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What to do when your desktop computer does not start

Is your desktop computer not starting up? Are no lights or fans coming on when you try to start your desktop computer? If so, here is what to do when your desktop computer does not start.

What to do when your desktop computer does not start

Dealing with a desktop computer that won't start can be a frustrating experience, especially if you rely on it for work, entertainment, or both. However, before you panic and assume the worst, there are a few things you can do to troubleshoot the issue.

Disconnect external devices

If your desktop computer is not starting up, it could be due to an external device connected to it having failed. Disconnect all external devices, including USB drives, external hard drives, and printers. Try booting up your desktop computer again and see if it works.

Check the power connection

Next, you will want to ensure your computer is properly plugged in and all cables are securely connected. This may sound obvious, but it's a common mistake that can easily be overlooked. Check that the power cable is plugged into the computer's power supply and an electrical outlet. Additionally, ensure that your monitor, keyboard, and mouse are all connected properly.

Check the PSU (Power Supply Unit)

If your computer still won't start, the next step is to check for any signs of life. Do you hear any sounds when you press the power button? Can you see any lights on the computer or monitor? If the answer is no to both of these questions, there may be an issue with your power supply.

Now, there are different types of desktop computers: Mid/Full-size Tower, Small Form Factor (SFF), All-In-One, Mini, etc. And with the different kinds of desktop computers come different types of power supplies. Some are external, and some are internal.

External power supplies

Mini, All-In-One, and some SFF computers are actually built on a laptop platform and use external power supplies. Remember that the output from any power supply, internal or external, will gradually diminish to a point where your computer will not start.

And even if you do not turn on and use your Mini, All-In-One, or SFF computer, the power supply is often connected to an AC jack, powered up, and energized. If your external power supply is over three years old, it is probably time to replace it.

Internal power supplies

All Mid/Full-size Tower and most SFF computers use internal power supplies and use the ATX (Advanced Technology Extended) specification for connectors. Mid/Full-size Tower power supplies are the most common and are readily available at your local computer parts store.

Almost all SFF computers that use internal power supplies are specifically made (dimensions, connectors, etc.) for that system. You would have to use the part number on the existing power supply to order another one online.

Note: The following procedures require opening the case of your computer. If you do not feel comfortable taking your desktop computer apart, don't hesitate to contact a local computer repair technician.

Most desktop computer cases are relatively easy to open. Just a screw or two secures the side panel to the case. If you need help determining how to open the case, you may need to find a user manual online. A quick Google search for the make and model of your desktop computer plus user manual should get you a manual. For example: Dell XPS 8950 user manual.

Now, all Mid and Full-size Towers and some SFF computers use power supplies with 20+4 motherboard connectors. You can perform a simple test to check the health of those types of desktop power supplies.

How to tell if your desktop computer power supply has failed

Check for debugging LEDs

If the power supply tests out well, the next step is to check for debugging LEDs. To find out if your motherboard has debugging LEDs, you must find a manual for it. A quick Google search for the make and model of your desktop computer or motherboard plus manual should get you a manual. For example: Dell XPS 8950 manual.

The debugging LEDs correspond to the POST (Pre-Operative Self Test) that happens every time you start your computer. The standard four (4) debugging LEDs are CPU (Central Processing Unit), DRAM (Dynamic Random-Access Memory), GPU (Graphics Processor Unit), and Boot drive.

If your motherboard has debugging LEDs, disconnect the power cord from the power supply and then hold down the power button for 30 seconds. Then reconnect the power cord and watch the debugging LEDs for any life. If your computer shuts down when a particular LED lights up, that is the component that must be looked at.

Reseat the components

If your desktop computer is still not starting, then try to reseat the components: GPU, memory, CPU, expansion cards, M.2 drives, etc. Make sure you disconnect the power cord from your desktop computer and hold down the power button for thirty (30) seconds to discharge any residual electrical current before attempting to reseat any of the components.

In conclusion, if your desktop computer doesn't start, several potential causes should be considered. Following the troubleshooting steps outlined above, you should be able to identify and fix the issue in most cases. However, if you still have problems after trying these steps, it may be time to consult a professional computer repair service.

How to estimate the power required for your custom-built computer

Whether you are building a new computer or replacing/upgrading your existing one, one of the most important considerations is the Power Supply Unit (PSU). The PSU is responsible for delivering power to all the components in your system, including the motherboard, CPU, graphics card(s), and other peripherals. Choosing the correct PSU is crucial to ensure stable and reliable performance and prevent damage to your components.

How to estimate the power required for your custom-built computer

Two (2) components in your computer will consume most of the power: the motherboard and the graphics card(s). The motherboard uses a relatively small amount of energy but supplies power to the CPU, memory, PCIe slots, and USB ports.

To determine the appropriate wattage for your PSU, you must first consider the power requirements of your components. Here are some guidelines to help you estimate how many watts your PSU should be:

  • CPU: The power consumption of your CPU depends on its model and clock speed. Generally, high-end CPUs require more power than budget models. You can find the power requirements of your CPU on the manufacturer's website.
  • Graphics card(s): If you plan on using a dedicated graphics card(s), these will be one of the most power-hungry components in your system. High-end graphics cards can consume up to 450 watts under load, so check the manufacturer's specifications before choosing a PSU.
  • Motherboard: Your motherboard's power consumption is relatively low compared to other components, but it still requires some power. Make sure to choose a PSU that can provide enough power for all the motherboard components, including the CPU and memory.
  • Storage: Hard drives and SSDs consume very little power, so you don't need to worry about them when choosing a PSU.
  • Other components: If you plan to use other components, such as a sound card, network adapter, or USB devices, make sure to factor in their power requirements when estimating your PSU wattage.

Now, some online power supply calculators can estimate the power requirements given the specifications of the components. You can use these websites to calculate a rough estimate of the amount of power your computer will require. Here are a few online power supply calculators.

Newegg - Power Supply Calculator

PC builds - Power Supply Calculator

Cooler Master - Power Supply Calculator

Once you have a rough estimate of the power requirements for your components, add some extra headroom to ensure stable and reliable performance. A good rule of thumb is to choose a PSU that can provide at least 20% more power than your estimated requirements.

In conclusion, choosing the suitable PSU is crucial to ensure stable and reliable performance for your computer. By estimating the power requirements of your components and adding some extra headroom, you can choose a PSU that meets your needs and provides room for future upgrades.

How to tell if your desktop computer power supply has failed

Updated March 18, 2024

There may be a time when your desktop computer does not start. There could be a few reasons why it does not start. The first thing that comes to mind is a failed power supply. Here's how to test your desktop power supply.

How to tell if your desktop computer power supply has failed

Living in Phoenix, we have one thing that takes a toll on a desktop computer. No, it is not the heat; it is the dust. Since our environment here is so dry, we get a lot of dust.

How to clean the dust out of your computer

And since dust conducts electricity, power supplies tend to fail. Even if you routinely clean your desktop computer, it only has a life span of 3 to 5 years. So, if you press the power button, your desktop computer does not start, and there are no lights that light up, you may have a failed power supply. Now, if you do not feel comfortable working around electricity or inside your desktop computer, please contact a local computer technician.

How to test your desktop computer power supply

  1. Disconnect the power cord that comes from the outlet to the power supply.
  2. After you have disconnected the power cord, open up the case and touch any metal part of the power supply or case to discharge any remaining energy.
  3. Make a note or take pictures of the connections that lead from the power supply to the devices. Once you have documented all of the power leads, then remove all of the connectors (SATA, Molex, PCI-e, ATX, ATX12V, etc.) that lead to all of the different devices and motherboard.
  4. Create a jumper from a piece of thin gauge wire or paper clip.
  5. Using the jumper you created,
    Motherboard power supply connectior
    connect Pin 16 to either Pin 17 or Pin 18 on the ATX 24-PIN (20+4) connector.
  6. Make sure the power supply is turned on and then plug the power cord back into the jack on the back of the power supply. If the power supply fan starts to run, the power supply has an output voltage and is in good condition. If the power supply fan does not spin, it is time to replace it.

If your power supply has failed, make a note of what type and how many connectors your existing power supply has.
Common desktop power supply connections
Also, check the stated output of your existing power supply from the label on the side.

I also recommend that you use a tape measure or ruler to measure the dimensions of the power supply, (Width x Height x Depth) as you will want to get as close as possible to these for the replacement power supply.

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