For checking a Desktop SMPS you need to do its POST (Power on self test) . This test is done to ensure whether the SMPS is working or faulty.
For doing this you basically need a wire, SMPS to be tested, SMPS cord
This method is useful if you don’t have a power supply or SMPS tester.
For performing POST take the 24 pin connector of the Desktop SMPS and keep the right on your right side.
Just put the wire with the ends open inside 4th and 5th socket of the SMPS as shown in the image above.
If the fan Spins the SMPS is working fine. If the fan does not turn on the SMPS is faulty.
This is just a test to ensure working of SMPS. However this test does not ensure that the SMPS is capable of handling required loads(computer components) as mentioned on its data sheet.
If the capacitors are weak the SMPS may give a postive POST output. Hoever on applying load the SMPS may trip and reset over and again.
I hope that you have understood the concept of POST in SMPS…:)