A20112 Power Supply Schematic -

For higher current applications, the schematic will show an error amplifier topology using Zener diodes as voltage references, driving heavy-duty NPN/PNP pass transistors (such as the 2N3055 or TIP2955 ) mounted to external aluminum heatsinks. 3. Interpreting Critical Schematic Symbols on the A20112

If the input to the regulator IC is correct but the output is dead or significantly below spec: Check for downstream shorts pulling the rail down.

The controls power MOSFETs to "shape" the current, ensuring it stays in phase with the voltage. a20112 power supply schematic

High-capacitance values, typically ranging from , rated for at least or higher.

Based on technical discussions and common repairs for this unit, the power supply generally includes the following sections: Input Stage For higher current applications, the schematic will show

Here’s a quick breakdown of what you’ll typically find in the :

[AC Input] ──> [Input Protection/Filtering] ──> [Rectification] ──> [Smoothing] ──> [Voltage Regulation] ──> [Stable DC Output] 1. Input Protection and EMI Filtering The circuit begins at the AC input terminal. The controls power MOSFETs to "shape" the current,

If you are repairing or building a circuit based on this model, keep these common issues in mind: Noisy Potentiometers:

| 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. |

If you are working with an A20112 schematic for repairs, remember: