Sharp AY-XP9LSR Service Manual page 33

2. Troubleshooting of outdoor unit electric components
NO
Does LED light?
YES
NO
Does LED flash?
YES
Normal
3. Caution in checking printed circuit boards (PWB)
3.1. Non-insulated control circuit
The GND terminals of the low-voltage circuits (control circuits for microcomputer and thermistors and drive circuits for expansion valve and relays) on
the control printed circuit board (PWB) are connected to the compressor drive power supply (320-VDC negative terminal). Therefore, exercise utmost
caution to prevent electric shock.
If a measuring instrument used for the test is grounded, its chassis (ground) has the same electric potential as the 0-V probe. Since non-insulated cir-
cuits have the following voltage potential difference from the ground, connection of the grounding wire results in a short-circuit between the 0-V line
and the ground, thus allowing an excessive current to flow to the tester to cause damage.
If the sheaths of the thermistor lead wires or expansion valve lead wires inside the outdoor unit become damaged due to pinching by the front panel
or other metal parts or contacting a pipe, a high voltage can flow and destroy the circuits. To prevent these problems, carefully conduct assembly
work.
YES
Is 230 V applied Is voltage between
between 1 and IPM pins (20) and
N on outdoor (24) 320 V or
unit terminal higher?
board?
NO
Check indoor
unit.
Is switching power
supply output of
13 VDC, 15 VDC
produced?
Is 5 VDC output
produced?
NO
5/ Short-circuit in DC fan motor
Short-circuit in IPM
Short-circuit in diode bridge
Blown fuse
Defective electrolytic capacitor
Wire disconnection, PWB pattern damage
YES
Short-circuit in PAM IGBT (Q5)
NO
Defective switching power supply circuit
Malfunction of 3-terminal regulator IC4, IC1
Short-circuit in expansion valve coil
Malfunction of transistor array IC7
Solder contact or other problems
YES
NO
Malfunction of 3-terminal regulator IC4, IC1
YES
Microcomputer oscillator error
Malfunction of microcomputer reset IC
Malfunction of microcomputer
Malfunction of serial signal circuit
Check wiring between indoor and outdoor units.
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AYXP9LSR