Bad Monitor, or Bad Graphics Card?
I have an iMac that is about 12 years old. The monitor started getting streaks a couple months ago, and now I can only see about 1/4th of the desktop. The rest of the monitor is just gray or black with colored stripes (see image below). Is this caused by a bad screen, or a bad graphics card?
iMac, OS X Yosemite (10.10.5)