Hitachi RAM-130QH5, Service Manual, Page: 53 / 84

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4. Power Supply Circuit
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Fig. 4-1 shows the power circuit.
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There are two switching power supply in Power PWB.
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Switching power supply 1 is generating the secondary power for control circuits and DC35V indoor unit 1.
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Switching power supply 2 is generating the DC12V for expansion valve and DC35V for indoor unit 2 and 3.
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Switching power supply performs voltage conversion effectively by switching transistor IC1 to convert DC330V
to high frequency of approximately 20kHz to 200kHz.
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Transistor IC1 operates as follows:
Fig. 4-1 Power circuit for P.W.B.