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Thread: Power Problems with a G3/500 MHz Snow iMac

  1. #1
    Join Date
    Feb 2002
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    Default Power Problems with a G3/500 MHz Snow iMac

    I am having power problems with a G3/500 MHz Snow iMac. When you press the power button the light goes on, but nothing else happen (no fan, no hard drive start up, etc..). What I've tried:

    - Preliminary checks: used different power cord, tried different AC outlet.
    - I opened the computer up and checked the PRAM battery. That was low so I replaced it with a good one. I reset the PMU according to the instructions in the Service Manual. That didn't help; the results were the same (power light turns on but nothing else happens). When I press the power butter, there is a green led indicator light on the logic board that goes on. Pressing and holding the power button will turn it off.

    What do I try next? Where do I go from here?

    Thanks.

  2. #2
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    Lightbulb

    Two near identical systems and similar problems?

    How about UPS?

    There is a "fix for Mac that won't power up" in the FAQ Index from Macosxhints to pull the battery and leave unplugged, then boot with battery out.

    I think the problems are so nearly the same they would be better in one thread unless that is too confusing or you think they are truly unique and different.

  3. #3
    Join Date
    Feb 2002
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    Default

    Thanks for the reply.

    - The computers belong to two different people.

    - I tried the fix suggested, but unfortunately it didn't help in either computer.

    - I was going back and forth trying to decide to have one post or two posts. In the end I decided on two since: the computers are pretty different (G3 iMac and G4 Tower) and the problems are a little different. The iMac consistently will only turn on the light (never getting past that) and the G4 is either completely dead (not even the led light on the logic board) or working fine.

    Any other suggestions?

    Thanks again!

  4. #4
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    Default

    Hi and welcome!

    Bad news. The imac is likely done for. The symptom you describe usually involves a hardware failure that is difficult to resolve. Apple recommends you replace the PAV (power/audio/video) board, which is actually harder than getting the logic board out, plus PAV boards are pricey the last time i checked. Some skilled tech savy types have ID'd the component that needs to be replaced, but you have to find this particular component, then desolder the bad one and solder on the new one. Not for the weekend do-it-yourselfer.

    Barring wanting a serious project, send the little guy off to Mac heaven, and grab a new/refurb Mini, and don't look back.

    You can find old threads here and on the web about imacs with no video.

    As for the other thread about the tower, it is unrelated to this; this is a unique G3 imac issue AFAIK.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  5. #5
    Join Date
    Aug 2005
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    Default

    Quote Originally Posted by kaps

    What do I try next? Where do I go from here?

    Thanks.
    Have you checks the voltages at the various points on the listed in the service maunal for power. There is a list of pin locations and voltages. if you don't have them I can send them of to you.

    Also has there been any change to the Ram since it last ran. I installed some ram that was running fine in My G3 beige, in a G3 400Mhz iMac, and it acted similar, no start, no error tones. Found out that the ram was registered, has an extra buffer in place and is not compatable. Mac sure there is no "R" at the end of the chip sequence PC100-322-620R at going to work PC100-322-620 will.

    Unc would like to send G3 iMacs to an early grave, (sorry unc) Can't really blame him given his have to deal with them in a business enviroment.

    Replacing a PAV can be a pain but thats relative to you patience, desire and budget.

    If I knew how to link a thread, I would, but search for No power imac.

    good luck
    bob

  6. #6
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    Default

    OK, maybe I am jumping the gun. Good call on checking RAM. My money is on a PAV issue, but would love to be wrong.

    It's not that I want the lil' guys to go to grave anytime soon, it's just that most users are willing to do a little work, not disect an imac. I guess I should have said: If you do your homework, are very patient, willing to spend quite a few hours of research, parts scrounging, and the actual repair, and you are tech savy, then you can fix it easy.

    Thing is, that might be something like 2% of computer users. Most will not wanna do much beyond swapping easy to get to parts: RAM, battery, HDs, etc.

    I'm no snob, but I have a hard time using much slower than about a G3 700 with OS 10. On my old G3 700 white ibook, I've pulled just about every trick I can to get 10.4 to be snappy. Every little bit helps.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  7. #7
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    Default iMac SE/400 unable to restart

    I have had a similar problem with an iMac SE/400 running 10.3. At first there were some video problems, and finally the inability to reboot......it seemed to gradually wind down with one more problem than before with every power-up. I thought if it were a pure video problem I could just FireWire connect to my iMac G5 and move the data, but I havn't been able to reboot even after changing the battery and performing PMU reset.....I'm just getting a lit power button that will turn on/off from the front without pulling the plug.

    Since I'm mostly interested in the data, would a good solution just be to buy an ATA box, remove the hard drive from the iMac SE and hope the directory is well enough to mount the drive?

  8. #8
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    Default

    Unless the drive was dying too, you should be fine. Any Firewire enclosure should work with most any Mac, and you could drop it in a a tower with a free ATA port, though you have have to monkey with jumpers.
    "Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining." -- Jef Raskin

  9. #9
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    Default

    Thanks UM.....I'm going to try a new enclosure and will post results when I get that done. I have gone back to some old posts and found where there were recommendations to let the PMU really die down....that is, leave the battery out of the machine for at least 24 hours....before reinstalling. I don't know how valid that is, but, I do remember reviving some very dead machines by having the patience to at least try that. I am going to give that one last shot before removing the drive.

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