stable and High then see (with the LP) if you are getting data (blinking LP indicators) on pins 11 through 18 (incoming data lines) of U17, and also pins 11 through 14 of U19 (Stat0 through Stat3). All should be busy if the MPU is running happily.

C) if any issues with logic line inputs in B), then check on the MPU board for the source logic lines...

Hope this helps, but you need basic electronic tools about now to speed up the process and to have a rough idea of what is going on in your game...

John :-#)#

These reference pins are on the Dot Matrix Controller (#520-5055-00), pg 98 of the Tommy manual I downloaded from IPBD...

John :-#)#