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  1. #1
    iMac G3 400MHz DV won't turn on
    I just got an iMac G3 400MHz DV Indigo at a garage sale. I wanted to try out a Mac and wanted to see what OS X was like.

    I turned on the computer, and all I got was a click like sound from the speakers and a click like sound from what I think was the CRT. The led on the power button does NOT light up. That's all that happens. I can hit the button forever and thats all that will happen.

    So I got the service manuals from the web and took it apart and read the section on checking power voltages. I checked the current of the PRAM battery. It registered as 3.63v so the battery is working. Then I hit the reset button for the PMU chip. When this didn't do anything I continued with the voltage tests.
    I checked the +5v trickle power, the Down Converter On voltage, and I checked the Power Board Fuse. All are ok.
    The service manual says that after all those the next thing could be that the Power/LED switch board is defective.

    Could that be it? I don't have any discs for the computer as the seller couldn't find them. I think the computer is on OS 9. I want to try out this Mac so badly.

  2. #2

    macEfan's Avatar
    Member Since
    Dec 01, 2004
    Somewhere in the world
    Powermac g4 400mhz, 10gb, 256mb ram, OS9
    The Power/LED board doesn't die often.... Its either a bad Power Supply, or the FBT (flyback transformer) for the monitor has gone bad. If its the Flyback transformer, the computer will turn on for a sec, then turn off, and wont turn on for a few hours after that.... Probally not worth replacing, as apple charges a bundle for the analog board, and installation is tricky...
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    Don't forget to use the rep system!

  3. #3
    It's possible that someone tried to upgrade this one to OS X without updating the firmware first. That is a common problem and can produce symptoms similar to what you describe. This site may be able to help you:

  4. #4
    Ok, I tried taking out the memory, the hd, and the cd drive. The computer will still not turn on.

    When you say the power supply could be bad. Do you mean the down converter board that is one the bottom side of the computer, where the logic board plugs into? They are on eBay if I need to buy one.

  5. #5
    Well, I finally got a new battery and it did not work. If you think its a gonner I guess I will finally let it go. Unless I should spend 40 bucks for a new down converter/power board.

  6. #6
    I seem to have the same problem, but mine wont give any hint of turning on when I ress the power button.

    I got the computer from my father inlaw. It was working for him, but was turning off after a few minutes. It was displaying symptoms of the un-updraged firmware, seen as he had upgraded to OS X. So when I got it, I pluged it in and got absolutly nothing to happen. No power light, so speaker clicks, no minitor sounds....nothing. I tried diferent outlets, and diferent power cords. Nothing.

    I take it to a Apple store. They plug it in and it powers up, but does not boot. The green power light came on and it seemed to be getting power.

    I take it home, and again, nothing at all. No power lite no nothing. Im baffled.

    I took it apart and tried to discharge the tube with my fancy fancy aligator clip and screw driver, but I heard no "pop". There was no charge on it.

    Here are my questions:
    1: Given I had no discharge, could the FBT be bad. And if it is bad, would that give the symptoms I have? (No noises, no power lite, no nothing?)
    The fuse for the power is good.

    2: When I took the computer to the Apple store, it was quite warm in the car. Could the heat in the car make the FBT get a temporary connection to get it to turn on for them, but after cooling down in my house with the AC on, make the connection break again giving me nothing at all?

    3: And if it is the FBT, where could I aquire a new one?

    4: If it not the FBT, what could the other possibilites be?

    Thank you for your help.

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