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모델 A1419 / Late 2013 / 3.2 & 3.4 GHz Core i5 또는 3.5 GHz Core i7 프로세서, ID iMac14,2

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No Screen, LED #2 Off, No Chime

Hi so the iMac will not turn on, the screen stays black and there is no chime.

I opened the iMac and noticed that LED #1 stays on but when I press the power button to try and turn on the iMac, LED #2 never turns on.

I can hear the HDD spin up when I power on the iMac but no fans turn on. So I’m not sure if the PSU is bad or not.

I tried to power on the iMac with everything put together, without an HDD, and without RAM, LED #2 never lit up.

I ran a test on the RAM and HDD and both passed, so my question is if it is more likely to be the PSU being bad, the cable to the logic board being bad, the logic board being bad, or the CPU being bad.

Thank you.

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It’s most likely not the CPU. Have you tried holding different boot keys? if everything leads to a black screen and single led. I would try pulling the cmos battery, reseating the video cable, cleaning it out and disconnecting as many components that are not necessary for the machine to post, Such as the webcam, DVD drive, etc. Try different memory. Power supplies are cheaper than Motherboards, and either could be the issue. However, be thorough with your checks first.

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as far as I know, I don't think the iMac has a CMOS battery. I've already checked the display cable. I also believe even with the display cable unplugged and memory removed you should still be able to see the diagnostic LEDs go from 1-4 if everything is working?

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This series does indeed use a CMOS battery!

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The power supply gets the worse of it! Yes, you need a new PSU.

You should take some actions to help prevent killing the new PSU. First make sure your outlet is properly wired and the ground service is good. Go to the breaker panel and make sure the sound service from there is good. It should be connected to your water line main (metal) to the street and/or a grounding rod. Make sure you have not overloaded the circuit as well as make sure nothing heavy (heater, AC or compressor …) is on same circuit.

Next you should have at least a good surge suppressor or better yet a good UPS!

Here’s the needed part iMac Intel 27" (Late 2012-Mid 2017) Power Supply and heres the needed steps iMac Intel 27" EMC 2639 Power Supply Replacement

iMac Intel 27" (Late 2012-Mid 2017) Power Supply 이미지

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thanks, I thought it was probably the PSU but I just thought that it was weird that the HDD was receiving power (as it was spinning up on boot) because I think the HDD power comes through the logic board?

and unfortunately I don't know how it died as it is a family member's iMac but I do currently have it plugged in at my room which has high quality surge protectors for my own stuff!

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You can loose one (or more) of the power legs from the PSU which explains the drive spinning up.

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Solved? I am interesed because I have the same problem

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As you can see there are two of us who fix systems telling Dylan (as well as you) the power supply needs to be replaced.

Even still... You also want to prevent future damage by making sure you've checked your AC outlet as well as your building grounding as I've outlined above. And lastly get a good surge suppressor (new as the one you have didn't work) or better yet get a good UPS!

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Dan is absolutely correct. Ungrounded buildings are not ideal for any appliance trouble shooting, or operation for that matter! Also remember to be safe when dealing with high voltages that come from the wall.

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Dylan, I’ve done this repair 3 or 4 times now - and with those symptoms - it is most likely your power supply. It COULD be the logic board, but I have yet to see that happen. Any time your computer (or any appliance or amp) is not powering on, you should at least SUSPECT the PSU.

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Side note - I am certain that is what your LED's are telling you, because that has been the case any time I've seen only the first LED lighting up. If the second LED were lighting up, it would mean that it is detecting proper functionality of the PSU.

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