Description And Function Of Components - Sharp R-307KW Service Manual

R307KW

[3] DESCRIPTION AND FUNCTION OF COMPONENTS

1. DOOR OPEN MECHANISM
The door is opened by pushing the open button on the control panel,
refer to the Figure D-1.
When the open button is pushed, the open button pushes up the
switch lever, and then the switch lever pushes up the latch head. The
latch heads are moved upward and released from latch hook. Now the
door will open.
Door
Latch
Heads
Switch Lever
Figure D-1. Door Open Mechanism.
2. DOOR SENSING AND SECONDARY INTERLOCK
SWITCHES
The secondary interlock switch is mounted in the lower position of the
latch hook and the door sensing switch in the primary interlock system
is mounted in the upper position of the latch hook. They are activated
by the latch heads on the door. 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
head on the door while the door is closed. The switch is intended to
render the oven inoperative, by means of blowing the monitor 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 its 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 secondary
interlock switch contacts close.
3) If the door is opened, and the primary interlock relay (RY2) and the
secondary interlock switch contact fail to open, the monitor fuse
blows simultaneously with closing of the monitor switch contacts.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST
THE DOOR SENSING SWITCH, PRIMARY INTERLOCK
RELAY (RY2), SECONDARY INTERLOCK SWITCH AND
MONITOR SWITCH FOR PROPER OPERATION. (REFER
TO CHAPTER "TEST PROCEDURE").
NOTE: MONITOR FUSE AND MONITOR SWITCH ARE REPLACED
AS AN ASSEMBLY.
Latch Hook
Door Sensing
Switch
Monitor Switch
Secondary
Interlock Switch
6 – 3
4. TURNTABLE MOTOR
The turntable motor rotates the turntable located on the bottom of the
oven cavity, so that the food on the turntable is cooked evenly. The
turntable may turn in either direction.
5. COOLING FAN MOTOR
The cooling fan motor drives a blade which draws external cool air.
This cool air is directed through the air vents surrounding the magne-
tron and cools the magnetron. This air is channelled through the oven
cavity to remove steam and vapours given off from the heating foods.
It is then exhausted through the exhausting air vents at the oven cav-
ity.
6. TEMPERATURE FUSE (MAGNETRON)
The temperature fuse located near the magnetron is designed to pre-
vent 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 temperature fuse
remains closed. However, when abnormally high temperatures are
reached within the magnetron, the temperature fuse will open at
302°F(150°C) causing the oven to shut down.
7. THERMAL CUT-OUT (OVEN)
The thermal cut-out, located on the top of the oven cavity, is designed
to prevent damage to the oven by fire. If the food load is overcooked,
by either error in cook time or defect in the control unit, the thermal cut-
out will open. 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
293°F(145°C), causing the oven to shut down.
8. TEMPERATURE FUSE (OVEN)
The temperature fuse, located on the top of the oven cavity, is
designed to prevent damage to the oven by fire. If the food load is
overcooked, by either error in cook time or defect in the control unit,
the thermal cut-out will open. Under normal operation, the temperature
fuse remains closed. However, when abnormally high temperatures
are reached within the oven cavity, the temperature fuse will open at
302°F(150°C), causing the oven to shut down.
9. MONITOR FUSE
1) The monitor fuse blows when the contacts (COM-NO) of the pri-
mary interlock relay (RY2) and the secondary 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 monitor fuse blows to prevent an electric shock or fire hazard.
10. NOISE FILER
The noise filter prevents the radio frequency interference that might
flow back in the power circuit.