PSU's that you may not want to scrap out!

Originally Posted by bigburtchino

Thanks for that clarification on FlexATX and testing. I have a lot to learn about computers and trying to catch-up as I can.

Since most of the computers you guys work on are PCs, if you want an excellent reference manual I would recommend this book:
Upgrading and Repairing PCs by Scott Mueller

The most recent edition (the 21st!!) came out in 2013 and costs about $34 at Amazon, but you can find used copies of older editions for much less. It's definitely worth owning -- this is the PC bible.

Complete testing of switch-mode power supplies is complicated, time-consuming, and requires expensive equipment -- which means almost nobody actually does it, including PC repair shops and IT people. (If you're interested in what a complete test involves, here's an example: Hardware Secrets Power Supply Test Methodology | Hardware Secrets.) On the other hand, it's easy to do "good-enough" testing of the ATX PSUs that are in just about every PC built since the standard was introduced in 1993. There are 2 ways you can do it:

1. If the PSU is still in a PC with working components, you can take multimeter readings. There are a lot of videos and articles on the Web about how to do this. A nice short explanation is at Test your power supply with a multi meter - Tech Support Forum, and a nice detailed one is at Isolating ATX SMPS Supply and power related faults - PC Hardware Troubleshooting. This kind of test is easy and tells you if the PSU operates at the right voltages with the loads in the computer it's powering. It's not a complete test, and since you guys usually don't know whether all the components in the test computer are working correctly, it could end up giving you misleading results.
2. The best easy, cheap tester for ATX PSUs is the ThermalTake Dr. Power II, which sells for approx. $30 at Amazon. It's really easy to use, and it gives actual voltage readings for each rail that are very accurate -- close to what you'd get using a good multimeter. This is the tester used by a lot of pros. The only thing it doesn't tell you is how the PSU responds to various loads, but I'm sure that almost no used PSU being sold for under $100 has been formally load-tested. If you use this tester, you can see if an ATX PSU is dead, you can see if it's operating at the right voltages, and the whole thing takes about a minute of your time.

One last bit of advice: If you're working with components that you might want to resell, remember to be careful about electrostatic discharge (that little zap you get if you drag your feet across the rug and then touch something metal), especially in low-humidity environments. It really can damage electronic components.