Hitachi RAC-50YH7, Service Manual, Page: 84 / 103

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1. Power does not come on (no operation)
Is AC 220-240V AC being generated
between terminals L and N on the
outdoor unit terminal board?
Is DC 35V being generated between
terminals C and D on the outdoor
unit terminal board?
Check the indoor/outdoor unit
connection cable, and correct any
defective section (wrong connection,
incomplete insertion reversed).
Check AC outlet and breaker, and
repair any defective part.
Check the outdoor unit power circuit,
and repair the defective section.
Is DC 35V being generated between
terminals C and D on the terminal
board?
Are control voltages (12V, 5V)
being generated normally? Check according to the proper method
for checking the power circuit.
No No
No
No
Yes
Yes
Do the air deflectors perform initial
operation when the power supply is
turned on and off? Check the indication P.W.B.
connection cord and light receiving
unit.
No
No
Is the microcomputer reset input
(pin 7 ) Hi ?
Replace the control P.W.B
Perform final operation check.
Check the reset circuit, and repair
any defective section.
Yes
No
Is the microcomputer clock signal
10MHz at pin
10 11
being
generated normally?
Replace the microcomputer and
oscillator.
Yes
Yes
Yes
CHECKING INDOOR UNIT ELECTRICAL PARTS