My PC's monitor goes blank after about half to one hour. The power light remains on. If I switch the monitor off then back on then it briefly comes on again then goes blank. I generally have to leave it for 10 ~ 15 minutes before I can use it again for abot half hour again if I'm lucky! The monitor is about 5 ~ 6 years old.
I connected an old CRT monitor to the PC and that is fine.