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Thread: MV-2 Flickering Pixels on edges

  1. #1
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    MV-2 Flickering Pixels on edges

    I've had this MV-2 for a long time, and it had vertical lines and very corrupt looking flickering graphics. Just a few days ago, I got around to addressing the problem - the old battery corrosion had destroyed almost all of the traces coming down from NEO-ZMC2, which does pixel multiplexing. The graphics are now almost perfect. I also repaired one bad ADPCM-A address trace to fix sound.

    I am left with only one problem. I've made sure my wiring from my repairs is correct and there are no shorts or egregiously long wires. The problem is that occasionally the edges of sprites will have flickering pixels that go between two states. This is most evident when H-shrinking is being applied but not always. I've tried to capture some evidence of it in a video:

    http://csh.rit.edu/~moffitt/img/mslug2.mov

    There are a few vias I can push on with my finger and make the dots change a little bit - something is definitely floating when it should be driven. The problem is I've followed the traces around and they are hard to follow as they go closer to the rest of the graphics chipset. I suspect the other end connects to ZMC2 but as they go under ZMC2 I can't really tell what is supposed to go where. If I can avoid de-soldering ZMC2 that would be great.

    If anyone has any pointers I would appreciate it. I'm so close to having this as a fully working board.

  2. #2
    Mizuki's Demon
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    403, check your file permissions sir

  3. #3
    SouthTown StreetSweeper
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    Whoops, try now.

  4. #4
    Mizuki's Demon
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    Yep, I can see it

    Sadly I'm probably of no help on this one, but best of luck.

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  6. #6
    SouthTown StreetSweeper
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    Unfortunately this is an MV-2 which has no NEO-B1 - just PRO-C0, which does connect to ZMC2's multiplexed pixels (both of them). All 8 connections look fine for that. It's correct so much of the time, and it only recurs on certain graphics tiles. I wonder if something is wrong with C rom addressing...

  7. #7
    JammaNationX
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    Then it would be the B0 and/or LSPC0. I had one that had that chipset that had that problem. I thought you had the MV2F so I tried to see which one it could be. I don't remember exactly what it was though.

  8. #8
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    With closer inspection, I've noticed it only seems to happen when sprites are placed on an odd H-position. It might be related to the way ZMC2 serializes pixel data two at a time - pixel A and pixel B. I spent a few hours probing about trying to figure out what should go where but we don't have schematics or pin info for this generation of the chipset so it's a bit harder than I wish it was...

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  10. #10
    SouthTown StreetSweeper
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    Yes, that's what I'm referring to - all of the graphics chipset I have are in the "to-do" section.

  11. #11
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    Changing the supply voltage makes the glitchy pixels move to other areas of the screen but I wouldn't say it really helped. Something is still definitely wrong.

  12. #12
    Sakura's Bank Manager
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    I'm seeing this on my 4-slot. Did you ever resolve?
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  13. #13
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    The fix was to remove the previous owner's "fix", which ran a jumper wire from some random point A to random point B.

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