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Dell optiplex 755 solid yellow light

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    Dell optiplex 755 solid yellow light

    Good day folks. I found this junker in my shop and decided to play around with it a bit, more to improve my skills than anything, since it's probably not worth the headache It's a Dell Optiplex 755 which doesn't turn on: power light is a solid amber, fan is spinning but that's it. None of the 4 diagnostic lights come on at the front. The PCI tester shows 00 all throughout...like the CPU is not present, though it is getting hot. Could be that VTT is present, but not VCC - haven't measured too in-depth due to the lack of a schematic.

    What I tried/ruled out so far but didn't work:

    1) Tried different PSU
    2) Removed 4 SMD capacitors near the CPU per a video I found on YT (and put them back shortly after, since nothing changed)
    3) Removed and flashed the flash SPI chip (which I hope I identified right, since it's the only one on there).
    4) No visibly bulged caps, though it doesn't mean they're good
    5) Heated up the board slightly
    6) Removing RAM causes no changes or beeps - normally it should beep AFAIK

    Is there anything else worth trying, or is some major component done for which would make it impossible/impractical to replace ? If someone has a schematic they can provide that would be wonderful, just to be really thorough.
    Last edited by Dannyx; 08-27-2018, 02:50 AM.
    Wattevah...

    #2
    Re: Dell optiplex 755 solid yellow light

    Is the CPU compatible? What about the RAM? I've had bad RAM cause a no-boot no-beep on Dell OptiPlex like that before.

    If the mobo has United Chemicon KZG or Rubycon MCZ caps, pull a few and test them - particularly the bigger ones around the RAM and chipset. These often go bad on BTX-style Dells (OptiPlex and Dimension).

    IIRC, memory slot order is not too important on these mobos, so try only 1 stick at a time and in different memory slots.

    Oh and last but not least... is the front fan going into "turbo" mode (i.e. spinning really fast) or just idling?

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      #3
      Re: Dell optiplex 755 solid yellow light

      The CPU is no doubt compatible since it came with it...unless it's dead. Not sure if the ones I tried were also compatible.

      Fan is idling if I remember correctly.

      I gave up on it momentarily because it seemed like such a chore to pull those caps out....you have to remove the board, it's pretty crowded in there...meh....
      Wattevah...

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