Description And Function Of Components - Viking VMOC206LE Service Manual

DOOR SENSING AND PRIMARY INTERLOCK
SWITCHES
The door sensing switch in the secondary interlock system
is mounted in the upper position on the latch hook, the pri-
mary interlock switch is mounted in the lower position on
the latch hook. They are activated by the latch heads on the
door. When the door is opened, the switches interrupt the
circuit to all components. A cook cycle cannot take place
until the door is firmly closed thereby activating both interlock
switches. The secondary interlock system consists of the
door sensing switch and secondary interlock relay located
on the control circuit board.
LATCH
HEADS
DOOR OPEN
BUTTON
Figure D-1. Door sensing switch, monitor switch, third
door switch and primary interlock switch
MONITOR SWITCH
The monitor switch is mounted on the middle position of
latch hook. It is activated (the contacts opened) by the lower
latch head while the door is closed. The switch is intended
to render the oven inoperative by means of blowing the C/T
fuse when the contacts of the relay RY1 and primary interlock
switch fail to open when the door is opened.
Functions:
1. When the door is opened, the monitor switch contact close
(to the ON condition) due to their being normally closed. At
this time the door sensing and primary interlock and third
door switches are in the OFF condition (contacts open)
due to their being normally open contact switches.
2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing
switch, third door switch and the primary interlock switch
contacts close. (On opening the door, each of these
switches operate inversely.)
3. If the door is opened, and the relay RY1 and the primary
interlock switch contacts fail to open, the C/T fuse blows
simultaneously with closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN C/T FUSE
TEST THE DOOR SENSING SWITCH, PRI-
MARY INTERLOCK SWITCH, RELAY(RY1)
AND MONITOR SWITCH FOR PROPER
OPERATION. (REFER TO CHAPTER "TEST
PROCEDURE").
NOTE: C/T FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
THIRD DOOR SWITCH
The switch is activated by the latch heads, while the door

DESCRIPTION AND FUNCTION OF COMPONENTS

LATCH HOOK
THIRD DOOR SWITCH
DOOR SENSING
SWITCH
MONITOR SWITCH
PRIMARY
INTERLOCK SWITCH
SWITCH LEVER
OPEN LEVER
is closed. When the door is opened, the switch interrupt
the circuit to the power transformer. This switch prevents
power transformer engaging and microwave when the door
opened.
THERMISTOR
The thermistor is a negative temperature coefficient type.
The temperature in the oven cavity is detected through the
resistance of the thermistor, and then the control unit causes
the heater relay to operate, thus the current to the heating
element is turned ON/OFF.
C/T TEMPERATURE FUSE
The C/T fuse located near the magnetron is designed to
prevent damage to the magnetron if an over heated condition
develops in the tube due to cooling fan failure, obstructed
air guide, dirty or blocked air intake, etc.
Under normal operation, the C/T fuse remains closed.
However, when abnormally high temperatures are reached
within the magnetron, the C/T fuse will open at 266
causing the oven to shut down.
1. The C/T fuse blows when the contacts (COM-NO) of the
secondary interlock relay (RY2) and primary interlock
switch remain closed with the oven door open and when
the monitor switch closes.
2. If the wire harness or electrical components are short-
circuited, this C/T fuse blows to prevent an electric shock
or fire hazard.
NOTE: This is fuse does not reset
OVEN THERMAL CUT-OUT
The thermal cut-out located on the side of the steam duct
is designed to prevent damage to the unit if the foods in the
oven catch fire due to over heating produced by improper
setting of cooking time or failure of control unit.
Under normal operation, the thermal cut-out remains closed.
However, when abnormally high temperatures are reached
within the oven cavity, the thermal cut-out will open at 302
ο
(150 C) causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
ο ο
closes at 266 F (130 C)
CONV. THERMAL CUT-OUT
The thermal cut-out located on the left side of the thermal
protection plate (left) is designed to prevent damage to
the heater unit if an over heated condition develops in the
tube due to cooling fan failure, obstructed air ducts, dirty or
blocked air intake, etc.
Under normal operation, the thermal cut-out remains closed.
However, when abnormally high temperatures are reached
within the heater unit, the thermal cut-out will open at 302
ο
(150 C) causing the oven to shut down.
When the thermal cut-out has cooled, the thermal cut-out
ο ο
closes at 266 F (130 C)
HEATING ELEMENT
The heating element is located at the left side of the oven
cavity. It is intended to heat air driven by the convection fan.
The heated air is kept in the oven and force-circulated and
reheated by the heating element.
15
O O
F(130 C)
ο
F
ο
F