MICROWAVE OVEN
Troubleshooting & Technical Data
6-4
PROCEDURE
LETTER
COMPONENT TEST
TEST PROCEDURES
A
B
MAGNETRON ASSEMBLY TEST
1.
Disconnect power supply cord and remove outer cabinet case.
2.
Open door and block it open.
3.
Discharge high-voltage capacitor.
4.
To test for an open filament, isolate the magnetron from the high voltage circuit. A continuity check across
the magnetron filament leads should indicate less than 1 ohm.
5.
To test for a shorted magnetron, connect the ohmmeter leads between the magnetron filament leads and
chassis ground. This test should indicate an infinite resistance. If there is little or no resistance the mag-
netron is grounded and must be replaced.
6.
Reconnect all leads removed from components during testing.
7.
Reinstall the outer cabinet case, then reconnect power supply cord.
8.
Run the oven and check all functions.
NOTE
:
Power output of the magnetron (also referred to as Microwave output power) can be measured by per-
forming a water temperature rise test. This test should only be used if above tests do not indicate a faulty mag-
netron and there is no defect in the following components or wiring: power transformer, high voltage capacitor
and silicon rectifier. This test will require a 16 ounce (453cc) measuring cup and an accurate mercury ther-
mometer or thermocouple type temperature tester. For accurate results, the following procedure must be fol-
lowed carefully:
The following test procedure should be performed with the microwave oven fully assembled.
WARNING
:
HIGH VOLTAGE IS PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD
BE OBSERVED.
1.
Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature of the water with a
thermometer or thermocouple temperature tester. Stir the thermometer or thermocouple through the water
until the temperature stabilizes. Record the temperature of the water.
2.
Place the cup of water in the oven. Operate oven at POWER 10(HIGH) selecting more than 60 seconds
cook time. Allow the water to heat for 60 seconds, measuring with a stop watch, second hand of a watch or
the digital read-out countdown.
3.
Remove the cup from the oven and again measure the temperature, making sure to stir the thermometer or
thermocouple through the water until the maximum temperature is recorded.
4.
Subtract the cold water temperature from the hot water temperature. The normal result should be 38°F to
78°F (21°C to 42.6°C) rise in temperature. If the water temperatures are accurately measured and tested
for the required time period the test results will indicate if the magnetron tube has low power output (low rise
in water temperature) which would extend cooking time or high power output (high rise in water tempera-
ture) which would reduce cooking time. Because cooking time can be adjusted to compensate for power
output, the magnetron tube assembly should be replaced only if the water temperature rise test indicates a
power output well above or below the normal limits. The test is only accurate if the power supply line volt-
age is 120 volts and the oven cavity is clean.
POWER TRANSFORMER TEST
1.
Disconnect power supply cord and remove outer cabinet case.
2.
Open door and block it open.
3.
Discharge high-voltage capacitor.
4.
Disconnect the primary input terminals and measure the resistance of the transformer with an ohmmeter.
Check for continuity of the coils with an ohmmeter. On the R x 1 scale, the resistance of the primary coil
should be less than 1 ohm and the resistance of the high voltage coil should be approximately 90 ohms; the
resistance of the filament coil should be less than 1 ohm.
5.
Reconnect all leads removed from components during testing.
6.
Reinstall the outer cabinet case, then reconnect power supply cord.
7.
Run the oven and check all functions.
WARNING
:
HIGH VOLTAGE IS PRESENT AT THE HIGH VOLTAGE TERMINAL. DO NOT ATTEMPT TO MEA-
SURE HIGH VOLTAGE AT THE FILAMENT.
P
P
P
P
rr
rr
ii
ii
o
o
o
o
rr
rr
tt
tt
o
o
o
o
S
S
S
S
e
e
e
e
rr
rr
ii
ii
a
a
a
a
ll
ll
N
N
N
N
u
u
u
u
m
m
m
m
b
b
b
b
e
e
e
e
rr
rr
1
1
1
1
2
2
2
2
0
0
0
0
0
0
0
0
1
1
1
1
5
5
5
5
4
4
4
4
