Panasonic NN-T221MB, Service Manual, Page: 15 / 21

15
9 Component Test Procedure
Caution
1. High voltage is present at the high voltage terminal of the
inverter unit, including the aluminium heat sink.
2. It is not necessary or advisable to attempt to measure this
high voltage.
3. Before touching any oven components, or wiring, always
unplug the oven from its power source and discharge the
high voltage capacitors.
9.1. Primary Latch Switch, Second-
ary Latch Switch and Power
relay B interlocks.
1. Unplug the lead connectors to power relay B and verify
the continuity of the power relay B 1-2 terminals.
2. Unplug the lead connectors to the primary latch switch
and secondary latch switch.
3. Test the continuity of the switches with the door open and
closed with an ohm meter on the lowest scale.
Normal continuity readings should be as followed.
9.2. Short Switch and Monitor Cir-
cuit
1. Unplug the lead wires from the HV inverter primary termi-
nals.
2. Connect the test probes of the ohm meter to the discon-
nected leads.
3. Test the continuity of the short switch with the door open
and the door closed using the lowest ohm scale.
9.3. Magnetron
Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose an open filament or shorted
magnetron.
1. Isolate the magnetron from the circuit by disconnecting
the HV leads.
2. A continuity check across the magnetron filament termi-
nals should indicate one ohm or less.
3. A continuity check between each filament terminal and
the magnetron case should read open.
9.4. Push Button Keyboard
Check the continuity between the switch terminals, by tapping
an appropriate pad on the keyboard. The contacts assignment
of the respective pads on the keyboard is as shown in the digi-
tal programmer circuit (schematic).
Door Open Door Closed
Primary Latch Switch infinite W (Open) 0 W (Close)
Secondary Latch switch infinite
W
(Open) 0
W
(Close)
Power relay B infinite
W
(Open) infinite
W
(Close)
Door Open Door Closed
Monitor switch 0
W infinte W