How to check if your PSU [Power Supply Unit] is dead?

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Power Supply Unit [PSU] is a vital part of your system, a good PSU gives your system stablity and plenty of head room if you're planning to upgrade your hardware in future. Follow these simple guidelines and you might save some money.

1. Start your PC, if it doesn't start when you press the button, try again.
2. After that just disconnect HDD's and other external components, if you have an Ethernet card and it's connected to the network leave it. Press the power button again, this time check if the Ethernet card and other components get the power. If nothing happens.
3. At this point simply hitting power button isn't working. Disconnect your PC and then take out the PSU.
4. Plug the power again and try to smell for burned components. If you can't detect anything wrong. Just put that PSU in some other system and see if it works. If it's working then, the PSU is in working state.
5. If the PSU doesn't respond, use a small wire and try to short the PSU connector pins. If nothing happens,
6. Open the PSU and check if the fuse is intact, if fuse is blown get a replacement, make sure to have a matching fuse. If that's not the problem and you see nothing wrong or if you see some leaked capacitors, consider getting a new PSU or get this one checked by a technician.
   

Don't try to go overboard, if you aren't comfortable with electronics I suggest you avoid step 6or if you do open the PSU just look for possible signs of damage.

Blog Link: http://dfg.tekgoblin.com/2010/07/18/how-to-check-if-your-psu-power-supply-unit-is-dead/

How to install a PSU.