LG LMAB1240ST Service Manual page 25

(PROBLEM 3) Display shows all figures set, but oven does not start cooking while desired
program times are set and START pad is touched.
CONDITION
1.Setting time
does not count
down when
touching START
pad.
2. Fan motor or
oven lamp do
not turn on.
(PROBLEM 4) Oven seems to be operating but little heat is produced in oven load.
CONDITION
Output is low.
NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.
Minimum 8.5˚C temperature rise is normal condition.
CHECK
Check continuity
of secondary
switch (with
door closed).
Check the con-
nection between
CN1 connector
and P.C.B
assembly.
Check fan motor.
Check oven lamp.
CHECK
Check the
power source
voltage.
Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.
Measure the
output power.
RESULT
No continuity.
Continuity.
Continuity
No continuity
Abnormal.
Abnormal.
Normal.
RESULT
Lower than 90% of
rating voltage.
Normal.
Abnormal.
Normal.
Abnormal.
5-14
CAUSE
Defective
secondary switch.
Defective P.C.B
assembly.
Loose connection.
Defective fan motor.
Defective oven lamp.
CAUSE
Decrease in power
source voltage
with load.
Defective P.C.B
assembly.
Defective
magnetron.
REMEDY
Replace
secondary switch.
Replace P.C.B
assembly.
Connect them
tightly.
Replace fan motor.
Replace oven lamp.
REMEDY
Suggest customer
contact local
electric power
utility co. or
qualified
electrician.
Replace P.C.B
assembly.
Replace
magnetron.