Toshiba MMU-AP0074YH-E Service Manual page 102

Procedure 2: replacing P.C. board
1
Replace the faulty P.C. board with a service P.C. board.
Be sure to replicate the old jumper setting (removal), switch setting (SW501), and connector short-circuit
setting (e.g. CN34) on the service P.C. board. (See the diagram at below.)
If a short-circuiting plug had been used on the replaced
P.C. board, reuse it on the service P.C. board.
2
It is necessary to establish a one-to-one correspondence between the indoor unit being serviced
and the remote controller.
Turn on the indoor unit using one of the methods described below according to the system configuration.
(1) Single (stand-alone) operation
Turn on the indoor unit and proceed to Procedure 3.
(2) Group operation
A) If it is possible to selectively turn on the indoor unit being serviced
Turn on the indoor unit being serviced and proceed to Procedure 3.
B) If it is not possible to selectively turn on the indoor unit being serviced (Case 1)
a) Temporarily disconnect the group control wiring from terminals A and B of the indoor unit being serviced.
b) Connect the remote controller wiring to the terminals, turn on the indoor unit, and proceed to Procedure 3.
* If this method cannot be used, proceed to the alternative method described below (Case 2).
C) If it is not possible to selectively turn on the indoor unit being serviced (Case 2)
a) Remove the CN41 connectors of all other indoor units in the same group.
b) Turn on the indoor unit and proceed to Procedure 3.
Case 1
Indoor unit
Case 2
Indoor unit
Remove CN41
connectors of all
other indoor units
in same group.
* Be sure to restore the temporarily removed group control wiring and CN41 connectors to their initial states after
Procedure 3 has been completed.
From left: CN112, 111 and 110
Indoor unit
P.C. board P.C. board
Group control wiring
Indoor unit
P.C. board P.C. board
Group control wiring
101
If a short-circuiting plug had been used on the replaced
P.C. board, reuse it on the service P.C. board.
Indoor unit (one being serviced)
Service P.C. board
Remove group control wiring from terminals
A and B of indoor unit being serviced, and
connect remote controller wiring.
Remote controller
Indoor unit (one being serviced)
Service P.C. board
Remote controller