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7. CIRCUIT DESCRIPTIONS
Refer to the wiring diagram on page 8.
1. When food is placed inside oven and door is closed
(B) The primary interlock switch is closed.
3, When the START pad is touched
The main relay and the power control relay are controlled by the
touch control circuit.
Primary Switch
H.V.Trans
Switch
eon
~0-
of
Main Relay
Power Relay
Fig. 1
Monitor Fuse
ns
HV.
th
i
Lin
Fig. 2
4. When the door is opened during cooking
Primary Switch
H.V.Trans
—O-G-
O-
.
Interlock
Monitor Fuse
Monitor
Switch
oT oO
oTo—o
.
om
Primary Switch
Power Relay
Fig. 3
{C} The fan motor stops.
8. Component Test Procedure
PRECAUTION
1. High voltage is present at the high voltage terminal of the high
voltage transformer during any cook cycle.
2. It is neither necessary nor 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 high
voltage capacitor.
:
:
12-1. High Voltage Transformer
1} Remove connectors from the transformer terminals and check
continuity.
2) Normal resistance readings should be as follows:
Secondary
Approx. 94Q
Filament
Approx. 092
Primary...
. . . Approx. 1.7Q
(Room temperature = 20°C)
Filament Terminals
Secondary Terminat
Primary
Terminals
12-2. Low Voltage Transformer
'
The low voltage transformer is located on the control circuit
board.
1) Remove the low voltage Transformer from the PCB Ass'y and
check continuity.
2) Normal resistor reading should be as follows.
Terminals
Resistance
12-3. Magnetron
Continuity checks can only indicate an open fitament or a shorted
magnetron. To diagnose an open filament or shorted magnetron;
1) lsolate the magnetron from the circuit by disconnecting its
leads.
2) A continuity check across the magnetron filament terminals
should indicate one chm or less.
3) A continuity check between each filament terminal and
magnetron case should read open.
Magnetron Antenna
Gasket Plate
12-4. High Voltage Capacitor
1} Check continuity of the capacitor with meter set at the
highest ohm scale.
2) Once the capacitor is charged, a normal capacitor shows
continuity for a short time, and then indicates 9MQ.
3) A shorted capacitor will show continuous continuity.
4) An open capacitor will show constant MQ.
5} Resistance between each terminal and chassis should read
infinite.
12-5. High Voltage Diode
1) Isolate the diode from the circuit by disconnecting its leads.
2) With the ohm-meter set at the highest resistance scale,
measure the resistance across the diode terminals. Reverse the
meter leads and read the resistance. A meter with BV, SV 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. The resistance of a normal
diode will be infinite in one direction and several hundred KQ
in the other direction.
12-6. Main Relay and Power Control Relay
The relays are located on the PCB Ass'y.
1) Isolate the relays from the main circuit by disconnecting the
leads.
2} operate the microwave oven with a water load in the oven and
the power level set to high.
3} Check continuity between terminals of the relays after the start
pad is pressed.
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