SLC S23 Week1 || Computer Repair - Power Supply

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Hello Steemians!

Welcome to the first week of the Steemit Learning Challenge Season 23, where I explore the fundamental and crucial topic of Computer Repair - Power Supply. The power supply unit (PSU) is an essential component in a computer, converting AC voltage from the electrical grid into DC voltage that computer components require. Understanding its function and different types will enable me to diagnose and repair common power supply issues effectively.

This week, I will cover the basics of power supplies, their essential components, and common troubleshooting techniques. Let’s dive into the world of computer hardware maintenance and learn how to fix power-related issues!

Introduction:

Computer components need a direct current (DC) electrical power source to perform their functions. However, local electricity companies provide alternating current (AC) electrical voltage, i.e. alternating current only. Therefore, the alternating voltage that we receive from the electricity company must be converted to direct voltage (DC) to suit the computer components. The power supply unit in the computer converts the alternating voltage (AC) to direct voltage (DC).

Not all computer components need the same value of direct voltage. Some need 3.3 volts, such as the processor or memory, and some need 5 volts and 12 volts, such as disk drives. The power supply unit also provides a direct voltage of -5 and -12 volts to feed some old control cards that need these values.

Definition of Power Supply:

There are several designs for power supplies, including:

• The power supply is inside a metal box called (Cover) that contains components responsible for distributing electrical power to all computer components, such as the processor, disk drives, and fans.

• A power supply that converts alternating current (AC) to direct current (DC) using electrical transformers and voltage regulators.

• An external power supply that receives alternating current of 120 or 240 volts and outputs it at different voltages such as 3.3V, 5V, 12V, -5V, -12V depending on the needs of the computer components.

• Power supplies come in different capacities, with units of 350 watts and others of up to 1200 watts or more depending on the needs of the device. The power supply can be seen installed inside the computer case, and usually contains a cooling fan and various connection ports to distribute power to the electronic components.

Components of Power Supply Unit – PSU and How it work?

In the previous pictures: You can see three electrical transformers in the browser. These are the transformers that reduce the variable voltage to the values required by the computer components. Also, we see on the left two cylindrical circular capacitors. These capacitors are used in smoothing circuits. We also see two large pieces of aluminum that are used to dissipate heat to cool the board. The aluminum piece on the left has a number of transistors installed. This transistor is responsible for chopping the voltage and providing a high-frequency voltage to the electrical transformers. The aluminum piece on the right has the diodes installed that are responsible for unifying the variable voltage and converting it to a direct voltage.

Power Supply Voltage

• The voltage and current values that can be input to the power supply units as well as the values that they provide.

• The voltage and current values that the power supply unit provides are usually written on a label attached to one of the sides of the power supply unit box, and they vary according to the type of power supply unit.

• This picture shows a power supply unit labeled with the voltage and current values input to the power supply unit, as well as the voltage and current output from the power supply unit.

Distribution of power consumption for devices in the computer

Each wire coming out of the Power Supply has an important and unique function, which varies according to its type and the distribution of the parts connected to it.

The following table shows the power consumption of some different computer components:

Device	Power (consumption in watts - W)
Intel Celeron Socket 478	45W-65W
ATX motherboard	40W-65W
PC133 RAM	12W
PC2100+ DDR RAM	10W
PC3200+ DDR2 RAM	7.5W
CD-ROM drive	20W
CD-RW drive	30W
DVD-ROM drive	25W
5,400RPM IDE hard drive	15W
7,200RPM IDE hard drive	25W
Floppy drive	5W
Network card or modem	5W
Sound card	7-18W
SCSI controller card	25W
FireWire or USB 2.0 controller card	40W
USB device	5W
FireWire device	8W
CPU or case fan	2W

Power Supply Types:

You should be aware as a user of at least two types of power supplies (Power Supply). The power adapters used in the computer provide the necessary power for operation and the motherboard. As it is known that Power Supply can change its type depending on the type of motherboard (Motherboard).

The following are these types and the most commonly used:

1- AT Power Supply
This type of power supply was the most common and used, and appeared since the mid-nineties. But after 1995, this type was no longer able to meet the needs of Memory Modules, Processor, and Expansion Slots, which led to its gradual replacement.

2- Baby AT
It has the same characteristics as the previous unit but smaller in size.

3- ATX Power Supply
This type is considered a modern standard for desktop computer architecture, and is currently the most widely used. One of its features is that it does not require an on/off switch, but is controlled electronically.

The Power Supply is installed as a unit connected to the Motherboard, and there are different types of it according to different systems such as Intel ATX Motherboards.

It was produced within the Pentium Pro series to provide better energy efficiency.

What is the main difference between AT and ATX as a design used in motherboards?

In ATX, cards and accessories can be easily installed without the need to modify the internal structure of the computer, unlike AT.
In addition, ATX Power Supply is characterized by the ability to electronically control the operation of the computer without the need for a mechanical switch.

Source

ATX Power Supply uses only one power connection, which is 20 or 24 PIN Power Connector, while AT contains several connections.
ATX Power Supply provides 3.3V as a power source for modern ICs, while AT needed an external Regulator to provide this voltage.

One of the most important things that appeared in ATX technology is the Soft Switch, which allows you to control the process of turning on and off the computer via Software or the main board, while in AT a mechanical technology was used to open and close the device.

Previously, it was necessary to press the Power button to completely turn off the device, but with Soft Switch it became possible to turn on the computer in Standby mode to be activated from the network using the Wake On LAN feature.

In modern motherboards, power is connected via the 24 PIN connector, while old boards used the 20 PIN connector.

Power Supply Connectors Recommendations and Wires:

Before connecting the wires, there are several things to consider:

How is the Power Supply connected directly or indirectly?

Are the electrical components connected directly to the power supply, or are they connected via the motherboard?
There are different types of connectors to supply Motherboard, Hard Disk, and other components.

Make sure the Power Supply is compatible with the computer specifications before installation.

As for the wires in the Power Supply, each one has a specific function and voltage output. They are as follows:

• Yellow = 12V+
  It is used to transfer voltage to the Hard Disk, Fans, Cooling Device, and System Bus Slots.

• Red = 5V+
  It is used to supply the Motherboard, CPU, and many computer components.

• Orange = 3.3V+
  It is used to supply some modern equipment such as CPU and some types of Memory (RAM) such as SDRAM and AGP graphics cards.

• White (White) = -5V
  Used in some electronic circuits that are mounted on the ISA Slot and some types of PROM memory.

• Blue (Blue) = -12V
  Used in some serial ports such as Serial Ports, and some types of PROM.

• Green (Green) = Power On
  This wire is responsible for turning on or off the computer's primary current.

• Black (Black) = Ground (COM)
  Used as a ground socket to complete electrical circuits with other voltages.

• Gray (Gray) = Good Power Line
  It is the wire responsible for checking the stability of the current and disconnecting the power if an electrical fault or short circuit occurs in the (Short Circuit) circuit.

• Purple (Purple) = Standby
  This wire provides a permanent voltage that enables the device to be kept in standby mode.

• Brown = 3.3V+ Remote Sensing
  This wire is used for sensing, as it adjusts the voltage difference precisely when needed.

Source

Good Power:

The power supply supplies the power needed to operate the motherboard and other components in the computer. However, it also sends a very important signal to the motherboard, which is PWR OK Power Good in ATX power supplies.

When the computer is turned on, the power supply automatically checks whether the required input and output voltages are correct. If they are not, it will not send a Power Good signal to the motherboard, meaning that the power supply can be relied upon. If this signal is sent and is in the (OFF) state, the CPU timing will interrupt this (Power Good) signal and send a (RESET) command.

The BIOS is also executed at this stage, and if this signal is encountered and is in the OFF state, the front I/O module will spin the drives and the power supply fan, but the BIOS will never reach its end and will remain stuck at this stage.

Power Supply Unit - Wattage Power:

The power of a power supply is measured in watts. Personal computers require sufficient power to operate properly. A personal computer with two hard drives and a CD-ROM drive requires 115 to 130 watts while running. While it requires 200 watts when booting.

So the power supply should have a power greater than 200 watts. Most power supplies have a power of 230 to 250 watts.
Just in case, this power is enough even if you add more devices in the future.

Power Supply Fan:

Each power supply unit has a cooling fan. The power supply fan cools the computer, so if it stops spinning, it can cause major problems.

If you notice that you can't hear the fan when you turn on your computer, it's broken and should be replaced before you turn on your computer again.

This fan not only cools the voltage regulator within the power supply units, it also provides a constant flow of cool air through the computer case. Without this current, the electronic chips inside the computer case quickly overheat and fail.

Common faults in the power supply unit - Power Supply Crash:

Question:/ How do you know if the power supply Power Supply is working or not?

Answer/ This is when you press the power button on the device. If it does not work, there are three possibilities:

The first possibility: The fault is in the power supply Power Supply!!! How do you make sure???

We unscrew all the power supply plugs from the Hard Disk and the Motherboard and the laser drives and fans.
Then we use the motherboard meter, and connect a small wire in the green wire input with the black wire input as in the following picture.

If the power supply fan works, then it is fine, otherwise it is faulty and must be repaired or replaced.

The second possibility: The fault may be in the motherboard, in which case it must be repaired or replaced.

The third possibility: It is from the power button (device power button), the fault is that the place of the computer power button has been replaced with a restart button to replace the device power.

This is done by opening the cover, then disconnecting the device power button socket, and moving it to the restart button port, then unscrew the restart button scale, and when you want to turn on the device, press the restart button to turn on the device.
Also, one of the most common and famous faults in Power Supply is a faulty fuse in the power supply.

It is located in the power supply as in the following picture:

What is the reason that led to its failure?

It is a high electric current entering the power supply (Power Supply) or the electricity was suddenly disconnected from it and then returned quickly, so you must change the fuse instead of the faulty fuse!!!
Also, one of the common faults is fan failure, so you must change it immediately so that the rest of the computer parts do not fail due to excessive heat.

Homework Tasks:

Task1: (2 points)

Examine the power supply unit of your computer or any other device and determine its type. Then, refer to the label on the unit to identify and note its input and output voltage specifications.

Task 2: (2 points)

ATX power supplies supply power to ATX cards through a 24-pin connector. List the wire colors used for each number in the following table.

Task 3: (2 points)

Look at the image above showing different power connectors on a computer power supply. Match each numbered connector to its specific use based on the information provided. Then, explain the role of each type of connector in the operation of computer components.

Task 4: (2 points)

What are the common signs that a computer power supply is failing, and what steps should you take to diagnose the problem before replacing the power supply?

Task 5: (2 points)

What precautions and best practices should be applied when maintaining and cleaning a power supply to ensure its proper functioning and extend its life?

Contest Guidelines:

• Title: SLC S23 Week1 || Computer Repair - Power Supply
• Tags: #dynamicdevs-s23w1, #country (e.g., #tunisia), #steemexclusive.
• Submission Period:
  • Monday, February 17, 2025, 00:00 UTC to Sunday, February 23, 2025, 23:59 UTC.
• Eligibility:
  • Posts must be #steemexclusive.
  • Plagiarism and AI-generated content are strictly prohibited.
  • Use original or copyright-free images with proper attribution.

Rewards:

SC01/SC02 will evaluate posts across all participating teaching teams. Upvotes are not guaranteed for all articles.

At the end of the week, top 4 users will be nominated based on content quality, not comment count.

Conclusion:

Understanding the power supply unit is essential for maintaining and repairing computers. A malfunctioning PSU can lead to performance issues, system instability, and even hardware damage. By learning how to identify power supply types, test voltage outputs, and troubleshoot common problems, I can ensure my computer runs efficiently. This knowledge is not only beneficial for repairs but also for selecting the right PSU when building or upgrading a PC. Mastering power supply concepts empowers me to handle hardware issues confidently and effectively.

Best Regards,
Dynamic Devs Team