Taito Arkanoid - Missing Sprites

[Bensonrad]

Picked up a couple of Arkanoid PCBs today, was hoping one might be Tournament, but both were original standard Arkanoids, slightly different PCBs though which seems to be the case with these. One of them has sprite issues, game boots up, credits up, plays sets, shows all Okay in test mode. However its missing all the main moving sprites, the paddle or ball might occasionally flicker at the very bottom of the screen for a spit second, but other than that you don't see the paddle, ball, the enemies, or falling power ups. I am guessing it might be the EPROM that contains such graphics, does anyone know which ROM contains those at all?

Pic of the PCB below, also a screen shot in attract mode when the ball has appeared with part of a sprite for a split second.

Bensonrad2019-06-09 12:18:48

 

[sttic]

Hi,
Gfx roms would be 3, 4 and 5, but since it's specifically the sprites that have issues and not other gfx I'd be more inclined to believe the issue be the RAM, check the 2016 chips on the same row as those ROMs.

-S

 

[Bensonrad]

Thanks, would it still having part of the old adapter soldered to the edge connector be a possible cause of issue, do you think?

 

[sttic]

Hi,
Randomly ran into this post again and noticed I hadn't replied, perhaps you solved it already but thought I'd say something anyway.

The soldered wires are attached to power and ground but where do they go? How's the voltages on the board?

If 5V is a bit low on the edge connector and since there's going to be voltage drop when going down the board, then yes, it might lead to issues with chips that are further away.

And, maybe not news, but having to crank up the PSU 5V line for maybe even half a volt is normal but if it still measures too low at the far end of the board then there's an issue that's bringing it down and you shouldn't try to adjust PSU any more to get it at 5V because it'll overload the chips closer to the connector.

(If interested try downloading specsheets for few different chips, they list the operating voltage tolerances, usually they take some abuse but if it's rated for 4-6V and given 12V wouldn't be surprised if it gets damaged). As an aside, if there's need to replace 74LS chips, go for 74HCT series instead they draw less current (less voltage drop, less heat, more life) but not for 74HC, they're a bit sensitive.

HTH,

-S