How to know when PSU is shot?

[Captain Murphy]

One of my computers doesn't seem to booting right anymore. Sometimes it will boot to the bios and then go to to a black screen. I put it to the side for awhile and recently hooked it back up to see if it would work. I had it working for a day or two and now it won't even boot. It has power because all the fans are running but it's not sending out any signal to the monitor and I know its not the graphics card because hitting the power button doesn't shut it down.

I've troubleshot most of the things and I'm thinking it might be the PSU. However, I have no idea what a PSU does when its getting to the end of its life. I always thought it would just stop giving out power. Is it possible that the PSU is just slowly dieing and not giving enough power for the PC to properly boot?

The PSU I bought way back when did have comments about it eventually dieing so maybe that's what it is.

 

[Slaymate]

Yes, that is most likely what is happening.