I have a 2007 iMac 20 and recently the screen has started flashing from dim to bright.
I can reboot and it runs fine for awhile then it starts again.
For the past couple of days I have had no incidences of this type.
While I was in town a week ago I went to a Mac store and they implied that the video card was going out.
ATI Radeon HD 2400XT.
I have done some research and discovered that a new card (identical type) would be about $250!
Can you upgrade video cards in iMacs (with say an ATI Radeon HD 2600XT) or do you have to replace it with an exact part?
I have built PC's for years, but this is my first Mac. I have already upgraded the memory with no problems,
but I have never "cracked" the case and don't really see a problem.
Can anyone advise?