The supervisor's full of crapola. I had mine repaired a couple of months ago. The salient caveats are:
iMac computers with affected video cards were sold between May 2011 and October 2012.
If your iMac has an AMD Radeon HD 6970M video card and is exhibiting any of the issues described above, choose one of the following options to arrange to have your iMac evaluated:
- Apple Retail Store: Set up a Genius Bar appointment.
- Apple Authorized Service Provider: Find one here.
- Apple Technical Support: Contact us for local service options.
If the iMac (27-inch) meets these requirements, Apple will replace the video card free of charge for four years after the first retail sale of the computer.
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Note that mine was a refurb bought from Apple in May, 2013. Since I had AppleCare, I qualified for onsite replacement. You might want to try again at another Apple repair station or via technical support.
27" i7 iMac (Mid 2011) refurb, OS X Yo (10.10.3), Mavs, ML & SL, G4 450 MP w/10.5 & 9.2.2