Coolmax PS-224 LCD Power Supply Tester
 

The Coolmax PS-224 Power Supply Tester is a great little gadget to have handy to take a quick look at any power supply when troubleshooting a PC. It takes the guesswork out of the equation and hits you with the hard cold facts, to show you if your PSU is still up for the job or not.
http://www.techpowerup.com/reviews/Coolmax/PS_224