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Apple Computing Products:
macOS - Desktop Hardware
21" imac late 2013 repair question
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<blockquote data-quote="Vogelek23" data-source="post: 1840528" data-attributes="member: 403831"><p>First of all, you need to re-assemble the machine (do not fit nor connect the screen yet). Then connect it to the power outlet (PLEASE BE VERY CAREFUL BECAUSE THERE IS A LIVE MAINS ON PSU!) and watch a diagnostic LEDs status (see attached picture). First LED is a Standby LED (means it should lit up as soon as the computer is connected to the mains). Second LED is AllPowerGood LED (means when all SMPSes fire up, this LED lits up). 3rd LED is a GPU LED (means when graphics chip is powered and initialised, this LED lits up). And the last one is Screen power LED (means when screen is properly detected and powered, this LED lits up).</p><p></p><p>[ATTACH=full]30957[/ATTACH]</p><p></p><p>If the first LED does not lit up, it is most likely dead PSU. If the first LED lits up but there is no signs of life when you try to switch it on, most likely it is bad SMC. If the machine turns on but switches off immediately, there is a short circuit on some low-side power rails etc. Please share your diagnostic LEDs readings.</p></blockquote><p></p>
[QUOTE="Vogelek23, post: 1840528, member: 403831"] First of all, you need to re-assemble the machine (do not fit nor connect the screen yet). Then connect it to the power outlet (PLEASE BE VERY CAREFUL BECAUSE THERE IS A LIVE MAINS ON PSU!) and watch a diagnostic LEDs status (see attached picture). First LED is a Standby LED (means it should lit up as soon as the computer is connected to the mains). Second LED is AllPowerGood LED (means when all SMPSes fire up, this LED lits up). 3rd LED is a GPU LED (means when graphics chip is powered and initialised, this LED lits up). And the last one is Screen power LED (means when screen is properly detected and powered, this LED lits up). [ATTACH=FULL]30957[/ATTACH] If the first LED does not lit up, it is most likely dead PSU. If the first LED lits up but there is no signs of life when you try to switch it on, most likely it is bad SMC. If the machine turns on but switches off immediately, there is a short circuit on some low-side power rails etc. Please share your diagnostic LEDs readings. [/QUOTE]
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Apple Computing Products:
macOS - Desktop Hardware
21" imac late 2013 repair question
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