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Thread: System16B issue: vertical lines on sprites

  1. #1
    Mr. Big's Thug
    donluca's Avatar
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    System16B issue: vertical lines on sprites

    Here's the story:

    bought a couple months ago a System16B board with a 5704 Rom Board, it was running Tetris on an encrypted FD1094 CPU.

    The boards were in a pretty rough shape, so I cleaned it up a bit, replaced some caps which were on the verge of leaking and tested it out and worked without an issue.

    After a week my EPROM programmer came in along with a truckload of EPROMs and a "normal" Motorola 68000 CPU, 10Mhz.

    I swapped the CPU, burned the ROMs for Altered Beast (used the unencrypted ones of course), checked the jumper configuration, fired it up and it worked without a single issue.

    After a month or so I managed to almost 1CC it and decided it was time for a swap, so I burned the EPROMs for Golden Axe, adjusted the jumper settings, fired it up and it looked like it was working without an hitch, but when the attract mode kicked in I noticed that some of the sprites had vertical lines on them. Some white, some transparent.
    Backgrounds, music, sound effects, title screen, all perfect, along with some of the enemy sprites, but the sprite of the heroes had those damn vertical lines on them.

    I checked the ROMs and verified ok, I even erased them and wrote them again just to make sure.
    Still a no go.

    Tried with another game, Cotton, same issue: perfect backgrounds, title screen and some enemies too were fine, but other sprites had the vertical lines on them.

    Again, I gave a go at Wonder Boy III, this time most of the stuff were perfect and only some parts of some sprites had vertical lines on them (the hero had vertical lines on his body but not on his face or hair, most of the enemies were fine, etc...).

    I went back to Altered Beast and to my dismay I found out that now the sprites (hero, enemies and the graves) had the same issue.

    Since the boards were still pretty dirty, I gave it a good deep cleaning using a toothbrush and Isopropyl alcohol, rinsed it with tap water, dried it with an air drier first and then let it dry in the sun for 4 hours.
    Now I tried it again and I have still the same issue and I'm out of ideas.

    I even closely inspected the boards for scratches and trace damage and couldn't find a thing. There were a couple of scratches but I measured continuity and they were all ok.

    Any help would be greatly appreciated!

    EDIT: oh and the games play just fine. Coins up correctly, controls all ok, plays without freezes, etc...

    Here are some pics:

    Spoiler:


    Last edited by donluca; 08-02-2017 at 03:08 PM.

  2. #2
    Crossed Swords Squire
    Sypth's Avatar
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    Have you used any other ROM board, or just kept swapping between EPROMs? I've run into troubles of EPROMs not failing, but becoming slow, which affected the graphics. I also had a graphical issue recently with an E-Swat that turned out to be a bad PLC chip, where it had vertical lines through only certain images.

  3. #3
    SouthTown StreetSweeper
    mikejmoffitt's Avatar
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    I don't think it is a ROM problem because System 16 sprites rely on ROM data to know when it is the end of a line. With bad sprite ROMs you get big horizontal streaks rightwards from the sprite, and I'm not seeing that here. IIRC sprites are linear, not planar, so these missing lines wouldn't happen from a bad ROM data line. Addressing is certainly looking fine.

    I don't know off the top of my head, but if there are data buffers after the sprite data lines, I would check those. It looks like a problem during buffering right after sprite data fetching, or during sprite data readout.

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