Chosen Solution
My GPU went bad so I decided to bake the 4670 that was in the iMac and put it back in and it worked great but only for a week. I decided to look if I could get a better graphics card and many sources said the 6750 radeon would work. I got one for $50 on eBay and put it in and now when I try and turn the mac on it chimes but the screen stays black like it has no power.. Looking for some help here. I tried to hook it up to external monitor and that didn’t work and double checked the Lcd and it looks like all the connections are in. Is the graphics card just not compatible so the screen won’t turn on?
Here’s the specs & performances numbers between the two AMD (ATI) GPU chips ATI Mobility Radeon HD 4670 ATI Mobility Radeon HD 4650 I would stick with the better GPU which is what your system came with 4670 GPU. I’m sure the systems firmware and OS drivers was not designed for the older board. You also have to have the MXM boards EEROM programed with Apples code.
