Lab 10 Power S

Home Up Objectives Sat AM Assignments Sound & Multi-Media Hard Drive Info Hard Dr Lab #1 Slides on Current Power Supply Notes Lab 10 Power S Lab11 Diags PC R II Sat Grades PC Repair II Labs Lab1 CDROM Lab 2 FDISK & P M Lab3 Upgrade HD Lab 4, Drive Image. Lab 5 Floppy Dr Lab 6 Memory Lab 7 Sound Card Lab 8 PC Prices Lab 9 Multimeter

Lab 10: Replacing a Power Supply

If you need to replace the power supply, follow this procedure. If you have the hardware available to you, use an actual PC and another power supply to replace the current one.

Procedure: (Check off each step as you complete it.)

I. Check the system before proceeding.  Does the power light come on when you turn on the PC?____  Does the fan turn briefly__________ or continuously________  ?

II. Remove the Power Supply

1.         Turn off the computer and remove its case.

2.            Remove the four screws that hold the power supply to the system unit.

Set these screws aside where they wonít get misplaced. Before removing the power supply, write down how the power supply is situated in the case. For example, jot down which side of the power supply has the power cord connectors.

3.            Remove the power connectors.

These four-wire power connectors are attached to disk drives and any other devices that require power. Wiggle or rock each connector back and forth until the connector is free.


You donít need to remember how the cables are connected because their ends are specially molded to fit only one way.

4.            Remove the pair of six-wire power cables that is connected to the motherboard.

Again, rock the connectors back and forth until they are each free. These two power cables are usually called P8 and P9, P1 and P2, or PS1 and PS2. When they are connected to the motherboard, note that each pair of black wires is next to each other. Again, these cables fit only one way.


Newer ATX power supplies simply have one keyed power connector to the motherboard.

5.         If you have a remote switch, free it from the front of the computer.

If you have a remote on/off switch, one that is not built into the power supply but is attached to it by a long wire, you need to remove that as well. The remote switch is usually found in tower and minitower cases. To remove the remote switch, you probably need to gently pry off the front bezel, or face plate, of the computer so that the screws that hold the remote switch in place can be removed. Remove the two screws that hold the remote switch and set them aside. You might also need to remove a plate that supports the switch when it is used. Set those two screws and bracket aside.


A newer ATX power supply does not require a mechanical switch, but instead has an ATX power switch lead attached to the motherboard. This lead is often next to the leads for reset, keyboard lock, system power LED, IDE LED, and turbo LED.

6.            Remove the power supply from the case.

If a remote switch is present, gently thread it and its cable back toward the rear of the computer so that it can be removed. Then, gently remove the power supply from its position.


7.         If the replacement power supply lacks an on/off switch, or if it arrived with the wrong type of switch, you must salvage the old one.  Instructors OK ______________________

Remove any black electrical tape that surrounds the old power supply switchís base, which exposes the four connectors to the switch. Note each wireís color going to each part of the switch. Usually the colors are, starting in the upper-left corner and going clockwise: white, black, brown, and blue. These colors might vary from manufacturer to manufacturer. Grasp each connector with the needle-nosed pliers and rock back and forth until each connector is free. Remove the switch from the new power supply, if it is present. Then place the old switch onto the connectors of the new power supply. Make sure that you replace the wires in the exact same order as the old power supply.

8.            Place the new power supply into the case in the same orientation as the old one.

Do not reattach any screws yet.

9.         If you have a remote power switch on the new power supply, thread the switch and its cable back into its original location.

Reinstall the supporting bracket and attach the switch to it. Next, reattach the front bezel, if you removed it.

10.        With the new power supply in place, use the four screws you set aside to attach it to the case.

11.            Attach the power connectors to the motherboard and other parts. Attach P8 and P9 (or P1/PS1 and P2/PS2) to the motherboard.

After the connectors are attached, check that the two pairs of black wires on each connector are next to each other. Next, attach the power cables to the disk drives and any other device that requires power. Note that the connectors are notched, or specially shaped, so that you canít put them on incorrectly. Make sure that the pins of each power supply connector are centered before you make each connection. Sometimes they might wobble or retreat as you put the connector on. Grabbing the base and a portion of the wires will hold these pins in place. You shouldn't have to unduly force the connector.

12.        With the case off, attach the electrical cord and briefly turn on the computer to test the power supply.


For your safety, do not touch any part of the case except the switch. Keep others away from the computer.

13.        You do not need to attach any other cables; you simply want to test the power.

Turn on the computer briefly to test whether the power supply and its switch work. You will hear the cooling fan start and the computer begin its warm-up testing. As soon as you know that the power works, turn off the computer.

14.            Replace the computerís case and return the PC to working order.
Instructors OK ______________________


Because you have been working inside the computer, check that the gray ribbon cables are firmly attached and were not dislodged during your work.


Home Objectives Sat AM Assignments Sound & Multi-Media Hard Drive Info Hard Dr Lab #1 Slides on Current Power Supply Notes Lab 10 Power S Lab11 Diags PC R II Sat Grades PC Repair II Labs Lab1 CDROM Lab 2 FDISK & P M Lab3 Upgrade HD Lab 4, Drive Image. Lab 5 Floppy Dr Lab 6 Memory Lab 7 Sound Card Lab 8 PC Prices Lab 9 Multimeter