Description And Function Of Components - Sharp R-21LTF Service Manual

[3] DESCRIPTION AND FUNCTION OF COMPONENTS

1. DOOR OPEN MECHANISM
The door is opened by grasping the door handle, refer to Figure D-1.
When the door handle is grasped, the handle lever is pulled. And then
the upper and lower latch heads are moved upward by the handle
lever, and they are released from the latch hook. Now the door will
open.
Latch Head
Handle
Lever
Door
Handle
Latch
Lever
Latch Head
Latch Switch
Lever C
Figure D-1. Door Open Mechanism.
2. DOOR SENSING AND SECONDARY INTERLOCK
SWITCHES
The secondary interlock switch is mounted in the upper position of the
latch hook and the door sensing switch in the primary interlock system
is mounted in the lower position of the latch hook. The secondary inter-
lock switch is activated by the latch switch lever A. The latch switch
lever A is activated by the upper latch head. The door sensing switch
is activated by the latch switch lever C. The latch switch lever C is acti-
vated by the lower latch head. When the door is opened, the switches
interrupt the power to all high voltage components. A cook cycle can-
not take place until the door is firmly closed thereby activating both
interlock switches. The primary interlock system consists of the door
sensing switch and primary interlock relay located on the control circuit
board.
3. MONITOR SWITCH
The monitor switch is activated (the contacts opened) by the latch
switch lever B on the latch hook while the door is closed. The latch
switch lever B is activated by the lower latch head. The switch is
intended to render the oven inoperative, by means of blowing the mon-
itor fuse, when the contacts of the primary interlock relay (RY2) and
secondary interlock switch fail to open when the door is opened.
Functions:
1) When the door is opened, the monitor switch contacts close (to the
ON condition) due to their being normally closed. At this time the
primary interlock relay (RY2) and secondary interlock switch 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 and the second-
ary interlock switch contacts close. (On opening the door, each of
these switches operate inversely.)
3) If the door is opened, and the primary interlock relay (RY2) and
secondary interlock switch contacts fail to open, the monitor fuse
blows simultaneously with closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE TEST
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE REPLACED
4. ANTENNA MOTOR
The antenna motor rotates the stirrer antenna located on the bottom of
the oven cavity, so that the food on the ceramic shelf is cooked evenly
during cooking. The antenna motor may turn in either direction.
Latch Hook
5. COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external cool air.
Latch Switch
This cool air is directed through the air vanes surrounding the magne-
Lever A
tron and cools the magnetron. This air is channelled through the oven
Secondary
cavity to remove steam and vapors given off from the heating food. It
Interlock
is then exhausted through the exhausting air vents at the oven cavity.
Switch
Latch Switch 6. MONITOR FUSE
Lever B
1) The monitor fuse blows when the contacts (COM-NO) of the pri-
Monitor
Switch
Door
Sensing 2) If the wire harness or electrical components are shortcircuited, this
Switch
7. THERMAL CUT-OUT 145°C (MAGNETRON)
This thermal cut-out protects the magnetron against overheating. If the
temperature goes up higher than 293°F (145°C) because the fan
motor is interrupted or the ventilation openings are blocked, the ther-
mal cut-out will open and line voltages to the high voltage transformer
will be cut off and the operation of the magnetron will be stopped. The
thermal cutout will not resume.
8. THERMAL CUT-OUT 125°C (OVEN)
The thermal cut-out located on the top of the oven cavity is designed
to prevent damage to the oven if the food in the oven catches fire due
to over heating produced by improper setting of the cooking time or
failure of control unit. Under normal operation, the oven thermal cut-
out remains closed. However, when abnormally high temperatures are
reached within the oven cavity, the oven thermal cut-out will open at
257°F(125°C) causing the oven to shut down. The thermal cut-out will
not resume.
9. NOISE FILER
The noise filter prevents the radio frequency interference that might
flow back in the power circuit.
6 – 3
THE DOOR SENSING SWITCH, PRIMARY INTERLOCK
RELAY (RY2), RELAY (RY3) SECONDARY INTERLOCK
SWITCH AND MONITOR SWITCH FOR PROPER OPER-
ATION. (REFER TO CHAPTER "TEST PROC
AS AN ASSEMBLY.
mary interlock relay (RY2) and secondary interlock switch remain
closed with the oven door open and when the monitor switch
closes.
monitor fuse blows to prevent an electric shock or fire hazard.
R21LTF