(often fully designated as the R2A20112ASP ) is an integrated circuit (IC) primarily used as a Power Factor Correction (PFC)
controller. It is commonly found in the power supply sections of high-end office equipment, such as HP LaserJet printers
(models E72525, E72535, M72625, etc.) and various 12V SMPS modules. Renesas Electronics Core Schematic Functions
The IC controls a boost converter to provide active power factor correction, which is essential for efficiency in larger power supplies. Renesas Electronics Critical Conduction Mode (CRM):
Adopts CRM for high efficiency and low switching noise via zero current switching. Interleaving Control:
It shifts the phase by 180 degrees to improve ripple current on input/output capacitors. Protection Circuitry: The schematic typically includes: Over-Voltage Protection (OVP): Two modes (dynamic and static) for stability. Feedback Monitoring: Built-in detection for feedback loop opens or shorts. Soft Start:
Gradually increases reference voltage to prevent power surges. Renesas Electronics Repair & Troubleshooting Context
In blog and community repair discussions, the A20112 is often cited for its role in switching power supplies (SMPS). AliExpress Direct Replacement: In printers, the board containing this IC is often the JC44-00250A Power Supply Board Common Symptoms:
Failure in the PFC stage often leads to the power supply being unable to handle full loads or failing to start due to Under-Voltage Lockout (UVLO) protections. Schematic Availability:
While full board-level schematics are often proprietary to manufacturers like HP or Renesas, the IC's official datasheet from Renesas
provides the standard application circuit required for troubleshooting the primary power stage. Renesas Electronics Are you looking to a specific device with this board, or are you a new power supply using this IC? Understanding SMPS: How Switch Mode Power Supplies Work
While "A20112" might sound like a secret government code, it’s actually a classic, compact LASCAR PSU20112
linear power supply that has been a reliable "silent partner" in the electronics world for years. The Blueprint of a Workhorse The story of the
(PSU20112) is one of simplicity and ruggedness. Unlike modern "switching" power supplies that can be noisy and complex, this is a linear supply. Imagine a steady stream of water versus a fast-pulsing sprinkler; the
provides that smooth, steady stream of power that sensitive electronics crave.
The Mission: Its primary job is to take high-voltage wall power (110V or 230V AC) and "step it down" to a safe, steady 12V DC at 500mA.
The Armor: It is encapsulated, meaning the delicate internal components—like its transformer and regulator—are sealed in a protective block. This makes it a favorite for OEM use (built directly into other machines) where it needs to survive dusty or industrial environments. A Tale of Two Guards
The "heart" of the A20112's schematic isn't just about moving electricity; it's about protecting it. It features linear regulator ICs that act like watchful guards with two specific "superpowers":
Over-Current Protection: If a device tries to pull too much power, the guards "throttle" the flow to prevent a meltdown. a20112 power supply schematic
Over-Temperature Protection: If it gets too hot while working, the system automatically shuts down to cool off, ensuring it doesn't burn out the equipment it’s powering. Where it Lives Today You won't usually see an
sitting on a desk; instead, you’ll find it hidden inside the "brains" of other systems. It is the go-to choice for:
ITE (Information Technology Equipment) where low noise and high reliability are critical.
Precision OEM devices that need a "set it and forget it" power source that won't interfere with sensitive signals.
It’s not the flashiest part of a machine, but without its steady 12V output and "unbreakable" encapsulated design, many of the industrial systems we rely on simply wouldn't stay awake. Switching Power Supply Technical Manual - ADM and MEAN WELL
Never exceed the rated output capacitor voltage (usually 16V for the A20112). Doing so will cause capacitor explosion.
If you have a schematic for the A20112, it will usually be divided into four distinct "blocks." Here is how to navigate them:
Note: While I cannot visually draw a schematic here, I will provide a detailed textual netlist and component connections. You can replicate this in EDA software like KiCad or Eagle.
The A20112 power supply schematic is a textbook example of a flyback converter with primary-side PWM control and secondary-side TL431 regulation. Whether you are repairing a dead monitor or designing a custom 12V power source, understanding this schematic gives you a massive advantage.
Key takeaways:
Final advice: Download a generic UC3842 flyback reference design from Texas Instruments; it will match 90% of the A20112’s topology. Then, adapt based on your specific board’s component callouts.
If you have a specific A20112 variant or an unusual failure, post clear photos of both sides of the PCB on electronics repair forums – with the knowledge from this guide, the community will help you map out the exact schematic.
Repair safely – always discharge the bulk capacitor (310V DC) with a 10kΩ resistor before probing.
typically refers to a 14-watt guitar amplifier power supply circuit
, most notably used in certain boutique or smaller tube amplifiers like those from or similar custom builds.
While a complete factory-released schematic for the "A20112" board itself is not often published as a single standalone document, the circuit is largely based on classic Class A tube power supply architectures. Circuit Breakdown & Common Features
Based on technical discussions and common repairs for this unit, the power supply generally includes the following sections: Input Stage
: Uses a standard IEC inlet with a main fuse (often 1A or 2A depending on the region). Power Transformer (often fully designated as the R2A20112ASP ) is
: Typically a custom-wound transformer providing high-voltage AC (B+) for the tubes and 6.3V AC for the heaters. Rectification : Often utilizes a 5AR4/GZ34 rectifier tube or a solid-state bridge rectifier to convert AC to DC. Filtering (B+ Rail)
: Uses a series of high-voltage electrolytic capacitors (e.g., 22uF to 47uF rated at 450V+) and often a choke or large power resistors to smooth the DC voltage. Switching Options : Some versions include a 7W/14W power switch
, which works by dropping the voltage to the screens of the power tubes (Pentode/Triode switching). Common Components in A20112 Supplies Component Type Common Value/Part Power Tubes 2x 6V6 or EL84 Main power section 5AR4 or Diodes Converts AC to DC Screen and grid resistors Capacitors 22uF - 50uF (450V) Filtering Ripple Troubleshooting Tip
If your unit has stopped working or is cutting out, users frequently report issues with the output transformer blown screen resistors
resistors on the tube pins). Check these first if the main fuse keeps blowing. Class A tube amp schematic that matches this 14W power profile for comparison?
Fixing noisy eico hf-12 amplifier with tube issues? - Facebook
Understanding the A20112 Power Supply Schematic The A20112 power supply schematic serves as a foundational blueprint for engineers and hobbyists looking to build or repair stable, portable power delivery systems. This specific design is often referenced in portable electronics for its ability to convert and regulate voltage efficiently. For those needing the full technical breakdown, you can access the A20112 Power Supply Schematic Portable documentation for detailed wiring and component layouts. Core Components and Functionality
A typical power supply following this architecture is designed to transform raw electrical energy into a stable output suitable for sensitive electronic devices. Most DC power supply circuits, including the A20112, rely on several key stages:
Transformer: Steps down the high-voltage AC from the grid to a lower, safer AC voltage.
Rectifier: Uses components like diodes (often in a bridge configuration) to convert AC into pulsating DC.
Filter Stage: Typically utilizes large capacitors (ranging from 1000uF to 4700uF) to smooth out the pulses and reduce voltage ripple.
Voltage Regulator: Ensures the output remains constant despite variations in input voltage or load. Types of Power Supply Designs
When analyzing schematics like the A20112, it is important to distinguish between the two primary design philosophies:
Linear Power Supplies: These are simpler, more reliable, and produce less electrical noise, making them ideal for low-power requirements or sensitive audio equipment.
Switch-Mode Power Supplies (SMPS): These use high-frequency transistors to "chop" the voltage, offering much higher efficiency and a smaller physical footprint, though they are more complex to design. Practical Implementation Tips
If you are assembling a supply based on this schematic, consider these best practices:
Thermal Management: Components like the LM7812 regulator can generate significant heat and often require a heat sink.
Current Margin: Always select a power supply or components that offer a slightly higher current rating than your device requires to ensure longevity and safety. To lower to 9V (for fans):
Component Quality: Reliable manufacturers emphasize that the quality of your transformer and filter capacitors directly impacts the performance and lead times of your build. Switching Power Supply Technical Manual - ADM and MEAN WELL
typically refers to the model number for a specific power supply board
(often associated with Victoria Amplifiers or similar vintage-style tube gear). If you are looking for the schematic or technical details for this specific unit, it is most commonly a 5F10 "Harvard" style circuit or a variant of a 12V switching power supply module in industrial contexts. 🛠️ Common Schematic Characteristics
Depending on whether your A20112 is a vintage tube amp board or an industrial SMPS (Switching Mode Power Supply), the schematic usually includes: Input Stage:
A bridge rectifier (often using 1N4007 diodes for solid-state or a 5Y3GT tube for vintage amps) to convert AC to DC. Filtering:
Large electrolytic capacitors (e.g., 16µF to 4700µF) to smooth out voltage ripples. Regulation: For 12V DC modules, you'll often see an voltage regulator to maintain a steady output. Protection:
Inrush thermistors and fuses to prevent circuit failure from power surges. Instructables 🔍 Troubleshooting & Technical Notes
If you are repairing or building a circuit based on this model, keep these common issues in mind: Noisy Potentiometers:
If the unit is an amplifier, "thin" sound or noisy volume pots can often be traced to improper grounding or bad bias resistors. Voltage Drops:
If your output is significantly lower than spec (e.g., reading 7V on a 12V rail), check for shorted output rectifiers or failing smoothing capacitors. Safety Warning:
Many industrial A20112 modules are "primary side controlled." This means parts of the board are live with dangerous mains voltage
(220V/110V AC). Always use an isolation transformer when probing the circuit. Key Components Checklist Common Value Transformer Steps down AC voltage 15V-0-15V or 12V AC AC to DC conversion 1N400x series or Schottky bridge Capacitors Smoothing / Filtering 4700µF 50V (DC) or 16µF 450V (Tube) Opto-coupler Voltage feedback loop Used in switching models for regulation
To give you the most accurate schematic or advice, could you clarify: Is this for a guitar amplifier (like a Victoria or Fender Harvard clone) or an industrial 12V power module Are you trying to a broken unit or one from scratch? Do you have the brand name
printed on the PCB (e.g., Mean Well, Victoria, or a generic Chinese manufacturer)?
Make a Simple 12 Volt Power Supply : 6 Steps - Instructables
Note: The designation "A20112" is most commonly associated with proprietary power supply boards used in arcade hardware (specifically Namco System 246/256 platforms used for games like Tekken 4, Time Crisis 3, and Soul Calibur II). Schematics for these specific AC/DC converter units are rarely released as public service manuals, as they are treated as "replaceable units" (FRUs) by the manufacturer.
The following report details the functional architecture, component analysis, and troubleshooting guidelines based on the known design topology of this unit.