How To – Changing A Dead Computer Power Supply

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    Well if you keep your computer long enough or if you get to that point where you no longer buy new computers but continuously add upgrades to the box you bought years ago eventually your power supply is going to die.

    In the computer that we are working on today is an older ATX power supply that has seen two motherboard upgrades, half a dozen different drives and mostly everything else that can be swapped out to add more power and features.

    ATX is the type of power supply… most computers today will accept an ATX power supply and the watts that they can output range from 85 watts for a tiny mini computer to 200watts for a power saver slimline and 300 to 400 watts for a general purpose desktop computer.

    Larger power supplies are available for people that are building home multimedia servers with many hard drives they can be rated at any wattage up to approximately 1000 watts.

    Finding the Type and Rating of your Power Supply

    Information about your power supply will be listed on a label placed on the side of the power supply box.

    The label should be visible when you open your case but may be on  an opposite side.

    What you are looking for is the wording ATX Power supply and the Wattage.

    There are formulas for calculating the exact wattage that you need but if your computer is operating normally and you do not plan to add more drives or special cards then you can purchase a power supply of the same wattage.

    Drive Power Connectors

    The drives in this computer are all AT IDE drives and take a four prong connector. If you have SATA drives you will need special power connectors or adapters.

    Since our new power supply is setup to provide power to both IDE and SATA Drives all we need to do is make sure there are enough connectors on the new power supply to attach all the drives. We have 4 drives and 4 connectors so we can save the extra SATA connectors if we install a new drive at a later time.


    The Motherboard Connector

    Older ATX motherboards accept a standard ATX Power connector and also require power for the CPU Fan.

    New motherboards may require an extended connector and our power supply can power the new boards also.

    If you have an older motherboard like we do then you simply break away the four prong extended connector.

    Do not use this connector for the fan power supply. It will look very similar to the fan power supply connector but it is not wired to provide the same connections. The shape of the connector pins are also slightly different but forcing them into place could result in a connection to the fan adapter on the motherboard.

    Some video cards also require additional power connections for fans and power.

    Removing the old power supply

    The first thing you need to do is remove the connectors to your hard drives and motherboard. If you also have a case fan remove that connector too.

    On the back of your case you will find 4 screws that hold the power supply in place.

    Before you remove the retaining screws make sure that you will be able to remove the power supply box and have clearance between it and your cards and CPU heat sink and fan.

    If you do not have clearance then you may need to loosen the motherboard to position it out of the way.  This will also require that you remove the screws from your accessory cards as they will also hold the motherboard in place.

    Once you believe you have the room and all of the power connectors have been removed you can remove the four screws on the back of your case that hold the power supply in place.

    As you can see we also have a fan and there are switches with screws .. to make sure you are removing the correct screws hold the new power supply in place near the old one and you will see the four holes that accept the screws for mounting.

    Cleaning Your Case

    The new power supply should fit right in place but before you install it you should thoroughly clean the dust out of your case.

    We have a brand new can of compressed air to remove all of the dust and we will use almost all of it.

    Some surfaces may retain dust that the duster can not clean away.

    You can use a small clean painters art brush that has never been used for painting to clean the dust off of theses surfaces. The softer the better. Once the brush is loaded with dust hit it with the air can to clean it and continue cleaning until all of the dust is out of your case.

    Inserting your new power supply

    Now that your case is clean and your fans and cpu heat sink are ready for action you can insert your new power supply.

    The power supply may have wires that exit from a different location then the original.

    This was the situation with our new power supply but the wires were located out of the way of our CPU heat sink and other problem areas.

    Screw your Power supply to the case and then begin reattaching your power connectors.

    The motherboard connector and fan connector are probably the hardest to attach so do those first and then your drives and accessory connectors.

    Routing your wires

    Once you are done making connections you will have a bunch of wires that take up a large amount of area. It is best that you locate them in a manner that they will not restrict air flow.

    Group the wires together and bind them with plastic ties.

    Try not to use wire ties  because you never know if you could cause friction or a short inside the case.

    Final Note

    Once everything is connected, clean and ready to put back in service you can reattach your keyboard, mouse and monitor then turn on the power supply switch.

    Your front case switch should be used to start your computer. If you find that turning on the back power supply switch turns on your computer then you probably have the front switch wired incorrectly to the motherboard.

    Allow your computer to run for a few hours.

    You may also want to boot into your Bios after this time and double check that your CPU is in a good temperature range.

    Replacing your Power Supply can be very cheap. The unit we purchased was a 300watt ATX for under $25 which was less then a new cheap case.

    With a new power supply this computer can last a few more years, be made into a storage center / server or be passed on to someone as a starter computer.

    The YouRepair Store sells a full line of computer products and replacement parts.

    Internal Desktop Components

    Power Supplies


    Computers & Accessories

    Computer Accessories

    Uninterrupted Power Supply (UPS)

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