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imac 21.5 2011 screen goes black after start up and will only come back on after pressing start button

My parents have a 2011 imac 21.5 inch. running 10.10.2 over the last few months the screen goes black and will not wake up with any movement of the mouse. It will only come back on after shutting off at the mains and restarting. This problems happens randomly but is steadily getting worse over the last couple of months I fear there is a major problem looming. Has anyone else had this issue and know of any solutions?

iMac, OS X Yosemite (10.10.2)

Posted on Mar 24, 2015 11:30 AM

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2 replies

Mar 30, 2015 3:41 AM in response to Kevin2323

Same system by the sound of it - I did find though that by sending machine to sleep - nitre/shift/eject and then pressing a key the display returned.

The machine was in fact still working even tho the screen had gone black - a second monitor continued to show 'live' images no problem

.

I did in fact take the machine to a nearby Apple Centre for a Genius Bar appointment. Needless to say the issue would not repeat itself whilst I was there but it was checked for video card and passed and the tech chap affirmed that as I was getting a picture/image on the second attached screen that the graphics card must be working ok.

It was agreed I would leave the machine and they would test it further-all very helpful.


They contacted me after 48 hours to say that whilst they had been able to replicate the problem of the iMac screen going black randomly there were no hardware faults causing it. It was suggested then that perhaps a program was a root cause- I did have a temp and fan speed monitoring program that the tech people mentioned had been noted to cause issues previously on occasion.

It was suggested and I agreed that the HD be wiped, a new OS Yosemite be installed and they monitor the impact of doing that.

They contacted me after a further 48 hours to say that no further occurrence of the screen going black had happened and the machine could be collected.

I did, re-installed data and apps from TM backup without a hitch(though was decidedly anxious as first time I had done such a thing). Machine behaved wonderfully until yesterday afternoon when the issue began again. There have been no new downloads of any software that I am aware of so I am at a loss again!

Hey ho - back to Apple I guess though trekking over to MK is a pain!

Thanks for the continued advice/support folks.

Apr 11, 2015 1:12 AM in response to nomad1951

Thank you four response, thankfully I think I have found the issue now and pleased to say it is not a hardware problem. I found some disscusions regarding Yosemite hanging at boot. Now I know this is not how my parents problems started, but when I started working on there machine I found that when I got the imac to boot in safe mode using the recovery disc the screen did not immediatlly turn black. Once I got it to boot in safe mode I then reset the NVRAM with CMD+ALT+P+R once this was done I then did a reinstall from the recovery disc. At this point I got an error saying that there was a problem with the HDD . I tried several times carrying out a disk repair, but continued to get the error: "Disk utility can't repair this disk. backup as many of your files as possible" Now I believe this was a secondary issue caused as a result of the imac being turned off many times without the screen being visible and being shut down incorrectly. I reformatted the disc with the disc recovery tools and reinstalled the software from the disc. During this process the screen remained on and did not black out. Once this was done I went through recovering all settings from the time machine and all now seems to be working OK. The imac now starts up without hanging at the start up bar and the screen does not black out after random amount of time of use. So I believe the issue was due to upgrading to Yosemite and the impact this may have had on the NVRAM.

I hope that this issue has also been resolved in the updates I have also done as a result of these issues and effectivly my pareny=ts imac has been out of action for about 3 months.

imac 21.5 2011 screen goes black after start up and will only come back on after pressing start button

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