View Full Version : Dual 500MHz G4 Won't Start.

Dec 3, 2005, 10:08 PM
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.

Dec 3, 2005, 10:13 PM
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

Dec 3, 2005, 10:20 PM

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.

Dec 3, 2005, 10:43 PM
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.