Description And Function Of Components; Door Open Mechanism; Turntable Motor; Cooling Fan Motor - Sharp R-1880LS Service Manual

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
open lever, and then the open lever pushes up the latch head. The
latch heads are moved upward and released from latch hook. Now
the door will open.
Figure D-1. Door Open Mechanism
LATCH
HEADS
DOOR
OPEN LEVER
SECONDARY SWITCH, THIRD DOOR SWITCH &
DOOR SENSING SWITCH
The secondary switch and third switch mounted parrallel to each
other horizontally in the upper positions of the latch hook, the door
sensing switch is mounted horizontally in the upper position of
the latch hook. They are activated by the latch head on the door.
When the door is opened, the switches interrupt the power to all
high voltage components, except the oven lamp . A cook cycle
cannot take place until the door is firmly closed thereby activating
all interlock switches. The secondary interlock system consists of
the door sensing switch and the primary interlock relay located
on the control circuit board.

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 switch and secondary
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 secondary interlock relay, primary switch and
secondary switch are in the OFF condition (contacts open)
due to their being normally open contact switches.
. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing switch,
primary switch and secondary switch contacts close. (On
opening the door, each of these switches operate inversely.)
3. If the door is opened, and the secondary interlock relay, primary

DESCRIPTION AND FUNCTION OF COMPONENTS

LATCH HOOK
DOOR SENSING
SWITCH
MONITOR FUSE
MONITOR
SWITCH
THIRD
DOOR
SWITCH
SECONDARY
INTERLOCK
SWITCH
switch and secondary 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 THE SECONDARY INTERLOCK
RELAY, S ECONDARY S WITCH, D OOR S ENSING
SWITCH, MONITOR SWITCH AND PRIMARY
SWITCH FOR PROPER OPERATION. (REFER
TO CHAPTER "TEST PROCEDURE").
NOTE: MONITOR FUSE, PRIMARY SWITCH AND
MONITOR SWITCH ARE REPLACED AS AN
ASSEMBLY.
TEMPERATURE FUSE (MG)
The temperature fuse located near the waveguide 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 temperature fuse remains closed.
However, the temperature fuse will open at 30
ing the oven to shut down.
THERMAL CUT-OUT (HOOD )
This thermal cut-out located on the base plate right. It is designed
to automatically turn on the hood fan motor whenever the hot air
rising from the conventional range below causes the temperature at
the thermal cut-out to rise to 140
this hot air from around microwave oven. When the temperature
around the thermal cut-out drops to 113
thermal cut-out shuts off the food fan motor.

TURNTABLE MOTOR

The turntable motor rotates the turntable located on the bottom of
the oven cavity, so that the foods on the turntable cook evenly during
cooking. Turntable will turn in either direction. The turntable motor
can be turned off by touching TURNTABLE ON/OFF pad.

COOLING FAN MOTOR

The cooling fan motor drives a blade which draws external cool
air. This cool air is directed through the air vanes surrounding
the magnetron and cools the magnetron. This air is channelled
through the oven cavity to remove steam and vapors given off from
the heating foods. It is then exhausted through the exhausting air
vents at the oven cavity.
HOOD FAN MOTOR
The hood fan motor is a two-speed, single-phase, double pole
induction type, requiring a hood fan capacitor. It is located outside
the upper rear part of the oven cavity, is to remove, from around
the oven, hot air rising from the conventional electric or gas range
over which it is installed. This air is then expelled either vertically
or horizontally through the customer supplied duct system, or
discharged back into the kitchen.

STIRRER MOTOR

The stirrer motor drives the stirrer fan to stir the microwave radia-
tion from the waveguide.
HOOD LAMP
17
R-1880LS/LST
ο ο
F (150 C) caus-
ο ο
F (60 C) or higher, thus removing
ο ο
F (45 C) or lower, the