Yellow vertical Lines on 27" iMac Screen

Question

Yellow vertical Lines on 27" iMac Screen

I have a 27" iMac - late 2009,

2.8GHz core i7

16GB Ram

1TB HD

ATI Radeon HD 4850 512MB

A couple of nights ago, the screen saver came on, then froze. Had to perform a reset, restarted the machine and was presented with a grey screen

I've tried starting in Safe Mode, although the machine works, there are 5 evenly spaced vertical lines across the screen. In normal mode, I can't get the machine to launch at all.

I've reinstalled Maverics but to no avail. Can't perform a hardware test, even from a DVD install disk of OSX 10.6 Leopard.

I'm guessing the Graphics card has gone kaputt. So, the crux of what I'm saying, does anyone know if I can buy a more upgraded card for this machine, if so, which one does anyone suggest.

Alternatively, if anyone knows another way of resolving this, i'd love to hear it.

Thanks in advance for your help

27" iMac core i7, Mac OS X (10.6.4), iPhone 4

Posted on Jul 26, 2014 3:14 AM

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Answer 1

Jul 29, 2014 11:15 AM in response to rkaufmann87

So, I've plugged the MacBook Pro in the Thunderbolt Port in the back of the iMac as a second screen and it works perfectly, which says to be it's definitely the iMac's graphic card.

I've got the screen to work on the iMac when NOT in safe mode by removing the "ATI" extensions from the Library Folder. The machine works but the display is really slow, I'm guessing that because I've removed the extensions, there's not graphic acceleration.

However, it's a relief the the machine can work normally and that I can use it as a second monitor, also that I've not lost any data. This whole process has accelerated my thoughts about buying a MacPro, something that was on the cards more towards the end of this year, so it's brought everything forward by six months, no big deal. And I've got a nice 27" monitor still...

I think I'll keep my eyes peeled for a cheaper graphics card, but I'm not going to lose any sleep if I don't find one. I use Cinema 4D, and the iMac works fine with "Team Render", so once I've gone through the initial start-up, I'll switch it over to be a second monitor to the MBP, it's all good

Thanks guys for the assistance.

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Answer 2

Allan Jones

Level 9

78,266 points

Jul 29, 2014 11:27 AM in response to Richard Dobell

I think I'll keep my eyes peeled for a cheaper graphics card,

Remember that model uses a proprietary gfx card that is unlike anything used in more conventional desktop computers. It is indeed an odd duck:

You have to replace it in kind.

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Answer 3

griff w

Level 4

3,622 points

Jul 28, 2014 12:59 PM in response to Richard Dobell

Hi there Richard Dobell,

You may want to make sure that all of your software and firmware is up to date. It looks like there is a firmware update that addresses issue with this specific GPU. Take a look at the link below for more information.

iMac EFI Firmware Update 1.4

http://support.apple.com/kb/DL823

-Griff W.

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Answer 4

rkaufmann87

Level 10

148,494 points

Jul 28, 2014 2:15 PM in response to Richard Dobell

You are correct, you have a hardware issue that needs fixing. To have it correctly diagnosed book an appointment at with a Genius or AASP. Trying to self diagnose is very difficult as you don't have the correct diagnostic tools. What you can do however is run Apple's Hardware Test (Using Apple Hardware Test) and run it in Extended Mode 2-3 times back to back. The reason for running multiple times is AHT can miss errors the first and even second time, however if it finds errors they are correct. All that will give you though is a code, in order to get it correctly translated you need to discuss with a Genius or AASP because Apple does not publish these codes. One item about AHT in Extended Mode, this is a lengthy test that can take up to 3 hours per.

Goot luck.

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Answer 5

Aug 28, 2014 3:53 PM in response to Richard Dobell

Hi, same problem here. I'm about to order a new here.

where exactly is that ATI extension?, so you just delete it and it worked? not 100% but that would do just find till I get the new card.

Thanks

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Answer 6

Jul 28, 2014 1:58 PM in response to griff w

whoa - I got soooo excited then... just tried the updater, but no. Says "This computer does not need this update".

Is there anyway that an updater can be forced, maybe there's a corruption in the code somewhere... i dunno...

Thank you anyway...

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Answer 7

griff w

Level 4

3,622 points

Jul 28, 2014 2:03 PM in response to Richard Dobell

If that is the message you are receiving, then it is likely that the update has already been applied. At this point, you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/

-Griff W.

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Answer 8

Aug 28, 2014 4:49 PM in response to Richard Dobell

So I found the ATI files and deleted them. Now I have audio, video and the Mac runs a bit faster. But I still have the 5 blue vertical lines. Do I need delete more files to get rid of them?

Thanks

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Answer 9

Mines

Level 1

0 points

Jun 27, 2015 11:19 AM in response to Richard Dobell

I have a 27" iMac - late 2009 too and my screen has yellow vertical lines. Now my iMac is running only on safe mode. It's too bad. The apple should do a recall.

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