Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor

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iMac not booting, is it worth it to replace power supply?


A friend of mine gave me an old mid 2011 iMac that she said was not working and I'm now trying to decide whether or not it is worth it to try to fix it:

When I plugged it in for the first time, the circuit breaker in my apartment went off. After resetting the breaker, plugging in the cord does not blow the fuse but neither does the computer start. It emits no sounds, so it seems obvious that the PSU is faulty.

I'm now considering buying a replacement PSU but I don't want to spend tons of money on it if it's actually the whole computer that is fried. Is there any way for me to check if that is the case beforehand?

Also, can anyone explain why there is such a large difference in price between these two PSU's? Which one should I get? They both seem to support the computer. and iMac Intel 27" (EMC No. 2309, 2374, 2390 or 2429) Power Supply

iMac Intel 27" (EMC No. 2309, 2374, 2390 or 2429) Power Supply Image
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There are LED diagnostic lights to the right of the RAM slots on the logic board. See if #1 is on (indicating trickle power to the PSU before attempting boot and see what happens when you try to boot.

LED 1 - Indicates that the trickle voltage from the power supply is detected by the main logic board. This LED will remain ON while the iMac is connected to the AC power. The LED will remain on even when the computer has been shut down or put to sleep. The LED will turn off only if the AC power is disconnected or the power supply is faulty.

LED 2 - Indicates that the main logic board has detected proper power from the power supply when the computer is turned on. This LED will be ON when the computer is turned on and the power supply is working correctly.

LED 3 - Indicates that the computer and the video card are communicating. This LED will be ON when the computer is communicating properly with the video card. If LEDs 1 and 2 are ON and you heard the startup sound, but LED 3 is OFF, then the video card might be installed incorrectly or need replacement.

LED 4 - Indicates that the computer and the LCD display panel are communicating. This LED will be ON when the computer is turned on and video signal is being generated. If the LED is ON and there is no image on the LCD display panel, the LCD display panel or inverter might be installed incorrectly or need replacement.

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Thanks! I saw those instructions in the service manual. The problem is what to do if led 1 is not on when the computer is connected to power. What is the probability that changing PSU will make it work? Should I just gamble or is there some way of checking the logic board without replacing the PSU?


Face problems as you come to them. If the LED is not on, replace the PSU. The problem is the light being on with a failed PSU.


Ok. Thanks! Do you have any idea about the difference between the two PSU units?


First let me know your exact machine. Go here and enter the serial number (located on the bottom of your stand) and tell me what you have:


Its the A1312/EMC2429, 3.1 GHz Core i5 (I5-2400) with 4GB ram and 1TB storage according to the site.


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