CPS1 vertical lines on sprites

littlecharlie

Quiz Detective
Joined
Jan 10, 2018
Posts
83
Hi, I've been using my SFII' board for a long time, and suddenly, now the board shows vertical lines on sprites and on other items (like the health bar).

BZG9jIs.jpeg


I discard a broken trace or anything similar because I haven't manipulated the board for a long time.

Also, I have a working SFII board, and I have used its A board with my B+C SFII' boards, and the game plays just fine, so it's definitely a problem with the SFII' A board.

So, can you please point me in the right direction? Maybe a problem with the RAMs?

Also, is it possible to use a logic probe just powering the A board? It's obviously almost impracticable to probe the components in the A board with the B board on top.
 

ShootTheCore

Genam's Azami Sharpener
Joined
Feb 11, 2015
Posts
1,509
Unfortunately the CPS-A custom chip has a very high failure rate and typically vertical lines through the graphics occurs when its on its way out.

You can get a replacement donor from another CPS1 A board or from a CPS2 A Board - a donor from a CPS2 will likely last longer.

There is a CPS1 Diagnostic ROM you can try that tests some of the RAM. You should also check the connectors on your A board and make sure none of the pins are bent or missing. Reflowing the solder on the CPS-A custom is a good idea too. Check for trace damage underneath the A board. Logic probe the DRAM and look for stuck lines - if you find some, trace them back to their source.

As far as logic probing the A board, you can either hit it from underneath, or buy one of these diagnostic spacer kits:

The A board will sit idle without the B+C board connected - not useful for diagnosing anything beyond making sure each chip has power and ground.

Take a look at this too:

1711779406365.jpeg
 

littlecharlie

Quiz Detective
Joined
Jan 10, 2018
Posts
83
Thanks for the information shootthecore.

The adaptors are awesome, but way too expensive (and just for troobleshooting one board). I'll try to buy a working A board for that price.

I'll test the Drams (which I think are the ones responsible for the sprites) from underneath and check anything suspicious (I have a working cps1 board so I'll try and compare).

Hopefully it's not the CPS-A ppu...
 
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