Check The Control P.w.b. (Power Circuit) - Hitachi RAS-18FH6 Service Manual

4. Check the control P.W.B. (power circuit)

Is 35V or 20V being output
1
at pin 5 relative to 0V at
pin 3 of CN3?
Yes
Is 12V or 7V being output
2
at (+) relative to 0V at (-) of
C114?
Yes
Is DC5V being generated?
Yes
: When the unit is not in operation, the voltage across the 35V line may drop to 20V.
1
: When the unit is not in operation, the voltage across the 12 V line may drop to 7V.
2
No
Check to see if the connection cables are
disconnected or reversed.
If normal, check the outdoor unit P.W.B.
No
Is ICP1 normal?
Normal if it is less than 1 .
Blown (open) if it is 1 or more.
Yes
(Normal)
Has the terminal board
thermal fuse blown (open)?
No
Replace Q111 and IC111.
No
Perform final operation check.
No
Replace ICP1. Check if the air
deflector motor is shorted, and
IC111, Q111, C114, ZD121 are
defective.
If shorted / defective, ICP1 will be
open again.
Yes
(Open)
Replace the terminal board.
Insert the connection cable
securely.
Replace IC121. Check if a short
occurs in the 5V line.
If the 5V line is shorted, ICP1 will
be open again.
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