Do you have computer troubles such as these?
- It won't turn on at all?
- Computer is slow to boot or won't boot?
- Nothing shows on the screen?
- It lights up but nothing else?
- It hangs on boot?
This guide is fundamental; it intends to provide a basic explanation of what happens when a computer powers up and what you should expect to find. It may not help all users, but it can get you started troubleshooting your computer by helping to identify which piece of hardware may be defective. The guide below shows common problems you may encounter when troubleshooting your device.
Warning: There are high voltages and sharp edges present inside your computer which may cause significant injury. Please be careful when measuring the power supply and other items. The PCman is not to be held responsible for any damage or injury that results from following the steps in this tutorial. These repairs should only be performed out by competent technical personnel.
Step 1 - Does It Power Up?
Plug your computer in, does the computer show any signs that it is getting power? Press the Power button does it power up?
Take the case cover off, Are there any lights lit on the motherboard?
If you get no signs that power is getting to your computer at this point, here are several causes. It could be the power supply, the motherboard, or on some motherboards the memory or the processor. Most modern computers will turn on with the motherboard having just the power supply and maybe some memory plugged into it.
If it doesn't, using a voltmeter measure the pins in the large connector that plugs into the motherboard. If you don't get a voltage of 3.3 volts or similar on one of the pins, the power supply may be defective. You will have to substitute it with a power supply that is known to be good to be sure. Even though you may measure 3.3 volts, the power supply may still be defective. Many different voltages are coming out of it one of them could be bad. For instance, when correctly powered and working, it is common to find 3.3 volts, 5 volts, and 12 volts.
Step 2 - It Does Power Up, But Nothing More
Using a voltmeter, measure the pins on the small connectors that plug into the hard drive. You should get +5 volts and +12 volts with the ground probe connected to the case. If you don't, the power supply is bad.
Disconnect everything from the motherboard except the power supply, the processor, the memory, and the video card with a monitor hooked to it. Before you disconnect everything, make a drawing of where everything goes or take a picture. Some wires go to the switch and lights on the front case. You don't want to remove those.
Press the power button, does it do anything? It should start to boot and show the computer manufacturer's logo or an error message saying "System Disk Not Found," which is OK because, in this state, there is no system disk. If you get nothing at this point, it could be the motherboard, the processor, the memory, or the video card. The only way to troubleshoot these items is by substitution.
I realize most people don't have extra processors and memory lying around, so you may not be able to complete this step. For people that do have hardware lying around, try substituting each piece until you get a changed result. A computer that was hit by lightning or a power surge may have multiple problems and may not react with a positive result when swapping hardware even though you did replace a defective component. There could be something further down the line that has failed. In a case like that, you may be out of luck in that you won't be able to figure out what is wrong. This tutorial is under the assumption that there is a single problem, which is usually the case.
Step 3 - It Powers Up, But It Won't Boot
Your motherboard should now have the power supply, processor, memory, and video card connected with a monitor connected to the video card. You should see something showing on the monitor screen that you normally would see, except it may not complete the process to boot fully. Unplug the computer and connect your hard drive to the motherboard. Please turn it on again; upon power-up, you should hear it spinning. If you don't hear a spinning sound unplug the computer, disconnect the hard drive signal cable but leave the power cable. If it still doesn't spin, the hard drive may be defective. Using a voltmeter, measure the voltages on the power connector pins. There should be +5v and +12v. If not, suspect the power supply.
If your hard drive is connected and you get a "System Disk Not Found" error, now that is incorrect. If you substituted the drive with a test hard drive, you might get that error because there is no operating system installed. If it is your original drive, it may have mechanical problems with the platters or head, or you may have gotten a virus that wiped out your boot sector or damaged the operating system's boot files. If a virus damaged the operating system's files, we suggest that you re-install the operating system. Perform a full format when it asks you about setting up the partitions. Then no corrupt files will be able to infect your new installation.
If you recently installed new hardware and now it won't boot, remove the hardware and see if it will then boot correctly. If the new item is a PC card there may be an IRQ conflict. Try plugging it into another slot. This action will assign another IRQ that may enable it to work because the conflict was resolved.
If it now boots, add each piece of hardware one at a time rebooting after each piece. If it hangs or won't boot, you will know which piece is causing the problem. If it is a PC card, try it in another slot of the same type (PCI-e/AGP). If that doesn't work, (1) try another driver, (2) don't use that piece of hardware, or (3) try replacing it with a different model number or brand.
We hope this computer repair tutorial and the help and tips enabled you to identify the problem that kept your computer from booting.