LG LMVH1750SB Service Manual page 37

(TROUBLE 5) No microwave oscillation even though oven lamp and fan motor run
(Display operates properly)
CONDITION
No microwave
oscillation.
NOTE: * Make sure the wire leads are in the correct position.
* When removing the wire leads from parts be sure to grasp the connector not the wires.
* When removing the magnetron, be sure to install the magnetron gasket in the correct position
and in good condition.
Output is full power
when you set lower
power level.
CHECK
Disconnect the
wire leads from
relay 8 and
check continuity
of relay 8.
(Operate the
unit)
Check high vol-
tage transformer
Check high vol-
tage capacitor.
Check high vol-
tage diode.
Check
Magnetron.
Disconnect the
wire leads from
relay 8 and check
continuity relay 8.
(Operate the unit)
RESULT
No continuity.
Continuity.
Abnormal
normal
Abnormal
normal
Abnormal
normal
Abnormal
Abnormal.
7-27
CAUSE
Defective P.C.B
assembly
Defective high
voltage
transformer.
Defective high
voltage capacitor.
Defective high
voltage Diode.
Defective
magnetron.
Defective PCB
assembly.
REMEDY
Replace P.C.B
assembly
Replace high
voltage
transformer .
Replace high
voltage capacitor.
Replace high
voltage Diode.
Replace
magnetron .
Replace PCB
assembly.