LG LMVH1750SB Service Manual page 35

(TROUBLE 2) Microwave oven does not operate at all, Display window does not display any figures,
and no input is accepted.
CONDITION
1. Fuse blows.
2. Fuse does not
blow.
CHECK
Check continuity
of monitor
switch (with
door closed).
Replace fuse
Check continuity
of primary
switch (with
door opened).
Disconnect one
side of the wire
lead connected
from transformer
to the high
voltage
capacitor and
operate the unit.
Check continuity
of magnetron
thermostat.
Check continuity
of power supply
cord.
RESULT
Continuity.
No continuity.
Continuity.
No continuity.
Normal.
Fuse blows again
No continuity.
Continuity.
No continuity.
7-25
CAUSE
Malfunction of the
monitor switch.
Shorted contact at
the primary switch.
Defective high
voltage capacitor.
Defective high volt-
age transformer.
Defective
thermostat.
Defective power
supply cord.
REMEDY
Replace fuse,
primary, monitor
switches, and
RELAY(RY8) of
P.C.B Assembly.
Replace fuse,
primary, monitor
switches, and
RELAY(RY8) of
P.C.B Assembly.
Replace high
voltage capacitor.
Replace high volt-
age transformer.
Replace
thermostat.
Replace power
supply cord.