Mitsubishi Electric MXZ-SM72TAM-U1 Service Manual page 98

8-7-5. Check method of M-NET power circuit board
M-NET power circuit board check
Check the voltage between M1 and M2 on the
transmission terminal block TB3.
24–30 V DC?
TB1
L1
L2
L3
208/230 V AC
± 10%
OCH800A_98
No
Yes
(24–30 V DC )
Is the incoming main voltage
208/230 V AC ±10%?
Disconnect the branch box - outdoor transmission
wiring from the terminal block TB3 , and check the
voltage between M1 and M2 on TB3 again.
• Check wiring.
Normal
• Replace the M-NET power circuit board.
Noise filter
circuit board
LI1
3
LI2
LI3
1
CNAC1 (WH)
208/230 V AC
± 10%
Note: To check the voltage of the parts on this board with a
multimeter is difficult due to its location.
Test points are limited.
No
Yes
(208/230 V AC )
Yes (24–30 V DC )
24–30 V DC?
No
CN1
• Check breaker and incoming power
supply.
• Check power circuit board.
• Check wiring.
• Correct the short circuit point on
the M-NET transmission line.
M-NET Power circuit board
CN2
Multi controller
1 2 3 4
circuit board
CNS1
2 1
(RD)
TB3 M1 M2
To indoor unit
24-30 V DC
CN102
(WH)
24-30 V DC
(Non-poler)