LG MH-657PL, Service Manual

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5-15
(TROUBLE 3) Display shows all figures set, but oven does not start cooking while
desired program times are set and START pad is touched.
(TROUBLE 4) Oven seems to be operation but little heat is produced in oven load.
CONDITION CHECK RESULT CAUSE REMEDY
1.Setting time does
not count down
when touching
START pad.
2. Fan motor or
oven lamp
do not turn
on.
No continuity.
continuity.
No continuity.
Continuity.
Check the con-
nection between
connector and
P.C.B assembly.
Defective
secondary switch. Replace
secondary switch.
Defective P.C.B
assembly. Replace P.C.B
assembly.
Check continuity
of secondary
switch (with
door closed).
Check fan motor.
Check oven lamp.
Abnormal.
Abnormal.
Normal.
Defective fan
motor.
Defective fan
motor.
Replace fan
motor.
Replace fan
motor.
Loose connection.
Connection then
tightly.
CONDITION CHECK RESULT CAUSE REMEDY
Output is low.
Lower than 90% of
rating voltage.
Normal.
Abnormal.
Abnormal.
Measure the
output power.
Disconnect the
wire leads from
relay 2 and check
on and off time
with multitester.
Defective P.C.B
assembly. Replace P.C.B
assembly.
Decrease in power
source voltage
with load.
Suggest customer
contact local
electric power
utility co. or
qualified
electrician.
Check the
power source
voltage.
Defective
magnetron. Replace
magnetron.
NOTE: Simple test of power output-conducted by heating one liter water for one min. if available.