IMac 2012 Random Shut downs

Hello, I've read through this thread and wanted to share my similar ( with some identical) situation.

I have a 2012 27" IMac with 3.4 GHz Intel Core i7 3TB Fusion drive. High Sierra, 10.13.2

a few months ago I started experiencing random shut downs. Took it into an Apple Genius Bar and they tried to replicate and couldn't. So they gave it back to me with upgrade to High Sierra and told me to reinstall without reinstating any settings or software automatically, but doing that manually in case it was a software issue.

Soon, it started happening again and I had to bring it back in. They ran the same test and could not replicate. They sent me home with no answers but did give me one of their newer cords to replace my older one in case that was the issue. It was fine for a while and then just a few days ago started happening again and now today it's shut down several times. I've made an appointment with the Genius Bar and now that I've read this thread, I think I might pay for them to install a new power supply board.

I'll update you on if that fixes the issue. Thanks.