Service manual

15
R-1855A
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
SECONDARY INTERLOCK SWITCH, THIRD DOOR
SWITCH & DOOR SENSING SWITCH
The secondary interlock switch and third door 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 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 second-
ary interlock switch and third door 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 primary interlock relay, secondary interlock
switch and third 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,
secondary interlock switch and third door switch contacts
close. (On opening the door, each of these switches
operate inversely.)
3. If the door is opened, and the primary interlock relay,
secondary interlock switch and third door 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 PRIMARY INTERLOCK RE-
LAY, THIRD DOOR SWITCH, DOOR SENS-
ING SWITCH, MONITOR SWITCH AND SEC-
ONDARY INTERLOCK SWITCH FOR PROPER
OPERATION. (REFER TO CHAPTER "TEST
PROCEDURE").
NOTE: MONITOR FUSE, SECONDARY INTERLOCK
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 302
O
F (150
O
C)
causing the oven to shut down.
THERMAL CUT-OUT (HOOD )
This thermal cut-out located on the base plate right and the
hood intake duct (left), 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
O
F (60
O
C) or higher, thus
removing this hot air from around microwave oven. When
the temperature around the thermal cut-out drops to 113
O
F
(45
O
C) or lower, the 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.
DESCRIPTION AND FUNCTION OF COMPONENTS
THIRD
DOOR
SWITCH
DOOR
LATCH HOOK
LATCH
HEADS
DOOR SENSING
SWITCH
MONITOR
SWITCH
SECONDARY
INTERLOCK
SWITCH
OPEN LEVER
MONITOR FUSE