Service manual

37
WIRING DIAGRAM
36
COMPONENT TEST PROCEDURE
1. High voltage is present at the high voltage terminal of the high voltage transformer during any cook cycle.
2. It is neither necessary not advisable to attempt measurement of the high voltage.
3. Before touching any oven components or wiring, always unplug the oven from its power source and discharge the
capacitor (see page 20).
1. High voltage transformer
(A) Remove connections from the transformer
terminals and check continuity.
(B) Normal readings should be as follows:
Secondary winding…… Approx. 100Ω¡ 10%
Filament winding…… Approx. 0Ω
Primary winding…… Approx. 0Ω
2. High voltage capacitor
(A) Check continuity of capacitor with meter on the
highest OHM scale.
(B) A normal capacitor will show continuity for a short
time, and then indicate 9MΩ once the capacitor is
charged.
(C) A shorted capacitor will show continuous
continuity.
(D) An open capacitor will show constant 9MΩ.
(E) Resistance between each terminal and chassis
should be infinite.
3. High voltage diode
The high voltage diode is located on the base near the
transformer.
(A) Isolate the diode from the circuit by disconnecting
the leads.
(B) 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 diodes
resistance will be infinite in one direction and several
hundred KΩ in the other direction.
4. Magnetron
For complete magnetron diagnosis, refer to
“Measurement of the Microwave Output Power”.
Continuity checks can only indicate and open
filament or a shorted magnetron. To diagnose for
an open filament or shorted magnetron.
(A) Isolate magnetron from the circuit by disconnecting
the leads.
(B) A continuity check across magnetron filament
terminals should indicate one ohm or less.
(C) A continuity check between each filament terminal
and magnetron case should read open.
Secondary
terminal
Primary
terminal
Filament terminal
Magnetron
antenna
Metallic
gasket
plate
Cooling fin
Magnetron
Filament
terminal