PC Engine colour issue (with images)

[jsteel]

Here's a link to some images showing a comparison between a working console and a console showing incorrect colours. Both are Core Grafx II consoles, same cables. What might be the most likely cause here?

The graphics I wouldn't say are "scrambled" which I think is common with RAM problems? But just the colours are incorrect. Even around the face, while it might first look scrambled, it might just be the colours that are wrong.

The caps look fine to me, no bulging, no leaking, the pads look shiny. 7805 is giving me 5v. I've thoroughly cleaned the slot pins. Just wondering what to try next.

I've followed many traces following a schematic, no issues found yet. I've checked all the chips do not run hot (they are barely warm after 5 minutes). RGB output from the expansion port has the same issue as composite out of the side.

Appreciate any thoughts or things to check. Would it be one of the chips gone bad? That would be a shame.

[Syntax]

Warm up or press down on the Hu encoder chip whilst its running and see if it makes a difference.
Else double check the cart slot.

[PC Engine Fan X!]

Could be that the Hu-Card cart slot needs a really good cleaning -- if it's dirty, garbled graphics and colors will appear on-screen. Also clean the booted up Hu-Card's cart interface as well.

One time, I bought a second-hand used NEC Arcade Card Duo and the Hu-Card's cart contacts (which had seen better days when it was in better shape/newer condition) were quite dirty and wouldn't boot up properly. Spent some cleaning the ACD Hu-Card's cart contacts and now it works as intended/as it should from the "get-go." It's well known that if you have some really dirty Hu-Cards, get the cart contacts all super shiny clean -- this little "general upkeep" trick of cleaning up game carts works wonders nowadays.

PC Engine Fan X! ^_~

[jsteel]

Thanks both for your suggestions. I have tried pushing down on chips while running, and it doesn't make a difference.

I have tried real games and also my Everdrive. With my Everdrive (and the lid off the console) I can insert it just enough that I can check continuity between the Everdrive pins and the console, and every pin gives me continuity. I have pulled all the caps and tested their capacitance, as well as their ESR. Everything looks good there. I might buy some new caps just to be 100% sure rather than putting the old ones back in (they look like the originals, so very old).

It makes me think maybe one of the chips is bad. I might just have to use this for spare parts, and when I get another broken system, swap some chips around to narrow down further. In the meantime, any other thoughts welcome. Thanks

[fernan1234]

Really looks like a chip problem. Would be very surprised if a recap helps at all.

I guess one more thing to rule out other causes would be to test video output from the EXT port instead of the AV port, though the graphical corruption points to issues other than that.