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4-1
No display on VFD, and buttons do not work
No
No
No
Yes
Yes
No display on VFD, and
buttons do not work
Check every supply
voltage on main board is
normal
Refer to Power supply board part
Check the U3’s pin 2,4,8 arrive the
U3’s pin 6,8,9 connect condition
Correct connection
Replace U2 or VFD
Yes
Yes
Yes
No
Check-24V+12V,VCC(+5v)
voltage on the power and front
board
Check the front board
signals on R24, R25,
R28.(SCK,SDA,STB)
1.Check whether bad solder
exists on U2 and pins of VFD,
2.Check whether the circuit
connected to K1, K2, K3, K4, K5
and K6 is broken.
Fix the connection JP1 on front board
and CN1 on power board
Trouble shooting chart
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