Question: Loud noise when PSU is connected, but functionality remains intact?
Question: Loud noise when PSU is connected, but functionality remains intact?
Hi guys,
I’ve given my 6-year-old computer to my partner. She now connects it to a smart switch that controls the mains power when not in use. But if the PC is disconnected for a while—about a day or more—it makes a loud bang when the mains comes back on. This only happens after a longer break, like a few days. If I disconnect it for just an hour, the bang disappears. The computer functions normally otherwise, with no smoke, smells, or damage before the donation.
I’m not an electrician, but it seems the power supply isn’t working right, possibly due to current issues. Any advice would be appreciated.
The PC specs are: Corsair RM650, GTX 1080, Ryzen 3700, 16 GB RAM, and 3 x HDD.
Thanks!
The computer is being shut off at the mains because the usual shutdown process is followed to complete its routine tasks before restarting. However, identifying the exact reason for the noise requires checking the power supply unit or other components inside the system. Generally, it might be related to expansion or contraction—turning it on after a brief warm-up or cooling period could cause parts to expand and create the sound. Begin by turning off the system, unplugging it, and opening the case. Inspect for any signs of damage, looseness, cracks, or contact issues. Restarting when the system is cold may help locate the source accurately. Proceed with caution and seek assistance if needed.
Would you characterize this bang as a sharp "crack" sound?
I often encounter these sounds when connecting laptop power supplies to live mains outlets or when inserting a live IEC lead into the rear of an ATX computer PSU.
The sound results from a brief high-current arc between electrical contacts, such as the plug tip and socket contact, or within the mains switch itself.
When you connect mains power to a switched-mode power supply, a short-term current spike—usually between 20A and 100A—flows into the bulk capacitor as the PSU builds up to 340V DC (from a 220V AC source).
This audible snap is often paired with a brief flash of white light, especially if you do it in a dimly lit space.
Any other sharp "bang" is unusual and may signal a fault has occurred.
High-quality ATX PSUs include a thermistor with a bypass relay to lessen the impact of these switch-on surges. Lower-quality units might not have even a basic thermistor and can carry significantly higher currents during switching.
Could you confirm whether the RM650 was connected to a different outlet or room? Did you use the smart switch on your PC? Does the noise originate inside the computer, such as the PSU, or outside, like from the smart switch?
I would suggest disconnecting the smart switch and connecting the PC directly to the wall outlet. The smart switch might not handle the high current spikes well.
Avoid opening the case and inspecting the power supply; it holds several Safety Critical Components that should only be replaced with matching parts, and there may still be dangerous voltages present after power is cut.