Recently, my friend’s desktop PC having problem where it cannot be turn ON due to PSU faulty. Power Supply Unit (PSU) in a PC turn the incoming 110v/220v AC into various DC voltages to power up computer’s components. PSU is a major component to PC, if it fail, it can cause many problems. To troubleshoot PSU, we need to remove it from the casing, performed jump start by inserting a pin/paper clip to “short” the PS_ON with GND pin. By doing this, we can power ON the PSU without motherboard & power switch.
Below is the ATX PSU connector diagram.
Once we able to power ON the PSU, we can use multimeter to measure the voltage output. For my friend case, even voltage is available, but still not able to power up the computer, suspect not enough amps to generate power ( watts ). After open up the PSU, found no burn marks, except few capacitor is not in good condition, where the surface is bulging and got some plague on top of it. Suscpect that’s the main cause. Technically, I can repair the PSU by replacing all the capacitors, but it is not an easy task. Therefore, the fastest way is to get another new PSU. 400Watts is enough for my friend’s pc, but the local IT shop only had the 475 Watts for Cooler Master brand. After replaced the PSU, the PC can be turn ON successfully.