Solved Mac Won T Boot Only 1Diagnostic Led Imac Intel 27 Emc 2429
Chosen Solution 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? Related post may help you Won’t power up and only 1 diagnostic LED