IMac 12.2 2011 GPU Upgrade need help

[bladeneaera]

Hello I am new here hopefully this is the right thread for my problem.



I have an iMac 12.2 2011 A1312 with i7-2600 , 32GB RAM and the AMD 6970m with 2GB. The AMD is thus broken, I bought a GTX880m with 8GB, vbios of Nikey22 is flashed in the GTX. Now to my problem. I put everything together, but the iMac do not start as long as the screen is connected. Only LED 1 is on, the fans spin briefly and that's it. If I unplug the display either the flex video cable or the black power plug next to the video flex, or both, the iMac starts up to LED 3 so fans go and boot sound too.
What is the problem? Can anyone help me would be really grateful. Have also photos and videos falls that is allowed I would show it to you. THANK YOU

 

[Nguyen Duc Hieu]

Possibilities:
1. Broken (shorted) LVDS slot on the logicboard.
2. Dying card (get shorted circuit when LCD is connected.)
3. Touching part when connecting the LVDS. => Reassemble the MXM card with proper isolation.

Check with an external display to see if it works.
Check with the GRML Linux USB to see if it works.

 

[bladeneaera]

I use the X Clamp it was allready on this GTX880m. As far i See with my eyes it doesnt Touch anything.

 

[bladeneaera]

Now i found a way to Boot Up ITS unusual .

I Just pull Out the Black Cable near LVDS , Start the Mac and before apple Sound starts i Plug it Back . And it Runs the iMac Show that ITS a GTX , but when i Shut down and try to start than all begins from new Led 1 only and Same behaviour . Also in this way to Boot the iMac i See some Strange symptoms Like USB Sticks got read and than ejected by iMac , or WLAN find's all wlans but cant Connect it Just spin around and dont ask for Password , the graphics Card doesnt Glitch / No Artifacts GPU seems OK even Run the Valley Bench. So maybe u have an Idea now whats the Problem could be Power Supply ? Or LVDS Cable or maybe Inverter ? Please someone that hast more knowledge give me some hints or Info what i can still try . thank you