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A2115 / 2020 / Prozessoren beginnend mit 3,1 GHz 6-Core i5, bis 3,8 GHz 8-Core i7. Markteintritt am 4. August 2020.

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Mac Won't start up

Hi all,

My Mac was asleep and the next day the power was off, so I tried to restart but nothing. I called apple they walked me through the basic troubleshooting (reset sec etc...) nothing. this was confirmed at the apple store. They suspected the power supply. So I took it home bought a tested used power supply and when it arrived installed it, but still nothing. Looked for the diagnostic leds... found 5 on the lower right hand side of the logic board (not where they are on any photos I saw online, but they look like them. However none are illuminated when connected to power. Where do I go now? I'm not by any means an electronics guy but understand some basic principles and have a multimeter.

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@jre356 that is right. Your iMac has the LED's on the bottom right (marker #1)

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Anyhow if LED1 does not light up at all, your iMac does not "know" that power is available. Follow the steps for the diagnostic LED's and let us know what you found out.

IMac 2020 Diagnostic LED

Could be a power supply issue or not connected to the logic board.

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Thanks oldturkey3, I have confirmed all of the tests except:

1. verify the connection with the logic board. What's the best way to do this?

2. verify the power supply. What's the best way to do this?


@jre356 you would Check the cable connection from the power supply to the logicboard, but if you have not even LED 1 light up, you may not get power to it. Start there. Outlet ok? Power cble ok? You got main power to the power supply? Trace it with your meter. Just remember its full main AC voltage so make sure you treat it with respect so it does not bite you;-) Keep your hands of the board and don‘t touch any of the components. Let the meter probes do the touching. I‘ll check to see if my schematics show where you can check the power supply on the board connector. The craziest thing here is that you do not get LED 1…..


Thanks for your help. I used the meter to confirm the ON button works, I disconnected the PS and checked the the input connector which went through the cord to the wall outlet and got 120 V. I checked back with the place I bought the PS from and the said it was tested and was in good working order. I carefully looked over my original PS and saw no indication of component failure or cold solder joints, so not sure it's bad either.


@jre356 you checked the connection from your power supply to your logicboard?


No, not sure where to check this. I just confirmed that 120V is getting to the PS.


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JRE356 wird auf ewig dankbar sein.

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