Hitachi Summit RAC-18YH6, Service Manual, Page: 38 / 96

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Input
Voltage
0V
0V
0V
Voltage
Smoothed
Voltage
Fig. 1-4
(3) C021 and C022
This smoothes the voltage rectified for operating the
compressor.
When the input voltage is taken for the sine wave as
shown in the top of Fig. 1-4, it is rectified by the DB2
and becomes the waveform as shown in the middle
of Fig. 1-4. After that, the voltage is smoothed by the
C021 and C022, and becomes the waveform shown
in the bottom of Fig. 1-4.
(4) DB1 and C41
The DB1 rectifies the input voltage and the C41
smoothes it for the control power supply.
If the units above have any failure, the control power
supply won’t operate. In such a case, replace the
main P.W.B.
(5) C001 to C003, C011, L101, and L102
They absorb electrical noise generated during
operation of compressor, and also absorb external
noise entering from power line to protect electronic
parts.
Be sure to connect the earth cable between the indoor unit and the outdoor unit. Otherwise, the
noise filter circuit won’t operate properly.
(6) SA1 and VS1 to VS3
These surge absorber and varistors absorb external power surge such as induced thunder.
Be sure to connect the earth cable between the indoor unit and the outdoor unit. Otherwise, the
surge absorber and the varistors won’t operate.
(7) R002 and R007
The resistor R002 protects the rush current when the power is turned on while the resistor R007
protects the rush current when the compressor starts.
When the R002 has any failure, the control power supply won’t operate. When the R007 has any
failure and a strong rush current is generated, the DB2, C021 or C022 may be damaged.