Model A1311 / Mid 2010 / 3.06 & 3.2 GHz Core i3 or 3.6 GHz Core i5 Processor

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Works but then display switches of after few minutes

I have an iMac, just over 1 year old, and it's started to switch the screen off, after a few minutes, so here is what happens.

1. Switch on (after being off for a while)

2. Starts and loads

3. working fine then screen goes black but still has backlight

4. all diagnostics LED are on

5. sometime hear noise coming from speakers (clicking-pulsing)

6. shuts of to 1 led but fans still running ( left for 5 mis)

7. short press of power button does nothing

8. holding power button switched off (still 1 led)

9. Machine switches on

10. starts and loads

11. Switches off after 2 mins (fans stop)

12. power button press fans work but 1 led

13. hold power switch fully off

14. press power starts again

15. this just keeps going.

not sure if power supply fault, anyone have any idea?

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This sounds like a failing power supply issue to me not a logic board problem. The #1 light will still be on even with a power supply failure. The fact that it shuts down and the LEDs go back to just the #1 light indicates this to me. Here's how to replace it: iMac Intel 21.5" EMC 2389 Power Supply Replacement

The power supplies can also be rebuilt by a couple of places on the net (they will buy the core), so don't throw it away.

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Ouch !!

Can you get to an Apple Store ASAP if you can they may still cover it under warranty, have a sad face and cry a little ;-)

Otherwise you'll need to bite the bullet as it could be costly.

From the sounds of it it does sound like logic board capacitors are going bad. But your comment on the diagnostic LED's is throwing me as the LED #4 should be off.

- LED 1 indicates that trickle voltage from the power supply has been detected. This LED will be ON when the computer is turned off and your power supply is working correctly.

- 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 LCD display are communicating. - This LED will be ON when the computer is turned on and video signal is being generated.

- LED 4 lights only if the computer detects an over-temperature condition. This LED will be OFF when the computer is turned on and running at the correct temperature.

Double check the LED's and if #4 is lit your CPU may have a problem.

Hopefully Apple will help you if not get back to us on the LED's

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Steve will be eternally grateful.
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