Apple A1312 Mid 2011 Won't turn on

[Shizey]

Hi everyone,
I have an A1312 Mid 2011 that won't turn on. The 1st LED diagnostic light will turn on but that is it. Occasionally when I press the power button the fans will blip on for a millisecond and stop spinning. No hard drive noise or anything and no other LEDs turn on.
I have replaced the power supply with a new one, I have replaced the video card with a new one and I just purchased a new logic board and it appears to be doing the same thing.
I have tried every combination of holding the power button on.
I can't for the life of me figure out why this thing won't turn on. I have looked over every cable and checked to ensure no cable was cut through or damaged by visually inspecting and using a multimeter. I've dug into it top to bottom and can't find anything. I've tried unhooking components one at a time to test and see if they are causing the issue. Nothing
I am losing my mind here. Any help would be appreciated. Thanks!

 

[chscag]

Welcome to our forums.

This appears to be a 27" Mid 2011 iMac. (Always helps if you identify your Mac and give us specs.)

It looks like you've spent quite a bit of money and time trying to repair this iMac. Assuming all the parts you replaced are good and working as they should, that pretty much leaves the possibiltiy of an assembly error on your part. Perhaps something you've overlooked? Don't know if you been there already, but a good place to start is at www.ifixit.com and look over their breakdown instructions. Since we can't see your iMac, we're not going to be much help.

 

[Shizey]

Shoot. I knew I should have taken some pictures of it before I left for work. But yes you are correct. It is a mid 2011. I have been to their site quite a few times. I have followed their guides with the same outcome.

The power button does work fine I have tested it with my meter. I have also tried jumping the pins on the logic board for the power switch as well.

One weird thing I found is if I have it unplugged and hold the power button and plug it in, the led light 1 doesn't come on until I release the power button. After the light turns on I press the power button and the fans will blip on for a second. Its very weird.

All through this though I never hear the hd try to spin up. I have also tried a complete reassembly before attempting to turn on and it has the same result.

Does anyone have the pin out for the power supply to the logic board? I have seen the other year a1312s but have not been able to find the mid 2011.

If I have the screen off I should be able to at least see the fans spin up and the second led light up right?

Thanks for the help everyone

 

[Shizey]

What pictures would be best??

 

[Shizey]

Serial number ends with FMDHJP. Logic board number is 639-2289

 

[SweetDoug]

Where are those darn LEDs?

Hi everyone,
I have an A1312 Mid 2011 that won't turn on. The 1st LED diagnostic light will turn on but that is it. Occasionally when I press the power button the fans will blip on for a millisecond and stop spinning. No hard drive noise or anything and no other LEDs turn on.

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I'm one ahead of you: Nothing turns on. Where are those LEDs? I can't find'em and can't locate the service manual.

Anyone have the service manual for this beast? I've got it apart, but can't find the LEDs or figure out how to test the power supply. I figure just disconnecting the output of the PS and the appropriate multi-meter settings in the output should do the trick?

Suggestions?

SweetDoug