I haven’t experienced this yet:
after hours of running time, my work PC makes a bang – and it was dark in the booth .
After a short search I find that the power pack be quiet PURE POWER BQT L7-640W has become defective.
Well, the PC has been running 12 hours+ almost every day since 2016 without any problems, it can happen.
The first NT that is used here, I’ve been using PCs and nothing for about 30 years, and that extensively!
The next day, the PC is replaced with a replacement device, which has also often been running for days without a shutdown since 2016.
The replacement PC also has a be quiet PURE POWER BQT L7-640W Power adapter.
The equipment of the replacement PC is significantly slimmer than the used work PC.
After about 2 hours of work on the replacement PC, there was a bang – and it was dark in the booth 
.
Both PSs have similarities: power supply, monitor, keyboard and mouse.
How can this be explained?
A NT can be defective, even 2, but in quick succession?
What should I look for to locate a possible source of error?
Thanks for reading, comments and hints,
wolf