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!

 

[kaisersose]

Hello,
i have a similar issue with a SF2 WW set :
89626A-4 90629B-3 90632C-1


as you can see there is a vertical line on the rigth side.
I have already carefully cheked the custom's pins and the tracks in the area near it.

The seller says B+C are working while the A board should be considered as defective.
I have not other CPS1 boards on which try swap for testing.

Do you think there is a chance the problem is instead related to the PAL 1A on the B board ?

 

[xodaraP]

If the seller is saying the A board should be considered defective they may have already tested it?

It could be a bad mask ROM but I wouldn’t buy a CPS1 set where the seller is saying the A board is bad

 

[kaisersose]

I wouldn’t buy a CPS1 set where the seller is saying the A board is bad

I took this A board on auction, declared with "some bad graphics", together with working B+C boards, only because i paid it a very low price.
This was my opportunity to have my fisrt CPS1 set. It is however working, apart from that (damned) line.

If the seller is saying the A board should be considered defective they may have already tested it?

I suppose the same but i've read this post on which djcalle is describing the same behaviour (vertical line) about working B+C board swapped on other A board and you suggested to replace the PAL 1A; moreover, on another thread user suggest the same for the same type of graphic issue.
So, not having at the time the possibility to test on another A board for the confirmation that it is faulty, i asked if, in the opinion of more expert users, it can have sense to suppose this is related to PAL 1A.

 

[xodaraP]

A broken PAL 1A usually causes the screen to turn into small squares but if it has fixed the issue for others, anything is possible

I don’t think this is the case because the line is the same through all layers of graphics. I think the seller has tested it using another A board and has confirmed that’s where the fault is and it was sold as same

Given it is only a single line however, it is very possible the issue is a bad trace and not a bad custom. Maybe look on the A board to see if there are any scratches that may have damaged a trace

 

[GoldenGlover]

I’m thinking it could also be a pin problem, especially those pins nearest the inner edges of the B board connectors. I’ve seen some oddly bend over time, especially if the plastic edges start to break away.

 

[xodaraP]

Yep could be that too. The black line is missing data. Don’t get your hopes up but it may be fixable