Hi folks!
I'm working on a Bally Xenon for a gentleman and I've got it just about buttoned up, for 30 minutes at least after about 30 minutes, the displays all start flickering (the dreaded strobe problem). Somewhere around this same time, if you're in the middle of a game, the mpu will crash.

If you turn it off and immediately back on, the board will not boot, you get the flicker but don't get the first flash. It's definitely heat related, if you let the backbox cool off a little bit it will boot right up and the displays work fine.

Sound is fine, switches are fine, solenoids are fine. When the MPU crashes, you basically lose the displays and the switches, but the flippers are still active.

Board has a new power supply, replaced connectors, solenoid board has been rebuilt, voltages all test fine after the crash and before (they don't change)... new connectors on the MPU, have swapped U9,10,11... replaced the 555 timer, replaced C16 (to the timer)..... no battery damage....

Next step i'm going to replace U20 although I can see that messing up the displays I don't think it would crash the board. Since you don't get the first flash after it crashes, i'm thinking maybe reburn the roms too. Might possibly be sockets which would be nearly impossible to figure out because they're fine when cool!

Any ideas? I've seen this before when the board won't boot but never with a heat related issue...

Appears to have been the U6 rom. Pulled it and it verified, I had already cleaned it.... burnt a new one, game doesn't act up anymore. I guess the clue was the no 1st flash which is what checks the roms, and that would explain why it crashes too during gameplay after it heats up. The displays were just another symptom....