Dell Studio 1558 Resurrection and problems

Hello!

Yes, the notorious Dell Studio 1558. This was the i3 version, first the power button died, then the power cable harness, then finally the mainboard. For reasons beyond my control I couldn't junk the notebook, so I had to come up with a fix.

Since I couldn't source an identical mainboard with Intel video, I looked for other options. Finally, I found  the 4Dknr 04Dknr version, with the Ati video chip and got the right cooling pipes as well.

Still, no joy. When I put it all together, it did not output an image to the notebooks screen. I attached an external monitor and what I saw were a bunch of artefacts.

Specifics:

1. Cooling is mounted properly, doesn't seem to be really hot

2. Tried different ddr3 modules, it is not related to memory

3. Bios version is A12

4. In the diagnostics, it passes all tests except the LCD EDID ( but the LCD is good, tested), when the LVDS cable is taken out it reports the cable as missing.

5. The notebook did show the diagnostics, with the red / green / blue / white full screen things correctly, but when it showed them combined, with  color bars, it got garbled again. As in image.

Question 1: Are these genuine artefacts, related to a video chip / memory corruption?

Question 2: is the 4Dknr 04Dknr mainboard totally compatible with my original i3 cpu? I didn't find relevant info about this. Would it be worth trying another cpu? I can source processors a lot easier than Dell mainboards :)

Question 3: is there a difference in LVDS cable type between the original G936P mainboard with Intel video and the new 4Dknr 04Dknr with ATI? Although the artefacts occur on the external screen even with the LVDS cable being UNPLUGGED, so I don't think it has much to do with it.