Dual 500MHz G4 Won't Start.

Discussion in 'Macintosh Computers' started by supachicken, Dec 3, 2005.

  1. macrumors member


    Oct 5, 2005
    Hi Guys,

    I have a G4 Dual 500MHz Sawtooth that wouldn't boot or show any signs of booting. I tried the battery in another machine, reset the PMU and various other procedures with no success.

    I then pulled out the PSU and and put in a old PSU from a working Beige G3 and I was shown some form of life.

    Now when I push the power button the optical drives flash on and there is a red LED next to the last stick of RAM labelled D55 illuminates and the fan cycles for about 5 seconds then stops.

    No activity on the monitor and the machine does not chime.

    Does this mean that the PSU was the original problem and the Beige PSU doesn't have enough power to boot the G4 or there still could be logic board problems?

    Thanks for all your help guys, I really appreciate it.
  2. macrumors 65816


    Jul 7, 2005
    well first of all they didnt make dual sawtooths
    the is a probally a dual digital audio machine

    sounds like a bad PSU
    and the old beige is not giving it enough power

    red light = not good

    im gonna read some more about this and post back
  3. thread starter macrumors member


    Oct 5, 2005

    Thanks heaps for your help, it was originally a 450MHz Sawtooth which was upgraded to dual 500MHz.

    Didn't think the Beige PSU would have enough juice.
  4. Moderator


    Staff Member

    Feb 1, 2005
    Land of 10,000 Lakes
    You may have logic board problems now as not all PSU pin-outs are the same from G3 to G4, or even G4 to G4 in some cases.

    If you suspect the PSU from the G4 to be bad, replace it. Have you checked (with a Volt meter) to see if any of the pins on the PSU are supplying the logic board with power?

    Resetting the PMU can sometimes be tricky. I had received a Digital Audio Logic board that absolutely did not want to power on. I had to attempt the PMU trick multiple times to get it to function correctly.

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