Strange iMac issue. Display locked up but works in background

[Krynn72]

We got this iMac in the other day and I'm stumped as to what is going on. It was checked in because the screen gets stuck on the apple loading screen with the spinning icon. Initially we thought that the whole computer was locked up, so we tested the HDD (2 SMART "startup" errors, no UNC or pending), tested with new RAM, etc.

But when we replaced the HDD and went to reload the OS on a known-good drive we noticed that the system isn't actually locked up, because the screen got stuck at the same part it always does, but then the voice assist from the OSX installer kicked in and started talking to us. See this video for what I mean. What you hear in the video is coming from the iMac.

So we're thinking its likely an issue with the GPU or the LCD, but these parts are so expensive that we'd rather get some additional opinions /ideas before ordering them and finding we wasted $100+ because it was another part. Any help would be appreciated!

EDIT: Forgot the specs. Its an Early 2008 Core 2 Duo iMac with a Radeion HD 2600 Pro gpu

 

[CLC]

I would lean more towards it being a GPU issue, not one I've seen before but I'm wondering how it could possibly even be the LCD? Sounds like until you get into more graphic intensive interfaces it runs fine correct? Also your video says its private, can't watch it.

 

[Krynn72]

Also your video says its private, can't watch it.

Sorry about that, fixed it. I've never seen an issue like this before, and can't think of any precedent to lead me any direction in particular. I only thought of the lcd being a problem because usually when the gpu is failing the whole system is affected, like running slow, artifacting and crashing apps, etc. This seems like the lcd is just "stuck" on this image and not refreshing. When you boot the machine back on, the apple logo isn't there for the first few seconds like usual, then it comes on and the loading circle is animated... then it just stops animating and hangs as you see it in the video.

 

[CLC]

I'm sure you have done this, but I have to ask if you've tried a different installer? Also that is the damndest thing I've ever seen lol.

Edit: Try an Ubuntu Live Disk?

 

[Krynn72]

I'm sure you have done this, but I have to ask if you've tried a different installer? Also that is the damndest thing I've ever seen lol.

10.9 and 10.8, though both with the Zalman drive. I'll try with an actual disk, but im not hopeful. And yeah, it startled the tech working on it initially haha. Never seen anything like it.

 

[altrenda]

Did you try booting OS X from an external drive. I find it a good idea to have one to eliminate any issues with the drive or controller. And there are tests and utilities that work better when they are not run on the boot drive.

 

[nlinecomputers]

I'm no Mac guy so this advice is worth what you paid for it. LOL

Sounds like a GPU issue. Seen things like that before on Windows system where screen resolution was changed and the GPU failed to respond to the request. So it is stuck the last command it received.

 

[Krynn72]

Did you try booting OS X from an external drive. I find it a good idea to have one to eliminate any issues with the drive or controller. And there are tests and utilities that work better when they are not run on the boot drive.

I did try it with the Zalman external drive via usb, and dvd. I just tried a ubuntu 12 live dvd (physical disk) and got this error (the lines and poor quality text were actually on-screen and not just from the camera quality)

I tried to let it continue in low-graphics mode and it ended up getting stuck while noveau (sp?) was trying to load the low-res display and never booted to the os. Just got hung up displaying the typical lines of text you see while its trying to load.

So we're pretty confident its a gpu issue, but I then noticed that the LCD gets very hot. I know iMacs run hot all over in general, but the lcd is very uncomfortable, borderline painful to even hold your hand on it after its been on for like 5-10 mins. Now I'm still not 100% convinced its gpu.

 

[CLC]

External monitor, not sure why I didn't suggest this. That would let you know if it's the graphics card I would think.

 

[cyabro]

It will be the video card.
We just recently (Less than two weeks ago) became an Apple Authorised Service Provider with myself and another tech becoming Apple Certified Mac Technicians!
We've already had 4 iMacs in all with bad graphics cards.
One of them, a 27" late 2011 model, is still covered by warranty as it is a known issue with its particular card.

 

[Krynn72]

Replaced the video card and its the same exact problem :/

I doubt its a bad replacement part if its failing in the same, very peculiar way.

 

[Markverhyden]

It will be the video card.
We just recently (Less than two weeks ago) became an Apple Authorised Service Provider with myself and another tech becoming Apple Certified Mac Technicians!
We've already had 4 iMacs in all with bad graphics cards.
One of them, a 27" late 2011 model, is still covered by warranty as it is a known issue with its particular card.

Congratulations. In the US they stopped setting up new ASP's several years ago.

 

[Markverhyden]

Replaced the video card and its the same exact problem :/

I doubt its a bad replacement part if its failing in the same, very peculiar way.

You said the LCD is hot. Where? On the front? Is the fan running?

This is an example of why I have working on AIO's. Yes, most of the time swapping the video boards works. But I've seen some cases where the gremlins seem to persist at a later date.

 

[cyabro]

Congratulations. In the US they stopped setting up new ASP's several years ago.

Yea they aren't taking in any more here in NZ either. We were lucky to get it and took a lot of work and about a year of back and forward with Apple.

 

[Krynn72]

You said the LCD is hot. Where? On the front? Is the fan running?

Fans are running, the LCD seems hot all over the whole panel. When I take it off, holding it on both the left and right, both sides feel about the same temp (very hot).