Model A1200 with 2.16 or 2.33 GHz Core 2 Duo processor

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No chime, black screen, white light steady

Hi guys,

If iMac is off, but power is plugged in, number 1 diagnostic LED is on.

If iMac is on, no chime, fans go max, black screen, white light stays steady and number 1 and 2 diagnostic LEDs are on.

If LCD unplugged and external monitor plugged in, can't turn off, it turns right back on, once external unplugged, it turns off.

Also tried with detaching everything (add on cards, hard drive, etc.), no results.

Maybe the power supply? Hope its not the logic board....

Any ideas?

Thanks!

Answered! View the answer I have this problem too

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3 Answers

Chosen Solution

LED Startup Sequence

LED #1 = Power available.

If no LED is visible:

• Verify AC source

• Verify known-good AC cable is connected

• Verify cable connection between AC inlet and power supply

• Verify cable connection between power supply and logic board

• Verify power supply

LED #1 + LED #2 = Power available, and system is powered on.

If second LED is not visible when power button is pressed:

• Verify power button connection to logic board

• Verify power button functionality

• Verify cable connection between power supply and logic board

• Verify power supply

• Verify logic board

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

If third LED is not visible after power on:

• Verify that MXM video card is seated properly

• Verify logic board

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Thank you for the prompt response.

• Verify logic board

What kind of tool is required for that?

Thanks.

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Exchanging the logic board with a known good one. Remember these instructions are for an Apple tech sitting there with all the resources in the world at his fingertips.

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Thank you, so if third LED is not on, most likely logic board.

by

Logic board or video card. I don't remember if this video card can be changed or not. I would check with these folks on a board repair: http://www.dttservice.com/imacintel.html

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+ Good Kung Fu

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Hi S.M.

Have you finally fixed your iMac? What is the problem?

I have an identical iMac and the same problem as yours.

Thanks.

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Hi,

since it turned out the motherboard went out, I decided to not change it. For a little more I could buy a new iMac...

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s m will be eternally grateful.
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