OSSC possibly bricked

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  • #24996
    Sega90s
    Participant

    I hooked up an old computer(XP machine) through vga port, then into an LCD panel. The computer was running for five minutes and then a loud pop came from the power supply. Immediately I checked , both the OSSC and lcd panel would now no longer power on. The tv was on its way out anyway, but I fear this fried the OSSC. I probed the board and it appears U5 output pin is shorting to ground. Is this fixable?

    #25036
    BuckoA51
    Keymaster

    I asked our technician about this here’s what he said:-

    If U5 output pin is shorting to GND then from my experience it could be just that U5 needs swapping out or it could be that the FPGA has blown. If after moving U5 the output trace still has a short to GND then it’s probably the later and if so then there could be more damage elsewhere as the FPGA is not usually the first to blow.

    #25065
    Sega90s
    Participant

    I lifted the right pin on the regulator and it still has continuity to the middle pin on the board.? Since the short went through the VGA port I’m pretty sure now the fpga is fried. Is there a circuit diagram that shows better where these traces go? Also is there a cheaper kit for sale with just the board and no plastic plates or power cord?
    Output pin

    #25076
    DevLatron
    Participant

    You can find schematics for KiCAD and Openboardview in the ossc_pcb github repository. A thorough visual inspection might give you some clues. If you fried the OSSC and the output LCD check the HDMI for faults, since 5V go there pretty much directly.

    #25077
    DevLatron
    Participant

    Here’s some more info:

    U5 supplies IOVDD / DVDD3V3, which is used to generate more power rails through U7 and U9, each of which has capacitors as well. You can quickly check these for shorts on their respective in/out sides: C32, C34, C93.

    IOVDD indeed goes just about anywhere on the board.

    VGA Input goes to the TVP (U1), and SN74LVC2G17 (U4).

    Thorough inspection with a microscope would probably be required, and maybe trying to identify the broken chip via heat (and isoprop) could help identify the issue.

    #26238
    Nodoka75
    Participant

    Hello,

    I suggest you to lift Input from U5. If the short has gone, then replace U5 ^^

    I remember that there was changes in the VGA pinout within years, one pin especially but I can’t remember witch on. Maybe the graphics card hasn’t the right pinout, causing the issue.

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