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Power-on Issues: Desktop Computer Troubleshooting Guide

Dan earned his CompTIA (CIOS) certification in 2010 and worked in the computer repair/networking industry for several years.


Everybody needs help with computer problems — even those who are tech-savvy. Because of their many shapes and forms, however, it’s practically impossible to write an all-encompassing article dealing with the many potential circumstances.

This article focuses on start-up issues related to desktop computers. It’s not intended as a comprehensive list of problems and solutions, but more of a guide for the most common issues, assuming only one operating system is installed.

The complexity of computers can depend on how they’re perceived. Whether the operating system in use is Microsoft Windows, macOS, or Linux, there are common steps that can be taken to resolve start-up problems. It should be noted, however, that while the tips listed herein are simple, they are not always feasible for an individual to apply without assistance.

Quick notes before proceeding: If a computer is shutting down at some point during startup, it’s probably due to the CPU overheating — please research computer cooling issues and solutions via the internet — in order to help with brevity, mitigating cooling issues are not covered here. Take note also that certain conventional terms used in this article are in italics and can be searched on the internet for precise definitions.

The Power Button

From the moment of pressing the power button, up to the point when the home/desktop screen is visible, the computer goes through a series of phases, each with distinct characteristics. Certain audio cues called beep codes will sound in the early stage of startup if there are major hardware problems — which helps in the troubleshooting process. Sometimes the beeps are manufacturer-specific, but generally, there is common ground between them all. Consult computer manufacturer documentation for the specific beep code meanings.

Troubleshooting: First Steps

  • Rule out common issues. When pressing the power button and nothing appears on the screen, it could be due to a loose monitor cable, accidental unplugging, or deactivation of the power stripe. Check said components. If the device appears to be starting but does not fully boot, continue below.
  • When the power button is pressed, one or more LED lights and cooling fans will turn on indicating the computer is generally receiving power. When the indicators are absent, it indicates a power problem. Proceed to rule out a faulty electrical receptacle in the wall by plugging the computer into another receptacle. Proceed below if the problem persists.
  • The next logical place to check is the computer power supply. An inexpensive voltmeter can be used to check the power supply pin voltages. The 5-volt pins should register within +/- 5%. The 3-volt pins should register within +/- 5%. The 12-volt pins should register within +/- 10%. Search Google for more detailed steps on this method. Alternatively, a faulty power supply can be determined by swapping it with one sufficient in wattage and known to be working— if the computer powers on, it can be concluded the problem was the power supply.
  • When a faulty power supply is ruled out, the motherboard is likely the culprit. Generally, relatively old motherboards are not repaired, they are replaced— repairing them is not economic. Even if the problem is found and fixed, the likelihood of it failing again is high if the computer is old— computer chips and parts eventually wear out.

Beyond Power Issues

When a computer is powered on, the first phase it goes through is what’s called a POST or power-on-self-test. Built-in software (on the motherboard) checks to make sure certain hardware is working and, when completed, moves on to the next phase of the boot process.

  • POST Detections

If the POST detects hardware issues it will display details on the attached monitor or signal with beep sounds. The beeps indicate what is wrong — they can be referenced in the computer manufacturer documentation. If no hardware issues are detected, the computer manufacturer (logo) splash-screen will appear, implying the POST has been completed successfully, and the boot process will continue.

  • POST Failure

Sometimes POST will not complete, rendering a dark, blank screen, and no beeps. If this is the case, re-seating power supply cables, peripheral devices, and RAM might resolve the issue, as sometimes connections can become loosened.

A failed POST can also be caused by failing RAM (memory) modules. Removing the suspected module and rebooting the computer can reveal which module is causing the problem. However, if there is only one module installed, the only option is to swap it with one compatible that is known to be working.

If purchasing a new module, be sure to get the correct type for the computer. DDR3 and DDR4 are the most common at this time — DDR1/2 are becoming phased out. The modules can be removed for gleaning information. Be sure the purchased module has a speed (in MHz) greater than or equal to the installed module.

Failing power supplies can also cause the POST check to fail. Checking the power supply should be done after ruling out RAM issues.

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Continuing the Startup Process

After POST has been completed, the built-in software called the BIOS passes control of the startup process to the primary data storage drive/component where the operating system is installed. Depending on the partitioning scheme on the drive (which can be customized), a couple of different things can happen.

Assuming they are working, the MBR (master boot record) or GPT (GUID partition table) located in a tiny section of the drive will point to the partition where the operating system is installed — then begin loading the operating system, e.g., Microsoft Windows.

If failed, some of the visual cues present will be a stalled or slowed startup process or stop errors and blue screens. Possible culprits to consider are a failing/loose drive (or drive cable), failing RAM memory, a failing power supply, a corrupt file system, corrupt operating system files, too many startup programs trying to load, or malicious software (viruses).

It’s possible for failing RAM memory to get past the POST, so troubleshooting RAM memory further might be needed. Troubleshooting some of these will be discussed further down, in Advanced Troubleshooting.

  • If the computer can be booted into safe mode, this will rule out hardware problems. Safe mode runs a slimmed-down version of the operating system and disables third-party programs. Another benefit of booting into this mode is that files can be recovered if repair is not a feasible option at the time.
  • To boot into safe mode in Microsoft Windows, start by first shutting off the computer. Power it back on and tap the F8 key until the safe mode boot options appear. If an internet connection is needed while in safe mode, select “safe mode with networking,” otherwise just select “safe mode.” Another way of accessing safe mode is by typing msconfig into the RUN-command app in Windows, selecting the boot tab, checking the boot box, adding the network support bubble, and rebooting.

Storage Device/Drive Troubleshooting

  • To rule out a failing hard drive, it can save time by first making sure the computer’s BIOS recognizes the device. Follow the manufacturer’s guide to entering the computer’s CMOS setup program. Once CMOS setup is on screen, look at the “Main” tab. The make/model of the storage device/drive will be listed, along with how many bytes of data it can hold.
  • If the device is missing in the “Main” tab, it’s likely the hard drive has gone bad and needs to be replaced — although it might just need to be reseated. However, drives integrated into motherboards, such as eMMC drives, cannot be reseated or replaced in a practical sense — the only option, in that case, is to work around the problem. Using external drive alternatives or buying a new computer is generally the way to go. If willing to tinker with gadgets, replacing the motherboard is an option.
  • If the drive is showing in the computer’s CMOS settings, further troubleshooting of the drive can commence. Using software tools downloaded from manufacturers or third parties can be installed onto a USB flash drive and configured as a boot option in the computer’s CMOS settings — to be used for further troubleshooting.

It should be noted, however, that if RAM memory is failing, booting from a USB flash drive might be unsuccessful. Rule out faulty RAM memory and power supply issues before moving on.

Advanced Troubleshooting

Even though hard drives are recognized by computers as indicated in the CMOS set-up program, sometimes their individual memory locations, also called sectors and blocks, can go bad. Checking for these issues can be necessary.

However, if there are mission-critical files or data stored on the computer, consulting with a data-recovery expert should be done to determine the cost of recovery. Attempting to scan hard drives can advance damage and render subsequent data recovery attempts useless.

  • Using a working computer, install the scanning software (downloaded from the manufacturer or third party) to a bootable USB drive. Plug it into the problematic computer and power it on for scanning faulty drives. If problems are found by the scanner, drive replacement procedures should be taken which implies an eventual reinstallation of the operating system. If drive replacement is generally unfeasible, purchasing an external hard drive could work — enable USB booting in the BIOS and install Windows to the new drive.

Once faulty hard drive sectors/blocks are ruled out, other culprits must be ruled out. The same troubleshooting software (typically a multi-featured program) can be used to test RAM memory, check for a corrupted file system, and repair/replace corrupted operating system files.

Operating systems, however, have ways to limit what programs start when a computer is powered on. If installed software is suspected to be causing a problem, it can be disabled by following a few simple steps in order to rule it out — consult the procedure available for the operating system installed.

  • In Microsoft Windows, do a search for the RUN-command app and type msconfig into it. When the menu opens up, select the startup tab and disable all programs set to run at startup time. Reboot the computer to check for improvement. Enabling one app at a time in the startup menu, and restarting the computer, can help determine which one is causing a problem. Macintosh OS, Linux, Android, and iOS have similar procedures.

Malicious software can be ruled out or fixed by following recommended procedures for the given symptoms and situation in general. There are several guides available on the internet for virus removal. Here is one of my own.

Moving Forward

The troubleshooting steps outlined in this article are generally applicable to the three mentioned operating systems. The procedures and features will look different onscreen depending on which is being used, however.

Several keywords exist herein that can be searched on the internet for more in-depth knowledge or details. The same steps can be applied to laptops, although since they are powered by batteries and chargers, troubleshooting power problems will be different. For common run-time problems with both desktop and laptop computers, see my performance boost guide.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2022 Dan Martino

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