CPS1 Graphical issues

[djcalle]

Hi All, I have SF2 WW CPS1 board with major graphical issues.

What I have done so far:

• Swapped with working boards:
  • my B+C boards with a known working A board has the same red scrambled graphics. (see pics)
  • my A board with a known working B+C boards works with a weird vertical black line on left side (see pic "sf2 ww cps1_3.jpg")
• Verified all roms and eeproms against mame code.
• Reburned chips 29 and 36
• WIP: To test sockets: verified continuity between chip pins and pins on bottom of board. Chips 1,10,20 OK. Rest yet to be tested
• Checked continuity from C board's CPS-B-17 pins to interconnectors: OK
• One of the "CCX" Tantalum caps (10uf 10V) was rusted and snapped off, I replaced it with an electrolytic 10uf 16V

Does anybody have any ideas of what to look at based on the above?

What I am thinking of doing but have questions:

• 74LS chips: I have a logic probe which I never used, what is the best way to test them out?
• To order 74LS replacement, do the numbers matter: 74LSxxx, or can they be interchanged?
• PALs and GALs, can any chip with the same numbers be used as replacement or are they programmed?

Cheers!

 

[trmm]

I have the same board with the exact same problem unfortunately I haven't fixed it either, if I flex it a bit where there are no chips it reacts but once you let go then goes back so I assume there is a cold joint or a broken trace somewhere but I haven't had a chance to sort it out.

At first I thought it was a graphics chip but they all tested ok, reflowing the sockets didn't help either so the problem is somewhere else for me.

I was thinking on servicing the whole board and replace all common components, a BOM for these boards could come handy, I'll follow your thread to see if someone with experience enlightens us.

 

[xodaraP]

Replace the PAL at 1A

 

[djcalle]

Replace the PAL at 1A

Thanks @xodaraP!


I was fortunate enough to find someone kind enough to provide me with a replacement PAL16L8 which they programmed and we did a swap at theirs, no change unfortunately. It could be that the PAL was not properly programmed somehow or that the traces or socket of the !a chip on my board are the issue. I'll check the traces and socket.

Any other ideas besides that?

 

[xodaraP]

Have you got another C board you can try? Could definitely be a loose or bad C custom.

 

[djcalle]

Have you got another C board you can try? Could definitely be a loose or bad C custom.

unfortunately not, when I swapped the boards around with my mate's working one, swapping the C board would not even boot, in any of the swap combinations, I assume it was a different revision and tied to the B board. Are there any tests that can be done for the C board custom?

 

[xodaraP]

Try pressing down on the C custom and see if it improves, this will tell you if it's loose and needs a reflow. Outside of that you need another B-17 to swap it out with to test

 

[Apocalypse]

Looks like a bad graphic ROM to me.
High failure rate on those mask ROMs.

 

[xodaraP]

@djcalle do you have a programmer/access to a programmer to test the mask ROMs?

 

[djcalle]

@djcalle do you have a programmer/access to a programmer to test the mask ROMs?

Yes mate, I checked them all against MAME romdumps I believe (did this a long time ago)

I will continue checking continuity between chip pins and pins on bottom of board to confirm chip legs and sockets are ok. If this tests all god I might test the mask roms again.
I am pretty sure there are in the right place but is there a sure way or some good pics that show which mask room should go where?

 

[xodaraP]

Did you try pressing down on the C custom to see if there's any improvement?

The mask ROM locations are in the MAME driver or if you download the MAME files the filenames match the location

 

[djcalle]

Did you try pressing down on the C custom to see if there's any improvement?

The mask ROM locations are in the MAME driver or if you download the MAME files the filenames match the location

yes I did, no change.I also checked continuity oon the pins of that chip.

Thanks for that I'll check MAME!