No VFD display
Check whether the
voltage between VFD
F1&VFD F2 is AC24V
Go
No
No
No VFD display
Yes
Fix the connection power board
CN502 & front board JP1
Check whether the voltage
+5V,+12V on the front board
is Normal work or Not.
Check DC5V to AC 24V switch circuit
Replace U4 or VFD.
Yes
Trouble shooting chart
5-5