Model A1224 / Mid 2007 and Early 2008 / 2, 2.4, or 2.66 GHz Core 2 Duo processor

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iMac Intel Duo won't boot. LEDs 2 and 3 on then off

IMAC Intel core duo 2.4 just stopped working. Power button does nothing. I disassembled and replaced PRAM battery--it was 3.08v with new 3.35v. Now LED light

No 1 is on, 2 and 3 light momentarily when power button is pushed and something tries to whirr--for a second or so, then gives up. Since led 1 is on, seems like power supply is good. What other things can I do to find the problem. Thank you So much

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My bet would be on a bad power supply but check the other things before ordering.

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

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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Just tried SMC reset. Now it boots to gong sound, once went to actual desktop, then after 30 seconds to a minute it shut down again. Then repeatedly sounds gong trying to boot again, but never made it back to Desktop. Sometimes when the leds flash, the fan tries to turn but like it doesn't have enough energy--Power supply? But then others have been commenting that after about three years logic boards are going bad on a lot of Intel machines. Any way to test these before starting to replace? I have multimeter but no real data or data points to test. Thanks again. John

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I'd start with the RAM. Try each RAM chip, using just one chip at a time in each of the slots.

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you can always go over the Power supply Pin's and test them for voltage, to see if the Power supply unit (PSU) is at least outputting what it should.

iFixit has an instruction located here:

iMac Intel 20" EMC 2210 Power Supply Output Voltage Test

althought note:, different revisions of PSU might have slightly different Pin outs (or the chart is wrong?), as the chart says that Pin 8 should have 12v on it on standby (plugged in and turned on at the wall, but with the imac still turned off itself), where as on my PSU, it is Pin 9 that has 12v on standby, etc..?

so maybe just be mindful that it might not be identical?

=)

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John Taylor will be eternally grateful.
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