Mitsubishi Electric CITY MULTI PUHY-P400YEM-A Service Handbook page 149

(8) Transmission Power Circuit (30 V) Check Procedure
If " " is not displayed by the remote control, investigate the points of the trouble by the following procedure and correct it.
No. Check Item
1 Disconnect the transmission line from TB3
and check the TB3 voltage.
2 Check if the following connectors are
disconnected in the outdoor unit's control
box.
MAIN Board: CNS1, CNVCC3, CNVCC4
INV Board: CNVCC2, CNVCC4, CNL2,
CNR, CNAC2
3 Disconnect the wires from CNVCC3 on the
Main board and check the voltage between
pins 1 and 3 on the wire side of the
CNVCC3.
Tester + ..... 1 pin
Tester ..... 3 pin
4 Disconnect the wiring from CNVCC2 on the
INV board and check the voltage between
pins 1 and 3 of CNVCC2.
Tester + ..... 1 pin
Tester ..... 3 pin
5 Disconnect the wiring from CNL2 on the
INV board, and check the resistance at
both ends of choke coil L2.
6 Disconnect the wiring from CNR on the INV
board, and check the resistance at both
ends of R7.
7 Check the resistance at both ends of F01
on the INV board.
8 Check the voltage between pins 1 and 3 of
CNAC2 on the INV board.
9 Check the voltage between L2 and N on
power supply terminal block TB1.
Judgment
DC24~30 V
Except the above-mentioned
Connector disconnected
Except the above-mentioned
DC24~30 V
Except the above-mentioned
DC24~30 V
Except the above-mentioned
0.5~2.5
Except the above-mentioned
19~25
Except the above-mentioned
0
Except the above-mentioned
AC198~264 V
Except the above-mentioned
AC198~264 V
Except the above-mentioned
-146-
Response
Check the transmission line for the following, and
correct any defects.
Broken wire, short circuit, grounding, faulty
contact.
Go to No. 2
Connect the connectors as shown on the electric
wiring diagram plate.
Go to No. 3
Check the wiring between CNS1 and TB3 for the
following, and correct any defects.
Broken wire, short circuit, grounding, faulty
contact.
If there is no trouble, replace the Main board.
Go to No. 4
Check the wiring between CNVCC2 and
CNVCC3 for the following, and correct any
defects.
Broken wire, short circuit, grounding, faulty
contact.
Go to No. 5
Go to No. 6
Replace choke coil L2.
Go to No. 7
Replace R7.
Go to No. 8
Replace F01
Replace the INV board.
Go to No. 9
Check the wiring to CNAC2 for the following and
correct any defects.
Broken wire, faulty contact.
Check the power supply wiring and base power
supply, and correct any defects.