Good evening , I am a new user but first of all I would like to thank you all for the contribution to this thread and helping me starting this proect to bring back to life my old 2011 27 imac but sadly I cant get it to work . I bought a nvidia k3100m and modded the heatsink , installed it with thermal paste on the die and k5 pro on the memories , I connected the gpu and reconnected all the small cables but sadly I only get a black screen after the boot sound , the fans starts but nothing ever appears on screen , since I opened it i also replaced the internal hdd with a kingston 500gb ssd (empty) but i doubt that it is the problem , I noticed that on the motherboard only the first two leds light up so the gpu is not properly communicating with the monitor, should I try getting a mini display port to hdmi adapter and try with an external monitor ? I did not flash the gpu before installing it so I do not know if that could be the problem but online it seems like people are able to boot even before flashing it . Thank you .
Boot sound is a good sign that your iMac is working, and you haven't screwed up during the assembling process.
First step has completed.
Next step is to flash the card with vBIOS compatible to the iMac.