Service Manual

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6. Circuit board diagrams
Circuit board diagrams and check points
(1) Control circuit board
Caution:
Before servicing (including replacing the circuit boards), be sure to turn off the power supply isolator
and check that all the LEDs on the control circuit board and power circuit board are not lit. A large-
capacity electrolytic capacitor on the circuit board may carry voltage for several minutes after the iso-
lator is turned off.
TM2
External control input
Voltage-applied signal
Volt-free contact signal
1 2
Y Z
Lot number indication
Fed with power: lit
Not fed with power: unlit
Remote controller
power supply indicator
(LED3 Green)
Error indicator
(LED1 Green)
Normal: unlit
Error: blinking
During delay operation: lit
M-NET indicator
(LED2 Red)
Registered: unlit
Not registered: lit
M-NET communication error: blinking
Fed with power: lit
Not fed with power: unlit
Power supply indicator
for the circuit board
(LED4 Red)
Function selection switch
SW2
SW5
Address setting switch
(tens digit)
Address setting switch
(ones digit)
SW12
SW11
Model selection switch
SW6
Indication of the microcomputer
software No.
GND
(Insulated)
13 V DC
(Insulated)
CN19, CN14
Power circuit board
connection
Power for the circuit
Power for the circuit
TM4
Remote controller
transmission cable
11 to 14 V DC
TM3
Monitor output
Circuit board name
CN32
Remote/Local switching input
CN12: For rewriting the
microcomputer software
CN38: For rewriting the
microcomputer software
CN50: For optional components
External monitor output device
CN26: For optional components
CO
2 sensor signal input
0–10 V DC signal input
External bypass switching input
Output ON: 0 Ω
Output OFF:
∞
Ω
TB5
M-NET transmission cable
A B
S
M-NET transmission cable
24 to 30 V DC
(When using M-NET)
Shielded wire
CN34: For optional components
CO
2 sensor display output
CN35: For optional components
CO
2 sensor error input
CN7
Outdoor air (OA) thermistor
CN5
Return air (RA) thermistor
CO2 sensor
power supply indicator
(LED5 Green)
CN17
External control input
Fan speed switching
CN105: For optional components
IT communication transmission cable
CN23: For optional components
CO
2 sensor power supply output
CN13, CN21
Power circuit board
connection [2]
(*Note 1)
*Note 1:
The connection is available only for the following models.
LGH-F940RVX2-E, LGH-F1200RVX2-E