Disclaimer: Run 3 is an independent website. It is not affiliated with any organizations.
Copyright © 2026 Iconic Canvas
Always check the glass fuse on the board. If it’s black, a MOSFET likely shorted.
This usually consists of two high-power MOSFETs or IGBTs mounted to a large heatsink. These are the most common points of failure if the lathe is overloaded.
AC mains enter through a fuse and pass through a bridge rectifier. jymc220bi schematic full
If you hear the relay click but the motor doesn't spin, check the brushes on the DC motor itself. Finding Documentation
A low-ohm power resistor (shunt) senses the current flowing to the motor. If it exceeds a preset threshold, the control IC reduces the PWM duty cycle to protect the board. Common Troubleshooting Tips Always check the glass fuse on the board
The is a widely used motor speed controller frequently found in mini-lathes, such as the Sieg C2/C3 and their various brand equivalents like Grizzly or Harbor Freight. Finding a "full" schematic for this specific board is essential for DIY repairs, as these controllers often fail due to component fatigue or motor stalls. Overview of the JYMC-220B-I Controller Go to product viewer dialog for this item.
Use a multimeter to check for continuity between the Drain and Source pins. If they are shorted, the motor will likely run at full speed or not at all. These are the most common points of failure
If you are working with this board without a physical diagram in hand, check these common failure points first:
Copyright © 2026 Iconic Canvas