Pismo PMU logic board squealing?

Discussion in 'MacBook Pro' started by kirk wilson, Aug 5, 2008.

  1. kirk wilson macrumors member

    May 18, 2008
    .. at least that is what I am figuring now. Today I ordered a new one..
    are they easy to put in?

    (my Pismo makes squealing sound all the time when plugged in; battery is
    junk but does have 40 minutes charge; squeal comes out of center of unit and not speakers; PRAM and PMU resets do nothing; unplugging it and plugging
    back in ALWAYS start the squealing- like when there is a storm or a brownout
    (common where I live)

    and then it goes away, after either the charge reaches 100 percent, or the audio cable is pulled, or the charger is unplugged and plugged back in to the wall, nine times.. not eight times or seven)

    It's not coming from the speakers or the screen; however the audio is screwy
    (one channel is louder and the other channel sounds like reverb, when I play music).

    Today the squeal is not so loud, like it's just tired.

    Oh, well- anyone else who has had PISMO squealing, out there?
    You will eventually.

  2. kirk wilson thread starter macrumors member

    May 18, 2008
    Update, if anyone cares..

    I mistakenly ordered a PMU board, not a logic board (mother board).
    I went ahead and put that in, and
    I also replaced the sound/power card. No change in the squealing.
    What I am finding is that it is most likely the mother board, with a bad capacitor or diode in it. So i'll order a new mother board.

    Unfortunately I have to buy a used one, which may well develop squeal
    all over again.

    (the squeal is the sound a camera flash makes while charging up)

    So, problem almost solved. It's the motherboard (i've replaced everything else)

  3. kirk wilson thread starter macrumors member

    May 18, 2008
    Problem Not Solved.

    Well, I went ahead and ordered a motherboard, and installed it.
    No change in the 'squeal'. Waste of time, and money.

    The only thing I have yet to replace-- is the processor.

    But.. as I said, the Pismo constantly whines (loudly) whether it is
    ON or OFF. It's all about whether it is plugged in to its charger.

    Perhaps the new PMU/battery board which I bought was bad?
    That's where the sound comes from.


  4. Fox McCloud macrumors newbie

    Aug 6, 2009
    Glue it!

    My Pismo had a similar problem (the noises wasn't always constant but appeared under similar circumstances).

    To fix it, start by removing the keyboard, next lift the piece of plastic that holds the power button and the sleep light. Inside is a long board. Make sure it's secured by the two prongs at the bottom and glue it so it's resting against the back of the case via a glue gun. Reposition the plastic and keyboard and thats it. No screws, no blues, no money spent as long as you already have a glue gun.

    Hope this fixes your problem. Happy Pismo-ing
  5. Macdctr macrumors 6502

    Nov 25, 2009
    Try replacing the Sound Card...

    I had a high pitched noise as well in my Pismo and when I changed out the AC/DC converter board (aka. Sound Card) I no longer had that high pitched noise. The Sound card is the board where the Power adapter connects to your Pismo. It's the weak point for the Pismos and they fail on occasion. If you start to hear a high pitched whine or tone then that's the sound card in the beginings of failing. Once the card fails then the Pismo will have issues with powering up. I have gotten a few from ebay just in case I have to replace this board again.

    Here is a good link to repair the Pismo. I used this until I became quite familiar with the internals of my Pismo. It has alot of great pics to help you along...hope this helps :apple:


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