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9-3. COMPONENT TEST PROCEDURE
• High voltage is present at the high voltage terminal of the high voltage
transformer during any cooking cycle.
• It is neither necessary nor advisable to attempt measurement of the high voltage.
• Before touching any oven components or wiring, always unplug the oven from its
power source and discharge the capacitor.
1. High voltage transformer
(A) Remove connections from the transformer terminals and check continuity.
(B) Normal readings should be as follows :
Secondary winding ... Approx. 100 ±10%
Filament winding ... Approx. 0
Primary winding ... Approx. 1.2
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
10MW once the capacitor charged.
(C) A shorted capacitor will show continuous continuity.
(D) An open capacitor will show constant 10M
(E) Resistance between each terminal and chassis should be infinite.
3. High voltage diode
(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 500V dc or higher voltage batteries should be used
to check the front-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 k 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 a shorted magnetron,
(A)
Isolate magnetron from the circuit by disconnecting the leads.
(B) A continuity check across magnetron filament terminals should indicate 0.1 or
less.
(C) A continuity check between each filament terminal and magnetron case should
read open.
5. Fuse
If the fuse in the primary and monitor switch circuit is blown when the door is opened,
check the primary and monitor switch before replacing the blown fuse. In case the
fuse is blown by an improper switch operation, replace the defective switch and fuse
at the same time. Replace just the fuse if the switches operate normal
ly.