MEASUREMENT AND TEST
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. H igh voltage transform er
(1) Remove connections from the transformer terminals and check continuity.
(2) Normal readings should be as follows :
Secondary winding ... Approx. 110
±10%
Filament winding .......Approx. 0
Primary winding ....... Approx. 0
2. H igh voltage capacitor
(1) Check continuity of capacitor with meter on the highest OHM scale.
(2) A normal capacitor will show continuity for a short time, and then indicate 10M
once the capacitor charged.
(3) A shorted capacitor will show continuous continuity.
(4) An open capacitor will show constant 10M
.
(5) Resistance between each terminal and chassis should be infinite.
3. H igh voltage diode
(1) Isolate the diode 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-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. M agnetron
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,
(1) Isolate magnetron from the circuit by disconnecting the leads.
(2) The continuity check across magnetron filament terminals should indicate 0.1
or less.
(3) The 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 normally.
