Component Test Procedure - Panasonic NN-E251W Service Manual

7. COMPONENT TEST PROCEDURE

CAUTION
1. High voltage is present at the high voltage terninal of the
high voltage transformer during any cook cycle.
2. It is neither necessary nor advisable to attempt mea-
surement of the high voltage.
3. Before touching any oven components, or wiring,
always unplug the oven from its power source and dis-
charge the high voltage capacitor.
7.1 High voltage transformer
1. Remove connections from the transformer terminals and
check continuity.
2. Normal continuity readings should be as follows.
Secondary winding ............ Approx. 120 Ω -160 Ω
Filament winding ............... Approx. 0 Ω
Primary winding ................ Approx.1 Ω - 4 Ω
7.2 High voltage capacitor
1. Check continuity of capacitor with meter on highest OHM scale.
2. A normal capacitor will show continuity for a short time,
and then indicate about 10MΩ once the capacitor is
charged.
3. A shorted capacitor will show continuous continuity.
4. An open capacitor will show constant about 10MΩ
5. Resistance between each terminal and chassis should be
infinite.
7.3 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 disconnection 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.
7.4 Diode
1. Isolate the diode from the circuit by disconnecting the
leads.
2. With the ohmmeter set the highest resistance scale,
measure the resistance across the diode terminals.
Reverse the meter leads and again observe the resis-
tance 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 direc-
tions. A normal diode's resistance will be infinite in one
direction and several hundred KΩ in the other direction.
7.5 Membrane keyboard
Check continuity between switch terminals, by tapping an
appropriate pad on the keyboard. The contacts assignment
of the respective pads on the keyboard is as shown in digi-
tal programmer circuit (schematic).
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