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ICP2
35V
ICP1
ZD121
(20V zener)
0V
12V power circuit
5V power
circuit
12V line
indoor DC fan motor
5V power line
M
˷
Other Caution
˹
1.Cautions for ICP (IC protector)
(1) Be careful not to short-circuit during servicing.
ĺ
If short-circuited, ICP will instantaneously open.
(2) If ICP Opens, remove cause, and then replace ICP.
ĺ
If repair is incomplete, ICP may open again.
Lock
Q111
S
D
G
S: Source
D: Drain
G: Gate
OK
Prohibited
(between gate (G) and 0V)
Prohibited
0V
IC111
ICP1
35V
Ɣ
Q111 is MOS-FET and its gate terminal is a high input resistor, If tester probe, etc, touches gate (G), gate drive
circuit and 0V line, Q111 will be turned on continuously, over-current will flow, and ICP1 may be blown, causing
trouble in Q111.
When switching waveform of Q111 is to be observed, measure gate (G) and drain (D) with source (S) as base
point.
2. CN3 (Power), CN10 (Fan Motor), CN13 (Temporary switch-P.W.B.) and CN4 (Indicating P.W.B.) are connectors
with lock mechanism: Release lock with finger before disconnecting.
3. Do not touch the following parts during voltage and waveform check; ICP1 may be blown or Q111
may be damaged:
4. Do not connect/disconnect CN10 (fan motor connector) when power is being supplied to P.W.B.: Over-current
will flow to fan motor and P.W.B. (microcomputer, IC, etc.) and cause malfunction. Always connect/
disconnect CN10 with power turned off.