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**FIXED** System16 - Golden Axe with very odd video issue

TJam

TJam

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Hi all
I've been repairing a long dead Golden Axe board and after patching several gouged traces on the underside (mainly related to 68K), the damn thing sprung to life. Although, complete with some pronounced sprite glitching and an odd streaky tinted overlay to the video. I replaced a dead Sony RAM at F4 to clear up the sprite issues, but am left with the strange washed out streaky tint effect over the whole picture..
I wondered if it might be color RAM, but that checks out as "GOOD" in the service menu. In fact, all the testable RAM does. To be fair, when I think palette ram issues, I reckon there'd be more obvious problems with sprite and background palettes generally. It feels more like bad analog stage interference, but would REALLY appreciate any help on this as it has me stumped. Anyone else seen this type of thing before?
I've linked a video, trying to capture the effect. Also take a look at the still shot of the colour bars. Green looks fairly nominal, but red/blue and as expected, white is looking pretty sick. The vertical darker tones seen through the white and red bars move/creep as it sits on that screen. The focus is compromised with the amount of colour bleed/flare going on. and I don't think the surround is supposed to be pink!!? In game, the whole effect is dynamic to whatever is on screen swooshing around like fast moving mist.. I hope I'm explaining this okay.

View: https://youtu.be/29udfZ3erH0


Thanks in advance ;)
 

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I managed to get to the bottom of the GFX issue detailed above and wanted to add a follow up in case it helps out others with System 16 (or other) repairs.

The odd overly bright palette bleeding, smeary overlay issue came down to a pair of NEC HC273 flip flips located at J11 and J12. I ran the board upside down so I could probe the pins of these noticing one in particular had a couple of outputs consistently held low. I pulled the chip, tested it out of circuit and it was indeed faulty. Socketed, pressed in a replacement and fired 'er up to test. Much improved, but GFX issue still there somewhat. Pulled the second chip of the pair and it tested sick too. After replacement the issue was resolved. Sooooo stoked! This PCB would have been out of action for 10-15 years from what I understand.

One factor I thought was interesting - I didn't have any "HC" 273s on hand, so thought I'd pull a couple of LS273s from a parts board and they are working just fine. Hard to say if they'll last being a slower performer that their HC brethren or perhaps the faster parts were an over-spec on SEGAs part. Dunno...

Anyway, gonna go play some Golden Axe :thumbsup:
 
While lavishing this GA board with some further attention I noted the OE CR2032 battery inside the FD1094 68k block had a batch date of "89-05"!! WTF? I can not believe this was/is still sitting happy at 3v after thirty five years of unflinching service. The Japanese certainly new how to make batteries. Or perhaps I've just been VERY lucky. I did, of course, replace it, but still...

Love to hear if anyone has seen a suicide battery last so long before. This is madness, frankly.

GA_OE-Batt_batch-date.jpg
 
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