|> Testing various PSs, I always find that one +5 V light is out, even on a couple of new ones. |
First, some supplies will output improper or deceptive voltages with zero load. Which ones? That is unique to each switching power supply design. Without a minimal load, some 'good' supplies will appear defective.
Second, a defective power supply may power a computer. Some assume if a new supply boots the computer, then that supply is OK. Obviously false.
More reasons why a multimeter is so useful and why a power supply is best tested (measured) when fully loaded by the computer.