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Model A1312 / Mid 2011 / 2.7 & 3.1 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac12,2

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Mac won't boot / Only 1diagnostic LED

Well, another case of boot failure with only the first LED (501) lit.

Actually, I’ve already tried everything that’s been recommended here.

On pin 4, 11 and 12 I measure 11,93 / 11,94 V.

Could this slightly lower voltage be the reason for the Mac failing to boot?

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crwdns2889612:0crwdne2889612:0 0

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The case for whether a voltage is good or bad is based in tolerance. Most power circuits have anywhere from 5 to 10% tolerance, but this can vary by spec. If the reading is within the +/- % tolerance, then the voltage is good.

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