Homebrew PC troubleshooting 101: Here’s where to start if your PC won’t

pc troubleshooting guide build a computer
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There are few things more frustrating than hitting the power button on your new, do-it-yourself PC — only to see nothing happen.

It’s tricky to diagnose an issue when you can’t reach the diagnostic tools like the UEFI, let alone the operating system. But help is out there.

Nothing happens at all

If nothing happens, we’re going to try one simple trick that sounds silly, but is much more common than you might think.

Is the power supply plugged in? Is the cord plugged into the wall?

If so, ensure the power supply is turned on by pressing down the 1 side of the toggle switch on the back.

Okay, just checking. Next we’ll make sure the buttons on the case are working properly. A quick way to make sure that isn’t the problem is by hitting the power button on the motherboard. If the computer starts, double check the front panel controls. These are a small set of thin cables that run from the front of the case (or wherever the buttons are) into the center of the case. The pin location and layout will vary, but it should look like a two-wide row of pins, usually encased in a plastic outer box.

The ends of the cables will say, for example “HDD LED” or “PWR,” and some of them have positive and negative contacts. Make sure these are completely seated on their corresponding pin, which is either marked next to the pins on the motherboard, or in the documentation.

Now that’s out of the way, if the system still isn’t making any sort of visible or audible effort to boot up, the options are a bit more limited. One of the problems could be with the power supply, but the only safe way to find out is to replace it with a properly functioning power supply, usually from a working system. A new power cable, or a different wall outlet, could be options as well, but are less likely culprits.

There’s noise or lights, but nothing appears on screen

If fans spin up and lights turn on, but nothing appears on the screen, it’s almost certainly a hardware issue. Before we start tearing out components, and hair, we’ll check a few more common issues with hand-built PCs that apply to recently moved or upgraded manufacturer systems.

PC build-out guide
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

Before we get started, it’s important to note that static electricity can be toxic to your computer’s guts. Always try and work on a hard, flat surface with plenty of room. It’s also ideal to work over a bare floor, and keep the power supply plugged in, but turned off, to use the case as a ground. In this state, touching the exposed metal of the case will neutralize the static electricity you’ve built up. It’s tough to damage modern components with static, but it pays to be careful.

Power

There are a lot of different power plugs in a system, and it’s all too easy to miss one of them. One of the most common is the 4-pin connector next to the CPU. There’a already a wide 8 or 12-pin connection closer to the power supply, which you should also check, but a lot of builders overlook the smaller CPU power connection.

Then, just run through the other parts in the PC and make sure there’s power running from the power supply to each one. In a typical build, that means hard drives and optical drives, but it could also include a PCIe expansion or graphics card. If you have a modular power supply, also ensure all of the cables are plugged into the correct spot on the PSU, and are running to the right component.

Error codes

There are two methods motherboard manufacturers use to communicate hardware issues with end users: error codes and beep codes. The latter was a common choice on older machines. The former is more common on newer motherboards, where a two-digit screen shows codes like 00 or EE to indicate the problem component.  Unlike Luke and R2-D2, we’ll need to refer to a manual to translate those noises and numbers into meaningful info.

Unfortunately, there’s no one set of codes and meanings, and different manufacturers speak their own languages, so to speak. You will need to refer to your motherboard documentation to see what the code means, then try the steps below that correspond to that component. We’ll walk through the pieces one by one below, so even if you’re sure you installed the CPU correctly, it’s worth double-checking.

CPU

A lot can go wrong during processor installation, but the good news is it’s easy to tell after the fact. Without even taking it off, it should be clear that the bottom of the cooler is sitting flush with the top of the chip, and the pegs or screws that hold it to the motherboard are nice and tight. An improperly installed cooler shouldn’t prevent the system from booting, but it’s a clear sign something might be wrong with the CPU. If the cooler doesn’t seem snug and flush, carefully remove it and examine the chip.

PC build-out guide
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

Intel CPUs only fit in one direction because of a pair of notches at one end of the chip that fit against notches in the socket. If you installed the chip yourself, there’s a piece of black plastic that sits in the motherboard slot to protect the pins, make sure it isn’t still there covering the chip. Then, a frame around the outside of the socket holds the chip in place, and a small arm right next to it should be clamped down and tucked underneath the clip at the end. It takes a fair bit of pressure to clamp the chip down.

PC build-out guide
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

With AMD CPUs, look for a golden triangle on one corner of the chip, and line it up with the triangle on the socket. Once it’s seated fully into the socket, carefully lower the arm next to the socket to clamp the chip in place.

An improperly installed processor can also mean bent pins, damaged cooler, and possibly a compromised motherboard. Check the surrounding area for damage, like bent pins in the socket or CPU, before reinstalling the chip.

If you do see bent pins, that’s the likely culprit. This damage can result in not only CPU errors codes, but also memory error codes, as a bent pin can impact how the CPU read and writes from RAM. You can try to fix the pens by using tweezers to bend them back into shape, but the pins are fragile, so you must use a light touch. Good luck!

Memory

A few different factors need to line up between the motherboard and memory. The biggest is which version of the DDR standard the motherboard supports. Most modern systems are built on DDR3, but the newest chipsets from Intel and AMD sport DDR4. The other option is speed, and in that case, your RAM has to be one of the supported speeds on the motherboard. Usually the supported memory types are listed clearly on the outside of the box, for example “DDR4 2133/2600/2800” would be a main feature of the motherboard, and you won’t have to hunt long to find the info.

Assuming you have the correct memory, it has to be installed in the proper slot or slots, facing the right direction, and fully seated. Check your motherboard documentation for the proper slot configuration. If you bought a dual-channel kit, with two identical sticks of memory, they usually have an empty slot between them, but it varies between Intel and AMD. After determining the proper slots, line up the notch on the bottom edge of the stick with the plastic riser in the slot. Push down firmly until the tabs on either side of the slot click inwards and grab the notches in each end of the RAM. If the notch is ajar, the RAM is not fully installed.

Graphics card

Not every system has a dedicated graphics card, but if your system does, it’s easy to find out whether that’s causing the problem. With the system powered down, and the power supply shut off, unplug the power connection from the graphics card. Hold the card, then remove the two screws that secure the card to the slot or slots on the outside of the case. Still firmly holding the card, reach down and press the little switch on the inside end of the PCIe slot and the card will come loose from the motherboard.

PC build-out guide
Bill Roberson/Digital Trends
Bill Roberson/Digital Trends

In order to test, you’ll need to plug the cable that runs to the monitor into the motherboard instead. Turn the power supply back on, then try booting again. If the system boots successfully, uninstall the Nvidia or AMD graphics driver, then download the latest version and install that before reinstalling the graphics card.

If the system still won’t boot with the video card, then the problem is a hardware issue. Make sure the card is connected to your power supply, if the card has an external power connector (most cards do). Ensure the card is firmly seated in the PCI slot. If there’s still no video, try a different PCI slot on the motherboard (if one is available). Still not working? Contact the video card manufacturer, as the card may be in need of repair or replacement.

Collateral damage

When all else fails, check every component on the board for physical damage. It may not be immediately obvious that something is wrong, so check thoroughly for anything that looks out of the ordinary, or even bent or damaged heatsinks and PCBs.

The other danger you face when building a computer is static electricity. Unfortunately, parts that have been damaged due to exposure won’t show any physical signs. If, for whatever reason, you suspect static buildup is responsible for a component failing, you’ll have to replace it with one that works to confirm that’s the issue. Again, error codes are your friend, and will help you identify parts that aren’t working at all.

Similarly, an electrical short is a gremlin that can be hard to track down. A short occurs when a component in a systems creates an improper electrical connect between components. For example, a frayed wire might be brushing the motherboard, or a portion of the case may be touching a component. Make sure all wires are intact, that no portion of the case is directly contacting exposed PCB, and that the motherboard is installed in the case on stand-offs that elevate it from the case surface.

The system begins to boot, but fails

If the system is successfully turning on, and a signal appears on the screen, but it doesn’t reach the actual operating system before shutting down, the list of possible problems is a lot shorter.

First, we’ll check the hard drive’s physical connections. Whether it’s an SSD or mechanical drive, it requires two connections, one for power, and one for data. The power cable should run from the power supply to the drive, but there may be other similar connections on the same cable for multiple drives.PC-Buildout-2016-SSD

Unless you’re working inside an older system, the most common data connection is SATA, a small, thin plug with an L-shaped bend in the tip. That cable will run from the drive to a row of plugs on the motherboard. There are a few different speeds and capabilities, but your motherboard manual will specify which plug is which, or it will be clearly marked on the motherboard.

If the computer displays an operating system logo before shutting down, it’s more likely there’s a problem with the OS installation. If that operating system is Windows, you can use another computer to create a recovery disk, or use the existing USB drive. Booting to this drive (see the motherboard launch screen for which key to press, usually F8) will allow you to run a diagnostic check, or reinstall the operating system completely.