S36012 Power Supply Circuit Diagram |top| -

: A series combination of heavy toroidal inductor coils and low-ESR electrolytic capacitors irons out the remaining high-frequency ripple, ensuring clean output voltage.

: Dual Pi-filters, consisting of safety X/Y capacitors and a dual-winding common-mode choke coil, prevent high-frequency switching noise from feeding back into your household mains grid. 2. Primary Rectification and Voltage Selection s36012 power supply circuit diagram

| | Possible Cause | Action Using the Schematic | | :--- | :--- | :--- | | No Output, No LED | AC power lost; Fuse blown; Input components failed. | Check voltage at "L" and "N" terminals. Visually inspect the fuse on the PCB. Check continuity of the bridge rectifier and primary capacitor. | | No Output, LED On | Start-up resistor open; PWM IC failed; MOSFET shorted. | Locate the high-value (e.g., 150k) start-up resistors feeding the PWM IC's VCC pin (e.g., pin 7 on UC3842). Measure voltage there. | | Output is Zero/Unstable | Faulty connection; Shorted output diode; Blown fuse in secondary. | Disconnect load and measure output voltage. If voltage returns, the issue is the load or wiring. If not, use the schematic to trace the secondary circuit, checking output diodes and capacitors. | | Output Voltage Low | High load; Output capacitor(s) failing; Feedback loop issue. | Measure voltage at "+V" terminal under load. Use the schematic to inspect feedback components like the TL431 and optocoupler, and check the output filter capacitors for swelling. | | Power Supply Shuts Down under Load | Overload protection triggered; Insufficient cooling. | Reduce load and retest. Check fan operation. Inspect the current-sense resistor on the primary side using the schematic. Check for overheating components. | | Excessive Ripple or Noise | Output filter capacitors dried out; Poor grounding. | Use an oscilloscope to check the output waveform. Replace the main output filter capacitors. Check the PCB ground layout. | | High-Frequency Whining/Buzzing | Loose transformer core; Failing switching capacitor. | Tighten or glue the transformer core. Inspect the snubber network components and the PWM controller's timing capacitor. | | Fan Not Working/Erratic | Faulty thermistor; Fan seized; Control transistor failed. | Locate the fan drive circuit on the schematic. Check the thermistor (RT3) and associated transistors. Power the fan directly to test it. | : A series combination of heavy toroidal inductor