Magnetron; Diode (U); Membrane Key Board (Membrane Switch Assembly) - Panasonic NN-S335BF Service Manual

NN-S335BF / NN-S335WF / NN-S335WM /
8.5.

Magnetron

Continuity checks can only indicate an open filament or a
shorted magnetron. To diagnose for an open filament or
shorted magnetron:
1. Isolate magnetron from the circuit by disconnecting the
leads.
2. A continuity check across magnetron filament terminals
should indicate one ohm or less.
3. A continuity check between each filament terminal and
magnetron case should read open.
8.6.

Diode (U)

1. Isolate the diode (U) from the circuit by disconnecting the
leads.
2. With the ohmmeter set on the highest resistance scale,
measure the resistance across the diode terminals.Reverse
the meter leads and again observe the resistance
reading.Meter with 6V, 9V or higher voltage batteries should
be used to check the front-to-back resistance of the diode,
otherwise an infinite resistance may be read in both
directions.
A normal diode's resistance will be infinite in one direction
and several hundred KΩ in the other direction.
3. With the ohmmeter set on the highest resistance scale,
measure the resistance across the protector diode
terminals. Reverse the meter leads and again observe the
resistance reading.
A normal protector diode's resistance will be infinite in both
directions. It is faulty if it shows continuity in one or both
directions.
8.7. Membrane key board
(Membrane switch assembly)
Check continuity between switch terminals, by tapping an
appropriate pad on the key board. The contacts assignment of
the respective pads on the key board is as shown in digital
programmer circuit.
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