Troubleshooting - LG MH-1355M Service Manual

TROUBLESHOOTING

CAUTION: 1. Check grounding before checking for other trouble.
2. Be careful of the high voltage circuit.
3. When checking the continuity of the switches or transformer, disconnect one lead wire from
these parts and then check continuity without turning the power source on.
4. Do not touch any part of the circuitry on the control circuit board, since electrostatic discharge
may damage this control circuit.
Always touch yourself to ground while working on this circuit to discharge any static charge built
up in your body.
5. First operate the microwave oven following the correct operating procedures.
6. If the oven becomes inoperative because of a fuse, check the primary, the secondary and the
monitor switches, before replacing the fuse.
CONDITION
The fuse opens when power
cord is plugged into wall
receptacle.
":0"does not appear in
display window when power
cord is first plugged into wall
outlet.
Display does not operate
properly when Clock is
touched.
CAUSE
OFF CONDITION
Shorted wire in power cord or
wire harness.
Defective monitor switch or out
of adjustment.
Microwave oven plug is not
inserted tightly.
No power at outlet.
Open fuse.
Open wire in power cord,
wiring harness, or wiring
between control panel
assembly units.
Defective membrane key of
P.C.B.
– 30 –
TEST PROCEDURE OR
CORRECTION
Replace power cord or check
and repair wire harness.
Test procedure monitor switch.
(See page 25.)
Insert microwave oven plug
securely.
Check home fuse.
Perform fuse test procedure
(See page 39.)
Replace or repair wiring.
Test procedure membrane key
of P.C.B. (See page 41.)