Fsp spi-200g

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  • pdavid
    Badcaps Veteran
    • Jan 2011
    • 279
    • Hungary

    #1

    Fsp spi-200g

    I need some help with an old AT psu thats in a pentium 200 machine.

    Recently it's started giving me some trouble. 5 Volt is about 5.7 and the 12V rail has dropped to 10. There is a trimer that goes to a KA7500B, but changing it only gives 2-3 millivolt difference. Also there is a 47 ohm resistor between ground and the 12V rail which isn't marked on the pcb. The original one got burned with the heatshrink on it too. I changed it but it still gets extremely hot after a while. I haven't measured the other resistors yet. The PSU turns on and works and nothing else seems to gone bad on it so I want to know how to fix it.

    Thanks!
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  • Th3_uN1Qu3
    Believe in
    • Jul 2010
    • 6031
    • Romania

    #2
    Re: Fsp spi-200g

    Are you using something to load that power supply's 5v rail? That's how they're supposed to be used.

    If no 5v load, remove that 12v resistor, it is entirely unnecessary, wastes power, heats up, and causes the low voltage that you see on the 12v rail. Even with that resistor removed you may still have low 12v without at least a small load on 5v. Try an old hard drive or something and see if it goes back in spec.
    Originally posted by PeteS in CA
    Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
    A working TV? How boring!

    Comment

    • pdavid
      Badcaps Veteran
      • Jan 2011
      • 279
      • Hungary

      #3
      Re: Fsp spi-200g

      The pc was freezing so I started to check the peripherals. There was about 3 ampers of load on the 5V rail when I tested it with light bulbs and hdd.

      I started measuring some resistors and so far 1 doesn't match it's color code, it's much higher. It's around that 47 ohm resistor, the pcb is slightly brownish there. If nothing else works I'll just get another AT psu.

      Comment

      • pdavid
        Badcaps Veteran
        • Jan 2011
        • 279
        • Hungary

        #4
        Re: Fsp spi-200g

        Well, I changed that out-of-value resistor, took out that 47 ohm one and everything is fine. The PSU ran for a day and both voltages are rock solid

        Comment

        • Th3_uN1Qu3
          Believe in
          • Jul 2010
          • 6031
          • Romania

          #5
          Re: Fsp spi-200g

          Good job. That resistor was likely in the feedback loop for the 5v rail.
          Originally posted by PeteS in CA
          Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
          A working TV? How boring!

          Comment

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