ShootTheCore
Legendary
In for repair is a DoDonPachi Dai-Ou-Jou PCB with Black Label EPROM installed that isn't displaying most text and isn't displaying backgrounds:
Interestingly, the game does display the countdown timer text on the Version Select boot screen, and text appears on the high score table.
DDP-DOJ is based on the IGS PolyGameMaster hardware, and the MAME driver shows that the backgrounds and text tiles are supplied by two ROMs - a PGM BIOS ROM located at U18 on the PCB and an art content ROM located at U19 on the PCB.
In MAME, filling the "pgm_t01s.rom" file with FF using a binary editor had no affect on the game booting and running at all. But when I fill the U19 ROM with FF and run the game in MAME, the behavior matches the PCB exactly.
I checked over the board carefully with a microscope and ensured that there wasn't any physical damage to the legs of either of the involved ROMs or to the large "IGS 023" custom in the center of the board they're connected to. For good measure, I reflowed the soldered connections on the U19 ROM, but it made no difference. There is evidence of prior battery leakage with associated prior repairs by another tech in the lower-left corner of the board.
ROM U19 is a 64 meg TSOP 44 mask ROM which doesn't appear to have a direct-fit flash equivalent. Assuming that the pinout for the U19 ROM is the same as the 16 meg TSOP 44 used for the BIOS at U18 would result in this pinout:
Breaking out the logic probe and checking the lines on both ROMs, I discovered the following:
- U18 and U19 share the same bus for Address and Data, with only the Output Enable (Pin 14) lines being unique to each ROM.
- Output Enable is generated by the PAL chip at U33. Pin 18 of U33 drives the Output Enable of the U19 ROM.
- The Output Enable signals are generating and getting passed to the ROMs correctly.
- The Address lines all showed proper High-Low pulsing activity.
- The Data lines seem to be holding mostly High.
Scoping out the Address lines versus the Data lines makes the problem even more apparent:
Address lines of U19
Data lines of U19
So it seems that the Data lines are trying to pulse Low but are being pulled High. I need to check around the board more to see if there's any other shared parts on the Data bus, but I did confirm that U18 and U19 Data lines do connect directly to the IGS 023 Custom in the center of the board.
At this point, I'm unsure if I should proceed directly to replacing the IGS 023 Custom with a donor from a PGM mainboard, or if I should try removing other parts that share the bus like the U18 BIOS ROM to see if they're pulling the signals High. I'm hoping the U19 ROM itself hasn't failed since there wouldn't be an easy way to replace it AFAIK. My gut feeling is that the Custom is bad, but I welcome opinions before proceeding further. Pinging @Fluffy , @iq_132 and @GC8TECH once again due to their familiarity with the PGM hardware.
Interestingly, the game does display the countdown timer text on the Version Select boot screen, and text appears on the high score table.
DDP-DOJ is based on the IGS PolyGameMaster hardware, and the MAME driver shows that the backgrounds and text tiles are supplied by two ROMs - a PGM BIOS ROM located at U18 on the PCB and an art content ROM located at U19 on the PCB.
In MAME, filling the "pgm_t01s.rom" file with FF using a binary editor had no affect on the game booting and running at all. But when I fill the U19 ROM with FF and run the game in MAME, the behavior matches the PCB exactly.
I checked over the board carefully with a microscope and ensured that there wasn't any physical damage to the legs of either of the involved ROMs or to the large "IGS 023" custom in the center of the board they're connected to. For good measure, I reflowed the soldered connections on the U19 ROM, but it made no difference. There is evidence of prior battery leakage with associated prior repairs by another tech in the lower-left corner of the board.
ROM U19 is a 64 meg TSOP 44 mask ROM which doesn't appear to have a direct-fit flash equivalent. Assuming that the pinout for the U19 ROM is the same as the 16 meg TSOP 44 used for the BIOS at U18 would result in this pinout:
Breaking out the logic probe and checking the lines on both ROMs, I discovered the following:
- U18 and U19 share the same bus for Address and Data, with only the Output Enable (Pin 14) lines being unique to each ROM.
- Output Enable is generated by the PAL chip at U33. Pin 18 of U33 drives the Output Enable of the U19 ROM.
- The Output Enable signals are generating and getting passed to the ROMs correctly.
- The Address lines all showed proper High-Low pulsing activity.
- The Data lines seem to be holding mostly High.
Scoping out the Address lines versus the Data lines makes the problem even more apparent:
Address lines of U19
Data lines of U19
So it seems that the Data lines are trying to pulse Low but are being pulled High. I need to check around the board more to see if there's any other shared parts on the Data bus, but I did confirm that U18 and U19 Data lines do connect directly to the IGS 023 Custom in the center of the board.
At this point, I'm unsure if I should proceed directly to replacing the IGS 023 Custom with a donor from a PGM mainboard, or if I should try removing other parts that share the bus like the U18 BIOS ROM to see if they're pulling the signals High. I'm hoping the U19 ROM itself hasn't failed since there wouldn't be an easy way to replace it AFAIK. My gut feeling is that the Custom is bad, but I welcome opinions before proceeding further. Pinging @Fluffy , @iq_132 and @GC8TECH once again due to their familiarity with the PGM hardware.
Last edited:
