Intro: Computer Repair Final By: Will Carlson
The Power Supply
Step 1: What Does the Power Supply Do?
The PSU converts AC power to DC low-voltage power for the internal parts of the PC. In order for the motherboard or hard drive to get power, the power supply is essential. Without it, the PC would not function.
Some PSU's have a manual switch for selecting input voltage, while others automatically adapt to the mains voltage.
There are 4 main types of PSU's.
Unregulated: Most basic form of the PSU. If input value varies then the output value of voltage will vary by a proportional amount. It is cheap,simple and efficient.
Linear regulated: Also known as "brute force." A typical linear regulator is designed to output a fixed voltage for a wide range of input voltages. It drops excess input voltage to allow max output value to the load. They are very large, heavy and expensive.
Switching: Mix of both linear regulated and unregulated. Switching power supplies work on the principle of rectifying the incoming AC power line voltage into DC, re-converting it into high-frequency square-wave AC through transistors operated as on/off switches, stepping that AC voltage up or down by using a lightweight transformer, then rectifying the transformer’s AC output into DC and filtering for final output. High efficiency, light weight and small size. Most common type of PSU.
Ripple regulated: Alternative to linear regulated. It transfers DC power to a large capacitor as needed to maintain the output voltage between a high and a low set point. Safe to work on and basically a less complicated switching PSU.
Step 2: Diagram of the Power Supply
Transformer: Device that converts high voltage AC into low voltage AC or vice versa. The ultimate goal of the PSU is to convert high voltage AC into low voltage DC.
Rectifier: it corrects the signal by removing the negative side of the sinusoidal signal. Full wave rectifiers are the most commonly used rectifiers in power supply. They simply allows the positive half cycle to pass through and inverts the negative half cycle to positive half cycle.
Filters: Filters filter out any AC component present and provides DC as the output.
Regulator:A regulator is an electrical or electronic device which maintains a constant output voltage irrespective of changes in load current, input voltage or temperature.
Load: the capability to maintain a constant voltage level on the output channel.
Step 3: Causes and Solutions to Power Supply Problems
The main problem that a power supply faces is a power surge.
A power surge is a spike in the home electric current. A vast amount of things can cause this including, lightning strike, power outage, short circuits, other large equipment on the same power line, and power company malfunction. Once a power supply is broken as result of a power surge, normally the only option is to get a new one. In the future you can get a Surge protector to protect against spikes in voltage.
Another huge problem is overheating in the power supply.
Power supply fan can collect dust and cause it to overheat. Again once your power supply doesn't work as result of overheating, the best option is to buy a new one. However in order to prevent this you can blow off dust every 3-6 months with compressed air.
Step 4: Tools to Fix the Power Supply
You can use a multimeter to make sure the power supply has the proper voltage or test for a defective power switch.
As said before you can use a Surge protector to protect against power surges.
You can use zip ties in order to keep cables neat and prevent them from tangling up.
You need a screw driver in order to install a PSU into the case as well as take off the PSU cover
Also use a can of compressed air in order to blow off dust in the fan to keep it from overheating.
There is not much software care for a PSU however before buying a PSU you can use a power supply calculator. This will assure that you have enough power to supply the PC.
Step 5: Multimedia Component
Tutorial on how to do a power supply calculator.