What causes a blank screen on an iMac?

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Level 1

4 points

What causes a blank screen on an iMac?

I noted this issue priviously, but by some reason my post disappeared. My iMac 27" (2011, i5 3.1, 4 Gb RAM, High Sierra) is staring and showing signs of life (after it worked fine for years), but always ends up with a white or blue screen. I have done all the standard diagnostics (shift// cmd-R// cmd-D (things appear to be ok)// op-cmd-R-P// unplug-replug). The result is always the same: either a white screen or a blue screen.

I have done a cmd-v of which I will try to include two screen shots (when it starts and the last moment it turned into a white screen). Perhaps someone will be able to read something out of it.

I am currently trying to connect the iMac to my macbook pro to try to analyse the HD of the iMac in target mode. But it looks like that I have to find a thunderbolt 2 cable for this first, which has become difficult these days. The iMac starts well in target mode (at least the scren displays the connection sign), but my macbook pro doesn't find the iMac HD when connected just via USB-A. So either a cable issue or iMac issue.

Any comments welcome!

[Re-Titled by Moderator]

Earlier Mac models

Posted on Apr 21, 2025 1:07 PM

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Answer 1

HWTech

Level 9

68,618 points

Apr 21, 2025 1:31 PM in response to Frog224

I cannot see anything in the pictures.

For a 27" iMac 2011 model, a bad GPU is always a possibility.

If Safe Mode works, the try running the third party app EtreCheck so we can examine it for possible clues.

How to use the Add Text Feature When Posting an EtreCheck Report - Apple Community

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Answer 2

HWTech

Level 9

68,618 points

Apr 21, 2025 5:25 PM in response to Frog224

Frog224 wrote:

Unfortunately safe mode doesn't work: ends up in a white screen also. Not sure if I will be able to run EtreCheck once I have set up target mode.

I thought this part of your first post was a bit suspect from the mentioned symptoms:

I have done all the standard diagnostics (shift// cmd-R// cmd-D (things appear to be ok)

Frog224 wrote:

A possible idea. But one might want to have a running iMac in the first place to be able to migrate programs and files to a new Mac.

You should already have frequent & regular backups just for this situation. If you don't, then make sure you start a backup regimen with your new Mac. With the newer Macs there are a lot more new ways to permanently lose access to the data stored on the internal SSD due to all of the hardware, software, and security changes. If you don't have backups for the recent Macs, then it is only a matter of time before you lose important documents.

If it is a GPU issue as I suspect, then you can try using Target Disk Mode since it doesn't require much functionality from the "bad" computer.

FYI, Since a 2011 iMac was only able to run up to macOS 10.13 High Sierra.......I would not migrate any existing apps to a new system since they won't work. Download & install the most recent versions of any apps you need. This would be a good idea even if Apple still used Intel CPUs, but with Apple's change from Intel CPUs to Apple M-series CPUs I think it is the only way to go.

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Answer 3

rkaufmann87

Level 10

148,452 points

Apr 21, 2025 1:29 PM in response to Frog224

It could be a failed main logic board, a failed display, a failed back light or any number of other issues. A 2011 iMac should definitely be recycled and replaced. You can use one of Apple's free recycling programs, just click Apple Recycling Programs in order to get started. If you replace the computer with a new Mac, you can migrate from the old one by following the directions in Setup Assistant and Migration Assistant

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Answer 4

Frog224 Author

Level 1

4 points

Apr 22, 2025 3:26 AM in response to HWTech

Thanks for your suggestions HWTech. The thing is, that I am still an old fart, really happy to work with High Sierra and all the programs, which happily run on it. I even run an accounting system on Windows 98 XP via VMware. All nicely without the need of a 1TB SSD or 32 Gb of Ram. Yes, and I also have a M1 series, which I hate, because it takes itself to be very smart without at the end much improvement in what it does. Just more restrictive of what one can do with it.

Anyway, backups are only as useful as the programs one can still load onto the new generation iOS. I.e. forget it and buy everything new. And then, try to read your old files ...

So at the end, what I am trying to find out is, what component has given up its life on my iMac and then buy another failed iMac 27" 2011, strip it and replace the parts. At the end, with these machines one can still do such things.

I will definately try the target mode once I have got hold of a Thunderbolt 2 cable. I will update once I get one and had a try.

Cheers

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