Hitachi RAC-18SX8 Service Manual page 151

(5) NF coils for C001, C002, C004, C005
These absorb electrical noises generated during a
compressor run. At the same time, they absorb external
noises coming in through the power line, thereby protecting
the electronics parts.
(6) Surge absorber and varistors 1 and 2
These absorb induced lightning and other external surges.
DC VOLTAGE
MESUREMENT
POINT(+)
DC VOLTAGE
MESUREMENT
POINT(-)
IPM
・The equipment is high-voltage. Therefore guard particularly against electric shocks. Guard also against short-
circuits due to erroneously connected measuring equipment. The board would otherwise become destroyed.
2. Board-purpose power supply circuit
The voltage specifications for the power supply circuit are as follows:
[Checkpoints]
Output Specified
name
voltage
±0.4
5 V
5 V output
±1
12 V
12 V output
±1.5
15.5 V
16 V output
B-12 V
＋3
12 V −1
output
・Check the corresponding voltage. If it satisfies the above voltage specifications, the board-purpose power supply circuit
should be normal.
TEST SWITCH
OUTDOOR FAN
MOTOR CONNECTOR
Main load ±
Microcomputer
Tester positive terminal: R18 (5 V display)
Thermistor
Tester negative terminal: J17 (0 V display)
Microcomputers
Tester positive terminal: J20 (12 V display)
IC2, 3, and 4
Tester negative terminal: J17 (0 V display)
Relay circuit
Compressor-purpose IPM Tester positive terminal: J21 （16Vdisplay)
IPM for DC fan Tester negative terminal: J17 （0Vdisplay）
Tester positive terminal: J9 （B-12V display）
Expansion valve
Tester negative terminal ： J7 （B-0V display）
※Be sure to ground the outdoor unit.
If ungrounded, the noise filter mentioned above will not
function normally.
※If the outdoor unit remains ungrounded, the "surge
absorber" and "varistor 1" will not function.
Be sure to ground the equipment.
CONTROL P.W.B.
CN30 FOR SELF-CHECK
measuring locations
Failure diagnosis lamp LD301
Failure diagnosis lamp LD301
Failure diagnosis lamp LD301
Failure diagnosis lamp LD301
– 184 –
LD301
LD302
LD303
Typical failure modes conceivable in an output failure
(Ref)
Outdoor unit inoperable with no display
Outdoor unit inoperable with no display
Blinks 3, 4, or 12 times and stops.
Blinks 5 times and stops.