My iMac won't boot

[Brandicm]

I sat down to do some editing and my iMac went crazy.  Lines across the screen.  I turned it off and back on and it gives a grey screen with lines across and the update bar as if it is downloading an update.  It will get halfway done and then reboot, starting everything again.  I called Apple support and they walked me through a safe mode boot and a PRAM but neither worked.  I have an appt with the store tomorrow but is there something else I can try?  Any ideas on what the problem is?

Thanks for your help.

I have not done the OS update to Capitan.  I have whatever is before that.

Edited May 28, 2016 by Brandicm

[Brian]

I'm sorry, there is nothing you can do at this point.

It sounds like the video card is faulty or possibly it is a motherboard issue. In some rare cases, it could be a power supply. For what it's worth, it doesn't sound like a HD problem to me at this point. Which is good. That means your data should be intact.

[Brian]

What year / model is your iMac? This problem sounds really familiar...

[Brandicm]

It's a mid 2011.  I took it to the apple store, it is the video card.  It does not fall within their 4 year  requirement for replacement.  It will cost $500 to fix.  The tech was nice enough to give me a name and number of someone in town who may be able to do it for less.  I've looked around online and cannot find the part any cheaper unless I wait for it to arrive from China.  I can't wait 2 weeks, so I will probably take it back to the store tomorrow.

[Brian]

Take it to the place that might do component level repair. This is a common problem and I immediately thought of your video card being the culprit. It's probably a faulty resistor and is way less than $500 to have replaced, if that place does that type of component level repair.