All You Need To Know About ATX PSU To Fix Stuff! The Complete ATX Power Supply Repair Guide Tutorial

Learn Electronics Repair

25 Apr 2022133:07

EducationalLearning

32 Likes 10 Comments

TLDRThe video delves into the intricacies of repairing an ATX power supply, highlighting the importance of safety and proper technique. The host shares an in-depth analysis of the power supply's design, focusing on the role of capacitors, transformers, and transistors. A step-by-step guide is provided for diagnosing and fixing common issues, emphasizing the significance of checking for short circuits, replacing damaged components, and ensuring the integrity of the power supply's various sections. The video also touches on the differences in modern ATX power supply designs and the use of synchronous rectification. A comprehensive and educational resource for those interested in power supply repair and understanding the inner workings of ATX units.

Takeaways

🔍 The video begins with an exploration of an ATX power supply, aiming to identify the cause of a lack of power output.
💡 The initial test involves connecting the power supply to a light bulb to check for current flow, which reveals no power is being drawn.
🔧 The presence of high voltage capacitors inside the power supply is noted, which can store voltage even when disconnected from the mains.
⚠️ Safety precautions are emphasized when working with ATX power supplies, highlighting the potential dangers of high voltage and the importance of discharging capacitors properly.
🔍 The video demonstrates the use of a modified ATX power supply tester analyzer to detect power output from different voltage rails, revealing issues with the 12-volt supply.
🛠️ The power supply is opened to visually inspect the internal components, noting the layout and potential points of failure.
🌟 The video provides a detailed explanation of the ATX power supply's design, including the function of transformers, capacitors, and switching transistors.
🔎 The process of testing for short circuits in the main switching transistors is described, as this is a common cause of failure.
💻 The role of the pulse width modulator and its position in the power supply circuit is discussed, as well as the function of opto isolators for safety and control.
🔄 The concept of power factor correction (PFC) is introduced, explaining its purpose and the impact of its failure on the power supply's operation.
🧰 The video concludes with a comprehensive overview of the various ATX power supply designs and the common issues that can arise, providing valuable insights for repair and maintenance.

Q & A

What is the main purpose of the video?
-The main purpose of the video is to explore and explain the process of repairing an ATX power supply, including its design, safety considerations, and troubleshooting techniques.
What is the educational value of the video?
-The video provides educational value by demonstrating the steps to diagnose and repair a faulty ATX power supply, offering insights into its internal components and functioning.
Why did the ATX power supply not draw any power initially?
-The ATX power supply did not draw any power initially because the main capacitors inside had not charged up, indicating that there was no power delivery to the system.
What is the significance of the light bulb in the current limiting light bulb setup?
-The light bulb in the current limiting light bulb setup serves as an indicator of power flow. If the power supply is functioning correctly, the bulb should flash to signify that power has been drawn into the system.
What is Active PFC and how does it affect the power supply?
-Active PFC (Power Factor Correction) is a circuit that improves the efficiency of the power supply by increasing the DC voltage input to about 380-390 volts before the power supply runs and drives the transformers to generate the outputs. It ensures the power supply operates more effectively and efficiently.
What are the safety precautions one should take while working on ATX power supplies?
-While working on ATX power supplies, it's important to be aware of high voltages, especially from large capacitors that can store power for a long time. One should also ensure that the power supply is isolated from the mains, and use appropriate tools and techniques to discharge capacitors safely to avoid hazards.
How does the tester analyzer help in diagnosing power supply issues?
-The tester analyzer is a modified device that helps indicate whether there is power coming from the power supply, regardless of which voltage rail is present. It provides a reading and shows that there is some power coming in from somewhere, which is crucial in diagnosing power supply issues.
What are the common components involved in the standby supply of an ATX power supply?
-The standby supply of an ATX power supply commonly involves a transformer, a transistor, and capacitors. It generates a 5-volt standby signal that is crucial for the power-on sequence of the system.
What is the role of the bridge rectifier in the power supply?
-The bridge rectifier in the power supply is responsible for converting the AC input into DC output. It consists of four diodes arranged in a specific configuration to allow current to flow in only one direction, thus rectifying the AC signal into DC.
What happens if the bridge rectifier is faulty in an ATX power supply?
-If the bridge rectifier is faulty in an ATX power supply, it can cause a short circuit, preventing the power supply from functioning correctly. This can lead to issues such as the power supply not delivering the required voltages or even causing damage to other components.

Outlines

00:00

🔍 Introduction to ATX Power Supply Examination

The video begins with an exploration of an ATX power supply for educational purposes. The host connects the power supply to a light bulb to test its current limit but finds no power being drawn. The power supply appears to be inactive, leading the host to open it up and discuss the potential dangers of high voltages stored in the capacitors. The modified ATX power supply tester analyzer is introduced as a tool for safely diagnosing power supplies.

05:02

💡 Understanding Capacitor Charging and PFC Circuits

The host explains how to check for charge in capacitors using a bridge rectifier and emphasizes the importance of knowing whether the power supply has an active PFC. The explanation includes a detailed discussion on the dangers of incorrectly testing for charge and the proper method for discharging capacitors using a power resistor. The host also advises against using a screwdriver to discharge capacitors due to safety risks.

10:02

🛠️ Safe Practices for Working on Power Supplies

The host outlines safety precautions when working on power supplies, including the potential hazards of high voltages in capacitors and the importance of discharging them properly. The discussion extends to the risks associated with the on-off switch and the potential for incorrect wiring that could lead to electric shock. The host stresses the importance of unplugging the power supply to ensure complete isolation from the mains.

15:03

🔧 Exploring ATX Power Supply Topologies

The host delves into the various topologies of ATX power supplies, explaining the function of the three transformers and the role of the main transformer in generating the primary voltages. The standby supply's role in powering the main supply and monitoring voltage and current levels is also discussed. The host illustrates the half-bridge circuit and its operation, providing insights into the functioning of modern power supplies.

20:04

📊 ATX Power Supply Design and Variations

The host presents different designs of ATX power supplies, highlighting the presence of two or three transformers and the use of MOSFETs in the main switching circuits. The explanation includes the function of the pulse width modulator, the role of rectifier diodes, and the importance of isolation between the high voltage and low voltage sides of the power supply. The host also discusses common failures in these circuits and their potential causes.

25:07

🌐 Further Insights into Power Supply Circuitry

The host continues to dissect the power supply circuitry, focusing on the active PFC circuit and its components. The explanation covers the function of the PFC controller, the role of the main switching transistors, and the importance of the controller chip located on the high voltage side. The host also discusses the use of opto-isolators and the concept of hot and safety ground in the context of power supply design.

30:07

🛠️ Repairing and Understanding Modern Power Supplies

The host examines a modern 1500-watt power supply with active PFC and a full bridge design. The discussion includes the function of the main switching transistors, the role of the PFC controller, and the use of synchronous rectification. The host also identifies a short circuit in the power supply and outlines the process for diagnosing and repairing the issue, emphasizing the need for careful inspection and testing of components.

35:08

🔎 Diagnosing and Addressing Short Circuits

The host focuses on diagnosing a short circuit in the ATX power supply, identifying the likely causes and the impact on the circuit. The explanation includes a detailed examination of the main switching transistors, the standby supply, and the potential for damage to other components. The host also discusses the process of desoldering the heatsink and transistors for further inspection and testing.

40:09

🧠 Component Analysis and Replacement

The host conducts a thorough analysis of the components in the power supply, including testing the transistors, diodes, and capacitors. The discussion covers the identification of faulty components, the process of finding suitable replacements, and the considerations for component substitution. The host also demonstrates the use of a multimeter and a component analyzer in diagnosing and confirming the status of the components.

45:09

💡 Final Thoughts on Power Supply Repair

The host concludes the video with a summary of the repair process, highlighting the need for replacement of the fuse, bridge rectifier, and two transistors. The host reflects on the importance of comprehensive checks and safety practices in power supply repair, and invites viewers to share their comments, criticisms, and insights to foster a community of learning and improvement.

Mindmap

Keywords

💡ATX power supply

ATX power supply is the main subject of the video. It refers to the specific type of power supply unit (PSU) used in desktop computers, which adheres to the ATX standard for motherboard power supply connection. The video discusses various designs, repair techniques, and components of ATX power supplies, emphasizing their importance in computer systems.

💡Power Factor Correction (PFC)

Power Factor Correction is a technique used in power electronics to improve the efficiency by minimizing the harmonic distortion in the current waveform. In the context of the video, active PFC is a feature in some ATX power supplies that helps to increase the power supply's efficiency and reduce energy waste. The script describes the presence of a PFC circuit in the power supply and its role in the overall functioning of the unit.

💡Bridge rectifier

A bridge rectifier is an electrical component that converts AC (alternating current) to DC (direct current) by using diodes arranged in a particular configuration. In the video, the bridge rectifier is a crucial part of the power supply's initial stage, responsible for converting the incoming AC from the mains into DC that can be further processed by the power supply.

💡Transformer

A transformer is an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction. In the context of the video, transformers are used in the power supply to step down the voltage from the main supply to the levels required by the computer's components. The video discusses the primary and secondary windings of transformers and their roles in generating the various output voltages.

💡MOSFET

A MOSFET, or Metal-Oxide-Semiconductor Field-Effect Transistor, is a type of transistor commonly used in electronic circuits for switching and amplification purposes. In the video, MOSFETs are used as switching devices in the power supply, controlling the flow of current and participating in the generation of output voltages.

💡Short circuit

A short circuit occurs when an electrical path with low resistance is created unintentionally, causing a large flow of current that can damage components or cause a malfunction. In the video, a short circuit is identified as the cause of failure in the ATX power supply, leading to the destruction of the main switching transistors and potentially other components.

💡Standby supply

The standby supply refers to the lower-voltage power supply circuit that is always active, providing power to certain components even when the computer is turned off. In the video, the standby supply is discussed as part of the ATX power supply design, which includes a transformer and a self-oscillating circuit that drives the standby function.

💡Opto isolator

An opto isolator is a component that provides electrical isolation between two circuits using light. It is used to protect sensitive circuits from high voltage or current surges. In the video, opto isolators are used in the power supply to control various functions, such as the standby supply and the main power supply, while maintaining a safe isolation between the high voltage and low voltage sides.

💡Synchronous rectification

Synchronous rectification is a technique used in switch-mode power supplies to replace diode-based rectifiers with MOSFETs, which can be controlled to achieve better efficiency and reduce power loss. In the video, this concept is discussed in the context of modern ATX power supply designs, where MOSFETs are used as rectifiers instead of traditional diodes.

💡Buck regulator

A buck regulator is a type of step-down voltage regulator that reduces the input voltage to a lower, stable output voltage. It is commonly used in computer power supplies to provide stable voltage rails for various components. In the video, buck regulators are mentioned as part of the design of modern ATX power supplies, each providing a specific voltage rail for the computer system.

Highlights

Introduction to the examination of an ATX power supply for educational purposes.

Observation that the power supply is not drawing any power, indicating a potential issue with the main capacitors or a short circuit.

Discussion on the importance of safety precautions when working with high voltage components.

Explanation of the function and testing of the ATX power supply tester analyzer.

Discovery of a major problem with the 12-volt supply from the ATX being absent, rendering the tester non-functional.

Demonstration of how to safely discharge capacitors using a power resistor to prevent hazards.

Explanation of the dangers of using a screwdriver to discharge capacitors and the damage it can cause.

Discussion on the proper way to discharge capacitors and the use of an insulated tool for safety.

Explanation of the power supply's design, including the function of the three transformers and the half-bridge circuit.

Discussion on the importance of understanding the power supply's topology for effective troubleshooting and repair.

Identification of common hazards when repairing power supplies, such as the presence of high voltage even when disconnected from the mains.

Explanation of the difference between safety ground and hot ground in the context of power supply repair.

Discussion on the various power supply designs and topologies encountered in ATX power supplies.

Identification of common failure points in ATX power supplies, such as short circuits in transistors or issues with the pulse width modulator.

Explanation of the function and design of the standby supply and its role in powering the motherboard.

Discussion on the differences between various ATX power supply designs, including those with active PFC and those with full bridge designs.

Conclusion on the steps required to repair the ATX power supply, including replacing the fuse, bridge rectifier, and main switching transistors.

Transcripts

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ATX Repair Power Supply Design Analysis Safety Precautions Electronics DIY Technical Guide Voltage Regulation Component Testing Bridge Rectifier Transistor Replacement