PowerMac G5 won't start; Power on light blinks.

Hi!

I have a PM G5 modell 11.2. The PM G5 froze so I had to power it off by pressing the powerbutton until it shut off. When restart I did not have any signal to the monitor and I found out that the LED 7 was blinking red. The machine went through apple support and the sad news was that the prosessor or mainboard (Logicboard) was broken..

Just a heads up, this happened to my Powermac G5 Saturday, and I've figured out how to fix it. One thing to test first is to see if pushing on the lower bank of RAM closest to the processor helps make it boot up. If it has, that's the area you need to fix.

So yes the logic board is bad, but if you have a soldering iron, and about 4 hours to waste, it's potentially repairable.

Here's what I did.
1. Spend an hour on Youtube looking for videos for disassembling your G5 - you'll need to know how to remove the logic board, and take out the processors. This isn't a trivial process, and putting it back is just as annoying, but it's do-able and you've got nothing to loose.

2. On the back of the Rev A logic board, you'll see a heat sink around the bank of memory closer to the edge of the board. The side that is furthest away from the edge is where you need to work (closest to the processor).

3. Using the soldering iron, carefully try to heat all the little contacts you can see for bank 1 and 2 of the lower set closest to the processor. If it's a Rev A, you don't need to remove the heat sink. You just need enough heat to melt the solder and let it harden again.

4. Re-assemble and test (remember to press the button on the motherboard to reset the motherboard settings if it gets beyond the 3 flashes and the Mac won't boot up).

In my case, the dual 2Ghz G5 (rev A) is working again, and as an additional bonus, it is noticeably snappier. 🙂

Good luck.

Great post/help Dean, thanks! 🙂

Hi Dean!

Is your PM G5 a modell 11.2 you repaired?

This post was my motivation to take apart my Power Mac G5 1.8 Single and fix the blinking lights problem. The symptoms were the same as Dean W’s: pushing on the lower RAM bank closest to processor made it boot.

I took my time taking the machine apart, watching various repair videos as needed. The ones available are for the dual G5 machine but were enough to get me down to the logic board. Once I found an overlooked screw beside the upper memory bank I was able to work the logic board out, barely clearing the power supply cables.

The area that needed soldering was partially shielded by a heat sink. I didn’t remove it and was worried that neglecting these pins would mean a failed repair but it was not obvious how to remove the sink and all the accompanying hardware. There were about 300 tiny pins that needed solder re-flowing. I used a magnifying glass to see where to aim my pencil-tip soldering gun. Some pins didn't seem to react to the heat; others instantly had their solder melt. To this point took about 2.5 hours. I put down my tools and left the re-assembly for the next day.

Before putting the machine back together, I went over the repair area checking for any missed pins or messy solder splatters. Re-assembly was easier than disassembly, once I remembered to put the power supply cover on before installing the rear fan unit. The order of assembly after that was fairly straight forward. The fiddliest part was re-attaching the cables along the top of the logic board. Another hour or so spent to complete the assembly.

Once assembled, the first attempt at power-up did nothing. I re-plugged the small connector from the front panel onto the logic board and then it booted up. Success! Except no video. Power down, reseat the video card, and now I have a functioning Power Mac, from which I am posting this comment.

Hi jehvicbc, and a warm welcome to the forums! 🙂

Great work, fantastic post thanks! 🙂

Hi Dean W. and jehvicbc -

How are you're repairs holding up - still working OK?

David

I have the same problem with my powermac g5, none of the ram slots work so i pressed on the BGA chip thats by the cpu and it booted. I knew it had to be soldering, so i bought a heat gun and heayed it and it worked for about 8hrs. Then the 3 blinking lights, and now I can't fix it. Did I melt something? Did my ram suddenly fail, has the pm decided to reject my ram?

Hi again guys,

Oh, well it looks like somebody else beat me to the point. 😟 But I was gonna say check out this thread, Ive not seen this method, but it appears to work well or so I think. 😉 http://discussions.apple.com/thread.jspa?threadID=2739578&tstart=30

Cheers.

—Matthew—