Troubleshoot Power Issues

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• PC components need a constant, stable supply of power to run
  • If the computer will not start, it is likely to be due to a power problem
  • If the PC suddenly turns off or restarts, power is a common cause
• When a computer is switched on, the power supply unit (PSU) converts the AC input voltage (VAC) to DC voltages (VDC)
  • DC voltage is used to power the motherboard components and peripheral devices\
  • The PSU supplies 12 V power immediately, and the fans and hard disks should spin up
  • PSU then tests its 5 V and 3.3 V supplies
  • When it is sure that it is providing a stable supply, it sends a power good signal to the processor
• To diagnose no power symptoms, check if the LEDs on the front panel of the system case are lit up and whether you can hear the fans
  • power issues can arise due to fault in:
    • the PSU
    • incoming electricity supply
    • power cables/connectors
    • fuses
  • to isolate the cause of no power, try the following tests:
    1. Check that other equipment in the area is working
       • may be a fault in the power circuit or a wider complete failure of power (a blackout)
    2. Try plugging another piece of known-good basic electrical equipment, such as a lamp, into the wall socket
       • If it does not work, the wall socket is faulty. Get an electrician to investigate the fault
    3. Check that the PSU cabling is connected to the PC and the wall socket correctly and that all switches are in the “on” position
    4. Try another power cable
       • There may be a problem with the plug or fuse
       • Check that all the wires are connected to the correct terminals in the plug
       • Check the fuse resistance with a multimeter or swap with a known good fuse.
    5. Try disconnecting extra devices, such as a plug-in graphics card
       • If this solves the problem
         • either the PSU is underpowered and you need to fit one with a higher wattage rating
         • or one of the devices is faulty
    6. test the PSU using a multimeter or power supply tester
  • If you still cannot identify the fault, then the problem is likely to be a faulty motherboard or power supply
  • If you suspect that a power supply is faulty
    • do not leave it turned on for longer than necessary
    • do not leave it unattended
  • Keep an eye out for external signs of a problem
    • E.g., smoke or fire
  • Turn off immediately if there are any unusual sights, smells, or noises

Info

You must take appropriate safety measures before testing a live power supply. PC power supplies are NOT user serviceable. Never remove the cover of a power supply.