Before embarking on replacing a power supply, the old power supply will have to be removed from the drive. The power connectors will then be pulled from the motherboard and external devices. When pulling, hold the white plastic part of the plug and wiggle it back and forth until it loosens enough to remove easily. The old power supply will be unscrewed from the case.
Before someone puts a new power supply in place, they are supposed to look at the back of it. At the back, just under the plug is the power code. This is used to set the correct power voltage. After this, the power supply will need to be inserted to the case in a way that will fit. There is a way in which the power supply will fit to the case. After it fits in the case, the power supply will be screwed so that it stays securely. There will be cables coming out of the power supply. The cables will then be sorted so that each cable group is isolated according to their functions.
After this, the first connectors to be connected are those for the motherboard. When connecting, one should be careful so that they do not connect the wrong way. One way to achieve this is to use the shape of the connectors and the clip and the notch on the motherboard where the connectors will be inserted. These are used to connect the motherboard.
After the motherboard power connection, connect the power connectors for other devices. The bigger connectors are used for hard-drives and CD-ROM while the smaller ones are used for the floppy drive. All the other hanging cables will have to be tied with plastic zip ties in an orderly manner. This will make sure there is free airflow in the case and make it easy to working in the case. After this, ensure that there are no hanging cables dangling around, no cable near a fan, and that the power supply is set to the correct voltage. Also, make sure that all drives have been connected. If the power supply is that of AT instead of AT-X, there will be need to connect an extra cable, power button connector.
Alex. (2011). Installing the new power supply. Retrieved August 23, 2011, from PC911: http://pcnineoneone.com/howto/powersupply3/
Billings, K. (1999). Switchmode power supply handbook. New York: McGraw-Hill Professional.