White iMac 24" , blank screen, GPU replacement, Target Disk Mode questions.

[Scottsdale]

Okay, a family member has a 2007 C2D 24" iMac that has a black screen, and since I supposedly know more about Macs it was given to me to fix. Problems here, as I am in over my head.

The iMac is definitely starting fine. It shows nothing on the display, but I hear startup chime and can toggle the Voice Over on and off and determine it's running properly.

I plugged in an external monitor with a known good adapter and there was nothing on the external display. This leads me to believe it's the GPU since the rest of the iMac seems to be fine. Can this GPU be replaced, and where do I even start?

I read that using Target Disk Mode I could troubleshoot the iMac and determine the exact point of failure, but that's way over my head as I have only used it for file transfer.

Please help. Are there any other tests I can do? How can I use TDM to my advantage?

Thank you greatly in advance for any and all assistance. I am a Mac user, but the only iMac I have ever own is a current 27" that hasn't had a problem. I am very frustrated in my lack of education as to how TDM should help but Apple.com isn't helping much.

Cheers.

 

[Hellhammer]

The GPU is discrete so it can be replaced. It uses ATI 2600 PRO, here is one I found.

I can't think how TDM would help. It gives you access to the hard drive but that won't help in determining is the GPU bad. Maybe you are confusing it with Target Display Mode? That would allow you to check that the LCD is working fine but it is limited to 27" iMacs.

You can try using screen sharing (if it has been enabled) to access it from another Mac to check that it is working.

 

[Scottsdale]

The GPU is discrete so it can be replaced. It uses ATI 2600 PRO, here is one I found.

I can't think how TDM would help. It gives you access to the hard drive but that won't help in determining is the GPU bad. Maybe you are confusing it with Target Display Mode? That would allow you to check that the LCD is working fine but it is limited to 27" iMacs.

You can try using screen sharing (if it has been enabled) to access it from another Mac to check that it is working.

Crap... Expensive. Probably no fun either. I just looked and iFixIt doesn't have a guide for this one either.

I guess the biggest fear is buying and determining there is another cause.

As to TDM, even in the MR guide it lists "troubleshooting."

http://guides.macrumors.com/Target_Disk_Mode

I don't know would there be some error reports on the drive I could lookup once I am in there.

Anyone understand how to check things via voice over? I can get in and turn it on but don't know how to use it.

Thanks for the reply.

 

[Shivetya]

When my white 24 died it was under Applecare, however they did show me a parts cost of nearly $1400 for both mainboard and GPU. I think the GPU was over $300.