The PWM Control CircuitAt the heart of the schematic is a dedicated PWM controller chip (often a TL494 or similar SG series IC). This chip generates a high-frequency signal. By varying the "duty cycle" of this signal via the front-panel potentiometer, the user tells the board how much power to send to the motor.
AC_L --- FUSE --- MOV --- DIODE BRIDGE ---+--- BULK_CAP --- IC_VIN | AC_N --------------------+---------------+ | (Return path through IC_GND) jymc220bi schematic 2021
Apply low-voltage AC (e.g., 12VAC) to the input for safe testing. Measure the LM324 supply pins (pin 4 = V+, pin 11 = V-) for correct voltage. The PWM Control CircuitAt the heart of the
A common variant is the , which is nearly identical but designed for lower-current applications. The JYMC-220A-I is rated for a 6.0 ADC output , compared to the 12 ADC rating of the standard JYMC-220B-I board. Another closely related variant, the JYMC-220B-II , is known to be used in lathes such as the Grizzly G0768Z series. AC_L --- FUSE --- MOV --- DIODE BRIDGE
PWM (Pulse-Width Modulation) via an integrated SCR/MOSFET switching matrix
Based on field reports and repair logs from CNC forums, here are the top issues:
Working with the JYMC-220B-I involves potentially lethal voltages. Always observe these safety guidelines: