iMac G5- Doesnt Power up- Has good trickle voltage

#1 Mon, 16 May 2011 - 21:13 68kMLA

I have an iMac G5 on the bench im fixing for a friend, It wont turn on, All the caps look good, The diagnostic LEDS show good trickle power, but it wont turn on

Any ideas on this

#2 Mon, 16 May 2011 - 22:33 68kMLA

It's possible that the SMU (System Management Unit) has gotten corrupted.

http://support.apple.com/kb/ht1767

I hope that helps. Let us know what you find.

73s de Phreakout. :rambo:

PS: I found this as well. I hope that helps, too.

#3 Mon, 16 May 2011 - 22:49 68kMLA

I had the same issue, turned out to be the power supply. I replaced it with an ATX conversion, and it worked fine.

#4 Mon, 16 May 2011 - 22:56 68kMLA

Well, power supply checked out, it was the logic board, So hes finding another one. Hes the president of our local apple club and it turns out they dont have a hardware person in the club, so i guess im on the phone tree now lol

#5 Mon, 16 May 2011 - 22:57 68kMLA

Apple club? That sounds cool!

#6 Tue, 17 May 2011 - 00:40 68kMLA

was the psu tested in another imac? apple told me the same thing, but the psu had a blown cap, and everything else worked fine

#7 Tue, 17 May 2011 - 16:59 68kMLA

Those logic boards suffer from bad caps all the time. It's cheap fix if you've got 15 minutes to spare with a soldering iron.

#8 Fri, 27 May 2011 - 13:04 68kMLA

Typically even if there is trickle power but the unit will not power on, only 1 LED lit on the logic board (the one for trickle), the power supply is typically at fault. If you have a spare power supply to test with you can boot the machine and look in the logs for "-110" . You will see, and a forget the exact wording, but something along the lines of "SMU Shutdown Cause -110". This is a clear indication of power supply failure.

In my experience the most common symptoms of logic board issues are, the obvious leaking and bulging capacitors, video corruption, and fans that constantly run at full blast even with lower CPU load. I have very rarely, if at all, worked on one of these that would not power on at all but no capacitor issues. However it doesn't mean it isn't possible.