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
: 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) a20112 power supply schematic
: 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 typically refers to a 14-watt guitar amplifier power
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.
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.
Provide a table-style BOM when transferring to PCB CAD; include reference designators, values, footprints, and supplier part numbers.
AC Input Section:
Primary Side Control:
Secondary Side:
Feedback Circuit:
Because the A20112 uses a TL431 feedback network, you can modify the output voltage within 20% safely.