Diagnosing iMac G5 A1076

[dcr]

At the office, we have a "dead" iMac G5, model A1076. I don't know the specs beyond that. What I remember is that, years ago, something in it died and the local computer/Apple repair store said it wasn't worth fixing, that for the cost of the parts/repair, you might as well buy a new Mac. So, it was replaced by an Intel iMac which I think was a Core i3 which puts it at around 2010.

So, this iMac G5 has sat on a display counter for about 12 years or so I'd guess. Anyway, so we're doing some rearranging and I thought, well, I'll try and see if this iMac does anything. I seem to recall it had a dead screen, but couldn't remember for sure.

So, I plugged it in. Pushed the power button. And, bing!, the boot sound starts and the display flickers then the Apple logo appears. It boots and the desktop background popped up. Then, it went dead. No smoke. No poof. No pop. No odor. There was the sound of the power going out but it wasn't a sound like something popped or anything.

Can't restart it. It's completely unresponsive. Even unplugging it, waiting and then plugging it back in to try again makes no difference.

I mean, I suppose I could wait another twelve years and try again, but I was hoping for something a bit faster.

So, hard drive seems good. Display seems good. I would sort of guess either a logic board or power supply issue, though if it were the power supply, I'd think maybe smoke or poof or something.

Anyway, so that's where it's at. Do the symptoms sound familiar to anyone? Any guesses where to start looking?

 

[Nixontheknight]

I'd suggest opening it up and checking the entire board to see if you smell a burned component or maybe some electrolyte

 

[Forrest]

I would check the electrolytic caps. I think a lot of counterfeit caps were used on computers at that time.

 

[Nixontheknight]

I would check the electrolytic caps. I think a lot of counterfeit caps were used on computers at that time.

yup, the capacitor plague did reach into the early 2000s, so that might be the case

 

[dcr]

Thanks!

Haven't opened it yet, but I could not smell anything through the vents.

Also, I suspect this is perhaps the same problem that resulted in it being pulled from service circa 2010, so would caps failure have been an issue at that time?

 

[Byrd]

… yes, the iMac G5 was the number 1 Mac for cap issues of this era. With the computer case removed it should be fairly obvious, bulging/leaking or distorted capacitors. A faulty GPU comes second, if you can get it to boot try safe mode

 

[3lectr1cPPC]

Hmm, it really depends on which revision you have. The first gen G5 iMacs have the worst of the cap issues. The second revision “ambient light sensor” models I believe have less of them, if at all? My AmbLight model uses a different manufacturer of the capacitors (rubycon IIRC) with “K” shaped vents. The earlier ones using “+” shaped vents are the ones that fail. Yours could be either so you’ll just have to pop the back and see.

 

[3lectr1cPPC]

Just did some more research. Seems there were at least three vendors. “K” vent, “+” vent, and then a Mercedes logo style vent. I saw one photo showing bulged “K” caps but they overall seem to be the good ones. The + ones are the ones that always fail and then my board in my iMac has a handful of those mercedes logo style vent caps which are fine on mine. Couldn’t find any photos of those being bad, but I couldn’t find any of them at all so who knows. Here’s a photo of my board showing the caps you need to check.

 

[dcr]

Holy cow, that's a lot of capacitors in a minimal amount of space.

 

[3lectr1cPPC]

That’s not even all of them!