A20112 Power Supply Schematic Jun 2026

4.2 Rectification and Bulk Filtering

Components like the LM7812 regulator can generate significant heat and often require a heat sink. a20112 power supply schematic

Apply an external 12V (current-limited) to the output. Measure TL431 Ref pin – should be 2.5V. If not, check R12/R13. Then check optocoupler LED voltage (should be ~1.1V). If both are fine, the optocoupler transistor side on the primary may be open. a20112 power supply schematic