Buzzing noise, turns louder when brightness is up
A couple of months ago I upgrades my iMac 2017, 21,5” model with a SSD and RAM.
It worked perfect. I was running BigSur. After the BigSur update from 11.0 to 11.1 I’m hearing a buzzing noise. I first I tought it was the fan, but I dont think so. I installed ‘Macs Fan control’ and turn down the speed. The noise didn’t go away/decrease.
When I decrease the screen brightness to almost 0 then the noise is almost gone.
What could it be?
I didn't repair the Mac. All functions were working, noise didn't get louder so I went with it.
After working on the Mac I shut it down and after 45 minutes I want to start working again…The Mac did not start up. Nothing, no noise, connection, screen. Also disconnected power cord.
What to do? Replacement of PSU?