Bubble Bobble - no sprites or playfield text

[trm]

Had an original Taito Bubble Bobble that decided to hate me a while back. The sprites, all text in the playfield area disappeared. Occasionally would show up as mainly white or infrequently coloured streaks about 8-16 pixels wide. The platforms were always present.

Video probing around showed no sprites and infrequently the noise lines. Most of the 373 latches had static inputs but occasionally (the harder I punched it) sprites would appear, often with horizontal noise over the top.

Reflowed the video PCB. The entire PCB. Twice. Put it back on the shelf.

Picked it up again today. The 163 counter at IC25 which generates half of the Object Address bus had an intermittent ground causing a couple of bits drop-out on the OA counters. Fixed and rock solid.

I still suck a bit at the game, but it's 100%

PS pins 8-10 of the LS32 at IC75 are unused so will float. Obviously another 4 micrometers of copper would have bankrupted Taito.

 

[guddler]

Sounds like a result! Makes me think I should have another go at my BB - the one you sent me some cables for many moons ago

 

[trm]

It was a proper git and the board I used for my Logic Analyser wot-it-does post which I belatedly realised after fixing it, so I may have to redo that.

Somehow this wasn't just putting the OA off by a bit-flip value, it was completely knocking it out. The dodgy 163 fed into the colour address bus too but I can't see how that would wipe the playfield motion objects either, even if the colour palette entries all ended up as null because I'd have seen them on the video probe.

Prob worth having a bash at that BB - they're mates-rates £250 a pop now!