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G5 dead logic board?

Posted: Tue Nov 29, 2016 6:15 pm
by SAQ
I was given a G5, and thought I'd play around with it - latest and best of the PPC and all that. It's a dual 1.8 PCI-X/AGP model.

Went to turn it on, white light flashes and goes off, fans come on, monitor doesn't come out of power save. Mouse light comes on, but caps lock doesn't toggle on the keyboard, nor does the light flash on power up. Pretty sure I can hear the disk drive come on.

I'm thinking that this might be a true dead logic board, though I suppose one rail of the PSU could be dead, or possibly the processor module isn't seated correctly. Did verify that monitor and keyboard work with another machine. No boot noise at all, but don't know if it is volume turned down or if the machine isn't getting to the boot noise point.

Any G5 gurus out there? It's not worth a huge time investment, but if someone has an "oh yeah, that, do ____" it could be cool.

Re: G5 dead logic board?

Posted: Tue Nov 29, 2016 10:51 pm
by tomvos
I'm no guru at all. But perhaps you want to have a look at the service manual. One of the last sections is called trouble shooting. Perhaps this will lead so some conclusion.

http://tim.id.au/laptops/apple/powermac/powermac_g5.pdf

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 12:30 am
by uunix
If you take the side panel off, you should get a better view of the diagnostic lights.
Funny, really, as one of my G5's has decided not to turn on with very similar symptoms. I haven't bothered looking yet.

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 1:22 am
by Shiunbird
I thought only the PCI Express G5s (dual core 970MP) had diagnostic lights on the motherboard.

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 2:51 am
by uunix
Shiunbird wrote:I thought only the PCI Express G5s (dual core 970MP) had diagnostic lights on the motherboard.

ooh, I don't know, I was just going off mine. :oops:

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 5:09 am
by SAQ
I know there's a red light that turns on if the fans aren't seated all the way or the air shield is off, but haven't seen anything like what the "bigger" computers have (e.g. SGI).

I'll probably try re-seating the processors.

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 6:29 am
by ClassicHasClass
There are LEDs in front but fewer than the later systems. Reseating the CPUs seems a good first step.

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 3:05 pm
by nyef
If I recall correctly, some G5-era systems fail due to problems with the lead-free solder which was relatively new at the time, sometimes fixable by careful use of a hair dryer. And there may have been a run of bad capacitors on the market as well...

Re: G5 dead logic board?

Posted: Wed Nov 30, 2016 4:08 pm
by ClassicHasClass
It's mostly the iMac G5 systems that had the bad caps, and even in those it was primarily a power supply problem (the symptoms here do not suggest the PSU is bad). I've had very few Power Macs die due to capacitors. The symptoms described are likely either going to be a bad CPU assembly or a bad logic board, unfortunately, but I'd also swap video cards and RAM just to see.