Panasonic NN-CT867MBPQ, Service Manual

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NN-CT867MBPQ NN-CT857WBPQ
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11.5. Inverter Power Supply
Caution
DO NOT try to repair this inverter power supply. Replace as a whole H.V. Inverter Unit.
Inverter power supply diagram
Figure 3
11.6. Inverter Power Supply Unit
Warning
Do not attempt to make any measurements in the high volt-
age circuitry of the inverter or magnetron.
See troubleshooting of the inverter circuit and magnetron on
page 27 to determine if the inverter power supply is still func-
tioning.
11.7. Temperature Sensor
A temperature sensor is mounted on the rear of the oven. The
resistance reading across the thermistor should read 300K ohm
within a temperature range of 10 to 30 degrees centigrade. This
would be the temperature range within a kitchen environment.
If the resistance measured is outside this range the thermistor
is defective and should be replaced.
NOTE: When measuring the resistance of the thermistor dis-
connect the connector from the digital programmer circuit.
NOTE: If the microwave oven has been operated allow to cool
to room temperature before attempting to measure the ther-
mistor resistance.
11.8. Humidity sensor and digital
programmer circuit.
1. Check the resistance across the sensor heater terminals.
Normal cold resistance should read approximately 4.5
ohms.
2. Check the voltage across the sensor heater terminals. It
should read approximately 2.5VDC
3. In order to determine if the auto cooking by humidity sen-
sor is working, perform the following test.
1. Place a water load (150cc) in the oven.
2. Press the auto reheat panel.
3. Press the start pad
4. The humidity sensor detects steam about 2 to 4 minutes
after the start pad has been pressed.
5. The auto cooking (T1) automatically switches to cooking
time. (T2)
6. The remaining cooking time T2 appears in the display
window. If 48s -1min 36 secs appears in the display, the
humidity sensor function is normal.