iMac unable to boot into desktop, safe-mode, or recovery-mode

Hello,

A customer has brought a iMac desktop to me that isn't booting. I've tried to boot it normally and I get the Apple logo followed by the spinning circle. Then without notice it goes to a white screen with chaotic characters all over it. I've tried safe boot and boot to recovery with the exact same result. I'm not terrible familiar with the Apple products so any help is appreciated.

-Chris
LVL 1
Christopher GayIT Operations ManagerAsked:
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strungCommented:
Try connecting an external monitor and see if that works. Sounds to me like it may be the video card though, and as that is integrated into the motherboard, it could require a logic board replacement.

Do you know exactly what model iMac it is?
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strungCommented:
If it is an iMac G5, the problem is likely capacitors. It is a well-known problem. A G5 is probably too old to be worth fixing.
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David AndersTechnician Commented:
The lowest level boot option is Firewire Target Mode (T key at startup)
The next lowest level boot options are Verbose Mode (Command - V) and Single User (Command-S)
https://support.apple.com/en-us/HT201573

http://www.maclife.com/article/howtos/how_use_os_x_boot_options_troubleshoot_your_mac
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Christopher GayIT Operations ManagerAuthor Commented:
I was able to get to the desktop by holding the shift key down continually. The result was an apparently functional desktop, but the screen looks like it doesn't know how to fully load. I've attached an image of the screen below. (Ref 1)

Upon restart, I get just that white screen with random characters. I've attached an image of that too. (Ref 2)
20150715-093611.jpg
20150715-094331.jpg
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David AndersTechnician Commented:
The exact model is sorta required to offer accurate advice.
iMac (27-inch): AMD Radeon 6970M Video Card Replacement Program
https://support.apple.com/en-us/HT203787
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serialbandCommented:
You've booted into safe mode and it seems like the video card/chip is bad.
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