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Thread: MVS issue - bad graphics, RAM all tests OK

  1. #1
    Pvt. Picklestein
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    MVS issue - bad graphics, RAM all tests OK

    Hi guys,

    I'm having some weird trouble with my MVS-1FZ. It was working pretty well except for a few issues when the Bust-A-Move logo scales during in the intro, but I chalked it up to a possible boot cartridge.

    Today it's acting very strange, the Neo Geo logo doesn't really flip properly during the system intro, and there's a portion of mostly-missing graphics in the center of the screen. Seems like.. the background layer and some sprites haha.

    I have a diagnostic BIOS which is showing me all tests passed and I've even tried another cartridge slot - I have a few other FZs. And of course I tried a few different carts, which work on other systems.

    I'm pretty sure this going to come down to a nicked trace or corrosion or something, anyone have an idea where to start? before I just start with the 'scope?

    Here's a bad video, ignore the changing brightness, that's just a framerate issue.
    https://photos.app.goo.gl/eZ7v1VHmTCNezcS33
    Last edited by The Webmiester; 10-26-2017 at 06:27 PM.
    callan's video game projects:
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  2. #2
    Hardened Shock Trooper

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    If you have access to a unibios you could use that and calculate the checksum for the roms and see if you get any errors that way. If it doesn't throw any erros it would rule out the cartridge slot at least.

  3. #3
    Pvt. Picklestein
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    Good idea, yes the UniBIOS shows game ID 47 and the CRC passes, so the cartridge is reading good.

    If it narrows anything else down, in the UniBIOS menu, the "Neo Geo" text/logo at the top glitches a bit but the regular text is all rock solid.
    callan's video game projects:
    -Basic NES Repro Tutorial
    -MMC3 NES Repro Tutorial
    -Castlevania III with full VRC VI sound
    -Super Mario All-Stars NES (4-game 10NES controlled multicart)
    -Colecovision power switch replacement
    http://www.callanbrown.com

  4. #4
    Angel's Love Slave
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    Quote Originally Posted by The Webmiester View Post
    Good idea, yes the UniBIOS shows game ID 47 and the CRC passes, so the cartridge is reading good.

    If it narrows anything else down, in the UniBIOS menu, the "Neo Geo" text/logo at the top glitches a bit but the regular text is all rock solid.
    The CRC check only checks the prog roms. Have you tried cleaning up the cart riser interconnect on the motherboard? Also inspect the cart connection under the PCB to make sure you haven't got any broken traces etc. Beyond that perhaps the ZMC2 chip.
    Last edited by GadgetUK; 10-27-2017 at 08:40 AM.
    My YouTube channel contains some MVS repairs and stuff:-
    http://www.youtube.com/user/GadgetUK164

  5. #5
    Pvt. Picklestein
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    Quote Originally Posted by GadgetUK View Post
    The CRC check only checks the prog roms. Have you tried cleaning up the cart riser interconnect on the motherboard? Also inspect the cart connection under the PCB to make sure you haven't got any broken traces etc. Beyond that perhaps the ZMC2 chip.
    I have more FZ boards so I did try other risers which had no effect. I have done a check for traces and corrosion.. though I haven't checked around the battery so maybe it's time to do that.
    callan's video game projects:
    -Basic NES Repro Tutorial
    -MMC3 NES Repro Tutorial
    -Castlevania III with full VRC VI sound
    -Super Mario All-Stars NES (4-game 10NES controlled multicart)
    -Colecovision power switch replacement
    http://www.callanbrown.com

  6. #6
    Pvt. Picklestein
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    Could this be the L0 ROM? Neo Geo dev wiki says it's responsible for the vertical shrinking lookup table. Since the Neo Geo logo isn't shrinking correctly..
    callan's video game projects:
    -Basic NES Repro Tutorial
    -MMC3 NES Repro Tutorial
    -Castlevania III with full VRC VI sound
    -Super Mario All-Stars NES (4-game 10NES controlled multicart)
    -Colecovision power switch replacement
    http://www.callanbrown.com

  7. #7
    Angel's Love Slave
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    Yes, that sounds possible! Isn't there a 74LS244 related to that too (I cannot rememeber without checking schematics).
    My YouTube channel contains some MVS repairs and stuff:-
    http://www.youtube.com/user/GadgetUK164

  8. #8
    Bashful Neophyte
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    Quote Originally Posted by GadgetUK View Post
    Yes, that sounds possible! Isn't there a 74LS244 related to that too (I cannot rememeber without checking schematics).
    I agree it is possible. I would check that and the area arond that for possible issues or damaged traces.

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