Imac startup long beep problem


macrumors newbie
Original poster
Jul 23, 2017
Hi to every one.
I have a late 2012 imac i7 32gb ram (owc) that I accidentally turn off from the multiplug outlet. Now the imac does not boot, black lcd screen. If I press the power button the external usb hard drive power on, fan power on, long beep (silent of 5 second) long beep again.
Long beep indicates no ram install. Replace ram with original one that had them (8gb) and same problem.

Logic board has 4 led light ( 1 and 2 led light on green) 3 and 4 do not light up.
This is been verified with lcd off, I reconect lcd but logic board 3 and 4 light never light on.

I think I have a bad logic board because I beleive the power supply working.
1 led=power supply has power
2 led = I press start button logic board has power

The power supply has a flex cable that goes from power supply to logic board next to rams, maybe the power supply does not send power to rams though the flex cable to rams and thats why logic board does not recognise rams install. Just gesing.
Can someone help me?
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