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I'd take it to an Apple store and ask them to run their diagnostics on it. Or take it to an independant Mac shop and let them swap PS's. Are symptoms of power supply failure and logic board failure similar on an Imac G5? More Less. Communities Contact Support. Sign in. Browse Search. Ask a question.

User profile for user: All replies Drop Down menu. Loading page content. Mac OS X Speciality level out of ten: You must leave at least 10 to 15 seconds if you think you need to press it again. If you do press the button twice you can crash the PMU which would cause the batttery which normally last for years to expire in 3 days. As well as keep your machine from ever booting again without replacing the logic board They are: Unlpug the power cord. Using a non-metalic tool your finger, if it'll reach push the PMU reset button location varies by machine ONCE and for no more than one second.

Wait seconds. Plug the power cord back in and hit the power button. Note that a bad logic board, processor or stick of RAM can cause the same symptoms described by the original poster so a PMU reset is no guarantee. I don't know where the myth came from that suggests if you crash your PMU you need to replace your logic board but it's not true. The most you can do crashing PMU is to expire the battery. For those that want the official procedure for resetting the PMU here it is.

The PMU is a computer within a computer. Its function is to: Be very careful when handling the logic board.

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If the PMU crashes and is not reset, the battery life goes from about five years to about two days. Many system problems can be resolved by resetting the PMU chip. When you have a computer that fails to power up, follow this procedure before replacing any modules: Disconnect the power cord and check the battery in the battery holder. The battery should read 3. If the battery is bad, replace it, wait ten seconds, and then proceed to step 2.

If the battery is good, go directly to step 2.

Powermac G5 failure: logic board or PSU?

Press the PMU reset button once and then proceed to step 3. Wait ten seconds before connecting the power cord and powering on the computer.


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If the computer does not power on, there is something else wrong with it; refer to the "System" section of "Symptom Charts" in this chapter. The above procedure resets the computer's PRAM. After resetting the PMU, be sure to reset the time, date, and other system parameter settings. I have had a number of clients with un-revivable logic boards who've told me that before bringing their machines in for service, someone they knew told them to either hit the PMU reset button several times in a row or even to hold it down for thirty seconds or more.

Granted, this is just a correlation and not a proven cause and effect - more likely these folks may have just had an ESD incident while they were dinking around inside their machines or the MLBs had already failed in some other way - but why take chances? BTW, thanks for posting the official procedure. It's reset by simply unplugging the power cord for 15 seconds. I would hazard a guess that Apple may be tired of all the warranty logic board replacements that they've done because the user did an improper PMU reset Here is another hint: A workaround is to get a small piece of paper something which is a bit stiffer than normal paper works best like a matchbook, index card, etc.

This effectively disconnects the battery. Wait a good minutes, then remove the paper, and start up. This is a copy of an email I sent in response to a mailing-list posting about a system that sometimes spontaneously re-boots after being shut down and sometimes won't boot when the power button is pressed it was a MDD PowerMac. My edited response to the poster was: It turns out that some of the ATI Radeon graphics cards e. I've found that using some VGA cables i.

Anyway, I hope this helps someone I bought a used G4 Quicksilver at auction. It looks in great shape, no damage, cracks or signs of misuse. Anyway I have no luck in getting it to power up. The Front panel light will not stay lit, but the fan is running and the little red light on the mother board is lit. I replaced the battery and used the info you guys posted about the power button located on the board also, but still no luck. Any other suggestions?

I have to to the same thing to power up my cube, the only problem is that it only works once.

After turning the power off I have to redo the hole procedure to start it up again. The following check list is from the cube engineers manual. The power lights on both the tower and cinema display were on, but the machine wouldn't wake up. I tried plugging and unplugging a few accessories. I tried waiting and finally pressed and held down the power button which I've had to do a few times before , but it wouldn't even turn off.

I finally shut it off by unplugging it, but it wouldn't start up. Remembering something like this happened when I left the plexiglass screen out once, I opened it up, looking for something obvious, but nothing. I googled the problem and found this link. One post mentioned "rolling" the PRAM battery, so I unseated and reseated the battery, closed it up and it powered on. My Quad G5 was driving me crazy with refusing to come on after being asleep.

After reading one tip about battery problem, I finally used an electronic voltmeter to read the battery voltage on the circuit-board side of the battery spring contacts: Zero volts! I removed the recently installed battery and scraped the two spring contacts to remove an apparently non-conductive film of oxidation? Reinstalled battery -- nada. Removed battery, re-scraped more vigorously and reinstalled. This time I read full battery voltage across the spring contacts.

It helped for about a month, but now it's acting up again. If it will hold out six more months, I'm going to buy a new computer. Oddly, I have quit putting it to sleep, just shut it down. It seems to come on normally, at least for the last two days. We do this on TV remotes when they go low. My advice, get a new battery. I have managed to get the power supply out of the chassis, and have opened it up to see if I could see what is wrong.

2.3Ghz Dual G5 Powermac

Does anyone have a power supply that they can look at for me that can confirm the resistance value and wattage of the one in circuit board position "R"? Perhaps there are some other components blown too, but with the fuse and resistor fixed I am hopeful that I can get this running again. Thank you for your time. Matt Comment on this posting Constantin von Wentzel says "The whole water-cooling assembly [on his G5] looks like it was adapted straight from the automotive industry with its microchannel heat exchanger, tiny Delphi pump, etc.

See http: Peering through the front of the chassis with a light beam on the likely chip locations on the motherboard, I saw the telltale crusties that indicate coolant leakage and evaporation. I didn't want to deal with convincing Apple that the machine was in trouble because there was no obvious leak i. I simply cast about the net for the detailed Apple instructions on how to disassemble the unit, then went in for the CPUs.

Removing them is a lot simpler and easier than putting them back in! But armed with a Viton ring from MSC, replacement hose and clamps, plus coolant from Newegg, I was able to bleed the acidic! The whole water-cooling assembly looks like it was adapted straight from the automotive industry with its microchannel heat exchanger, tiny Delphi pump, etc.

Purging all air from the unit was not easy as the old assembly apparently was charged through a single port by evacuating the inside and letting the coolant rush in! I plan on re-piping aspects of this assembly at some point for better flow and two proper fill valves but have to find the time. Oh, and I had to hit the main reset button on the motherboard at least once after replacing the CPUs, as otherwise my G5 simply sat there, doing nothing This afternoon I was on the phone and watched my computer shut down.

I could smell burning and think the power supple is out again. Yes again. It would have been nice to have a lifetime warrenty on something that keeps failing. See this link for the procedure for non liquid-cooled models: I was in the adjacent room when I smelled the tech nightmares 'burnt carbon' smell that had me running into the room.

Low and behold the pilot light on the power button was off and my screen was black. I can't remember the expletive I used but I'm sure they heard me upstairs. Then I got that 'bad feeling' knot in my gut. I jumped behind the Mac, unplugged the power plug from the back of the Mac, re-inserted it, and no 'snap sound'. Another expletive. Power supply!. No way!!. I do the war dance, mock UFC ground and pound, cry me a river show. I'm depressed about the prospects since I used to do PC repairs on Windows machines and I can't really afford to go there at this time.

My G5 was purring like a kitten until the "incident".

Power Mac G5 power supply repair program - CNET

Had not started doing video editing on it full time yet. Ambient temps in my Mac were 46 degrees 'C' average. Once a week maintenance and system cleans. Purring like a kitten. Five years of ownership and 'Poof! I decide to do a web check and found you fine people and many similar stories. Does Apple have more conspiracies in the closet?. I'd offer technical information but the site has ample advice and cogent spec information: Part of me is disgusted and pretty pissed. Waiting for an update from the repair shop: It I can trust. Still in shock.

More expensive up here. Seems 5 years is the magic number on years till these things crap out. My dual G5 was running like a champ till August of Purchased in summer of ' Logic board went out Changed twice Tech reinstalled Leopard on drive one.. Told him to back them up to secondary drive Two weeks ago, decided it didn't want to start up anymore. Push button, clicks on and clicks off in an instant Power supply?

Transfered drives and better video card to it and all is well Really disappointed in Apple's handling of this "repair". Three "geniuses" and a moron later Always loved the fact that Macs would either break right out of the box or they would run forever! My FCP box dual G5 power supply finally gave up the ghost. We've had brown-out issues which I think have aided the demise, but otherwise, this machine has been "ON" for nearly 5 years straight.

I would occasionally 'shut-er-down' for a weekend here or there but otherwise it was on running like a champ! That's like 35 in dog years Can't complain much about that. Not happy but that's a lot of 'Uptime' hours. Thanks for the service good 'ole G5. I guess it knew we've already ordered new Mac Pro boxes and got a bit jealous. Another sad G5 power supply failure here. I loves me my Macs, but this is making me want to go back to PC-lland. I had to replace the power supply. You may want to get another quote: My first-gen Power Mac G5 1.

We had two short power failures, and two days later the power supply failed. Computers last a long time when they have 1 nice clean power from the wall, 2 have no dust covering their insides, and 3 a reasonably cool place to run. When one or more of these are not there, capacitors will fail Capacitors are designed to fail, but fail in a way that does not destroy the circuit. The junk is electrical signals at the "wrong" frequency.

When the cap acitor works your computer does not send junk to the video, to the cpu, firewire controller, disk drive controller, etc. When these bits get the junk they act up in all the ways documented here, and a few more. There are lots of little capacitors on the mother board to handle the higher frequency junk.

When the power from the wall is dirty, the power supply capacitor will die and pass junk into the computer. This junk wears out the smaller capacitors. Capacitors are rated to filter a certain amount of junk for a certain amount of hours at a maximum temperature hours of junk. Notice your lights dim from time to time? Every time they dim, they just whacked the capacitor with a few seconds of junk, a little dimming, a little junk, a big brownout, and you can hear your computer scream in pain.

I have " LCD's, Plasmas that have failed. I have two really nice HP color printers I repaired. I have never found bad capacitors on a motherboard unless the power supply had first started to fail. Not ever! The truth is that Apple or more accurately Sony designed the G5's so well that they work until the capacitor literally "explodes". I have scattered around my house. I would suggest you spring for a VA system so you can plug your pretty display in as well. Tripp Lite has been making these for 20 years.

The biggest printer you will ever buy will happily work on a w unit. Did you know there is a computer in most high end stoves and refrigerators? If you are lazy and cheap like me, you can put even a refrigerator on a power line conditioner. I have stopped at the stove as I specifically bought a refrigerator without a computer controller.

It is worthwhile to install very good line conditioners or surge protectors to minimize the surges. I have been involved in surge testing our company's industrial products to insure that the design will withstand line power surges as defined by IEC Consumer products may or may not be designed to do so. Protect your computer. Daemeon Reiydelle makes several interesting points, but he seems to ignore the obvious. While it is well known that bad power can greatly shorten the life of electronics, this does not explain why specific model devices like PowerMac G5's suffer a disproportionate number of failures compared to other model Macs and PCs in general.

But we don't see huge numbers of people complaining about power supply and motherboard failures in their G4 systems or their Intel systems or in their PCs. Some of the G5's problems are definitely due to that boatload of defective capacitors that just about every manufacturer used at that time, and we know some are due to leaks and failures of the liquid-cooling system.

I'm sure that there are other more subtle design issues at play here as well. You can't just point to everybody experiencing a failure and claim that it was because they didn't have a UPS attached. All rights reserved. Power Mac G5: Power Supply Failures Jan. Many thanks Comment on this posting