Super Turbo w/ Weird Graphics Glitches

[kazuo]

When I got it, it was suicided. No sign of corrosion or leaks whatsoever, very clean board. Installed an Infinikey and it came back to life, but I'm seeing some weird rows of "dots" (pixels) almost in a grid pattern across the screen during startup, the warning screens, and the intro. However, during actual gameplay (character select, stage/character intro, gameplay), it works flawlessly. Memory test passes with everything showing "OK".

Obvious stuff I already did: visual inspection (no corrosion, no physical damage), pushed down on all the socketed chips to ensure they're seated, checked the "A" board for bent pins or other damage and blasted it with deoxit. No change.

Anyone have any ideas?

Thanks!

 

[Big_P Big_p]

Could be A B board connection, try seating the b board without its plastic shell. I find the cps2 really fussy about connections. That's probably not the best way to describe it, everything is fussy about connections, it's more like I find it really easy to not have good connections. Pressing can help but I run mine uncased because I find it makes better connection.

 

[kazuo]

Thanks for the suggestion! I actually did try running it decased (before & after the deoxit bath), but the problem persisted... I kinda low-key suspect this might be a problem with the A board.

I'm just really hesitant to spend $200+ on another A board and then it turns out that something's up with the B board. Kinda crazy how much CPS2 prices have spiked lately...

 

[Big_P Big_p]

I'm just really hesitant to spend $200+ on another A board and then it turns out that something's up with the B board. Kinda crazy how much CPS2 prices have spiked lately...

Yes it is kinda crazy. I have a persistent fear about needing to get a new A board. I almost purchased a cheapish one a few weeks back as a backup but it sold before I could.

Good news (maybe) is that if it's a board issue it's more likely one of the LS245s, CGA or CGD on the B board, so maybe try a known working B board on that A board before you commit to anything.

Considering your symptoms I would guess its one of the ls245s as the CGA and CGD handle character and background sprites from memory.

 

[kazuo]

Appreciate the insight! I did end up getting another A board, and lo and behold, having the exact same problem. Funny thing is, this A board also has a different problem (the colors are all messed up), which is convenient because now I can return it!

I may try replacing the LS245's since they're (probably?) cheap, and I suspect I can get them locally. I probably have another B board somewhere, so I'll give that a go before I start desoldering ICs most likely.

 

[Big_P Big_p]

So sorry I didn't get back to you quicker. I thought someone else may have chimed in. Glad you can return that A board.

 

[And One]

Everything your describing that this board does sounds normal to me.

 

[kazuo]

It's very clearly not normal and it is a graphical glitch; my multi doesn't do it, and my other ST board (also JP, exact same revision) doesn't do it.

 

[Big_P Big_p]

Yeah was about to say that while I have not seen a SSF2T A + B board only combination for a while, the behaviour described does not sound normal or like what I get out of my multi, but @kazuo beat me too it.

 

[kazuo]

Update: Got some time to play with this again.

I buzzed out the LS245's at 10L & 10M (below CGD & CGA customs), seemed to be continuous, but I bought spares so I decided to just shotgun 'em anyway. No change.

Thanks to hatmoose's detailed repair threads, I found this pdf, and this spreadsheet, but I couldn't quite make sense of the sheet and I ran out of time to look at the schematics today. So I might come back to it again eventually.

Somewhat related: Does anyone know if LCX245 are suitable replacements for the LS245's on these? The pinouts on the datasheets look basically identical and it's all I can get locally, so if it'll work, I might just shotgun all of them once I've buzzed them all out.