LG LTM9020W Service Manual page 29

(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 thermostat.
Check continuity
of power supply
cord.
RESULT
Malfunction of the
Continuity.
monitor switch.
No continuity.
Continuity.
Shorted contact at
the primary switch.
No continuity.
Defective high
Normal.
voltage capacitor.
Defective high volt-
Fuse blows again
age transformer.
No continuity.
Defective
thermostat.
Continuity.
Defective power
No continuity.
supply cord.
-28-
CAUSE REMEDY
Replace fuse,
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
Replace fuse,
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
Replace high
voltage capacitor.
Replace high volt-
age transformer.
Replace
thermostat.
Replace power
supply cord.