iMac black and white lines

Hi guys,

My 2011 iMac just completely shut down on me today. I was in the middle of surfing and sending an email when the screen just switched to black and white lines (see attached) and I had to manually turn off via the power button.
When I tried to reboot it just hung. I did notice that the machine was hot but when are they not?
Anyway I have left it to cool down for an hour and I'm back up and running and typing this.

I was contemplating a safe boot with verbose and then a disk check but its "ok" at the moment.
It felt like the graphics card or something just gave up. I would like to say heat but my iMac has always run hot at the back.
Just wondering if anyone had any thoughts?
Many thanks in advance

An iMac does not normally run hot. Your 2011 has three fans: hard drive, CPU, and optical drive. How about downloading a utility which will give temperatures and the RPM of the fans to see what may be going on. Cool air is drawn in from the bottom vents right below the display and warm air is expelled from the top vents. The back of the machine should not be warm to the touch.

iStat Pro widget menus (Free)

Ive got istat and smc already. What is the "usual" temp for these? Especially the CPU & GPU. When I say 'usually runs hot' I mean the ali rear chassis at top exit vent.

Since posting its happened again a few times but each time different processes were being done, email, Facebook, you tube, excel etc... At least my time machine is up to date.

When I get time I'm going to open it up and give it a good clean. Hopefully a dust build up somewhere. I was thinking about upgrading the mxm board but now I will hang on until this is resolved.

I'd say chances are high that you either have a dust blockage or a fan (particularly the one cooling the GPU) has stopped working correctly. I predict this is going to need a big $ fix if the dusting doesn't clear up the issue.

orgazmojedi said:

Anyway I have left it to cool down for an hour and I'm back up and running and typing this.

Click to expand...

Given the fact that it's working again after an hour of "cooling"…I would agree with the comments above to investigate things to confirm that all the fans are working properly…and do a good clean-out with some compressed air.

Also (just out of curiosity)…after the hour of cooling & the computer working ok. How long did you use the computer at that point? 5 minutes, 30 minutes, an hour, etc. Trying to get an idea of its stability duration.

- Nick

I think it worked for about another 15/20 mins before it froze again.
Been away on business so I haven't got round to cleaning yet. Hopefully tomorrow

well oh dear. I don't know whether to start a new topic now?
Tried to turn on today to make sure my backups were 100% before I went messing inside but it won't even boot now!

Safe boot = Goes 50% through loading bar then blue flash into black screen

Option/alt boot = Gets through to drive select screen ok but...
a) SSD/OSX = grey screen
b) Hdd/Bootcamp = Loads Windows 7 splash but then black
c) Disk Utility/Recovery = Straight to blue screen only

I can Single user ok and verbose gives no errors but I'll be honest and say I'm stuck.

Could this be a bad GPU (cannot MDP to external screen either)?
Bad Logic!!??

A little part of me wanted the SSD to be dead (easy fix albeit annoying) but with Bootcamp/ Recovery not booting I fear the worst.

Anything I can try to isolate the issue?

addition -

I can boot into Bootcamp but only in safe mode??
This makes me more confused

Opened up anyway to check for dust and to honest there wasn't a lot. Fans given quick brush and canned air it all over.
Checked all cables
RAM out and back in one stick at a time

Recently had a meltdown of my own. IMac starts to boot, load bar starts, and then gray screen.that's it,no safe boot,no boot to disk utility,won't load from disc,,,I think I'm in for a very expensive week. My guess,logic board,or video card,both costly.

orgazmojedi said:

A little part of me wanted the SSD to be dead (easy fix albeit annoying)...

Click to expand...

You're forgetting about the video issue. A bad SSD wouldn't cause this.

- Nick