Hitachi RAM-68NP3B, Service Manual, Page: 46 / 79

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Check each voltage. If the above specifications are satisfied, the main power supply circuit can be considered
normal.
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Due to high voltage, be particularly careful to avoid electric shock. Further, take care to avoid short-circuit
accidents caused by incorrect connection of measuring instruments. Otherwise, the board could be damaged.
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Even after the power is turned off, an electric charge remains in the smoothing capacitor, and a voltage of 260V to
360V is applied between the terminals of the smoothing capacitor.
LD351 blinks 3, 4 or 12 times and then stops.
LD351 blinks 2, 4, 8 or 14 times and then stops..
LD351 blinks 8 times.
LD353 (green) does not blink. LD351 (red) does
not blink. Outdoor unit does not operate.
LD351 (red) blinks 5 or 6 times (related to
refrigerant cycle error) and stops.
LD401 ~ LD403 (green) do not light or blink.
Examples of Possible Failure Modes for
Output Failures (for Reference)
Tester
⊕
terminal: 16V indicator (J9)
Tester
⊖
terminal: 0V indicator (C891)
Tester
⊕
terminal: 12V indicator (WH65-2)
Tester
⊖
terminal: 0V indicator (C891)
Tester
⊕
terminal: 5V indicator (R814)
Tester
⊖
terminal: 0V indicator (C891)
Tester
⊕
terminal: B-5V indicator (J4)
Tester
⊖
terminal: B-0V indicator (J5)
Tester
⊕
terminal: B-12V indicator (R120)
Tester
⊖
terminal: B-0V indicator (J5)
Tester
⊕
terminal: B-15V indicator (L107)
Tester
⊖
terminal: B-0V indicator (J5)
± Measurement Location
Compressor IPM
DC fan drive circuit
Converter circuit
IC2, 3, 4, 5, 6
relay circuits
Inverter
microcomputer
Main
microcomputer
thermistor
Expansion
valve
Indoor/outdoor
communication
Primary Load
15.5
±1.5
V
12
±1
V
5
±0.4
V
5
±0.4
V
12
+4,-2
V
15.5
±1.5
V
Voltage
Specification
16V output
12V output
5V output
B-5V output
B-12V output
B-15V output
Output
Name
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Inverter Microcomputer Power Control
The power to the inverter microcomputer is turned ON/OFF by commands from the main microcomputer.
Q502, PQ102, Q101, and Q102 are related.
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Specifications and Checkpoints for Main Power Supply Circuits