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fails at P.O.S.T, POWER, fans on full

hi, I HAVE AN IMAC THAT FAILS AT P.O.S.T

The machine powers up, LED 1 and 2 are lit.

fans come on full blast.

The P.O.S.T alarm is three beeps, however memory, psu, capacitors, screen all ok, so was HD and combidrive.

the white light flashes with P.O.S.T signal of three flashes.

Any one got the Apple P.O.S.T details..

btw P.O.S.T is power on self test.

this happens before any software is activated and is testing onlyt hardware, cant power up till it passes..

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Here's what the Apple book says:

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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2 Comments:

hi,

Ok form begining

computer of, plugged in and led 1 lit up ok

press teh on button and led lit up okay.

white light comes on and computer GIVES THREE BEEPS.

screen remains blank..

fans on full tilt even when cold..

the white light flashes three times then goes off for about a minute tehn repeats teh three flashes as long as teh computer is left on.

press teh button on the back of teh computer and it turns of again.

the computer is not getting beyond the POWER on self test..

what i need is teh codes for teh POWER ON SELF TEST..

the third and forth led will not come on until after teh single beep as they happen after P.O.S.T (power on self test)

psu supplies tested okay,Hd ok Memory okay..

I have read every article on this help site that is why i posted I need teh P.O.S.T codes..

thankyou hopefully i have been clear

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Thre three beeps and flashes indicate bad RAM. First try reseating the RAM, if that fails, replace it

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