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  1. #1

    new2macs19's Avatar
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    iMac Doesn't Turn On...DEAD
    Hello fellow forum members. I'm in need of some help. I hope you guys can assist. Thank you in advance for any replies/suggestions.

    I got this 2Ghz iMac Intel 17" Late 2006. It shows no sign of life what so ever. When the power button is pressed nothing happens. Nothing on the screen, no fans spinning up, no lights. Nothing. It just happened out of nowhere. One day it was ok, the next it wouldnt power on.

    I'm pretty good with PCs, not so much with Macs, but If the same principles apply, I would suspect a bad power supply. I've checked to make sure the outlet where it is plugged in works.

    What can I check or do to get this computer working again? Is the power supply the only suspect in this case?

    When it comes to PCs, I've been able to test the power supply using a multimeter. Can I test the power supply on this iMac? I've stripped it down to the guts, removing the power supply, and hard drive. On the power supply I only see two wires coming out of it. Very different from a PC's power supply unit where it has many different wires.

    Also, one thing I am conserned about is the integrity of the hard drive. It is a Western Digital with SATA interface. I was wondering if I can connect the hard drive to my other computer, a PC running Windows 7, via an external enclosure to test it and confirm that all the pics, videos, and documents are still there.

    Any help will be greatly appreciated.

  2. #2

    chscag's Avatar
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    Since you have everything already taken apart you might want to consult with the steps for checking and changing out the power supply at this web site:

    iFixit: The free repair manual

    and also: Mac Repair - Mac Parts and Service for Apple Macbook, iPhone, iPad

  3. #3

    new2macs19's Avatar
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    Thanks for the reply but neither of the links you provided details how to test the PSU

  4. #4

    new2macs19's Avatar
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    New Findings
    I reinstalled the PSU and plugged in the power cord. Since I have the iMac taken apart where I can see the logic board, I noticed a green LED light on the logic board come on. It is labeled as "LED601". When I press the power button on the back of the iMac, another LED comes on, this one labeled "LED602". Also, on the right speaker there is a light that also comes on when I pressed the power button. This light has a light blue color to it. I also noticed that the fan right below the Super Drive tried to spin, but it didn't actually spin.

    I'm hoping the aboe information helps in trying to find out what the problem is with this iMac. I'm really thinking power supply or logic board.

  5. #5

    new2macs19's Avatar
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    Found the following:

    iMac won't start, diagnostic LED's checked, what it mean? - iMac Intel 17" - iFixit

    According to this the "LED603" is supposed to be on as well. But in my case it is not. So am I looking at a video/graphics problem? By the way, when I press the power button, the hard drive does not spin up and none of the two fans start up.

    Please help...

  6. #6

    harryb2448's Avatar
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    Can't help any further sure sounds like a dead power supply.
    Hang on to those original install discs like grim death! Using OS X.7 or later make a bootable USB thumb drive before running Installer!

  7. #7


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    Symptoms as described have been resolved by an electrolytic capacitor change on the power supply. From memory 4 reservoir capacitors on one end, cut the sealant carefully under a large capacitor on the mains input side and there are 2 small capacitors under it, change both. Again, from memory, they are 22uF and 47uF. Use same voltage or higher and 105 deg C high ESR types. I repaired 2 like this recently. Only undertake if you are familiar with soldering and are aware that the large HV reservoir capacitor bent over at 90 deg most likely needs discharging before handling. Apple have used power supplies by 2 different manufacturers in these iMacs, so yours may differ from what I've described.
    Steve
    UK

  8. #8

    new2macs19's Avatar
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    Quote Originally Posted by techiesteve View Post
    Symptoms as described have been resolved by an electrolytic capacitor change on the power supply. From memory 4 reservoir capacitors on one end, cut the sealant carefully under a large capacitor on the mains input side and there are 2 small capacitors under it, change both. Again, from memory, they are 22uF and 47uF. Use same voltage or higher and 105 deg C high ESR types. I repaired 2 like this recently. Only undertake if you are familiar with soldering and are aware that the large HV reservoir capacitor bent over at 90 deg most likely needs discharging before handling. Apple have used power supplies by 2 different manufacturers in these iMacs, so yours may differ from what I've described.
    If I wasn't comfortable doing the capacitor repair, would just replacing the PSU with a new one fix the problem I am having?

  9. #9

    chscag's Avatar
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    Unless you're comfortable with the procedure as described, I recommend swapping out the entire power supply instead. It would certainly be less expensive to follow what Steve said as you can buy those capacitors at any Radio Shack store for a few dollars each.

  10. #10

    new2macs19's Avatar
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    Quote Originally Posted by chscag View Post
    Unless you're comfortable with the procedure as described, I recommend swapping out the entire power supply instead. It would certainly be less expensive to follow what Steve said as you can buy those capacitors at any Radio Shack store for a few dollars each.
    I am about to order the power supply. I don't feel comfortable messing with the caps.

    Again, based on what I've explained, symptoms and all, a new power supply should fix the problem correct?

    I want to make sure before buying the power supply. Could there be any possibility that the problem is the logic board instead?

  11. #11

    chscag's Avatar
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    There's no absolute guaranty the power supply is going to cure the problem. It appears that it will, but there's always the chance that you have a dead logic board. As long as you go at it with that in mind, you'll be OK. I don't know off hand if you could return the PS if it turns out it doesn't fix the problem. You might want to ask before ordering it.

  12. #12

    new2macs19's Avatar
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    Quote Originally Posted by chscag View Post
    There's no absolute guaranty the power supply is going to cure the problem. It appears that it will, but there's always the chance that you have a dead logic board. As long as you go at it with that in mind, you'll be OK. I don't know off hand if you could return the PS if it turns out it doesn't fix the problem. You might want to ask before ordering it.
    This is where I am going to order the power supply from:

    Apple iMac G5 iSight 17" & 20" 185W Power Supply 614-0378

    If this power supply doesnt fix the problem then I am going to assume the problem is the logic board. Where on the logic board can I find the part number; this way can look for one and have an idea of what I am looking at price wise.

  13. #13

    new2macs19's Avatar
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    Fixed
    Received the power supply in the mail today. Installed it, put everything back together, and iMac turned on. Glad it wasn't the logic board.

    Throughout this whole experience I wondered why Apple puts such low wattage power supplies on their computers. 185 watt power supply seems very low compared to other computer system. Even though in this case the problem seemed be a bad capacitor, it still seems odd to me that the power supply is only 185 watt.

    Anyhow, thanks for your help.

  14. #14

    chscag's Avatar
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    Low wattage power supplies are more "green" than higher wattage ones and they definitely take up less space. Apple has always been concerned with being "green". But I agree, it does seem under rated compared to the power supplies I've worked with on some PC desktops.

  15. #15


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    Hi, I know this thread was started a while ago but I was wondering if it could be my power supply I have 2009 20" iMac that the screen is black when I turn it on. The fans run and lights 1 & 2 come on. If I understand it correctly, these lights were on in this case as well and it turned out to be the PS. I replaced the logic board but it didn't resove the issue. Any help is much appreciated!!

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