LG LMC1575BD Service Manual page 29

(TROUBLE 4) Oven seems to be operating but little heat is produced in oven load.
CONDITION
Output is low.
NOTE : Simple test of power output-conducted by heating one cup of water for 30 seconds if available.
Minimum 20˚C temperature rise is normal condition.
CHECK
Check the power source
voltage.
Check install Condition.
Check the inverter PCB
Measure the output
power.
RESULT
Lower than 90% of rating
voltage.
Normal.
Installed like Built – in.
(it locate with not enough
distance from wall.)
Normal.
Abnormal.
Normal.
Abnormal.
5-17
CAUSE
Decrease in power source
voltage with load.
Bad air flow make inverter
PCB overheated.
Main PCB reduce power
to protect inverter from
overheating.
Defective PCB assembly.
Defective magnetron.
REMEDY
Suggest customer contact
local electric power utility
co. or qualified electrician.
Reinstall.
Replace PCB assembly.
Replace magnetron.