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Late 2013 27" iMac not powering on at all.

I

iMacUser2016

macrumors newbie
Original poster
Jan 9, 2016
7
0
Hello,
I've got a problem with my iMac.

When I plug the power cable in, the first LED turns on and the PSU is silent.

When I try to power on the iMac (press power button for 10secs and release) the PSU starts to make a noise.

If I press the power button again (short press, guess it shuts the mac down again) the noise stops. Sometimes the first LED goes off for a brief moment and comes back on again.

Is it the power supply or is it the logic board?

Did somebody had a similar problem?

Please help me.
Thanks in advance!
 
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Nope, my iMac shows no sign of life besides the diagnostic LED. -> it's save to say, that it is hardware related.

Apple retail is far too expensive in Germany. The iMac is out of warranty since a long time.
Logic Board exchanges cost around 1000€, PSU would cost around 200€.

The Logic Board it self could be purchased for around 300€ - 350€, the PSU 100€, hope it is "just" the PSU. But would be nice, if there is someone here (perhaps some iMac technician) who repaired a iMac with such symptoms, so that I don't buy the unneeded spare part. :(
 
I think it may be the power supply.
Does it stay on long enough to boot to the built-in diagnostics?
(Restart, holding the D key, see if you can get the test to run)

Do you hear the boot chime at all?
Do you get any change after a PRAM reset? Restart while holding Option-Commmand-P and R.
If you hear the boot chime, hold the same 4 keys until you hear the boot chime two more times, then release the keys.

If you never get the second LED, then most likely the power supply now. A service shop would replace that first, too. But, they would also be able to put the old power supply back in the event that doesn't help.
 
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Goatllama said:
Eek. Yeah, not a technician so I can't help you there. I feel like most of them hang out in the Power PCs area, though.
Click to expand...

****, can't move my thread over there :(
Do you know some users, so I could PM them.

Nevertheless, thank you for your help!! :)

DeltaMac said:
I think it may be the power supply.
Does it stay on long enough to boot to the built-in diagnostics?
(Restart, holding the D key, see if you can get the test to run)

Do you hear the boot chime at all?
Do you get any change after a PRAM reset? Restart while holding Option-Commmand-P and R.
If you hear the boot chime, hold the same 4 keys until you hear the boot chime two more times, then release the keys.
Click to expand...

It doesn't go on at all, so I can't run the diagnostics.
And there is not boot chime.
Would love to hear it again :(

Really hope it is the PSU, but would love to get some more opinion, because ordering a PSU in Germany is not so easy, it needs to get shipped from the US, which ends in high costs, with no/bad possibilities of return.
 
Did somebody call? ;)

Sadly, it's near impossible to prove without swapping in a replacement module. However, my first port of call would be the power supply. It contains two power supplies in one board. A standby power supply which provides a small +5 volt rail to allow for soft power on. When you press the power button, this powers up the other part of the power supply which provides higher current and additional voltages to run the machine.

It would seem that the second power supply is NOT powering up. I've seen people adapt a standard ATX power supply as a troubleshooting/permanent solution, BUT, without a pinout guide of the 27" Late 2013 PSU, I'd recommend against it, simply because applying the wrong voltage to the wrong pin could damage your motherboard.

The other thing to try is to unplug the mains power for an hour, and try again. Some complex Switch Mode Power Supplies have the ability to shut-off completely if a faulty condition is reached, only clearing the shut-off when mains power is removed for an extended period of time - NOTE I'm not suggesting this is a permanent solution, but it may assist in troubleshooting.

I don't have experience with this particular model of power supply to make better suggestions, though it would appear that you are not alone with a failed power supply in a late model Intel iMac causing the same symptoms.

If you have removed the power supply, a good hi-res picture of both sides of the board MIGHT reveal a problem.
 
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iMacUser2016 said:
Apple retail is far too expensive in Germany. (...) PSU would cost around 200€.
Click to expand...

Isn't there a local repair shop available? Here in The Netherlands, I know a guy who runs a one-man-shop repairing Apple stuff. He has lots of things in stock and he's not as expensive as Apple retail.

Why not check out your local equivalent of eBay/Craigslist etc. (And if you happen to live close to the Dutch border, simply driving to The Netherlands could be an option).
 
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MacTech68 said:
Did somebody call? ;)

Sadly, it's near impossible to prove without swapping in a replacement module. However, my first port of call would be the power supply. It contains two power supplies in one board. A standby power supply which provides a small +5 volt rail to allow for soft power on. When you press the power button, this powers up the other part of the power supply which provides higher current and additional voltages to run the machine.

It would seem that the second power supply is NOT powering up. I've seen people adapt a standard ATX power supply as a troubleshooting/permanent solution, BUT, without a pinout guide of the 27" Late 2013 PSU, I'd recommend against it, simply because applying the wrong voltage to the wrong pin could damage your motherboard.

The other thing to try is to unplug the mains power for an hour, and try again. Some complex Switch Mode Power Supplies have the ability to shut-off completely if a faulty condition is reached, only clearing the shut-off when mains power is removed for an extended period of time - NOTE I'm not suggesting this is a permanent solution, but it may assist in troubleshooting.

I don't have experience with this particular model of power supply to make better suggestions, though it would appear that you are not alone with a failed power supply in a late model Intel iMac causing the same symptoms.

If you have removed the power supply, a good hi-res picture of both sides of the board MIGHT reveal a problem.
Click to expand...

Thank you! I'll try to remove the power supply and take some good pictures.
I did unplug the power cable for some days now and try to power it on here und then -> nothing :(
Or did you mean to unplug the "internal connection" between PSU and logic board?
 
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iMacUser2016 said:
Thank you! I'll try to remove the power supply and take some good pictures.
I did unplug the power cable for some days now and try to power it on here und then -> nothing :(
Or did you mean to unplug the "internal connection" between PSU and logic board?
Click to expand...
Just the external mains cable. It was worth a try.

See how you go with 'crossing the border'. ;)
 
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MacTech68 said:
Sadly, it's near impossible to prove without swapping in a replacement module. However, my first port of call would be the power supply.
Click to expand...

That would be my take on it also, but I hate to see OP throw parts at it himself then be stuck if it turns out to be something else. This might be one of those times where it is better to pay a shop so the risk of needlessly buying parts is on them.
 
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Hey at all.
Sorry for my late response, but I was quite busy because of some exams.
The iMac just stood around for a while. Still not powering on. :(
 
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Your details about the USB stick that appears to power on briefly, should indicate that you almost get power.
But not enough power to actually boot.

Your first choice should be replacing the power supply.
I am pretty confident that you can expect your iMac to work after replacing the power supply.
 
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I had the same problem with a Late 2010 iMac. First LED lit, nothing else happens when you press the power button. I replaced the power supply myself and the iMac started right up normally.

The way I understand it the second LED lights up when the logic board gets a POWER OK signal from the power supply. In this way the iMac does not attempt to run on incorrect power and possibly get damaged.
 
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hi guys, I have the exact same issue with my late 2013 27" iMac... is there already a solution to this problem?
 
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