Viking Designer DMOR200SS, Service Manual

Page: 9 / 37

9
DMOR200SS
OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and primary
interlock switch. (In this condition, the monitor switch contacts
are opened.)
When oven is plugged in, 20 volts A.C. is supplied to the
control unit. (Figure O-).
. The display will show flashing "Welcome Press Clear and
Press Clock".
To set any program or set the clock, you must first touch
the STOP/CLEAR button. The display will clear, and " : "
will appear .
COOKING CONDITION
Program desired cooking time touching the NUMBER pads.
When the START button is touched, the following operations
occur:
. The contacts of relays are closed and components
connected to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY CONNECTED COMPONENTS
RY Oven lamp / Fan motor / Turntable motor
RY2 Power transformer
RY3, RY4 Hood fan motor
RY5, RY6 Hood lamp
2. 20 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.3 volts A.C.
output on the filament winding, and approximately 2000
volts A.C. on the high voltage winding.
3. The filament winding voltage heats the magnetron filament
and the H.V. winding voltage is sent to a voltage doubler
circuit.
4. The microwave energy produced by the magnetron is
channelled through the wave guide into the cavity feed-
box, and then into the cavity where the food is placed to
be cooked.
5. Upon completion of the cooking time, the power transformer,
oven lamp, etc. are turned off, and the generation of
microwave energy is stopped. The oven will revert to the
OFF condition.
6. When the door is opened during a cook cycle, monitor
switch, door sensing switch, secondary interlock
switch,third door switch and primary interlock relay are
activated with the following results. The circuits to the
stirrer motor, the cooling fan motor, the turntable
motor, and the high voltage components are de-
energized, and the digital read-out displays the time
still remaining in the cook cycle when the door was
opened.
7. The monitor switch is electrically monitoring the operation
of the secondary interlock switch, third door switch and
door sensing switch is mechanically associated with the
door so that it will function in the following sequence.
() When the door opens from a closed position, the
primary interlock relay, door sensing switch, third
door switch and secondary interlock switch open
their contacts, and then the monitor switch
contacts close.
(2) When the door is closed from the open position, the
monitor switch contacts first open, and then the
contacts of the secondary interlock switch, third
door switch close.
If the secondary interlock switch and third door switch fail
with their contacts closed when the door is opened, the
closing of the monitor switch contacts will form a short
circuit through the monitor fuse, secondary interlock switch
and third door switch, causing the monitor fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 20 volts
A.C. is supplied to the power transformer intermittently through
the contacts of relay (RY2) which is operated by the control
unit within an interval second time base. Microwave power
operation is as follows:
VARI-MODE ON TIME OFF TIME
Power 0(P-HI) 32 sec. 0 sec.
(00% power)
Power 9(P-90) 30 sec. 2 sec.
(approx. 90% power)
Power 8(P-80) 26 sec. 6 sec.
(approx. 80% power)
Power 7(P-70)
24 sec. 8 sec.
(approx. 70% power)
Power 6(P-60) 22 sec. 0 sec.
(approx. 60% power)
Power 5(P-50) 8 sec. 4 sec.
(approx. 50% power)
Power 4(P-40) 6 sec. 6 sec.
(approx. 40% power)
Power 3(P-30) 2 sec. 20 sec.
(approx. 30% power)
Power 2(P-20) 8 sec. 24 sec.
(approx. 20% power)
Power (P-0) 6 sec. 26 sec.
(approx. 0% power)
Power 0(P-0) 0 sec. 32 sec.
(0% power)
Note: The ON/OFF time ratio does not correspond with the
percentage of microwave power, because approx. 3
seconds are needed for heating of the magnetron
filament.