Computer Bench Test

A computer bench test is a necessary evil when building a computer. There’s nothing more frustrating than a freshly built PC that will not boot. Normally, you’re starting with all new components and you’re not sure if any of them work to begin with. This article deals with a few common techniques computer technicians use when dealing with this common problem.

The Computer Bench Test Process

computer bench testBefore you begin yanking out cables and components, just go over your connections one last time. A common mistake is the connection from the case power and reset switches to the motherboard. Carefully review the motherboard’s manual to make sure these connections are right. Not only do the connectors need to be on the correct pins, they must also be in the correct orientation. If that is good, make sure the | / O switch on the back of the power supply is in the “|” position. Then, give the computer a little shake. Do you hear any screws bouncing around between the motherboard and the case? This can cause the system to blow or go to ground. Lastly, make sure the CMOS jumper is on pins 1-2. If it is on pins 2-3 the motherboard will not boot. This jumper is located near the watch-like battery on the motherboard.

Still no POST? Now carefully remove any PCI and AGP cards. Unplug the power supply and IDE cables to make life easier. You may already be able to get to the screws that hold the motherboard to the case. Personally, I like to remove everything except the CPU and heat-sink before pulling the motherboard.

Once all components are out of the case, place the motherboard on an antistatic bag (use the bag the motherboard shipped it, if possible) or a piece of cardboard to continue the computer bench test. Be sure not to leave the motherboard running on the cardboard unattended because there is a remote possibility it could cause a fire.

You may need to rest the cardboard and bag on top of the case depending on the amount of wire you have with the case wires and the power supply leads. You can short the pins on the motherboard to boot without actually using the case wires but we are not going to cover that here.

Now make sure you only have the bare minimum of components connected to the motherboard. This means only one stick of memory (if the motherboard allows only one stick), the CPU and the video card. Nothing else. The only thing we’re trying to do here is get the system to POST. A successful POST should result in a single, short beep. Make sure the motherboard has a built in speaker or you will need to connect an external speaker via pins on the motherboard.

Computer Bench Test Fails

If you still get nothing, begin swapping out spare parts if you have them at your disposal. Otherwise, you will need to start returning the components, starting with the motherboard, then the CPU. Before returning them, look for visible signs of damage (scorch marks on the CPU, bubbling capacitors on the motherboard, etc…).

If you have questions about how to perform a computer bench test, join our free computer repair forums and ask.