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Model A1311 / Late 2009 / 3.06 or 3.33 GHz Core 2 Duo processor

iMac doesn't turn on if Screen is connected.

Hello team,

I am trying to fix this old iMac. I get the first 3 diagnostic leds however, when I turn it off and I connect the second cable of the lcd screen - the flat cable - if I try to turn it on none of the leds turns on.

If I try to turn the Mac on while just the LCD power cable is connected, the Mac starts as well as the fans.

Any suggestion?

Update (11/18/2018)

I am still thinking about buying a power supply. I have completed the installation of the OS after connecting the iMac to the TV and using this as screen however the OS won’t start unless on safemode. Do you think there’s something else broken or you believe is still a matter of power supply?

Airport is disabled and the Mac can’t recognise any internal sound output but I believe that is related to the safe mode.

Any ideas?

Answered! View the answer I have this problem too

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The screen puts an additional load on the power supply. I suspect a partially failing PSU. Here’s how to replace it:

iMac Intel 21.5" EMC 2308 Power Supply Replacement

Giving us a history of the machine and the way it failed would help with diagnostics.

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Here's a link to a replacement PSU.

iMac Intel 21.5" (Late 2009-Mid 2011) Power Supply

Be sure to follow the instructions on the guide VERY carefully as you do not want to get zapped by touching a capacitor or an exposed soldered joint!

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Hi, and thank you for your reply!

The machine has been a gift from someone that didn’t know much.

I thought it might be the power supply however I think its weird that it fails even if I’m connecting just the data cable of the LCD without connecting it to the power given by the inverter.

What do you think? Can it be the PRAM battery? It’s a pain to change it…

Just an update, it seems to work by using my TV as external monitor

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I have never seen one of the new round PRAM batteries fail or need replacing.

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Hi there, new update. I tried with a brand new SSD and after the installation get stuck with a white page, only starts in safeboot. At this point it can’t be the hard drive, can it be a failed motherboard or video card? I never heard of a broken power supply that doesn’t allow the system to boot if not in safe mode

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belfast123 Ewew will be eternally grateful.
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