I replaced the power supply in my home-built desktop computer. Everything is plugged in properly as far as I can tell, but now nothing shows up on the monitor. It’s completely blank, even though it’s plugged in and turned on. From the sound of it, it’s booting up as it usually does.
Any ideas as to what the problem may be?
Without physically seeing the setup some of the comments might be weird.
Did you plug the monitor cable into the motherboard connector instead of a display card connector?
Did you verify that the device manager is using the correct driver? or the correct driver for the connector you have the monitor connected to?
How did the previous power supply die? Did it send something that killed the monitor? (over voltage/current)
Can you get the OSD menu to show up on the display?
Maybe your building has faulty wiring and your power supply and monitor got fried at the same time?
etc.
Your suggestion about the OSD menu inspired me to try something I should have tried before: I unplugged the monitor and then plugged it in again. That appeared to reset the monitor, and now it’s working. 
Thanks! 
The old power supply was working, but the fan bearing was on its last legs, making an awful sound. I knew it needed replacing soon, and the noise was quite annoying.
Dyn-O-Mite!