How to Remove Dust from iMac G5

"I need instructions on what and how to disassemble."

Depends on which model/generation you have.
http://docs.info.apple.com/article.html?artnum=301724-en How to identify your iMac



http://docs.info.apple.com/article.html?artnum=300205 iMac G5 DIY (Do-It-Yourself) Instructions



Google & YouTube search for disassemble instructions for your model/generation. Video instructions would be best.




!http://i45.tinypic.com/jl0z95.jpg!

Compressed air in a can is your best bet until you get the instructions you need.



!http://i45.tinypic.com/jl0z95.jpg!

This illustrated guide is excellent. Better than the DIY from Apple. I think this is your model, but if not go back to the home page.
http://www.ifixit.com/Guide/Device/iMacG5_20%22_ModelA1076

While it is open, check for leaking, bulging capacitors on the logic board. Very, very common issue for these earlier models. Might be responsible for the shutdowns. Not 100% sure about this, but I think if it were a thermal shutdown, it would just go to sleep, not shutdown, to cool off. Maybe Spudnuty can confirm or correct me on this.

Nello,

I assume the shutdowns are due to overheating.

Have you run Temperature Monitor to verify that this is the problem? Based on what else you found probably that's the case.
You should also look at Applications>Utilities>Console and see if there's anything in the logs that would show what's going on.

WZZZ what I've found is that both shutdown and instant sleep can happen. I think it depends on the severity of the temperature rise.
Also Nello as WZZZ says you should look at those caps.

when I looked at the air intake grill at the bottom of the display I found that it was very clogged with dust.

So clearly that's an issue.

Can anyone tell me how to remove/inspect/clean the plastic housings at the bottom of the case to the right and left of the power supply? These housings are right behind the air intake grill and I'd expect to find more dust there that needs to be removed.

Also inside the fans and the plenum for the CPU. Email me if you need good instructions. A large part of the air moving system might have to come apart. The fans could be seized/sticky also. I had a case where an iMac G5 was just shutting down suddenly. Turned out the CPU fan was disconnected.
There was also a post around here a while back where the CPU fan was noisy and sticky.
Richard

Message was edited by: spudnuty

Message was edited by: spudnuty

In Console, System Log (has to be System Log, or All Messages; Console won't necessarily show you enough) on the next reboot after a shutdown do you see.

"AppleSMU -- shutdown cause = -110" (if you see shutdown cause =1 or 2, that's normal.)

This could mean a flaky power supply. Do you see "unexpected shutdown"?

Have you looked at the caps on the logic board? They should all be perfectly flat at the tops. No brown gunk. You won't easily be able to look inside the power supply, though.

I've seen the -122 associated with random shutdowns as well, but don't know exactly what it means. From unfortunate personal experience, I know first hand about the -110 and the power supply failing. You could try googling "AppleSMU -- shutdown cause = -122" putting everything in quotes, and maybe come up with something more definitive. And look back in older logs for other entries related to shutdowns.

You could also try re-setting the SMU (be warned, it's normal to see the -110 after doing this.) This might or might not help, but it's really easy to do.
http://support.apple.com/kb/HT1767

Nello,
Well read this:
http://www.gibbilicious.com/2006/02/troubleshooting-mysterious-122-shutdown.html
"That is to say, when you see the “-122” code, it means that there was a sudden and catastrophic loss of power to the main logic board. Unfortunately, it doesn’t tell you the actual reason behind it."
Soo like WZZZ says "power supply".
I've got five G5 iMacs go through my shop recently; 3 17"ers a 1.6 and two 1.8s they all had bad power supplies one I repaired the supply using Jim Warholics site and the other two an Apple employee handed me a box of parts that was left over from someone trying to repair 4 G5 iMacs. In that box was 2 perfectly good 17" power supplies. One the guy had tried to open w/ a chisel and prybar. I replaced the case on that one and put the power supplies in to the two remaining iMacs and they are both working fine.
I also had two 20"ers both 1.8 that also had bad power supplies and I repaired one of those. The other also has a bad GPU so that's waiting while I'm replacing the GPU chip on an iSight so we'll see how that does.
I was able to boot all of the ALS iMacs using the hacked ATX power supplies and an old PowerBook Charger. I did have trouble w/ sleep issues using that hack but it was very good for diagnosis.
To verify the diagnosis you'd have to open the power supply. That will take a security Torx or drilling out that security pin. I did that for a while before I realized I had a security bit.
Like WZZZ says a bad cap can just have a tiny bulge in the top. I had one like that that looked totally clean except for about a 1/4" bulge in the top. It tested totally dead on my ESR meter.
Richard

Message was edited by: spudnuty

Nello,

So, I take it that you think I need to replace the power supply. Am I understanding you correctly?

Probably, but a complete diagnosis would be to open your power supply. You need to find a smoking gun.
With my hacked supply I can bypass the power supply and run the iMac for hours testing without having to spend the $120 or so for a new supply.
I wouldn't replace the supply unless I found bad capacitors in the power supply.
When you do that there are some monster caps in there so don't touch their leads.
Look here:
http://www.google.com/#hl=en&source=hp&q=jimwarholic+imac&aq=0p&aqi=g-p2g8&oq=Jim&fp=64df356c6a3f8304
for caps evaluation tips.
Richard

Hey Nello,
The techs at the Northbrook store are very good. I could have given you a recommendation to the guy I know there but $171 is as good as you could have done. I doubt that I could have matched that price. Those power supplies are more like $120 on eBay used. Will they give you back the bad supply? Probably not but I have a 20" that needs one. I also have a whole drawer full of replacement capacitors.
Here's hoping that repair cures your problem.
Oh a thought, are there a lot of rugs in the room where the iMac is used? or pets? Both can accelerate the the dust buildup that you saw. So a periodic cleaning would keep your machine healthy.
Richard

Message was edited by: spudnuty

Message was edited by: spudnuty