I've been trying to get this Bubble Bobble PCB working but I'm not having much luck. It's currently 'dead' - no sound, no video. The clock inputs at all 3 Z80 CPUs are good and the /RESET line is high. I have a sync output from the video board, but no RGB outputs and there is no activity on the address inputs of the graphics ROMs. Test mode does nothing different. Here's what I've done so far:
- the PROM socket at IC41 on video board was broken in half, replaced it
- pulled all ROMs and PROMs, dumped them, all verified in ROMIdent
- logic probed both boards, found a floating output at pin 19 of the "PS4" MCU. Swapped in another "PS4" chip, no change. Traced this output to a 74LS74 at IC30, replaced it, now that signal is high. All other ICs look okay (no floating signals anyway).
- hooked up the 9010a - all bus, ROM and RAM tests passed on all 3 CPUs, except for ROM 52 from the main CPU - looks like this is banked, with the PAL at IC43 decoding the ROM's /CE, A14 and A15 signals. Is there any way I can read this ROM with the Fluke?
- used the logic comparator on almost all the ICs, found nothing bad
- replaced all 3 Z80 CPU's
- continuity tested all signals in the ribbon cable, all good
I'm at a loss for what to try next. Anyone have any suggestions? I'd highly appreciate any help I could get on this.
- the PROM socket at IC41 on video board was broken in half, replaced it
- pulled all ROMs and PROMs, dumped them, all verified in ROMIdent
- logic probed both boards, found a floating output at pin 19 of the "PS4" MCU. Swapped in another "PS4" chip, no change. Traced this output to a 74LS74 at IC30, replaced it, now that signal is high. All other ICs look okay (no floating signals anyway).
- hooked up the 9010a - all bus, ROM and RAM tests passed on all 3 CPUs, except for ROM 52 from the main CPU - looks like this is banked, with the PAL at IC43 decoding the ROM's /CE, A14 and A15 signals. Is there any way I can read this ROM with the Fluke?
- used the logic comparator on almost all the ICs, found nothing bad
- replaced all 3 Z80 CPU's
- continuity tested all signals in the ribbon cable, all good
I'm at a loss for what to try next. Anyone have any suggestions? I'd highly appreciate any help I could get on this.


