Schematic Diagram - Viking VHSO205SS Service Manual

VHSO205SS
(REHEAT, POPCORN, COOK, DEFROST)
Microwave options of Automatic cooking will automatically
compute the microwave power, cooking time or defrosting
time. And the oven will cook according to the special cook-
ing sequence.
FIRE SENSING FEATURE (MICROWAVE MODE)
This model incorporates a sensing feature which will stop
the oven's operation if there is a fire in the oven cavity
during microwave cooking. This fire sensing feature will
operate when the microwave power level is set to 80% or
more. This is accomplished by the LSI repeatedly measur-
ing the voltage across the temperature measurement circuit
(thermistor) during it's 3-seconds time base comparing the
obtained voltage measurements. If the most recent volt-
age measured is 300 mV greater than the previous voltage
measured, the LSI judges it as a fire in the oven cavity and
switches off the relays to the power transformer, fan motor
and convection motor. The LSI also stops counting down
and closes the damper door so that no fresh air will enter
the oven cavity. Please refer to the following section for a
more detailed description.
Operation
Please refer to the timing diagrams below.
1. The fire sensing will start after 30 minutes when the oven
is started.
. The thermistor operates within a 3-seconds time
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
. CLOCK APPEARS ON DISPLAY.
BLK
L
FUSE
20A
GRN
GND
L
WHT
NOTES:
1. Circuits / Wire Colors subject to change without notice.

SCHEMATIC DIAGRAM

NOTE: " " indicates components with potential above 50V.
RED RED
MG.
TEMP.
FUSE
LV TRANSFORMER
BRN
TOP HEATER
THERMAL
CUT-OUT
D9
A6 A1 A2 A3 A4
A8
FUSE1
2.5A
CONTROL
UNIT
RY6
BLK
BLK
GRN
BRN WHT
GRN
GRN
N.O.
GRY SECONDARY
GRY
GRY INTERLOCK
SWITCH
Figure O-1. Oven Schematic-OFF Condition
10
base and it is energized for three (3) seconds and off
for 9 seconds. Two () seconds after the thermistor
is energized, the voltage across the temperature
measurement circuit is sampled by the LSI and twenty
five (5) seconds after the thermistor is cut off the LSI
turns on the convection fan for three (3) seconds.
3. The above procedure is repeated. If the difference
between the first voltage measured (in step 1) and the
voltage measured when the procedure is repeated (step
) is greater than 300 mV the LSI makes the judgment
that there is a fire in the oven cavity and will switch
off the relays to the power transformer, fan motor and
convection motor. The LSI also stops counting down and
closes the damper door so that no fresh air will enter the
oven cavity.
0 2 3
CONVECTION
MOTOR ON
OFF
3 sec.
THERMISTOR
ON
OFF
ON
Sensing
Voltage
OFF
Sensing the voltage across temperature measurement circuit.
SIDE HEATER
THERMAL
CUT-OUT
BLK
RED
BLK
SOLID-STATE RELAY
ORG
BRN
BLK
RED
SOLID-STATE RELAY
COM.
WHT
WHT
28 31 32 (sec.) 64 (sec.)
3 sec.
BLK
BLK
FUSE
F10A
RED
BRN
BRN