Learn Basic Knowledge to Repair Power Supply PC

Repair Power Supply PC 101

Do you want to learn about repair power supply pc? Passionate computer geeks and even regular users rarely think about their systems’ power supplies, because, for most of the time, if things go smoothly and the computers boot and power up, nobody really cares about those boxes in the units.

There is often confusion as to the importance of these power supplies, since, most of the times they don’t influence the way the computers behave as other sub-ensembles, like the motherboard, the graphics cards, the hard drive and so on.

Repair Power Supply PC 101

But the fact is that when the power supply is a powerful one, exceeding 600 watts, with a level of power efficiency above the 80, 85% range, buying a new one can be a real hassle.

The supply repairs are thus vital for keeping one’s budget down, especially of the unit is a quality one, one that delivers power to a serious enthusiast or above system.

In terms of issues that can occur with the supply, a few are more common: the cables can rupture, or have their sleeves cut or shorted.

Better power supplies offer protection against electric surges, over voltages and other calamities, but these too can suffer when an actual larger than usual discharge happens.

Most of the times however, the power repairs are demanded when suddenly the PC won’t start and the other components are not at fault.

In these cases the power supplies can have a condenser blown or some wiring ruptured and much more.

Modern and quality power supplies are very intricate electric and electronic devices, often times containing chips which guarantee a clean current delivery to many of the components on need of being powered.

But generally, the most demanding components are the high end graphic adapters as well as the motherboard.

computer power supply electric diagram

In an effort to protect a computer or other electric installations from closing unexpectedly or to protect them from electrical surges, the UPS (uninterruptible power supply) is used as an electrical buffer to this end.

The UPS repairs are oftentimes tasked either with actual repairs of these units but also with maintenance tasks such as replacing exhausted battery packs inside them, changing fuses or other components.

What you should know about PC power supply?

Knowing the separate components of your laptops power supply as well as what each does will ultimately save you a lot of heartache and money in the long run.

Many people take their power supply for granted until their computer starts powering off at odd times for seemingly no reason at all.

Arm yourself with the basic knowledge about each piece and it can help you diagnose simple problems that may arise.

power supply pc cable color knowledge

The first thing that you need to consider when you are looking at your power supply is the power strip that you plug into the wall.

This will help regulate the amount of power that goes into your computer and prevent potentially fatal power spikes.

Many people think that they can skip this component of their laptops power supply, but once they lose a valuable electronic device due to a power surge, they often never go without.

The next thing in line is the AC power adapter. This is another point that helps regulate the amount of power going into your computer.

It will also convert the alternating current from your wall socket and turn it into direct current that your computer will use to power the laptop as well as to charge the battery.

Once the power enters your laptop through the female adapter, the point at which your power cord ends and your laptop begins, the power is routed to the computer power board.

This piece of hardware serves two functions: one to send power to the mother board; and two to send power to your battery for charging.

Another often overlooked piece of hardware that is part of your laptops power supply is the computer cooling fan. The cooling fan makes sure that your computer doesn’t overheat.

Overheating problems will cause your computer to power off at odd times. The processor for your computer is usually the element that will generate the most heat in your computer so if you ever decide to get a stronger processor.

It is very important that you check and make sure that the computer cooling fan you have installed in your laptop is strong enough to properly cool your laptop.

Other issues that people commonly encounter with the fan is that the intake gets clogged with hair and dirt or the intake gets covered up to the point the fan is rendered ineffective.

This can actually cause a couple of different situations that may cause your computer to suddenly shut down.

Learn to Diagnose Power Supply PC Problems

The Power Supply convert’s your regular household current into low DC voltage used by the computer. When this component fails,there is simply no activity going on with your computer.

Remember to do the easy troubleshooting first.Inspect the Power Supply for any damage.Double-Check all connections.

pc power supply troubleshooting

Learning how to check your power supply and how to replace it when needed can be a life saver if you’re a computer buff or in business with the trusted PC.

Don’t take for granted the simple pleasure of turning on your PC and everything works just fine.

We turned on one of our computers recently and in about one hour,it just re-booted itself. And it continued doing so about 10 times a day until we found out the power supply was the culprit.

Things to look for when your power supply is going bad or just dies on you are the following.


Here you must first check the wall outlet for power by connecting another device such as a radio or lamp to be sure power is present.

If the computer is connected through a surge protector, check it as well.

If the wall out has power, check the power cable going to the PC to see if AC voltage is making its way to the system unit.

no power on pc power supply

Do this with the use of a multimeter.

If there is power,you will have to open the PC and check for power from the power supply to the motherboard.

When using a multimeter to check voltage,be sure you have a good ground for the black lead of the multimeter.


One main problem you may face with an ailing Power Supply is that it may re-boot the computer without any warning.

All information is lost and it seems as though this happens at the worst possible time.

Booting errors when the computer first start’s up is another indicator of this component going on the blink.


When the power supply begins to fail,you may receive power at one device and not another. For example,the Hard Drive may receive power but the CDROM Drive has nothing at all.

multimeter check for power troubleshooting pc power supply
Hands using voltage meter

Another headache with would cause re-booting is the intermittent power going to the drives or the motherboard itself.

Follow the steps below to check your power supply should you experience some of the above problems.


If the wall outlet,and the power cord are good,make sure the connection at the motherboard is secure.

Then you may have to face the fact that the power supply itself is bad.If you have a Multimeter you can test the power supply output before purchasing a new one.Simply follow these steps.

Turn off the PC, but do not unplug it,open the system unit. Set the multimeter to read DC volts in the next range higher than 12 volts.

Locate a power connector similair to the hard drive,or cdrom drive connector that is unused and turn on the PC.

main problems pc power supply

You can also unplug a drive connector and use it as well.Turn on the PC and insert the BLACK probe into the power connector on one of the BLACK wires.

Touch the RED probe to the YELLOW wire on the power connector.

The multimeter reading should be +12 volts Now touch the RED probe to the RED wire and the reading should be +5 volts.

If no readings or different readings occurred, you’ll have to replace the power supply.If the readings were correct,you should check the P8 or P9 connectors at the motherboard.

These connectors may also be named P4 and P5.To check these connectors,perform the following…

Insert the BLACK probe into P8 at one of the BLACK wires. Insert the RED probe into the P8 connector at the RED wire. The reading on the multimeter should be +5 volts

Check the power going to the Motherboard connections by inserting the RED probe into P8 at the YELLOW wire and you should get +12 volts.

Leave the BLACK wire touching the black wire at the P8 connector.Check the BLUE wire and the reading should be a -12 volts.

Now move the BLACK probe to the BLACK wire on the P9 connector.Test the WHITE wire by inserting the RED probe and the reading should be -5 volts.

Check the RED wires on the P9 connector and you should get +5 volts on each red wire.You won’t get exactly 5 or 12 volts but the readings will be very close, such as 5.02 volts.

If the Power Supply is a couple of volts off, in either direction,such as when the RED wire should be reading -5 volts but it reads -8 volts,or if there are no readings, replace the power supply.


DO NOT remove the power supply from the system unit case when performing these tests.

DO NOT perform these tests if you do not feel comfortable.Be sure to remove any and all electrical static build-up from your clothes and body BEFORE touching any parts inside the system unit.

NEVER open the power supply case for any reason,since high voltage may be present.