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PowerMac G5 won't boot =(

Discussion in 'PowerPC Macs' started by haravikk, Jun 1, 2010.

  1. macrumors 65816

    Okay, my old PowerMac G5 which is now what my dad is using seems to have decided to throw a wobbler. It simply won't start up, it either doesn't display anything at all, or gets to the grey apple logo and apparently freezes.

    Now, I've run through all the usual stuff, but it won't start up from any CD except for the Apple Hardware test. While the test reports everything as a success, the fact that it is the only disk that the computer will start up from is suspiciously similar to what happened to my MacPro a little while ago when its graphics card stopped working properly, because as I understand it the hardware test skips the GPU part and just draws directly to the monitor using the graphics card's monitor connector.

    However, unlike with my MacPro which was obviously still working away quite happily despite its lack of ability to draw to a screen, the G5 doesn't appear to be making any hard drive noise indicating start up. This has me suspicious that it may be a more serious problem like the power supply, which would make sense if it were running the GPU that is the problem if doing so causes the power to step up but it isn't getting enough. I'm not sure what the power drain is like for two hard drives though, but if the GPU is drawing too much it's possible the hard drives just can't get any power either. I've reset the PMU with no luck there, can't seem to get far enough to reset PRAM, and that's all I know to try for a power supply issue.

    Now, I'm in the difficult position that I've run out of things to try to confirm where the problem lies. I'd like to exhaust all things I can test for myself before I take it in for repair, but I don't have any other machines with AGP graphics cards that I could try, at least I don't think I do; I have a blue & white G3 with ATI RAGE 16mb, is the graphics card removable on that, would it work in the G5? I don't really want to go digging it out from whatever corner its disappeared to if it's going to be a dead end!

    So, don't suppose anyone has any other ideas of things to try?
  2. macrumors 68040


    Sure, as long as your G5 is AGP (i.e. has PCI or PCI X slots - i assume from your post that it is). Try it and post results. Does it chime when give no video? Did you checked RAM? Is it watercooled one maybe? (Dual 2.5 or 2.7 - if so, look for coolant leaks - see other threads about this issue).
    Could you provide more details?
  3. macrumors 65816

    Oh sorry, meant to do that at the end of the post! It's a late 2004 G5 PowerMac, Dual 2.5ghz (liquid cooled), two 160gb SATA drives (the stock seagate barracudas), 4gb of RAM (4 x 512mb, 2 x 1gb), and the NVidia GeForce 6800 Ultra 256mb.

    There was no sign of coolant liquid, a lot of dust but I've cleared that out with compressed oxygen. First thing I tried after struggling with all software approaches was to remove all hardware except for the graphics card, CD drive, and two RAM sticks, and ran the hardware test using that, then again with everything placed back in when it didn't find any obvious problems.

    Machine chimes normally, but won't re-chime if attempting to clear the PRAM, no unusual beeps or other noises. I'll try the G3's card later today when I get a chance to fish it out, though if it is a power problem as I suspect then it still won't prove that either way as the RAGE card will draw a lot less power I think?
  4. macrumors 68040


    If leak is small, you will not notice it until you do not remove CPU cover or even entire CPUs module. Those symptoms may indicate leak starting... but it's hard to tell for sure without machine disassembling. Test with this G3 PCI card, if it won't change anything, go to Apple Service to diagnose your unit.
    If it will be coolant leak, you will get free repair (at least) or even new Mac Pro - like some of MR memebers did.
    2.5 DP was most frequently leaking machine of all three liquid cooled G5 models.
  5. macrumors 65816

    Okay, I tried the G3's ATI RAGE 16mb card in one of the PCI slots after removing the NVidia 6800 Ultra, and it doesn't appear to work any better; exact same issue with it getting no farther than displaying the grey apple logo when starting with anything other than the hardware test CD.
    So it seems that that eliminates the 6800 Ultra as having failed, and possibly also a power issue since the RAGE is powered only by the PCI slot (it has no additional power connector).

    I removed the CPU cover to see if I could see a leak and don't see any, though removing the cover doesn't really reveal that much, I've also tried leaving the machine tipped on its front for an hour to see if any fluid would move somewhere more easily visible and didn't see anything, so it doesn't seem likely to be a leak.

    Is there much more to try? I was thinking of possibly resetting the firmware to see if that could be corrupt or something, but I'm uncertain if that can be done when I can't boot to anything other than the hardware test?
  6. macrumors 68040


    For some weird reasons, G5's hard drives are particularly difficult to diagnose when they are failing. Try a new hard drive. If that doesn't work, Then call Apple and tell them you think this might be a leaky processor which it might well be and take it in.
  7. macrumors 65816

    I've tried removing both hard-drives and just booting from a CD, but that didn't work either unfortunately. Seems it's off to the repair shop for this one!
  8. macrumors 6502


    haravikk, my call is the logic board.

    That is what i have experienced with most of the older G5's. The CPU is usually just fine. The fact that it does not seem to respond to your keyboard commands points to that fact.

    You could get a replacement logic board but sadly its kind of a pain in the ass for the G5's but doable.
  9. macrumors 65816

    Keyboard seems to work okay, only zapping the PRAM doesn't appear to work, and I can't seem to use alt to select a start-up drive. However, holding C will boot from CD instead of trying (and failing) to boot from the hard drives, eject (sometimes) works to open the CD drive, though most of the time I have to use the pinhole to open it.

    I've booked it in for repair tomorrow, hopefully the engineers have more luck finding the problem than I have! I suspect you might be right though on the logic board, apple hardware test gives it a clean bill of health but as far as I can tell I've ruled out pretty much everything else so it must be some part of the board the hardware test doesn't use.
  10. macrumors 65816

    Repair shop thinks it's the logic board, but Apple no longer provides them for repairs (even so they say it would be close to £1000 to repair).

    I've been looking on eBay to see if I can find a compatible one to try installing myself, but I've not found one for my specific G5 model (Late 2004, 2 x 2.5ghz processors), I'm wondering which logic board part I actually need, are boards from other machines compatible?

    I'm still a bit dubious about whether I will attempt a repair, once I get it back from the repair shop I'll disassemble it to see if I can find anything they didn't (since they don't seem to actually take the machines apart except to try different RAM, Graphics Cards etc.), if I do then I may as well repair it, otherwise I'll just eBay the parts to see if I can offset the cost of a new machine.

    Actually on that note; I'm curious to know if anyone has switched from a similar G5 to one of the newer Mac Minis? The machine is used a lot for photo editing, but it's always been plenty powerful, so if a Mac Mini is comparable then it might be a suitable replacement, might see my local Apple Store will let me try a few sample files.
  11. macrumors 68040


    A new Mac Mini will be much quicker just get a quick hard drive for it.
  12. macrumors 68040


  13. macrumors 65816

    I think the £1,000 mark was for the price it would have been from Apple + the cost of repair. Unfortunately, buying from eBay it's still more than I'd really want to spend when there's the possibility it may still be some other component that's at fault, plus the amount of work replacing it myself, and the risk of my damaging something else while doing it. I think we've decided to just go with a low-end iMac, as the screen the G5 currently has isn't that great, and with the price hike on the Mac Minis they're actually not that attractive a machine to buy when the iMac's only around £300 extra and a lot more powerful.

    Thanks for looking though, but I'll probably just be harvesting the G5's parts and throwing them onto eBay to try to offset the cost of a new machine. Does anyone know if there's a good repair manual available online for the G5? I found the original Apple Tech's manual for the G3 iMac a while back when I was having trouble with mine, which allowed me to diagnose the exact part that had failed by testing various parts with a multi-metre. Since I'd be disassembling the G5 to get all the parts out anyway, if I could find a manual I might be able to do more thorough tests than the repair people seem to. From the sounds of it they basically just run the repair version of the apple hardware test, scratch their heads, and try some different parts.
  14. macrumors newbie

    I bought a new and sealed logicboard off ebay for about $200,- there are still more left. It was worth it. But it is a hassle to exchange it. You have to remove everything from the PM and than calibrate the cpu's again with an Apple Service Disc 2.5.8.
  15. macrumors 68040


    Catch ;)
  16. macrumors 65816

    Where would I get the service disc, can it be downloaded legally?

    Thanks! That should certainly help as otherwise I have no idea how to swap the logic board :D

    I've actually managed to get a hold of a logic board for a dual 2.0ghz G5 which I believe is compatible, it'll reduce the speed of the processors but it might give my old G5 a new lease of life, with a bit of luck anyway. If not it just means I have an extra part to sell :)

    It's my dad that was using the G5 anyway, and he's decided to just get a new iMac either way, but if I can bring the G5 back to life then it'd be nice :)
  17. macrumors 68040


    Google it ;) But "legally" isn't right word for that... ;)
  18. macrumors newbie

    Any luck yet?

    Did the new logic board solve your problem?

    I am having the same prob and was wondering if it was the logic board, even though AHT passes it ok.

    Interested to know how yours is going. Thanks.
  19. macrumors 65816

    I'm still awaiting delivery, (actually I'm still awaiting dispatch, the seller is taking their sweet bloody time), I'll post an update once I've put it in!
  20. macrumors 65816

    Okay, trying to install the logic board today but I've hit a slight snag; obviously the dual 2.5ghz is liquid cooled, and the dual 2.0ghz model of the same generation was not, and it's a dual 2.0ghz logic board that I've now received as a replacement. This in itself should not be a problem as it just means that the processors will be under-clocked.

    However, the power connector for the liquid cooling system is absent from the dual 2.0ghz logic board! Bah!

    So now I need a cable to somehow connect power to the liquid cooling. Immediately next to the LCS power connector is a 10-pin connector for the front-fan, the LCS connector is a 6-pin one, I'm wondering if it's possible to get a 10 pin cable that splits off into a 10-pin and a 6-pin connector so I could use the same socket for both?

    I'm thinking that that probably wouldn't work though, another possibility is a y-cable from the DVD drive's power connector, into the same connector (so I can still use the DVD drive), and also into a 6-pin (male) connector. The alternative is that I have to try and find a heatsink unit suitable for a G5.

    Don't suppose anyone has any ideas here?

    I've attached the picture from the G5 technical guide, but it's not a very good picture of the right-hand cable. The cable is completely unmarked so I can't even look up what it is. Interestingly the actual part it connects to in the LCS only has four pins, but it has the gaps where other pins would be.

    Attached Files:

  21. macrumors 601


    Have you tested the 2.5 CPUs in the 2.0 logic board? I'm wondering if it's compatible? You can tap into the molex connector on the optical drive for 12v. It would be the yellow wire if you use a splitter. The pump would run full blast all the time...

    Only the 2.7 and 2.5 DP G5s were liquid cooled. Ever think of finding some heatsinks off the air-cooled G5s and swapping them onto your 2.5 CPUs and just eliminating the LCS altogether?
  22. macrumors 65816

    I haven't been able to find any heat-sinks so far, except attached to processors and going for fairly silly prices. I don't suppose heat-sinks from elsewhere would work?

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