Schematic Culprit: Shorted input bridge rectifier diodes or a punctured primary electrolytic filtering capacitor.

Correct wiring is critical to avoid damaging the SCR or the LM324 logic chips. The board typically features clearly labeled terminal blocks:

A low-value, high-wattage resistor that senses output current. If the load exceeds 12A, the control circuit reduces voltage, protecting the motor. 3. JYMC-220B-I Schematic Diagram Overview (Typical)

variant, which shares many similarities with the -I model, including the potentiometer and line filter configurations. 2. Circuit Analysis & Trimpot Functions

Current limit or IR compensation to maintain speed under load.

Disconnect input power entirely. Use a multimeter to test continuity across the main power SCR components mounted directly along the primary aluminum cooling heatsink. Replace any shorted components or swap out the entire logic board assembly. Symptom 2: Blown Main Line Fuses Upon Powering On

): A 6.3A to 12A fast-acting fuse sits on the hot AC rail to protect against catastrophic component shorts. Suppresses grid voltage spikes and surges.

: 0–90V DC (for 110V units) or 0–180V DC (for 220V units). Current Rating : Typically 12A to 13.5A DC.

AC mains enter through a fuse and pass through a bridge rectifier.