Bad power supply vs faulty capacitors?

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Level 4

2,577 points

Bad power supply vs faulty capacitors?

I have a first generation iMac G5... it is in the serial number range that suffered from the faulty capacitor problem. And in fact several of the capacitors failed just over a year after purchase (back in early 2006). Apple replaced the logic board and power supply at that time as part of their extended repair program for this issue.

Now the machine is showing similar symptoms. It starts the boot process but either during boot or within just a minute or so of logging in the power just cuts off.

Following the diagnostic steps on Apple's support website - powering up with the back off and watching the LEDs indicates the power supply needs to be replaced. As far as I could tell the capacitors do NOT look swollen or leaking like they did back in 2006.

So I'm just wondering if someone with more h/w experience might comment on how likely it would be to just be a failing power supply or if there's a good likelihood that it's also the logic board again... i.e. any experience with the replacement logic boards also failing and/or failed capacitors that don't swell or leak?

Thanks for any input,
Steve

20" iMac G5, Mac OS X (10.5.5)

Posted on Mar 15, 2010 9:24 AM

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Answer 1

WZZZ

Level 6

13,238 points

Mar 15, 2010 9:38 AM in response to Steve Herman1

Spudnuty probably can tell you what the tell tale signs are better than I, but look in the System Log for shutdown cause= -110 or -122 (those are most likely related to the PSU.) Do you hear a pop just before it happens? Also, open it up and look for swollen or leaking caps on the board. Tops should be perfectly flat.

Other than that, I can't resist saying that the topic sounds like two softball teams facing off. (Sorry, I'm becoming very cynical about this extremely common issue; just waiting for this to happen to me all over again, sooner or later, after three replacements of each. 😟

I hope Power Supply wins; it isn't so expensive and can be replaced yourself.

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Answer 2

MGW

Level 7

27,047 points

Mar 15, 2010 11:32 AM in response to Steve Herman1

f you are technically inclined, you can replace the caps fairly inexpensively, if it's the logic board, that's another matter. Look at [jimwarholic.com] or [synaptech.com] for more information and help.

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Answer 3

spudnuty

Level 5

7,128 points

Mar 15, 2010 11:58 AM in response to Steve Herman1

Hey Steve,
Sure sounds like a PSU problem. My ultimate test is to plug in a hacked PC (ATX) supply. You could also open up the power supply and check for bad caps. Some take a security Torx driver. You'd be looking for the same swelling.

As far as I could tell the capacitors do NOT look swollen or leaking like they did back in 2006.

Just a tiny bit of convex swelling indicates a bad cap.
Richard

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Answer 4

Steve Herman1 Author

Level 4

2,577 points

Mar 17, 2010 9:25 AM in response to Steve Herman1

Thanks for the replies everyone.

I took the machine to a nearby Apple Store. The guy at the Genius Bar said they actually had a new power supply on hand. He offered to hook it up, let it run for a while and see what happened. If the machine still malfunctioned with the new power supply then he'd put the old one back in and let me decide what I wanted to do from there. He said if the new power supply did not fix the problem he would not charge me any bench fee or diagnostic charge for testing it out with the new power supply (the other Mac reseller I contacted in town wanted a $125 diagnostic fee paid in advance before they'd even look at the machine).

Luckily, with the new power supply the machine booted up and continued running for approx. 30-45 minutes while we watched and waited in the store. He also visually inspected the capacitors on the logic board and said they looked OK to him.

So I ended up paying about $185 for the new power supply + labor. That's probably about $50 - $75 more than it would've been had I just ordered a power supply off the web and tried installing it myself. But, for me, the peace of mind from having someone with more h/w experience inspect the logic board as well as getting the job done quickly and on the spot rather than having to wait for the power supply to arrive in the mail pretty much offsets that extra cost.

All-in-all I'm very pleased with the service I received. Kudos to the Apple Store and the guy who took care of my machine.

So far the machine has been happily humming along at home for a couple of days now... so I'm keeping my fingers crossed that it'll last until I can afford a newer one.

Thanks again,
Steve

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Answer 5

MGW

Level 7

27,047 points

Mar 17, 2010 9:40 AM in response to Steve Herman1

Thanks for posting back, hope things continue to work well,

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Answer 6

Mar 18, 2010 10:01 AM in response to spudnuty

And just for the record -- ALL capacitors fail eventually. I work on historic railroad equipment... by the time it gets to the museum, all the capacitors are shot. This stuff is industrial grade and American made too. Same thing with all our mercury vapor lights - the caps on the main-boards all go. shrug there's a reason fluorescent lights have replaceable ballasts.

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Answer 7

Steve Herman1 Author

Level 4

2,577 points

Mar 18, 2010 10:36 AM in response to Wolf Harper

Thanks, I certainly understand. I have no expectation that components will or should last forever.

I was just hoping for some input about the likelihood of my problem being a bad power supply rather than a logic board problem that was causing the power to cut off. I didn't want to invest in a new power supply only to find out that the problem still persisted.

Steve

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