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

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How to tell if its power supply or motherboard problem?

I've got an iMac EMC 2308 I'm working on. Once you press the power there is no video, no bong and nothing on the display but I can hear the hard drive spinning and a slight fan noise. How can I tell if its a bad power supply or motherboard?

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Did you find out which part was broke? My EMC 2308 is doing the same thing and so far no post i've found has helped much other than by saying it is either the logic board or the power supply.

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same issue here, 3 out of the 4 LEDs on the logic board light up and the fans start spinning up as usual but there isn't any display or sound, from what i know, if there are only 3, the MOBO and GPU have a connection established, but a video output isn't being displayed

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@Austin Null this is where the startup sequence becomes important:

LED #1 + LED #2 + LED #3 + LED #4 = Power available, system is powered on, video card

found, and internal LCD found.

If fourth LED is not visible after power on:

• Verify cable connections between LCD panel and logic board

• Inspect LCD display cables for cable damage

• Verify external video functionality, and according to result check the following items:

-If external display works then verify/replace LED backlight board

-If external display works then verify/replace LCD panel

-If external display does not work verify/replace logic board

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There are indicator lights built onto the motherboard that will light up to show you what parts are getting power. Here is a post that should help you.

Where are the diagnostic led's on this model's logic board

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