White Pixelated Rectangles On Screen Imac Intel 20 Emc 2133 And 2210

Chosen Solution

The iMac powers up and chimes but the screen has these little white rectangles on top of a black pixelated background. Tried to use an external monitor through HDMI but just get “no input detected” on the external monitor.

Here’s how to replace the GPU: iMac Intel 20" EMC 2133 and 2210 Video Card Replacement

You’ll need a new GPU board if you can find it: ATI Radeon HD 2600XT, P/N 661-4672 ATI Radeon HD 2400XT, P/N 661-4673 More likely you’ll find a full logic board these days with the GPU board attached. 20” iMac Alu - Logic Board - 2.4GHz, P/N 661-4674 20” iMac Alu - Logic Board - 2.66GHz, P/N 661-4675