Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 353

(3) Error diagnosis procedures at the indoor unit side
To diagnose the error, measure the voltage (AC, DC), resistance, etc. at each connector around the circuit board of indoor unit
based on the inspection display or the operation state of unit (no operation of compressor or blower, no switching of 4-way valve,
etc.). If any defective parts are discovered, replace with the assembly of parts as shown below.
(a) Single-unit replacement parts for circuit board of indoor unit. (Peripheral electric parts for circuit board.)
Indoor unit printed circuit board, thermistor (return, heat exchanger), operating switches, limit switches,
transformers, fuses.
Note (1) Use normal inspection methods to determine the condition of strong electrical circuits and fro-
zen cycle parts.
(b) Replacement procedure of indoor unit microcomputer printed circuit board
Microcomputer printed circuit board can be replaced with following procedure.
(i) Confirm the parts numbers. (Refer to the following parts layout drawing for the location of parts number.)
Model
FDTN(P), FDEN(P)
FDKN(P)208
Parts layout on the indoor unit PCB
Models: FDTN (P), FDEN (P) series
Power
supply
Transformer, primary side
Model: FDKN (P) series
For test mode selection
(Shortcircuit : Test mode)
SW5
SW3
SW4
External input /
output function
Receiving unit
(
Backup switch
Indiction lamps
Parts number
PJA505A069
PHA505A007
9 7 6 3 4 8
52X6
52X5 52X4 52X7 52X1 52X2 52X3
Transformer, secondary side
(
Power supply connector
for PCB
Thermistor
(Return air, heat exchanger)
)
Model
FDKN(P)258, 308
FDT, FDR, FDU, FDFL
SW3
13
SW3 SW2
SW4
SW5
CNV CNT
External input /
) output function
Transformer, secondary side
(
Power supply connector
for PCB
Transformer, primary side
Power
supply
FDT ( N ) -H
Parts number
PHA505A008
PJA505A092Z
SW2 (Only case of FDTN)
(Optional : For auto lift panel)
SW4
For test mode selection
(Shortcircuit : Test mode)
Thermistor
(Return air, heat exchanger)
SW5
Receiving unit
( )
Backup switch
Indiction lamps
)
351