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DIY OSSC 1.5 no power

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This topic contains 4 replies, has 2 voices, and was last updated by  BonzoBits 1 month ago.

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  • #15153

    BonzoBits
    Participant

    I’m gonna pull out the tools and do some investigating, but I’m hoping for a legup from some more experienced folks.

    My OSSC has been working fine since last October, but today it carked it. Luckily I’d finally finished SNES F-Zero King mode on Master a few minutes earlier 😀 😀

    Anyway, the OSSC just switched itself off. Then when I switched it back on, the LED lit up (no text just the backlight) and flickered for 2-3 seconds before going dark.

    I’ve tested the PSU and that’s outputting a solid 5V.
    Neither F1 nor F2 are blown.

    I self installed an audio board about 2 months back. No problems with the install or the OSSC (until now).

    Any tips on where to investigate next?

    #15214

    marqs
    Participant

    I’d measure all regulator voltages, check that audio board gnd is properly connected to mainboard gnd, and that 27MHz oscillator is outputting clock correctly. If you have USB Blaster, you should check whether you can communicate with the FPGA.

    #15294

    BonzoBits
    Participant

    Thanks Marqs.

    The regulators seem fine, the only off results are as follow:

    – U5 input 4.81V
    – U6 input 4.78V
    – U13 output 2.49V
    – U14 output 1.19V

    Are any of these significant? Other than those four, all inputs/outputs are bang on the expected voltages.

    The ground connection for the audio board is good.

    Using USB blaster I wasn’t able to detect the hardware. The JTAG debugger says incorrect clock value – is that of any use?

    How do I measure the output clock of the oscillator?

    One final observation, when doing these tests I notice that the LCD backlight does come on when the unit is powered on, but only very faintly.

    Thanks again for your help.

    #15372

    marqs
    Participant

    If you cannot detect hw via JTAG and voltages are good (as they seem), then FPGA is definitely the problem. I’d reflow/resolder all its pins.

    #16310

    BonzoBits
    Participant

    Found multiple loose pins on the FPGA. Reflowed those and now working fine.

    Thanks again, Marqs.

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