I've just finished resurrecting a Mega 1 board, and had it working fine with the diagnostic cartridge, however it crashed one time and now won't boot.
The CPU is running but two of the address line pins are stuck high as it boots hence why it just has a white screen.
I've traced the lines across the board and no shorts are apparent, i've also switched out all the components that use the bus where applicable (cpu, glue, mmu) but still no joy - the only thing i can see left that uses these lines is the RTCPAL but i have no way of checking this? (this doesn't have a blitter installed and is disabled).
any ideas where to go next? thanks