Psikyo Strikers 1945 graphical glitch

[astro_zombie138]

So I recently aquired this board from another member with graphical glitches. Gameplay and audio work fine. Most of the graphics are actually fine and its perfectly playable. Opening screens show a line pattern in the background. I've seen lines appear during explosions in the game as well. I've recapped all of the electrolytics and reflowed everything on the top of the board with an exposed leg. No difference from when it was received. Does anyone have a clue as to what the issue could be?

 

[astro_zombie138]

 

[ImportantBet]

Can you pull out the EPROMs and check if the legs are clean? Might as well cleanse out the sockets while you're at it.

 

[astro_zombie138]

I tried that with some iso but may have to get more aggressive with some light sanding. You think it's the connection with the eproms?

 

[twistedsymphony]

I don't think it's an issue with any of the socketed EPROMs, this is clearly graphics related.

Last time I had a board with a graphics issue like this it ended up being a failing MASK ROM.

Graphics ROMs, Graphics RAMs and the logic chips between them are the things to check.

Given the repeating nature and it appears to be static all the way through the image I'd guess one of the video RAMs is the issue if you find a good working spare you can "piggy back" it on top of one of the existing RAMs to see if the issue goes away. if you're unfamiliar with this approach it's when testing a DIP IC that is not socketed you get a duplicate of that IC and bend the pins inward slightly then clamp it over the suspect IC such that each of the legs of the good working chip are putting pressure on the suspect chip. This allows the good working one to function in parallel with the failing one. You can do this with logic chips, ROMs, RAMs and even CPUs.

I've had some luck with that approach, it can be a good way to test without having to desolder anything.

 

[astro_zombie138]

Thank you for the detailed response, that makes a lot of sense. I did a simple continuity test on all the pins of the EPROMS and found them all to be making good contact so I was hesitant to investigate them further. I'll have to see if I have anything laying around but this gives me some solid insight to work with. Thank you @twistedsymphony. I actually have a logic probe arriving tomorrow, figured it was time to add it to the arsenal. Would this be a decent exercise to take it for a spin?

 

[twistedsymphony]

yeah logic probes are great for this stuff. you'll want to focus on the graphics areas and look for stuck or floating pins.

 

[astro_zombie138]

Perfect timing, thank you!