Definition: The PSU (power supply unit) is the box inside a desktop that converts mains electricity into the steady low voltages your motherboard, processor, graphics card and drives need. It’s rated in watts.
Signs of a failing PSU
The PC does nothing when you press the power button, turns on for a second then dies, restarts or shuts off during games, or smells of burning electronics. A clicking or buzzing from the back of the case can also point to the PSU.
Upgrading your graphics card?
Modern GPUs can draw a lot of power. Fitting one into a PC with an undersized or ageing PSU is a common cause of crashes under load. We check the wattage and connectors before recommending an upgrade.
Safety note
Power supplies can hold a dangerous charge even when unplugged. Never open the PSU itself. If it’s faulty, the whole unit is replaced.
Related terms
→ POST — if the PC powers on but won’t POST, the PSU may not be the problem
→ GPU — the most power-hungry part in a gaming PC
PC won’t turn on?
Free diagnosis to find whether it’s the PSU, the motherboard or something else.