A20112 Power Supply Schematic (SAFE ✰)

power supply schematic refers to the circuit diagram for the HP JC44-00250A

Low Voltage Power Supply (LVPS) board. This component is a critical power module used in several high-end HP LaserJet printers to provide stable voltage to the logic board and laser assembly. AliExpress Compatible Models a20112 / JC44-00250A board is compatible with the following HP LaserJet AliExpress Managed MFP Series : E72525, E72530, E72535 MFP Series : M72625, M72630 Color Managed Series : E77830, E77822, E77825, E77422 Key Specifications & Troubleshooting Part Numbers : Often listed as JC44-00250A JC44-00249A

: Restores power when a printer fails to turn on, shows error codes, or exhibits unstable performance. Service Manual

: Detailed pinouts and engine installation guides for these models can be found in the HP LaserJet MFP M72625/M72630 Engine Install Guide HP LaserJet E72525 Service Manual Common Failure

: Printers that press the power button but do not turn on often require a reset of this power module. AliExpress Procurement Options

If you are looking to purchase a replacement or find a specific technician-level schematic:

: You can find this board at specialized parts retailers like or on marketplaces such as AliExpress : Bulk orders are typically available through on this board with a multimeter?

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 a20112 power supply schematic

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)

: 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

The Victoria 20112 is a revered boutique recreation of the classic Tweed Deluxe 5E3 circuit, known for its "creamy and warm" tone. For many amp technicians and DIY enthusiasts, looking at its power supply schematic is the first step in diagnosing issues like volume drops, sputtery sounds, or complete power failure. The Core of the 20112 Power Supply power supply schematic refers to the circuit diagram

The 20112 typically follows the traditional tube-rectified design, often utilizing a 5Y3GT or 5AR4/GZ34 rectifier tube to convert AC power from the transformer into the high-voltage DC (B+) needed for the vacuum tubes.

Rectification & Filtering: High voltage AC enters the rectifier tube and emerges as "pulsating" DC. This is smoothed out by high-voltage electrolytic capacitors (the "filter caps").

The "Dog House": In these vintage-style builds, these large capacitors are often housed in a metal cover under the chassis known as the "dog house".

Modifications: Some 20112 owners add a 1/2 power switch or an attenuator like a hotplate to make the amp more manageable for smaller gigs or home use. Common Troubleshooting Stories

When a 20112 stops working, techs often look for these common "characters" in the story of the circuit:

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.

Part 2: The Core Topology of the A20112 Schematic

Almost every A20112 unit uses a Flyback Converter Topology. This is the industry standard for power levels under 100W because of its simplicity and isolation capability.

Here is the block-level breakdown of the A20112 power supply schematic: Part 2: The Core Topology of the A20112

Section 4: How to Read and Use the A20112 Schematic for Repair

4. Detailed Schematic — Functional Sections

Below are detailed functional descriptions and reference circuit suggestions. For clarity, two reference implementations are described: A) Isolated flyback (mains input), B) Non-isolated synchronous buck (DC input).

4.1 AC Input and EMI Filtering (mains)

• IEC inlet → slow-blow fuse (F1, 2–3 A rating depending on inrush)
• NTC inrush limiter (e.g., NTC 10D-9) in series with hot line
• EMI filter: Common-mode choke (CMC) rated for mains, X2 safety capacitor across line (0.1–0.22 µF X2), two Y capacitors (47 nF) from each line to earth
• Safety-rated mains surge MOV (optional) and gas discharge tube for lightning protection
• Earth connection to chassis

4.2 Rectification and Bulk Filtering

• Bridge rectifier: 1 A–6 A rating depending on selection (e.g., MB6S/KBPC)
• Bulk capacitor: 100–470 µF, 200–400 V electrolytic (low ESR), use two in parallel for ESR reduction; ripple current rating adequate
• DC bus EMI decoupling: 0.1 µF ceramic across DC rails

4.3 DC-DC Regulation — Flyback (isolated) reference

• Primary switching MOSFET (e.g., N-channel 700–900 V rated such as STP10NK60Z or SiC alternatives for efficiency)
• Controller IC with primary-side regulation or PWM: e.g., TOPSwitch, UCC28740, or similar
• Transformer: custom flyback transformer with turns calculated for primary clamp, duty cycle, and isolation; primary inductance for desired switching frequency (50–250 kHz)
• Snubber: RCD clamp or active clamp to protect MOSFET
• Secondary rectifier: Schottky diode rated 30–40 V, or synchronous MOSFET for higher efficiency (e.g., Si4425)
• Output LC: low ESR electrolytic (220–470 µF, 25 V) + 10–47 µF solid polymer + 10–22 µF ceramics; output inductor if post-regulation or synchronous rectifier requires it

4.4 Output Filtering and Sensing

• Place bulk electrolytic close to output connector
• Add 10 µF tantalum or polymer for transient response and ceramic 1 µF decoupling
• Voltage sense via resistor divider into TL431 (if using optocoupler feedback) or into controller

4.5 Protection: Overcurrent, Overvoltage, Thermal

• Current sense resistor on primary or low-side MOSFET sense for secondary OCP; use comparator in controller to shut down or foldback
• Implement hiccup mode or latch with manual reset (use PTC or latch circuits)
• OVP: zener clamp on secondary with crowbar SCR if severe OVP risk; simpler: comparator to disable switching via controller
• Thermal: thermistor on PCB near MOSFET and transformer feeding controller’s thermal shutdown input or microcontroller

4.6 Control and Feedback Loop

• Use TL431 with optocoupler (e.g., PC817 or MOC) for isolated feedback; include compensation network (R-C) around TL431 to ensure loop stability
• Compensation: Phase lead/lag network chosen based on output filter LC; target phase margin >45°
• Soft-start capacitor to limit inrush and prevent overshoot at startup

4.7 Indicators and Connectors

• Power LED with series resistor from 12 V output
• Output connector: 2.1 mm barrel jack or screw terminal rated >3 A
• Test points for sense, Vout, ground, current sense