DIY PC Not Working?

So, you finally convinced your parents to buy you PC parts for Christmas. Or you’re a first-time builder that just got your crazy powerful new parts and can’t wait to get gaming. Now you’ve got everything put together, but can’t get it to turn on!

First off: don’t panic. There’s a lot of things that can prevent a computer from completing POST (Power-OSelf-Test), and some of them are super simple mistakes anyone can make on their first, second, or even hundredth build.

On the other hand, we’d argue that, if you have any self-doubts, saw sparks, smelled smoke, or know for a fact that anything got bent or damaged during installation, it’s probably best if you stop where you are, and bring the computer by for us to check everything out. If you made enough mistakes where it won’t turn on, there’s a possibility there’s a serious error somewhere which could damage your components. A complete teardown, inspection, and rebuild (complete with clean cable management) usually costs less than $150.

That said, a handful of common problems are very simple to troubleshoot, so if you’re reasonably confident you did everything right, let’s check over those things real quick.

EPS connector: the EPS connector(s) is usually on the top left corner of the motherboard, near the CPU. On most boards, there are at least eight pins (the connector on your power supply will usually be a 4+4 configuration), and on many midrange to high-end boards there will be a second 8-pin connector as well. If you have a particularly powerful CPU or intend to overclock, it’s best to have both of these connectors populated if possible. If not, populate the connector on the right first.

This connector feeds power directly to your CPU and your PC will not power up correctly without it connected. This connector may be quite difficult to access and connect once your board is installed in your system, especially if you have a large heatsink installed. Also keep in mind that if you mix this up with an eight-pin PCIe power connector, you’re going to have a very bad time — the pins on those are inverted, meaning you’re sending 12v to ground!

Front panel header: Make sure your front panel leads are connected properly! Pretty much all front panel headers look like this one (some boards may have some extra pins on the right side that you don’t need to worry about). The button leads can connect in either orientation, but the LEDs must be connected with power and ground as shown. If this is connected improperly, your PC will not power on, or may power on but behave improperly.

PSU kill switch: Most quality power supplies include a kill switch next to the power input. If this switch is off, the ground connection still passes through, enabling you to work on your PC with less concern of static as long as it’s connected to the wall. However, to get it to turn on, you’ll have to flip this switch to the on (“I”) position.

Monitor connections: All of your monitors should be connected to the graphics card, assuming you have one. If discrete graphics are present, the output connectors on the motherboard either will not work at all, or may not properly utilize your GPU’s power.

This is the #1 “it doesn’t work” diagnosis we get for gaming PCs.

GPU power connection: Make sure your GPU is getting power! Loose cables, an improper number of connections, or inadequate power supplies can cause GPUs to be unresponsive, or cause severe problems. The modern 12VHPWR connector, shown in the image on the left, can even melt or catch fire if not properly seated. Make sure your connectors are firmly pressed in until the latch clicks.

Other things to check:

RAM: Make sure your RAM is firmly seated in its slots. Ensure you oriented it properly when installing and pressed firmly with your thumbs on opposing ends of the RAM module until both ends click into place.

CPU: We really really hope you installed this correctly. Mis-orienting or mis-installing the CPU can critically damage the CPU, motherboard, or both.

CPU cooler: Ensure that your cooler is properly mounted with the correct tightness on all screws/bolts/nuts. Make sure you removed any protective films from the cold plate and properly installed a sufficient amount of thermal paste.

Just wait longer: If you’ve built an AM5-based system, these frequently take a long time to complete their first POST. If it’s not making any unpleasant noises or sparking, maybe give the PC up to 10 minutes to make up its mind whether it will work or not.

Check the diagnostic LEDs: If you have a “gaming” or enthusiast motherboard, it likely has four diagnostic LEDs in the top right corner (near the RAM and power connector). These LEDs are usually labeled CPU, DRAM, VGA, and BOOT, and light up in sequence during POST. If one of these LEDs is stuck on and the computer isn’t starting, it means there’s a problem with that (or an associated) component. Sometimes these LEDs are inaccurate – the DRAM LED may light up even if the problem is with some other component – but it’ll give you a place to start!

Still dead? Come and see us!

Don’t worry, we’ve seen it all. We’ll thoroughly inspect and test (when necessary) your components, and reassemble them carefully. Once we’ve got it working, we’ll provide a thorough explanation of what went wrong and why, and how to avoid it in the future.

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