How do I fix my all in one computer not turning on?

Quick Diagnosis

If your all-in-one computer is not turning on, there are a few quick things to check before diving into more complex troubleshooting:

  • Make sure the computer is plugged into a working outlet and the power cable is securely connected to the back of the computer.
  • Press and hold the power button for 10-15 seconds to reset the power supply.
  • Check for any loose connections, especially where the power cable connects to the back of the computer.
  • Make sure none of the internal power cables have become unplugged, for example the cable connecting the power button to the motherboard.
  • Try disconnecting all peripherals and accessories like USB devices, and try turning on the computer with just the power cable connected.

If the all-in-one still won’t start up after checking these basic issues, there are a few key components that could be faulty and preventing the computer from powering on. The main suspects are the power supply, motherboard, RAM modules, CPU, or internal power cables and connections. Continue reading for detailed troubleshooting steps for each component.

Power Supply Issues

The power supply is the most likely culprit if your all-in-one PC won’t turn on. Here are some things to check with the power supply:

  • Make sure the power cable is firmly plugged into the power supply and wall outlet.
  • Try a different power cable if possible to rule out a faulty cable.
  • Check for damage, burnt smells, or noises coming from the power supply.
  • Press the power button – if no fans spin, no lights turn on, and there are no beeps or sounds, likely a bad power supply.
  • Test the outlet with another device to verify power is flowing properly.
  • If available, connect a multimeter to the 24-pin motherboard power connector to check for proper voltages.
  • Try a compatible replacement power supply if available.

If the fans spin briefly then the system immediately powers off, this points to an overcurrent protection issue with the power supply. The unit is defective and needs to be replaced.

Make sure to use a power supply specifically designed for your model all-in-one computer. Using the incorrect voltage, wattage, or connectors could damage the system. Most all-in-one PCs use external power bricks with standardized connector tips. Purchase an OEM replacement if possible.

Motherboard Issues

The motherboard is essentially the home base for all other components and systems in the computer. If it isn’t providing the proper power, signals, and connections, the computer will fail to start up. Here are some motherboard checks:

  • Inspect for any burnt, discolored, or damaged components on the motherboard
  • Reseat RAM, GPU, and any other removable components
  • Try removing unnecessary components like wireless cards, secondary storage drives
  • Test the power switch and other front panel connectors
  • Clear the CMOS to reset BIOS settings
  • Check for bent or broken pins in connectors
  • Check for bulging, leaking, or popped capacitors

Unfortunately, faulty motherboards generally need to be replaced. All-in-one PCs integrate the motherboard with the display, making them difficult to replace alone. Check your warranty and contact the manufacturer for support if under warranty.

You may be able to find replacement motherboards online from places like eBay. Just be sure the replacement is an exact model match. Also be aware of the delicate process of disassembling the computer to access and swap the motherboard.

CPU Issues

While less common, a bad CPU can prevent powering on. Here’s how to test this:

  • Verify the CPU fan is spinning when attempting to turn on
  • Reseat the CPU and check for any bent pins
  • Clear CMOS to reset BIOS settings relating to CPU
  • Try reapplying thermal paste between the CPU and heatsink
  • Attempt booting with just CPU, heatsink, and one RAM stick installed
  • If available, swap in a compatible replacement CPU

If there are any signs of physical damage to the CPU or socket pins, the motherboard most likely needs to be replaced as well. Overheating can also damage CPUs, so check proper contact between the CPU, heatsink, and thermal paste application.

RAM Issues

RAM problems can prevent an all-in-one from turning on. Try the following RAM troubleshooting steps:

  • Reseat RAM sticks in their slots
  • Try booting with just one RAM stick installed
  • If multiple sticks, test each one individually in each slot
  • Listen for beep codes indicating RAM issues
  • Inspect RAM sticks for dirt, oxidation, physical damage
  • Check for bent pins in RAM slots
  • Try new compatible RAM if available for testing

If you get graphical glitches or freezing when the computer is on, that likely indicates a RAM problem as well. Powering off issues usually point to bad RAM slots or incompatibility rather than the RAM sticks themselves going bad.

Internal Cable Issues

Loose or disconnected internal power cables can cause failure to turn on issues:

  • Check cable from power button to motherboard
  • Reconnect front panel connectors like power LEDs
  • Check proper connections of SATA and Molex power cables
  • Reseat ribbon cables attaching components like WiFi card
  • Check for signs of damage to internal cables

Pay special attention to internal power connectors. Make sure the main 24-pin ATX connector is fully seated. The 6 or 8-pin CPU power cable must also be connected properly. SATA and Molex connectors provide power to drives and accessories.

External Connections

While not as common, external cables and connections can also prevent powering on:

  • Try disconnecting all peripherals and accessories
  • Check display cable connections from PC to monitor
  • Inspect cables for damage or bent pins
  • Test components like keyboard, mouse, and display individually
  • For laptops, remove battery and test power adapter separately

Issues with connected devices and cables probably won’t directly prevent powering on, but can keep a signal from reaching the display or other key components. Eliminating these external factors helps isolate potential internal issues.


Troubleshooting an all-in-one computer that won’t turn on involves methodically checking internal hardware like the power supply, motherboard, CPU, and RAM as well as internal cabling. External peripherals and cables should also be inspected. The modular nature of components means issues can be isolated by testing parts individually. Replace any confirmed faulty parts like the power supply or motherboard. For powering on problems, the issue is most likely related to main system components versus more peripheral accessories and wiring.