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iMac G5 problems

NastyComputers

NastyComputers

macrumors regular
Original poster
Aug 14, 2010
144
25
Tehachapi CA
So I got this iMac G5 that is having some issues. Sometimes it comes on sometimes it doesn't. When it does come on it will freeze at the grey apple screen, or start to boot from the disk and start to install the OS, then freeze at some point during the install. Again it doesn't always start up or chime...thinking it is a logic board. Oh and all the Caps are good...what are your thoughts?
17" 1.8 non isight
 
Have you tried booting from the installation disks and then running the hardware test, instead of beginning the installation process?

Hard to tell without more details, but I would suggest checking the RAM and the HDD for errors, if you are able to boot. The only other thing that comes to mind might be the power supply, but your problems don't really sound power supply related.

If you can provide some more detail I'd be happy to try to help.
 
i assume you tried to reset Pram and tried to repair permissions before checked the logic board for bad caps, but there are 2 things that could be the cause of sometimes not starting up or shutting down without warning or not even react on pressing the powerbutton and thats the little pram battery , but as its a G5 1.8 ghz and like the 1.6ghz and the 2.0 ghz 20" it sounds more like a failing psu which was a very common thing to fail about as often as the bad caps , apple had a repair extension program dont know if it is still ongoing always worth a try ...but apple just stops these programs without prewarning ok most times they dont even announce such program, because of fear too many would come to get their Mac's repaired free

i personally always stayed clear of the G5 iMac's despite i would like one , but as they are still not cheap i do not take the risk spending that kind of money and having a dead computer standing around as unlike with the eMac 1.42 which is basically problem free model of the range in apple terms (optical drives may fail or harddrives like on any computer ) but there is no problem free iMac G5 model , either bad caps , or psu or screen fail not to mention overheating issues... ok some work well but as i do not think to be that lucky to grab one of those ....
as with my iBook g4 as i assumed perfect and had been happy about it working , suddenly had a exploding logicboard which is as common as the bad soldering :(
 
DSPalpatine said:
Have you tried booting from the installation disks and then running the hardware test, instead of beginning the installation process?

Hard to tell without more details, but I would suggest checking the RAM and the HDD for errors, if you are able to boot. The only other thing that comes to mind might be the power supply, but your problems don't really sound power supply related.

If you can provide some more detail I'd be happy to try to help.
Click to expand...

Thanks DSP, I have checked the RAM and bought a brand new HDD. I have run the hardware test and everything thing passed.
 
Detrius said:
This will not fix a system that is freezing or that fails to power up.
Click to expand...

i know that ,but i assumed thats what nasty computers among other things had done ,as thats what most people do first ,before ripping a iMac apart to look for the bad caps
 
NastyComputers said:
Any other ideas Detrius?
Click to expand...

First things first: if nothing happens when you press the power button, software is irrelevant. This is what you need to focus on. You've already taken the back off the machine to verify that the capacitors are good. Next, you should verify the LEDs on the logic board. If the AC is plugged in, at least one of the LEDs should be on at all times.

http://support.apple.com/kb/HT2831?viewlocale=en_US

If you short the two pins that connect to the power button, then the second LED should come on along with the machine chiming.

If you don't get this far, you either have a) bad power cord, b) bad power supply, or c) bad logic board.



After this, I can't make any assumptions without more information. Different people use the word "freeze" to mean different things. More often than not, when customers say "freeze," they mean the spinning beach ball came up, so for all I know, your system is still running just fine, but you have a slow hard drive.
 
MacHamster68 said:
i know that ,but i assumed thats what nasty computers among other things had done ,as thats what most people do first ,before ripping a iMac apart to look for the bad caps
Click to expand...

As a technician, I'll rip the iMac apart, look at the caps, pull the hard drive out, and test it long before I'll repair permissions. It's more efficient, since there are so rarely actual problems caused by permissions issues. For every machine that I see a permissions repair fix its issues, I see fifty with bad hard drives.
 
Detrius said:
As a technician, I'll rip the iMac apart, look at the caps, pull the hard drive out, and test it long before I'll repair permissions. It's more efficient, since there are so rarely actual problems caused by permissions issues. For every machine that I see a permissions repair fix its issues, I see fifty with bad hard drives.
Click to expand...
I guess for every machine fixed by permissions repair you see one user that screwed around with /System/Library/Extensions in some way.
 
Detrius said:
As a technician, I'll rip the iMac apart, look at the caps, pull the hard drive out, and test it long before I'll repair permissions. It's more efficient, since there are so rarely actual problems caused by permissions issues. For every machine that I see a permissions repair fix its issues, I see fifty with bad hard drives.
Click to expand...

yes that what you do and i would do the same on a iMac G5 as their problems are most times hardware related
Nasty computers has too already looked for the bad caps ,
but i always think about some novice people who never have taken apart a computer , and they might have the same problem , and look in here for a answer ,but telling them "first rip your iMac apart and check for bad caps and a broken hardrive ... before you reset PRAM , repair permissions ....."
might not be a sensible thing to do , but efficient in case of a G5 iMac or on a eMac ...i have to admit, as you can rule out the hardware first
 
Detrius said:
First things first: if nothing happens when you press the power button, software is irrelevant. This is what you need to focus on. You've already taken the back off the machine to verify that the capacitors are good. Next, you should verify the LEDs on the logic board. If the AC is plugged in, at least one of the LEDs should be on at all times.

http://support.apple.com/kb/HT2831?viewlocale=en_US

If you short the two pins that connect to the power button, then the second LED should come on along with the machine chiming.

If you don't get this far, you either have a) bad power cord, b) bad power supply, or c) bad logic board.



After this, I can't make any assumptions without more information. Different people use the word "freeze" to mean different things. More often than not, when customers say "freeze," they mean the spinning beach ball came up, so for all I know, your system is still running just fine, but you have a slow hard drive.
Click to expand...

Well freeze to me means the computer stops, does not function.... now as far as the LED's in the back I do have the #1 light on when connected to power. When I short the power button #2 lights up BUT no chime. The light on the front does come on but NO #3 LED (Which means no Video right?) But I don't get why it sometimes comes on and sometimes doesn't. I have tried new RAM. And I may be wrong about this but it should still fire up even if there is no HDD hooked up. Anything else I can try?
 
MacHamster68 said:
yes that what you do and i would do the same on a iMac G5 as their problems are most times hardware related
Nasty computers has too already looked for the bad caps ,
but i always think about some novice people who never have taken apart a computer , and they might have the same problem , and look in here for a answer ,but telling them "first rip your iMac apart and check for bad caps and a broken hardrive ... before you reset PRAM , repair permissions ....."
might not be a sensible thing to do , but efficient in case of a G5 iMac or on a eMac ...i have to admit, as you can rule out the hardware first
Click to expand...

Now I don't know this for sure but I can't reset PRAM without a chime right?? And as far as repairing permission... I can't get to that without a working computer right, I think you can do it in target mode but if the computer doesn't start in the first place then how can I get it into target mode?
 
nope first you need to get the iMac to work, the iMac G5 has a PRAM battery change it to a new one so we can rule out that one
as one of my iMac g3's had a dead PRAM battery and no chime and sometimes would not power up or shut down randomly but was otherwise working , after changing that battery the chime was back and it powered up ever since and did only shut down when i wanted it to shut down ,if i remember it right on the g5 the PRAM battery is hidden under the airport card
 
MacHamster68 said:
nope first you need to get the iMac to work, the iMac G5 has a PRAM battery change it to a new one so we can rule out that one
as one of my iMac g3's had a dead PRAM battery and no chime and sometimes would not power up or shut down randomly but was otherwise working , after changing that battery the chime was back and it powered up ever since and did only shut down when i wanted it to shut down ,if i remember it right on the g5 the PRAM battery is hidden under the airport card
Click to expand...

I did change that PRAM battery but maybe I will try another one...
 
STOOOOOPPPPPPPP!!!!!!!

Yes, the power supply is fully closed, and should remain as such unless you know what you're doing. Opening up a power supply is a great way to give yourself a really nasty shock, and while mucking around in there, if you cause a short, you've got a real chance at starting an electrical fire once you plug the machine back into an outlet.

So, unless you have a ton of experience, I wouldn't go messing about with the PSU.

I still think, given the symptoms you described, it might be a failing logic board or bad RAM. Leaking or burst caps are one way for an LB to fail, but not the only way. You might have a broken solder, for instance, that could be causing these issues. Or, perhaps the machine overheated (heat dissipation was not the best on these models).

However, even if the hardware test didn't indicate bad RAM, that doesn't mean your RAM is good. I was having all kinds of issues with my machine around the time that Apple released 10.5.8. It was crashing, it would boot to the grey screen and then stop booting, and when I tried to re-install Leopard, the installation would fail. When I took it to the Genius Bar, the Genius played with it for a bit, and then diagnosed it with a bad logic board. I took the machine home to pull the machine apart and try to salvage what was on the HDD.

I posted the problems on a message board, and someone said to try to swap out the RAM and see what happened. I had purchased a 2GB kid from Crucial a while back, which had been in the machine for a while. Desperate, at this point, I pulled the Crucial RAM and re-installed the original 1 GB from Apple. Then, I wiped the drive, and installed Tiger, fully updating it, and then upgraded to Leopard. Everything worked perfectly. I send the RAM back to Crucial, who confirmed that it had went back, and sent me a new 2 GB kit within a few days.

My point of this long jeremiad? Without seeing your machine, my best advice would be to take a good look at the hardware again, and if possible, swap out the RAM, and also if possible, boot from an external HDD. Also, if you boot from the installation disks, what happens? Does the computer freeze, or can it run off the disks?
 
DSPalpatine said:
STOOOOOPPPPPPPP!!!!!!!

Yes, the power supply is fully closed, and should remain as such unless you know what you're doing. Opening up a power supply is a great way to give yourself a really nasty shock, and while mucking around in there, if you cause a short, you've got a real chance at starting an electrical fire once you plug the machine back into an outlet.

So, unless you have a ton of experience, I wouldn't go messing about with the PSU.

I still think, given the symptoms you described, it might be a failing logic board or bad RAM. Leaking or burst caps are one way for an LB to fail, but not the only way. You might have a broken solder, for instance, that could be causing these issues. Or, perhaps the machine overheated (heat dissipation was not the best on these models).

However, even if the hardware test didn't indicate bad RAM, that doesn't mean your RAM is good. I was having all kinds of issues with my machine around the time that Apple released 10.5.8. It was crashing, it would boot to the grey screen and then stop booting, and when I tried to re-install Leopard, the installation would fail. When I took it to the Genius Bar, the Genius played with it for a bit, and then diagnosed it with a bad logic board. I took the machine home to pull the machine apart and try to salvage what was on the HDD.

I posted the problems on a message board, and someone said to try to swap out the RAM and see what happened. I had purchased a 2GB kid from Crucial a while back, which had been in the machine for a while. Desperate, at this point, I pulled the Crucial RAM and re-installed the original 1 GB from Apple. Then, I wiped the drive, and installed Tiger, fully updating it, and then upgraded to Leopard. Everything worked perfectly. I send the RAM back to Crucial, who confirmed that it had went back, and sent me a new 2 GB kit within a few days.

My point of this long jeremiad? Without seeing your machine, my best advice would be to take a good look at the hardware again, and if possible, swap out the RAM, and also if possible, boot from an external HDD. Also, if you boot from the installation disks, what happens? Does the computer freeze, or can it run off the disks?
Click to expand...

Yeah that is what I thought on the PSU.... this thing is so messed up I don't know what to think... so I took of the HDD and it chimed but still no video, turned it off and fired it back up and chimed again but no video, and now no chime. I'm guessing it is the logic board but it is just odd that it works sometime and others it doesn't. In a PC if the motherboard is bad it just doesn't work...I give up, anybody want to buy it??
 
Again, if the caps on the motherboard look alright, then chances are that the PSU isn't able to deliver enough power/clean power for a good boot.

Yes you have to remove the PSU cover to check the caps, and yes as DSPalpatine mentioned, it can be dangerous if you don't know what you are doing. Generally, leaving the iMac unplugged for several hours or overnight is enough to allow the charges to dissipate from the PSU.
 
CubeHacker said:
Again, if the caps on the motherboard look alright, then chances are that the PSU isn't able to deliver enough power/clean power for a good boot.

Yes you have to remove the PSU cover to check the caps, and yes as DSPalpatine mentioned, it can be dangerous if you don't know what you are doing. Generally, leaving the iMac unplugged for several hours or overnight is enough to allow the charges to dissipate from the PSU.
Click to expand...

Thanks for your help, I have never opened up a power supply, as a PC tech I just replace them it they go bad but I know a guy that runs a shop and is a Mac freak and he is going to take a look at it for $10 so I am going to have the it looked at tomorrow morning. I hope that is what is wrong with it so I can just get an answer already. I would like to put it to use. But again thanks everyone, I will give you an update when I get home from the shop.
 
NastyComputers said:
Thanks for your help, I have never opened up a power supply, as a PC tech I just replace them it they go bad but I know a guy that runs a shop and is a Mac freak and he is going to take a look at it for $10 so I am going to have the it looked at tomorrow morning. I hope that is what is wrong with it so I can just get an answer already. I would like to put it to use. But again thanks everyone, I will give you an update when I get home from the shop.
Click to expand...

Hey guys so I chose to open the PSU myself and it has ONE bad cap that I could tell, so I took it to my guy and he is going to take it all apart and at least replace that one. I really hope this is the problem. What do you guys think?
 
that was the big problem with the iMac g5 a lot of things went wrong , from simple things logicboard and psu ,the screens had been another problem and the fact that the iMac's G5 did run really hot even when perfectly working didn't really make things easier , this hot G5 in such a small case with only this little slot where the heat could find a way out and sometimes the symptoms had been nearly identical so you could not clearly point to a specific part ...thats the one, apart from the bad caps on the logicboard as these are easy to spot
 
MacHamster68 said:
that was the big problem with the iMac g5 a lot of things went wrong , from simple things logicboard and psu ,the screens had been another problem and the fact that the iMac's G5 did run really hot even when perfectly working didn't really make things easier , this hot G5 in such a small case with only this little slot where the heat could find a way out and sometimes the symptoms had been nearly identical so you could not clearly point to a specific part ...thats the one, apart from the bad caps on the logicboard as these are easy to spot
Click to expand...

Well I hope that this bad cap on the PSU is the answer if not I don't know what else I can do. I think I have done everything else besides a new logic board...
 
OK guys I got a new power supply and that wasn't the problem. (The old one had a bad cap) The first time the started it it did chime but no video. Every time after that no chime just the light in the front. Im pissed that I have put the money into this thing when I could have just bought a running machine already :mad:

Anyway just looking for any other thoughts or ideas to try before I sell it for parts. Thanks again!
 
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