Step by Step How to Diagnose and Replace a Failed PC Power Supply (part-1)

When a PC power supply dies or begins to wear out, it must be replaced. With a few simple tools and the help of this guide, you can do this job yourself and save on expensive repair fees
1. Familiarize yourself with proper ESD procedures before doing any kind of PC repair work which requires opening a computer. If you neglect this step, you may damage your computer.
2. Verify that the power supply needs replacement. The most obvious clue is that the system will do absolutely nothing when you hit the power button. If there is no sound and no monitor activity of any kind, the power supply has probably died. While this can also be caused by a faulty switch, it is usually the result of a burned-out power supply. Another clue is that the system boots, but the system makes rapid, short beeps repeatedly and does not boot.

• o Test the power supply. Use a power supply tester (typically between $10 and $20 USD).

• o Test basic functionality. Disconnect the power supply from the motherboard. Take a paper clip and short pins from the green and any black terminal of an ATX power connector (largest connector, typically 20-24 pins total) to power it on. Don’t leave the paper clip connected, just short it until it powers on. Check to see if the fans spin (ie: inside the power supply). If so, your power supply is providing a 12V supply. An obvious clue of component failure is faint smoke or a burnt smell.

3. Once you are satisfied that the power supply is the culprit, disconnect all external connectors (including the power cord) from the machine. This may include keyboard, mouse, network cable, speakers, etc.
4. Remove the case cover, placing any screws somewhere where they will not get lost.
5. Identify the power supply unit. It will be connected to almost every component inside the computer case and will look something like this:
6. Using proper anti-ESD practices, disconnect all connectors which run from the power supply to the devices inside your PC.
7. Unscrew the mounting screws on the back of the case which hold the power supply in its housing. Place the screws in a handy location.
8. Gently remove the old power supply from the case. This is usually a simple process, but if there is very little room in your PC, it may be necessary to remove other components in order to get the power supply out. If you don’t feel comfortable removing other components, replace the mounting screws and enlist the help of a PC expert before continuing. Do not try to yank a power supply out by force.
9. Purchase a new power supply of the same type as the old one. Most power supplies used in modern computers are of the “ATX” variety, but if you aren’t sure, take the old unit to the store with you to compare. The simplest rule of thumb is that the new unit should be exactly the same width as the old one. It’s fine if the new unit is a bit longer, as long as it will still fit into your case. Do not hesitate to ask the salesperson or technician for help in identifying the correct unit to purchase.
10. Unpack the new power supply and make sure it physically fits correctly. If the new unit has a large bottom mounted fan, the bottom rear bottom flange on some cases might get in the way. Add it to the case in the same place the old unit was, and use the mounting screws to fasten it down.
11. Using proper ESD procedures, connect the devices in your PC to the new power supply. The connections should be the same as they were before. It can require a bit of force to insert power connectors correctly, but if if you have to strain a great deal to push them in, you may be trying to connect them backward. It is very difficult to connect most Molex connectors improperly, but if you are determined (and strong) enough, it can be done. If you have to force too hard, try turning the connector around.
12. Verify that no cables or unused connectors are stuck in the CPU fan or touching other moving parts. If the CPU fan is stopped by a loose connector (or any other obstruction), the processor can be destroyed very quickly. You may wish to restrain unused cables to prevent them from getting tangled up in fans.
13. Replace and fasten down the case cover.
14. Replace all external connections to the back of the computer (power cord, mouse, keyboard, monitor, network cable, speakers, etc).
15. Power up the system and enjoy.
16. If your system doesn’t start up correctly here, your failing power supply could have taken out the motherboard.