LG MS-2642W (serv.man2) Service Manual ▷ View online
1. Incomplete segments.
• Segment missing.
• Partial segment missing.
• Digit flickering (NOTE:Slight flickering is normal.)
• Partial segment missing.
• Digit flickering (NOTE:Slight flickering is normal.)
2. Colon does not turn on or blink.
3. A distinct change in the brightness of one or more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooking.
3. A distinct change in the brightness of one or more numbers in display.
4. One or more digits in the display are not lighting.
5. Display indicates a number different from one touched, for example, key in 5 and 3 appears in the display.
6. Specific numbers (for example 7 or 9) will not display when key pad is touched.
7. Display does not count down with time blinking or up with clock operation.
8. Display obviously jumps in time while counting down.
9. Display counts down too fast while cooking.
10. Each indicator light does not turn on after setting cooking cycle.
11. Display time of day does not reappear when cooking is finished.
12. Beep sound is not heard when correct key is touched.
11. Display time of day does not reappear when cooking is finished.
12. Beep sound is not heard when correct key is touched.
5-12
(TROUBLE 1) The following visual conditions indicate a probable defective control circuit.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. No input can be
programmed.
Continuity
No continuity
Defective PCB
assembly.
assembly.
Loose
connection.
connection.
Replace PCB
assembly.
assembly.
Connect them
tightly.
tightly.
Check the conn-
ection between
membrane key
assembly and
PCB assembly.
ection between
membrane key
assembly and
PCB assembly.
2. Some inputs
cannot be
programmed.
programmed.
3. Display shows a
number or figure
different from one
touched.
different from one
touched.
4. Random
programming
when touching
other pads.
when touching
other pads.
5. Display is fixed
at some figure
and can not
accept any
input.
and can not
accept any
input.
Everything works
as specified.
as specified.
Still have trouble.
Defective key
membrane
assembly.
membrane
assembly.
Defective PCB
assembly.
assembly.
Replace key
membrane
assembly.
membrane
assembly.
Replace PCB
assembly.
assembly.
Replace key
membrane
assembly and
check operation.
membrane
assembly and
check operation.
5-13
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Fuse blows.
Continuity.
No continuity.
Continuity.
Shorted contact at
the primary switch.
the primary switch.
Replace fuse,
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
No continuity.
Normal.
Defective high
voltage capacitor.
voltage capacitor.
Replace high
voltage capacitor.
voltage capacitor.
Fuse blows again
Defective high volt-
age transformer.
age transformer.
Replace high volt-
age transformer.
age transformer.
Malfunction of the
monitor switch.
monitor switch.
Replace fuse,
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
primary, monitor
switches, and
RELAY(RY2) of
P.C.B Assembly.
Check continuity
of monitor
switch (with
door closed).
of monitor
switch (with
door closed).
Check continuity
of primary
switch (with
door opened).
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.
side of the wire
lead connected
from transformer
to the high
voltage
capacitor and
operate the unit.
Replace fuse
2. Fuse does not
blow.
No continuity.
Continuity.
No continuity.
Defective power
supply cord.
supply cord.
Replace power
supply cord.
supply cord.
Defective
thermostat.
thermostat.
Replace
thermostat.
thermostat.
Check continuity
of thermostat.
of thermostat.
Check continuity
of power supply
cord.
of power supply
cord.
(TROUBLE 2) Oven does not operate at all; Display window does not display any figures,
and no input is accepted.
NOTE : All these switches must be replaced at the same time. Refer to page 5-6, 5-7
5-14
CONDITION
CHECK
RESULT
CAUSE
REMEDY
1. Setting time
does not count
down when
touching START
pad.
down when
touching START
pad.
2. Fan motor or
oven lamp do
not turn on.
not turn on.
No continuity.
Continuity.
Continuity
Defective PCB
assembly.
assembly.
Loose connection.
Replace PCB
assembly.
assembly.
Connect them
tightly.
tightly.
No continuity
Abnormal
Check fan motor.
Defective fan motor.
Replace fan motor.
Abnormal
Normal
Check oven lamp.
Defective oven lamp.
Replace oven lamp.
Defective
secondary switch.
secondary switch.
Replace
secondary switch.
secondary switch.
Check continuity
of secondary
switch (with
door closed).
of secondary
switch (with
door closed).
Check the con-
nection between
CN1 connector
and PCB
assembly.
nection between
CN1 connector
and PCB
assembly.
(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 operating but little heat is produced in oven load.
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.
CONDITION
CHECK
RESULT
CAUSE
REMEDY
Output is low
Lower than 90% of
rating voltage.
rating voltage.
Normal
Abnormal
Defective PCB
assembly.
assembly.
Replace PCB
assembly.
assembly.
Normal
Abnormal
Measure the
output power.
output power.
Defective
magnetron.
magnetron.
Replace
magnetron.
magnetron.
Decrease in power
source voltage
with load.
source voltage
with load.
Suggest customer
contact local
electric power
utility co. or
qualified
electrician.
contact local
electric power
utility co. or
qualified
electrician.
Check the
power source
voltage.
power source
voltage.
Disconnect the
wire leads from
relay 2 and
check on and off
time with
multitester.
wire leads from
relay 2 and
check on and off
time with
multitester.
5-15
CONDITION
CHECK
RESULT
CAUSE
REMEDY
No microwave
oscillation.
oscillation.
No continuity.
Continuity.
Abnormal
Defective high
voltage
transformer.
voltage
transformer.
Replace high
voltage
transformer.
voltage
transformer.
Normal
Defective PCB
assembly.
assembly.
Replace PCB
assembly.
assembly.
Disconnect the
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)
wire leads from
relay 2 and
check continuity
of relay 2.
(Operate the unit)
Check high vol-
tage transformer.
tage transformer.
Abnormal
Defective circuit
protector.
protector.
Replace circuit
protector.
protector.
Normal
Check circuit
protector.
protector.
Abnormal
Defective high
voltage capacitor.
voltage capacitor.
Replace high
voltage capacitor.
voltage capacitor.
Normal
Check high vol-
tage capacitor.
tage capacitor.
Abnormal
Defective high
voltage diode.
voltage diode.
Replace high
voltage diode.
voltage diode.
Normal
Check high vol-
tage diode.
tage diode.
Abnormal
Defective
magnetron.
magnetron.
Replace
magnetron.
magnetron.
Check
magnetron.
magnetron.
(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run.
(Display operates properly)
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