2011 IMAC 21.5 - No Power and Diagnostic LED #4 Briefly Lights Up

Sep 9, 2014
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Hello Mac Forums!

Hoping I can beg for some advice.....

I just couldnt afford a new IMAC, so I perhaps stupidly bought a 2011 IMAC 21.5", Core I5 that would not power up. It came with no ram and no HD.

I found the IMAC Apple Service Guide for the Mid-2011. I'm having trouble with the trouble shooting flow. I cant really afford to just buy a new Logic Board and Power Supply in the hopes that fixes the issue. I can try the Power Supply if needed as I think I can find one for around a hundred, but the Logic Board....ugh.....300-500 it seems.....

I now have Ram and a new Solid State HD to install......but need to figure out this problem before any of that can be installed.

When the Power Button is depressed, no response.
I watched Utube and removed the LCD....very carefully!
I exposed the Diagnostic LED's.
When AC power is plugged into the IMAC, LED #4 would illuminate and then would go out if you pushed the Start Button. If you pushed the Start Button again, no response and the LED remains out/dark.

I removed the coin battery to check it and it was fine. When I put it back, now the LED #4 will only briefly illuminate and then go dark. The power button still has no effect.

The Technician Guide is confusing as this LED #4 is supposed to be for communication between the Logic Board and the LCD.

I really cant afford to just start buying parts......if its just the Power Supply.....that's not so bad.....about 100. If I have to try the Logic Board....ugh....thats approaching 4 or 500!!!

I'm hoping someone may have some experience with this issue. I've searched and searched, but cant find a post for this scenario. I found a comment on a Sales site for MAC stuff that seemed to point to the Logic Board, but it was just a comment......

This is for my wife....she always wanted a MAC.....and I've always been a windows guy.....but I'm willing to learn! If anyone has any thoughts or advice on how I can test these parts or if I need to take some other path.....

I really really appreciate any advice.


Well-known member
Staff member
Jan 23, 2008
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Keller, Texas
Your Mac's Specs
2017 27" iMac, 10.5" iPad Pro, iPhone 8, iPhone 11, iPhone 12 Mini, Numerous iPods, Monterey
The only advice I can offer is to visit the ifixit web site and post your question there. Perhaps one of the techs who volunteer their time can advise you. www.ifixit.com

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