MDD PSU fan replacement

Discussion in 'PowerPC Macs' started by philz4life, Mar 6, 2013.

  1. philz4life macrumors member

    Jan 15, 2013
    Hey everyone
    I am the proud owner of a dual 1.25 GHZ PowerMac G4 MDD that I continue to use every day. However, the fan noise is ridiculously loud, so I have done some research and purchased fans to replace those in the power supply. However, I'm worried about actually replacing them. I know that power supplies are dangerous and have high voltage capacitors, but I have heard many different things about how to safely operate on them. Some people say that you can just wait a few minutes, others say several days, but I have also heard that you must use a special tool to discharge the caps. Has anyone done this before? Is replacing the fans easy, and what safety precautions should I take? Thankyou :)
  2. seveej macrumors 6502a


    Dec 14, 2009
    Helsinki, Finland

    Those capacitors can zap you pretty bad. And a accelerated discharge may also ruin the PSU.

    But there's a work-around: Don't touch anything. Get a set of electrician's tools, sturdy plastic tweezers are a must. Steady your hands. Open the PSU, unscrew the fans, pull out the fan wires (rewire the new fans to the old connectors if needed), put in the new fans, connect the wires. Close the PSU.
    Done. If your connectors match, it can be done in <5 mins.

    BTW, If you have some thin cell plastic (I used a wool thread covered with electrical tape...) you can use to physically isolate the PSU fans from the MDD internal chassis, it will significantly reduce resonance and rattling.

    N.B! The thermal design of the MDD's PSU sucks big time. The components which need cooling the most are aside from the main air flow channel... Make sure your replacement fans move enough air, otherwise you will soon have a dead PSU.
  3. havokalien macrumors 6502a


    Apr 27, 2006
    Kelso, Wa

    Don't worry about the voltage too much. Unplug the machine and hit the power button. Done deal.

    As for the fans if you can get the right size it's a super easy swap.

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