The A20112 connects to the Namco I/O board via a custom connector block (usually a friction-lock header).
| Pin Number | Voltage | Wire Color (Typical) | Function | | :--- | :--- | :--- | :--- | | 1 | +12V | Yellow | Drive / Fan Power | | 2 | +12V | Yellow | Drive / Fan Power | | 3 | GND | Black | Common Ground | | 4 | GND | Black | Common Ground | | 5 | +5V | Red | Logic Power (CPU/GPU) | | 6 | +5V | Red | Logic Power | | 7 | +3.3V | Orange | I/O & Logic | | 8 | +3.3V | Orange | I/O & Logic | | 9 | GND | Black | Common Ground | | 10 | GND | Black | Common Ground |
(Note: Wire colors may vary based on revision. Always verify with a multimeter.)
Here is a troubleshooting table directly derived from the A20112 schematic logic.
| Symptom | Likely Fault (per schematic) | Diagnostic Step |
|---------|-------------------------------|-----------------|
| No output, fuse blown | Shorted MOSFET (Q1) or bridge rectifier | Check diode mode across drain-source of MOSFET. Replace both MOSFET and current sense resistor. |
| Output cycles on/off (ticking sound) | Overcurrent protection active | Check secondary Schottky diode (short) or output capacitor (high ESR). Measure CS pin voltage – should be <1V. |
| Output present but drops under load | Failed bulk capacitor (C5, 400V) | The capacitance drops below 50µF. Replace with 105°C rated Lelon or Nichicon. |
| Very low output (e.g., 3V) | TL431 or optocoupler failure | Temporarily disconnect optocoupler; if output jumps high, FB loop is the issue. |
| No standby power, but fuse OK | Startup resistor (R2, 1MΩ) open or VCC capacitor (C13, 47µF 50V) dried out | Check R2 resistance; replace C13. |
The A20112 is a switch-mode power supply (SMPS) designed for the Namco System 246 and 256 arcade motherboards. Unlike standard PC ATX power supplies, the A20112 utilizes a custom form factor and a dedicated single-row output connector to interface directly with the arcade I/O board. It is a high-efficiency unit capable of delivering substantial current on the +12V rail to power the console's cooling fans and disc drives, while maintaining stable low-ripple voltage for the sensitive CPU and RAM (+3.3V and +5V).
Before analyzing the schematic, we must understand the context. The A20112 is typically a single-output or dual-output AC/DC converter with the following common specifications:
Common applications include:
Knowing the application helps in reverse-engineering: the schematic often reveals protection circuits tailored to capacitive or inductive loads.
Official schematics are rarely public. However, you have three viable paths:
Warning: Avoid scam "schematic download" sites asking for credit cards. Legitimate schematics are shared freely in repair communities.
A very specific request!
The a20112 power supply schematic is a detailed diagram of the power supply unit (PSU) used in various computer systems, including some laptops and desktops.
Here's a detailed report on the a20112 power supply schematic: a20112 power supply schematic
Overview
The a20112 power supply is a switching-mode power supply (SMPS) that converts AC power from the mains to DC power for the system's components. The schematic diagram shows the various components and their connections, which I'll outline below.
Components
The a20112 power supply schematic consists of the following components:
Connections and Signal Flow
The connections and signal flow between components are as follows:
Key Parameters
Some key parameters of the a20112 power supply schematic include:
Conclusion
(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): The A20112 connects to the Namco I/O board
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" is often a generic identifier for specific industrial or hobbyist power supply modules, information on its schematic and operation can be found in detailed guides for similar Switching Mode Power Supplies (SMPS)
. Most units in this category are compact, high-efficiency converters that transform mains AC into stable DC. Core Components and Design
A standard switching power supply like this typically follows a four-stage conversion process Input Protection & Rectification
: Filters out noise and converts AC to high-voltage DC using a bridge rectifier. Switching Circuit : Uses a high-frequency driver (like the TNY268PN IC ) and MOSFETs to "pulse" the electricity. Magnetics & Isolation : A high-frequency transformer
provides galvanic isolation while stepping down the voltage. Output Regulation
: Rectifies the high-frequency AC back to DC and uses feedback loops to maintain a constant output (e.g., 12V or 24V). Useful Technical Resources Circuit Walkthroughs : For a deep dive into the electronics, Instructables The A20112 is a switch-mode power supply (SMPS)
offers a comprehensive breakdown of SMPS sections, including under-voltage lockout and clamp circuits. Schematic Analysis Electronics For U
provides a simple 12V SMPS circuit diagram with detailed design data for transformers and duty cycles. General Basics : If you are new to power electronics, the Cadence PCB blog
explains how transformers, rectifiers, and regulators work together to ensure a smooth output. build a custom power supply from scratch?
The "A20112" identifier is most commonly associated with a 12V 10A (120W) switching power supply board often found in DIY 3D printers, CCTV systems, and universal AC-to-DC converters . The "Story" of the A20112 Power Supply
In the world of hobbyist electronics and repair, the A20112 serves as a "workhorse" component. It is frequently the core power unit for devices like the Tronxy X-3 and FLSun i3 clone 3D printers .
The Component's Journey: Unlike proprietary power bricks, the A20112 is a bare-board or aluminum-cased switching mode power supply (SMPS) designed for integration into larger projects . It is prized for its 120W capacity, allowing it to handle high-power demands—like heating a 3D printer's bed or running multiple security cameras—without failing .
The Schematic Context: While a specific "A20112" schematic is often sought by repair enthusiasts looking for "PCB0100B-V07" board layouts , its design follows the standard SMPS anatomy:
Input Filtering: Protects the circuit from power line spikes .
Rectification: Converts AC mains voltage to high-voltage DC .
High-Frequency Switching: Uses a transistor to "chop" the DC into high-frequency AC for efficient transformation .
Final Rectification & Filtering: Outputs a stable 12V DC signal . Key Technical Specifications Output Voltage Output Current Total Power Enclosure Typically an aluminum "mesh" case for cooling Common Uses 3D Printers, CCTV Monitor Systems, LED Strips Common Identification Errors
If you are searching for this part, be aware that "A20112" is also used for unrelated items in different industries: Switching Power Supply Technical Manual - ADM and MEAN WELL