I was able to get a 2014 A1419 27' imac to run outside of it's case using a TV as an external monitor. I removed the power receptacle, the power supply, cpu fan w/duct and the motherboard from the case and got it running on the bench using a mini display port to HDMI adapter. It worked well enough to get through internet recovery to install a new OS on a 1TB SSD. CPU fan seems to be running all out. Working on that next.