User pulled iMac mains power plug

komatsu

macrumors 6502
Original poster
Sep 19, 2010
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A user here pulled mains power plug on their 2012 iMac - how startup chimes can be heard but screen is totally black...

PRAM and SMC reset did not work

Any suggestions?
 

meson

macrumors regular
Apr 29, 2014
160
52
Smack the user and give them a Windows Vista machine.

What happens if you hook it up to a second display? I think it should mirror the display by default. From there you can start to trouble shoot.

Did the machine topple during the incident, or was it a case of grabbing the wrong cord in a power strip?
 
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komatsu

macrumors 6502
Original poster
Sep 19, 2010
481
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Smack the user and give them a Windows Vista machine.

What happens if you hook it up to a second display? I think it should mirror the display by default. From there you can start to trouble shoot.

Did the machine topple during the incident, or was it a case of grabbing the wrong cord in a power strip?
Thank you for the answers so far.

ok, as per your suggestion, I just tested with a second display. Nada.

To double-check connection, I got display adaptor and plugged it into my MacBook Pro - screen came on immediately.

But it's not happening with this iMac. User never mentioned anything about a fall!

Any other suggestions?
 

trsblader

macrumors 6502
May 20, 2011
424
161
Ah, misinterpreted what you meant. Sorry I couldn't be more help with that issue but I hope you figure it out.
 
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colodane

macrumors 6502a
Nov 11, 2012
793
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Colorado
Even though it is something we all try to avoid, yanking the power cord should be no harder on the Mac than any unexpected power failure - perhaps even less severe since there would be no period of low voltage or transients on the line before losing power.

The Mac is, of course, designed to withstand this scenario and should power up after the power is restored (either automatically or manually depending on the option selected in the System Preferences menu).

So something is wrong with the Mac for sure. But don't be too hard on the "plug puller". They didn't kill the Mac - something inside failed that wasn't supposed to.
 

Fishrrman

macrumors P6
Feb 20, 2009
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Have you had any luck booting from an EXTERNAL drive (connected via USB) that is "bootable to the finder" ... ?

The proper Mac user ALWAYS keeps around an EXTERNAL drive that has a copy of the OS on it and is bootable to the finder. This will reveal IMMEDIATELY whether the problem is related to the internal drive or is "somewhere else" within the Mac.
 

AppleHaterLover

macrumors 68000
Jun 15, 2018
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Even though it is something we all try to avoid, yanking the power cord should be no harder on the Mac than any unexpected power failure - perhaps even less severe since there would be no period of low voltage or transients on the line before losing power.

The Mac is, of course, designed to withstand this scenario and should power up after the power is restored (either automatically or manually depending on the option selected in the System Preferences menu).

So something is wrong with the Mac for sure. But don't be too hard on the "plug puller". They didn't kill the Mac - something inside failed that wasn't supposed to.
Props to the user for admitting it instead of going all "it suddenly died".
 

mikehalloran

macrumors 68000
Oct 14, 2018
1,606
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The Sillie Con Valley
Have you had any luck booting from an EXTERNAL drive (connected via USB) that is "bootable to the finder" ... ?

The proper Mac user ALWAYS keeps around an EXTERNAL drive that has a copy of the OS on it and is bootable to the finder. This will reveal IMMEDIATELY whether the problem is related to the internal drive or is "somewhere else" within the Mac.
Absolutely. This will tell you where the problem lies.

Yep. I've seen this before but there are 4 common causes:.

A bad NV RAM battery can cause this — pulling it out is the diagnosis. It won't retain settings but the display will come back to life. It's the first thing I suspect if the power cord has been pulled.

The HDD can also be the problem. A bootable external will diagnose this quickly. Run Repair in Disk Utility from the external. If anything is red, plan to replace the drive.

It can also be the backlight. Let it chime, give it time to power up. Shine a bright light onto the display at a 45° angle. If you see data, there's your problem.

Perhaps it's the GPU.

The cause of all the above is heat.
 
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komatsu

macrumors 6502
Original poster
Sep 19, 2010
481
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Ok I created an External Bootable Disk...it was not seen by the system. Screen totally black. Tried a bright light. Nothing.

Two interesting things of note:

1) I questioned user again (nicely...) - Q: "why did you pull power plug?" Ans: "Because screen totally froze including mouse and keyboard". Q: Anything else strange with this iMac recently? Ans: it sometimes got hot to feel and the fans would start.

2) This iMac was connected to the WLAN here about six months ago - the iMac can still be seen on my MacBook but it will not allow you login to it.

Any more suggestions?
 

Mr_Brightside_@

macrumors 68040
Sep 23, 2005
3,129
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Toronto
How is a bootable external drive going to fix a display that doesn’t turn on?
Target disk mode would be better for this.
 
Last edited:

Fishrrman

macrumors P6
Feb 20, 2009
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Sounds like this could be a display problem (display itself or perhaps GPU?), rather than a "drive-related" problem...