This short article will help you diagnose and repair your computer specifically on systems that power up, light up, fans turn on, but has no display at all.
Confirm if your monitor functions properly. Make sure that your LCD monitor is plugged in firmly into the wall socket and is powered on. Check you VGA or HDMI cables if it is connected properly.
Diagnose the beep codes. The motherboard is the main board of your CPU where you plug in components of your system and allow them to communicate, such as memory or processor. Your motherboard may create series of beeps if it detects something wrong with the components making your computer not to restart. Look for the specific motherboard brand and model beep codes on the internet and try search for the manual of the code. For example, if your computer has two short beeps and two long beeps, and the manual says it is a memory problem then you may want to replace the memory.
Clear the BIOS memory. A BIOS is a small program used by the microprocessor to get the computer started after turning it on. Thus, a false configuration may prevent your computer from starting up. Clearing your BIOS memory or CMOS will reset it to the default factory settings. There are two common ways to reset your CMOS (make sure that your completely is completely powered off with no cables attached to the CPU):
1. Remove the motherboard battery. You can find it anywhere on the board (a silver button-cell battery, just like the one below). Wait for around five minutes. Put it back.
2. Using the motherboard jumper. Look for the “CLEAR CMOS”, “CLEAR”, “CLEARPWD” jumper on the motherboard (like in the photo below). Move the jumper pin over the two other pins (if there are three pins) or remove the pin at all (for two pins). Put it back. Turn on the computer.
Most systems will tell you that they were reset and requires you to configure, such as date and time.
Reseat all components and unplug and plug and the cables. Removing and placing back all the hardware connected to the motherboard mostly work. Most technicians do this first to see if the problem is caused by lose and bad connections. This includes memory chips, cables, video cards, and other expansion cards.
Make sure that the computer is completely turned off and the power cable is removed before doing this.
Troubleshoot each component. Remove and reseat or replace each component one at a time with a working one (or don't replace it if the computer can start even without the component, for example, a sound card), then turn on the computer every time you remove and/or place one. Doing so will identify which hardware causes the problem and replace it with a working one.
You may also confirm if your hardware is working by testing it using other functioning system.
Check your power supply unit. It is essential to check the PSU as it the one which drives the CPU's components. The easiest and safest way to check is by having a tested, true-rated, 400w-600w power supply (borrowed from a friend, perhaps) and try it on your system. If the system powers up, your PSU might be defective or “underpowered”. Another way to test it is by using a multi-tester and maybe with a help from an electrician.
Replace the motherboard. If all the steps have failed, replacing the motherboard is the last option to do (this may require an expert's advice). If you are also unsure of what kind of computer motherboard you need, tell the shop owner the kind of processor do you have (for example, AMD A4-6300, Intel Core i3-4160), and the memory type (DDR2, DDR3 or DDR4), or simply bring the defective motherboard. This will ensure that your processor and memory are compatible with your new board.
To replace, simply remove all the components and cables from the old motherboard, unscrew it, then put the new motherboard. Don't worry about the cables because the biggest ones (like the power supply and hard disk cable) fit with their respective slots. Smaller ones such as pins, has labels serving as guides.
If all the steps above does not work, try consult an expert for help.
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