Page 1
6. Troubleshooting
WARNING FOR HIGH VOLTAGE
4000 VOLTS EXIST AT THE HIGH VOLTAGE AREA. DO NOT OPERATE THE OVEN WITH
CABINET PARTS REMO VED. DO NOT REMOVE THE CABINET PARTS IF THE POWER SUPPLY
CORD IS PLUGGED IN THE WALL OUTLET. UNPLUG THE POWER CORD BEFORE SERVICING.
6-1 Electrical Malfunction
Parts Cause Diagnosis Remedy
Fuse blows
out when
door is
opened.
Fuse is
Open
Oven lamp
does not
light.
Defective primary
interlock switch
ary winding.
Defective interlock
monitor switch
Layer short of the
secondary coil of
H. V. Transformer
1) Fuse blown out Check fuse. Replace the fuse.
2) Poor contact of
power cord.
3) Defective lamp The fan motor rotates, but lamp does not light. Replace the lamp.
4) Defective timer
contacts
Check continuity of the primary switch terminals
with wire removed using a multimeter. If there is
continuity inter between switch terminals when door
is opened,the switch is defective.
Check continuity of the monitor switch terminals
with wire removed by using a multimeter.
If there is continuity between switch terminals the
door is closed, the switch is defective.
The fuse will not blow right away, but if it blows in
a few seconds, then there is a layer short If the
fuse blows with H. V. Trans secondary open, the
transformer may be faulty.
Check continuity of power supply cord. Also
check whether the power cord is securely wired.
Check the terminals of timer for continuity,turning
the timer knob ON and OFF repeatedly.
Replace the primary
interlock switch
Replace the interlock
monitor switch
Replace H. V.Transformer
Adjust or replace
the power supply cord
Replace the timer.
Fan does
not operate.
5) Thermal cutout
S/W open
1) Defective fan
motor.
2) Defective contacts of timer
In this case the oven lamp and fan do not turn on
If 230V is found at motor terminals, the motor
should be replaced.
The oven lamp does not light and fan motor does
not operate.
NOTE:Interlock monitor switch must be replaced when the fuse is blown out.
Replace the thermal
cutout S/W
Replace the motor.
Replace the timer.
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6-1 Electrical Malfunction(continued)
part Cause Diagnosis Remedy
To increase the oven
water into water into
the oven.
Replace thermal cutout
switch.
Microwave
turns off during
cooking cycle.
1) Too small
a load
2) Defective
magnetron
thermal
cutout S/W
If a small amount of food is heated for a long time,
period of microwave may turn off during operation.
Check to see if the magnetron thermal cutout switch
is activated at a temperature higher than 150.
properly
shock is
felt.
Door doe not
operate
properly
Timer does
not operate.
Cooking tray
does not
rotate.
In complete
grounding
1) Broken door
hinges
2) Missing or
loose screw
1) Defective
timer motor
2) Defective
contacts of
timer S/W
1) Defective
drive motor
1) Blocking of
the ventilatior
Make sure that qrounding of the power supply cord
has been done properly.
Remove the cabinet for inspection. Check the door
hinge.
Check if the screws are secured well to the door
hinge.
If the timer does not operate with 21V applied to
the terminals, the timer motor amy be faulty.
The lamp does not light. Replace timer
Check to see if 21V exists at the motor terminals.If
so, motor will be defective.
Check if the air inlet or outlet ventilation is blocked
by the wall or other objects.
Rewire.
Replace door hinges.
Fasten or tighten.
Replace timer.
Replace drive motor.
Keepadistanceof
100mm from the wall
or the objects.
Magnetron
thermal
cutout
switch
OFF
2) Defective fan
motor
3) Too small a
load or no
load
If the fan motor does not operate with 230V applied
to the terminal, the motor may be faulty.
If a small amount of food is heated repeatedly over
a long period of time, microwave turns off during
operation.
Replace fan motor.
To increase the oven
load, place a glass of
water into the oven.
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6-2 Unsatisfactory Cooking
Parts Cause Diagnosis Remedy
Food is
not heated.
1) Open cathode of
magnetron
2) Defective
H. V. Diode
3) Shorted
magnetron
4) Defective
magnetron
5) Poor contact of
primary interlock
switch
6) Open coil of
H. V. Transformer
7) Shorted H. V.
capacitor
8) Monitor fuse
blown out
Check the terminals with a multimeter to see
if the heater circuit is open.
Check the H. V. Diode for continuity in the reverse and
normal directions using megger. If there is continuity
in the reverse direction, the H. V. Diode may be faulty.
(In this event H. V. Capacitor will be hot)
Connect megger leads to quick-connect terminal &
body of the magnetron if there is continuity, the
magnetron may be fuse will be blown) faulty. (In this
case the main fuse will be blown)
If there is a crack in the magnetron antenna (dome),
the magnetron is defective.
Check if the screws are secured well to the door hinge.
and pressing it ON and OFF repeatedly.
Check the continuity of primary coil and secondary
coil. If there is no continuity, H. V. Transformer is
defective.
Check the continuity of capacitor.
If the capacitor shorts, the fuse blows
Check the monitor fuse (on the noise filter)
Replace magnetron.
Replace H. V. Diode.
Replace magnetron.
Replace magnetron.
Replace or adjust.
Replace the
H. V. Transformer.
Replace the
H. V. Capacitor.
Replace the
Monitor fuse
6-3 Part Check List
Symptom Related Parts Check Points Remedy
1) Check if the primary and secondary coil is open or shorted.
* Resistance of primary coil: . 2.5Approx
Replace.
Replace.
Replace.
Microwave
cooking does
not work.
Fan motor
does not
rotate.
H.V.Transformer
H.V.Capacitor
H.V.Diode
Fan motor Check if the motor coil is open. Replace.
Resistance of secondary coil: Approx. 151.5
2) Check if the MGT Heater Voltage is approx. 3.3V AC.
Caution : High voltage !
Check continuity of capacitor between two
terminals with H.V.wire lead removed.
The resistance should be approx. 10MΩ,it’sfailure..
1) If there is no continuity in forward, direction the H.V.Diode is open.
2) If there is continuity in reverse direction, it’s shorted.
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