Moonwalker sound & graphics glitch

[c0nn0r]

Hey gang, I have a desuicided Michael Jackson’s Moonwalker PCB here that I bought as non-working, and am making the attempt to fix this bad-boy myself.

There are three separate issues:

(1) Missing foreground sprites (bad IC-17 - Sony CXK5814 chip)
(2) PCM audio from the rebranded Ricoh RF5C68 smt chip (rebranded as ASSP 5C68A) is garbled
(3) Board fails half of the V.D.P. test. I’m not sure what this is, nor can I see any adverse effects on the graphics (aside from the missing foreground sprites) - perhaps this is a symptom of the bad IC-17?

Questions:

(1): Where can I buy working replacement parts for the chip st IC-17 - Sony CXK5814 or compatible?
(2): Where can I purchase a working replacement RICOH RF5C68 chip?
(3): What the deal with failing half of the V.D.P. test?

Here’s what I know thus far from my research and testing:

(1) Foreground graphics issue is likely tied to a bad work-ram at IC-17. I know this because the excellent memory test SEGA provided told me (and per this post: [url="https://forum.arcadeotaku.com/viewtopic.php?t=11206"]https://forum.arcadeotaku.com/viewtopic.php?t=11206[/url]). It looks like a previous owner attempted to fix this issue as the current chip at IC-17 is socketed. Looks like they just socketed the same chip as it matches the one at IC-16. I took out the chip, cleaned the pins and re-seated it. Still comes up as bad.

(2) PCM audio from the RICOH sound chip is garbled. FM synth still working properly, so the z80 is probably good. Pretty sure that I need to replace the RICOH chip (as per: [url="http://www.jammarcade.net/michael-jacksons-moonwalker-repair-log/"]http://www.jammarcade.net/michael-jacksons-moonwalker-repair-log/[/url]), but am having a tough time sourcing a replacement part. I’d prefer to buy a NOS chip, but as I understand it the same chip is used in the SEGA CD, so I may have to take one from scrap.

I’m hoping that if I can manage to replace these chips I will have a working Moonwalker.

[Lordsxo]

Just a shot in the dark, did you validate the ROM chips? I had garbled PCM sound on CPS1 board and found that the ROM with the samples didn't check. The garbling went away when I re-burned them.

[c0nn0r]

Thanks for your thoughts. I did the built-in diagnostic test - you can see the results here (click the right arrow to see the ROM/RAM check result:

It does include a ROM check, but not sure if it's checking all the roms.

[Lordsxo]

It only test the program ROMs, but it may be the video ram after all now that I think about it. I have a Shadow Dancer board that had a bad ram chip at IC 42 that cause most of the spites to disappear. The chip you have at IC17 is a Sony CXK5814 and a cross reference part is a Toshiba TMM2018 and maybe a UM6116, try to use those search terms.

You might be able to get it from a junk CPSII or a earlier MVS single slot boards boards.

[Lordsxo]

So I just looked at my Shadow Dancer board and IC17 on mine has TMM2018AP-35 in there. So that is something that can be used. I checked a few of my PCB, and there is a ton on a Cabel board that have, invact it's both CXK5814P-35L and TMM2018 used as it seems, interchangeably. Mine is fully working, but you can find them on the cheap if its the trackball version.

[c0nn0r]

You might be able to get it from a junk CPSII or a earlier MVS single slot boards boards.

Good to know! I have a junk CPS1... I'll take a look at that, otherwise I have fond a source for parts at http://buyicnow.com, but have never ordered from there. Comes recommended by trusty folks though.