A1311 Blank Screen; Fans run at a low RPM, Sometimes at a high RPM

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4 points

A1311 Blank Screen; Fans run at a low RPM, Sometimes at a high RPM

Firstly, No. I will not be getting a new iMac I love this thing.

Secondly, Mainboard has power. It used to boot to login screen and then violently kill itself, resulting in a restart. Now only the fans run at low RPM, sometimes high RPM. SMC has been reset. PRAM reset with no success. LED 1 is illuminated. Power button has been tested and works. I'm getting voltage at the PS, but it's not being routed back to the mainboard. power cables have been checked and were found to be good. Nothing's burnt, nor are any pins bent or spread out. No other LEDs illuminate anymore.

Tried another PS, seeing as their quite inexpensive. That did not work. Tried unplugging all other accessory components. That didn't work either.

Show me what you got guys. I know all 'y'all smarter than me.

iMac 21.5″

Posted on Feb 28, 2024 10:41 AM

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Answer 1

Feb 28, 2024 12:47 PM in response to Chris_Cave

It appears "A1311" can represent a 21.5" iMac from Late-2009 to Late-2011 covering four slightly different models.

Remove the PRAM (aka CMOS) battery since it may be bad which can prevent a Mac from powering on or boot. The Mac should be able to power on without the battery installed.

Otherwise if the power supply did not make a difference, then it seems you have a bad Logic Board assuming there is no small cable on the front to connect the power supply to the Logic Board. Also assuming the Power Supply you received is good as well & the power connector is fully seated to the Logic Board.

FYI, you can disconnect the power button cable & just short the two pins on the connector to simulate a button press easily removing a power button issue, just be careful not to touch anything else.

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Answer 2

Chris_Cave Author

Level 1

4 points

Feb 28, 2024 10:52 PM in response to HWTech

Mid 2011 iMac 21.5"

So I did the right thing and checked the thread. I removed the CMOS battery as per the suggestion, and plugged in my iMac. Shortly after pressing the power button, (on the bottom right of the board where the GPU fan is seated) I had a direct short causing the steel pin of whatever was connected to the board to melt into SLAG. (Uh-ho)

Now I'm assuming that I need another board, (They're pretty cheap as of 3-1-24 on eBay) so I'll be getting one. To whomever is reading this thread in the future, sorry I couldn't help you out.

Although I'm assuming that if you're having this issue, I can recommend that you get a used mainboard (They're not that hard to remove)

And thanks to @HWTech for the suggestion.

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A1311 Blank Screen; Fans run at a low RPM, Sometimes at a high RPM

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