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Thread: NEO-GEO MVS 6-slot problems

  1. #1
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    NEO-GEO MVS 6-slot problems

    I have a NEO GEO 6 slot. Originally it had an video ram error message - address:8000 write:5555 read:0055 or 5500 (I can't remember). It was most likely to be one of the two CXK5814 (video RAM) chips, I didn't know which one at the time so I changed 1 first (made no difference) then changed the other. I have read here on aussiearcade and other sites people not knowing which chip but I have since found out (listed on wiki I think) that the first 2 digits in read are for the upper video RAM chip and next 2 for the lower RAM chip. When I plugged the MVS board in after replacing the second chip it just displayed a light green screen except for a tiny section that was white in the lower left quarter. It stayed the same for 10-12 minutes and than it went to a cross hatch. After I turned it off for 30 secs and then back on the light green screen displayed for about 10-15 secs and then went to the cross hatch again (maybe it has to warm up and took so long the first time but when it use to work fine it never took anytime) so I tried several combinations of carts in slot 1 and 2 but the cross hatch still would only appear after the initial green screen. Finding out which chips to replace for the video RAM error took me a long 10 hours to find and I was hoping that would be the only problem but with this new problem I don't know where to begin because no error message is displayed.

    I have another MVS 6-slot board that works but vertical lines are displayed in portions of moving and background graphics and are present with any game cart. I once had a single slot MVS that sometimes displayed a very similar issue with some carts but that was easily resolved by pushing the carts in and out a few times to clean the pins but in this case it seems to lie within the mother board. Any best bets on where I should start first (it has 2 huge boards).

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    This link can be a good source of information https://wiki.neogeodev.org/index.php?title=Main_Page. I cant really help with the 1st board but the 2nd i've seen before and for me it was track leading to the slots that had become disconnected. You'll need to check each trace leading to chips and slot to see which one doesnt have continuity. @Arcade King did a great schematic located here https://www.aussiearcade.com/showthr...=neogeo+repair

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    You need to look carefully for physically damaged traces and for battery damaged connectors between the upper and lower boards.

    The Program ROMs cannot be read by the CPU. You have an issue with one or more address and/or data lines.

    RJ

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    What would be the likelihood of it relating to the chips I replaced (the soldering/tracks checked ok with a continuity test after replaced). Any idea why it takes 10min to go to cross hatch when turning from cold first time?

    - - - Updated - - -

    great thanks for the wiki link, it has so much info on neo geo!

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