Okay…so maybe you
have a bad power supply. You want to put a new one in. First, you need to know what kind
to get.

One consideration in buying a power supply is its
wattage. The more gizmos you have on your computer, the more powerful power supply it will
need. The old computers, like the XT, work fine on a 130 watt power supply. Today’s
computers need a 230-250 watt supply. Sometimes more, but most desktops require no more
than 250. If you don’t put in a big enough supply for your computer, it will simply sit
there. On the other hand, if you put a bigger supply in that it really needs, it will just
hog more power, making your electric bill higher without increasing the performance.

The other consideration is the form
factor. If you have an ATX motherboard, you need an ATX power supply.
These supplies have one 20-pin power connector to the board. An AT
power supply, though, has two power connectors, P8 and P9, that power
the board.

Okay, read below for installation. Once again, you must
follow these instructions. NEVER try to repair a power supply. They are only safe when
they are closed. Besides, they aren’t expensive.

1. Turn off the PC, unplug it, and take off the
   case cover. Before removing anything, you may want to take note of how everything is
   connected. You will be disconnecting many wires from the parts of the system, and you need
   to know where to put them back.
2. Now you need to disconnect the power supply
   wires from all of the various parts. The power supply is that big, silver box in the
   corner of your case, or in the case of a tower, in the top rear. A bunch of little wires
   come out of it and connect to the motherboard and the drives. Disconnect the motherboard
   and the drives. The connectors for the drives come in two different size plugs,
   each having four colored wires coming out. These wires are often red, black, and yellow in
   color. Be ginger in disconnecting these items. The connections are often quite snug. And
   make sure you pull on the connector itself, not the wires.
3. You may need to disconnect the switch, too. On some power
   supplies, the on/off switch is built right on. On AT supplies, a set of wires with tabs connect
   the supply to a front mounted power switch. In this case, disconnect these wires from the
   four little tabs. Make note of which wire goes on which tab. It can be difficult to figure
   it out otherwise.
4. Some supplies are held in by a large bracket.
   You need to remove the screws from this bracket and get it out of the way. Next, remove
   the screws that hold the power supply in. These screws can be found on the back of the PC.
   There are four screws. With the case off, you can tell which screws hold it in. Make sure you don’t loosen any
   screws that might hold the fan in the power supply. Usually, the screws that are nearest
   the outside edge of the case are the right ones.
5. Lift the power supply out. You might need to
   fiddle with it to get it out. Don’t be afraid to really yank. Power supplies are very
   sturdy.
6. Stick the new one right where the old one came
   from. Just line up the screw holes and tighten the screws in place. Replace the bracket that holds it in, if your computer has such
   a thing.
7. Reconnect all the wires. Just the reverse of
   what you did to remove them. In the case of an AT power supply, the P8 and P9 connectors must sit on the motherboard so that
   the black wires sit side-by-side. Use the notes that you should have taken.
8. Reconnect the power supply to the power switch,
   if necessary. You should have noted down which tab goes where, but here is how they go.
   You have four tabs, having blue, black, white, and brown wires. Looking at it from the
   front, the white one goes front right, black is front left. Blue is right behind white,
   and brown is right behind black. If your tabs are oriented differently in relation to the
   case, use the same setup, but rotate the whole thing. Each wire is still in the same place
   in relation to the other wires.
9. If you have any remaining, unused
   connectors,
   bound them up with a tie and place them on top of your power supply or any other place
   that has room. Tie them up so they aren’t just flapping around and stay out of the way.
10. You’re almost done. Before testing your work,
    make sure the voltage is set correctly. There is a little switch on the back that
    lets you switch between 120 or 220 volts. In the United States, its 120. If you are in a
    country overseas, its most likely 220. If you use 220, make sure the cord is rated for it.
    It should say on the side of the cord.
11. Connect the power cord and turn it on. Does it
    work? You should hear a fan whirring away. If you hear the fan and your PC starts working,
    you’re through. If not, try flipping the power toggle switch on the
    back of the power supply. Most power supplies have a master power
    switch on the back that overrides the position of the case power
    switch. If you rule out all options, you probably need to take it back out and get another one. They
    sold you a bad power supply. First, though, plug something into the wall outlet and make
    sure it works. If it does, head back to the store. Don’t attempt to stick things into the
    power supply and start the fan spinning. Trust me, it doesn’t work.