Sharp R308jsf Service Manual

							R-308JK
R-308JS
R- 308JW
R- 309JW
In the interest of user-safety the oven should be restored to its origin\
al
condition and only parts identical to those specified should be used.
WARNING TO SERVICE PERSONNEL: Microwave ovens contain
circuitry capable of producing very high voltage and current,
contact with following parts may result in a severe, possibly fatal,
electrical shock. (High Voltage Capacitor, High Voltage Power
Transformer, Magnetron, High Voltage Rectifier Assembly,  High
Voltage Harness etc..)
TABLE OF CONTENTS
Page
PRECAUTIONS TO BE OBSERVED BEFORE AND DURING SERVICING TO
AVOID POSSIBLE  EXPOSURE TO EXCESSIVE MICROWAVE ENERGY ................... INSIDE FRONT COVER
BEFORE SERVICING ........................................................................\
.............................. INSIDE FR ONT COVER
WARNING TO SERVICE PERSONNEL ........................................................................\
........................... ............. 1
MICROWAVE MEASUREMENT PROCEDURE ........................................................................\
........................ ... 2
FOREWORD AND WARNING ........................................................................\
................................... .................... 3
PRODUCT SPECIFICATIONS ........................................................................\
................................. ..................... 4
GENERAL  INFORMATION ........................................................................\
................................... ........................ 4
OPERATION ........................................................................\
.............................................. .................................... 6
TROUBLESHOOTING GUIDE ........................................................................\
.................................. .................... 9
TEST PROCEDURE ........................................................................\
......................................... ........................... 10
TOUCH CONTROL PANEL ........................................................................\
.................................... ..................... 17
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE  ................................................................ 21
PICTORIAL DIAGRAM ........................................................................\
...................................... .......................... 27
CONTROL UNIT CIRCUIT ........................................................................\
................................... ....................... 28
PRINTED WIRING BOARD ........................................................................\
................................... ...................... 29
PARTS LIST ........................................................................\
............................................. ................................... 30
PACKING AND ACCESSORIES ........................................................................\
................................ ................. 34S2402R308JPW/
R-308JK
R-308JS
R-308JW
R-309JW
MICROWAVE OVEN
MODELS
  SERVICE MANUAL
SHARP CORPORATION
This document has been published to be used for after
sales service only.
The contents are subject to change without notice.
R-308JW 
						

							R-308JK
R-308JS
R-308JW
R-309JW
PRECAUTIONS TO BE OBSERVED BEFORE AND
DURING SERVICING TO AVOID POSSIBLE
EXPOSURE TO EXCESSIVE MICROWAVE
ENERGY
(a) Do not operate or allow the oven to be operated with the door open.
(b) Make the following safety checks on all ovens to be serviced before activating the magnetron or other
microwave source, and make repairs as necessary: (1) interlock operation, (2) proper door closing, (3)
seal and sealing surfaces (arcing, wear, and other damage), (4) damage to or loosening of hinges and
latches, (5) evidence of dropping or abuse.
(c) Before turning on microwave power for any service test or inspection within the microwave generating
compartments, check the magnetron, wave guide or transmission line, and cavity for proper alignment,
integrity, and connections.
(d) Any defective or misadjusted components in the interlock, monitor, door seal, and microwave
generation and transmission systems shall be repaired, replaced, or adjusted by procedures described
in this manual before the oven is released to the owner.
(e) A microwave leakage check to verify compliance with the Federal Performance Standard should be
performed on each oven prior to release to the owner.
BEFORE SERVICING
Before servicing an operative unit, perform a microwave emission check as per the Microwave
Measurement Procedure outlined in this service manual.
If microwave emissions level is in excess of the specified limit, contact SHARP ELECTRONICS
CORPORATION immediately  @1-800-237-4277.
If the unit operates with the door open, service person should 1) tell the user not to operate the oven
and 2) contact SHARP ELECTRONICS CORPORATION and Food and Drug Administrations
Center for Devices and Radiological Health immediately.
Service personnel should inform SHARP ELECTRONICS CORPORATION of any certified unit found
with emissions in excess of 4mW/cm
2. The owner of the unit should be instructed not to use the unit
until the oven has been brought into compliance. 
						

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WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of pro-
ducing very high voltage and current, contact with
following parts 
 may result in a severe, possibly
fatal, electrical shock.
(Example)
High Voltage Capacitor, High Voltage Power Trans-
former, Magnetron, High Voltage Rectifier Assem-
bly,  High Voltage Harness etc..
Read the Service Manual carefully and follow all
instructions.
Before Servicing
1. Disconnect the power supply cord          , and then remove
outer case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
WARNING: RISK OF ELECTRIC SHOCK.
DISCHARGE THE HIGH-VOLTAGE
CAPACITOR BEFORE SERVICING.
The high-voltage capacitor remains charged about 60 sec-
onds after the oven has been switched off. Wait for 60
seconds and then short-circuit the connection of the high-
voltage capacitor (that is the connecting lead of the high-
voltage rectifier) against the chassis with the use of an
insulated screwdriver.
Whenever troubleshooting is performed the power supply
must be disconnected. It may, in some cases, be necessary to
connect the power supply after the outer case has been
removed, in this event,
1. Disconnect the power supply cord, and then remove outer
case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4.Disconnect the leads to the primary of the power transformer.
5.Ensure that the leads remain isolated from other components
and oven chassis by using insulation tape.
6. After that procedure, reconnect the power supply cord.
When the testing is completed,
1. Disconnect the power supply cord, and then remove outer
case.
2. Open the door and block it open.
3. Discharge high voltage capacitor.
4.Reconnect the leads to the primary of the power transformer.
5. Reinstall the outer case (cabinet).
6.Reconnect the power supply cord after the outer case is
installed.
7. Run the oven and check all functions.
After repairing
1.Reconnect all leads removed from components during
testing.
2. Reinstall the outer case (cabinet).
3.Reconnect the power supply cord after the outer case is
installed.
4. Run the oven and check all functions.
Microwave ovens should not be run empty. To test for the
presence of microwave energy within a cavity, place a cup of
cold water on the oven turntable, close the door and set  the
power to HIGH and set the microwave timer for two (2) minutes.
When the two minutes has elapsed (timer at zero) carefully
check that the water is now hot. If the water remains cold carry
out Before Servicing procedure and re-examine the connec-
tions to the component being tested.
When all service work is completed and the oven is fully
assembled, the microwave power output should be checked
and a microwave leakage test should be  carried out.
Dont Touch !
Danger High Voltage 
						

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MICROWAVE MEASUREMENT PROCEDURE
A. Requirements:
1)Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave oven should
not exceed 1mW/cm
2 at any point 5cm or more from the external surface of the oven, measured prior to acquisition by a
purchaser, and thereafter (through the useful life of the oven), 5 mW/cm2 at any point 5cm or more from the external surface
of the oven.
2) Safety interlock switches:
 Primary interlock relay and door sensing switch shall prevent microwave radiation emission in excess of the requirement as
above mentioned, secondary interlock switch shall prevent microwave radiation emission in excess of 5 mW/cm
2 at any point
5cm or more from the external surface of the oven.
B. Preparation for testing:
Before beginning the actual measurement of leakage, proceed as follows:
1) Make sure that the actual instrument is operating normally as specified in its instruction booklet.
Important:
Survey instruments that comply with the requirement for instrumentation as prescribed by the performance standard for microwave
ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
2) Place the oven tray in the oven cavity.
3) Place the load of 275±15 ml (9.8 oz) of tap water initially at 20±5˚C (68˚F) in the center of the oven cavity.
The water container shall be a low form of 600 ml (20 oz) beaker with an inside diameter of approx. 8.5 cm (3-1/2 in.) and made
of an electrically nonconductive material such as glass or plastic.
The placing of this standard load in the oven is important not only to protect the oven, but also to insure that any leakage is
measured accurately.
4) Set the cooking control on Full Power Cooking Mode.
5) Close the door and select a cook cycle of several minutes. If the water begins to boil before the survey is completed, replace
it with 275 ml of cool water.
C. Leakage test:
Closed-door leakage test (microwave measurement)
1) Grasp the probe of the survey instrument and hold it perpendicular to the gap between the door and the body of the oven.
2)Move the probe slowly, not faster than 1 in./sec. (2.5 cm/sec.) along the gap, watching for the maximum indication on the meter.
3)Check for leakage at the door screen, sheet metal seams and other accessible positions where the continuity of the metal has
been breached (eg., around the switches, indicator, and vents).
While testing for leakage around the door pull the door away from the front of the oven as far as is permitted by the closed latch
assembly.
4)Measure carefully at the point of highest leakage and make sure that the highest leakage is no greater than 4mW/cm
2, and that
the secondary interlock switch and the primary interlock relay do turn the oven OFF before any door movement.
NOTE:  After servicing, record data on service invoice and microwave leakage report. 
						

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SHARP ELECTRONICS CORPORATION
SHARP PLAZA, MAHWAH,
NEW JERSEY 07430-2135
SERVICE MANUAL
MICROWAVE OVEN
R-308JK/ R-308JS/ R-308JW/ R-309JW
FOREWORD
This Manual has been prepared to provide Sharp Electronics Corp.
Service Personnel with Operation and Service Information for the SHARP
MICROWAVE OVENS,R-308JK, R-308JS, R-308JW and R-309JW.
It is recommended that service personnel carefully study the entire text of
this manual so that they will be qualified to render satisfactory customer
service.
Check the interlock switches and the door seal carefully. Special attention
should be given to avoid electrical shock and microwave radiation hazard.
WARNING
Never operate the oven until the following points are ensured.
(A) The door is tightly closed.
(B) The door brackets and hinges are not defective.
(C) The door packing is not damaged.
(D) The door is not deformed or warped.
(E) There is no other visible damage with the oven.
Servicing and repair work must be carried out only by trained service
personnel.
DANGER
Certain initial parts are intentionally not grounded and present
a risk of electrical shock only during servicing. Service person-
nel - Do not contact the following parts while the appliance is
energized;
High Voltage Capacitor, Power Transformer, Magnetron, High
Voltage Rectifier Assembly,  High Voltage Harness;
If provided, Vent Hood, Fan assembly, Cooling Fan Motor.
All the parts marked “*” on parts list are used at voltages more than
250V.
Removal of the outer wrap gives access to voltage above 250V.
All the parts marked “∆” on parts list may cause undue microwave
exposure, by themselves, or when they are damaged, loosened or
removed.
PRODUCT DESCRIPTION
GENERAL INFORMATION
OPERATION
TROUBLESHOOTING GUIDE AND
TEST PROCEDURE
TOUCH CONTROL PANEL
COMPONENT REPLACEMENT
AND ADJUSTMENT PROCEDURE
WIRING DIAGRAM
PARTS LIST 
						

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ITEM DESCRIPTION
Power Requirements 120 Volts / 13.5 Amperes
60 Hertz
Single phase, 3 wire grounded
Power Output 1100 watts (IEC TEST PROCEDURE)
Operating frequency of 2450MHz
Case Dimensions Width 20-1/2 Height 12-1/4
Depth  17-3/8
Cooking Cavity Dimensions Width 14-1/2 Height 8-1/8
1.0 Cubic Feet Depth  15-1/4
Control Complement Touch Control SystemClock ( 1:00 - 12:59 )
Timer (0 - 99 min. 99 seconds)
Microwave Power for Variable Cooking
  Repetition Rate;P-HI .................................................. Full power throughout the cooking time
P-90 .................................................................... approx. 90% of Full Power
P-80 .................................................................... approx. 80% of Full Power
P-70 .................................................................... approx. 70% of Full Power
P-60 .................................................................... approx. 60% of Full Power
P-50 .................................................................... approx. 50% of Full Power
P-40 .................................................................... approx. 40% of Full Power
P-30 .................................................................... approx. 30% of Full Power
P-20 .................................................................... approx. 20% of Full Power
P-10 .................................................................... approx. 10% of Full Power
P-0 .................................................... No power throughout the cooking time
POPCORN pad, MINUTE PLUS pad
SHORT CUTS pads, REHEAT pad, COOK pad
DEFROST pad, Number selection pads
POWER LEVEL pad, TIMER/CLOCK pad
STOP/CLEAR pad, START pad
Oven Cavity Light Yes
Safety Standard UL Listed                FCC Authorized
DHHS Rules, CFR, Title 21, Chapter 1, Subchapter J
SPECIFICATION
GENERAL INFORMATION
GROUNDING INSTRUCTIONS
This oven is equipped with a three prong grounding plug. It must be plug\
ged into a wall receptacle that is properly installed a nd
grounded in accordance with the National Electrical Code and local codes\
 and ordinances.
In the event of an electrical short circuit, grounding reduces the risk \
of electric shock by providing an escape wire for the e lectric
current.
WARNING: Improper use of the grounding plug can result in a risk of electric shoc\
k.
Electrical Requirements
The electrical requirements are a 120 volt 60 Hz, AC only,
15 or 20 amp. fused electrical supply. It is recommended that a separate\
 circuit serving only this appliance be provided. When
installing this appliance, observe all applicable codes and ordinances.
A short power-supply cord is provided to reduce risks of becoming entang\
led in or tripping  over a longer cord.
Where a two-pronged wall-receptacle is encountered, it is the personal r\
esponsibility and obligation of the customer to contact  a
qualified electrician and have it replaced with a properly grounded thre\
e-pronged wall receptacle or have a grounding adapter
NOTE: Internal capacity is calculated by measuring
maximum width, depth and height.
Actual capacity for holding food is less. 
						

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5
properly grounded and polarized. If the extension cord must be used, it
should be a 3-wire, 15 amp. or higher rated cord. Do not drape over a
countertop or table where it can be pulled on by children or tripped ove\
r
accidentally.
CAUTION: DO 
NOT UNDER ANY CIRCUMSTANCES CUT OR REMOVE
THE ROUND GROUNDING PRONG FROM THIS PLUG.
OVEN DIAGRAM
1 Door opening button
Push to open door.
2 Oven door with see-through window
3 Safety door latches
The oven will not operate unless the door is securely closed.
4 Door hinges
5 Door seals and sealing surfaces
6 Turntable motor shaft
7 Removable turntable support
Carefully place the turntable support in the center of the oven floor.
8 Removable turntable
Place the turntable on the turntable support securely. The turntable will
rotate clockwise or counterclockwise.
Only remove for cleaning.
9 Ventilation openings (Rear)
10 Oven light
It will light when oven is operating or when the door is open.
11 Waveguide cover: DO NOT REMOVE.
12 Auto-Touch control panel
13 Time display: 99 minutes, 99 seconds
14 Power supply cord
NOTE:
Some one-touch cooking features such as MINUTE PLUS are disabled
after three minutes when the oven is not in use. These features are
automatically enabled when the door is opened and closed or the STOP/
CLEAR pad is pressed.
3-Pronged
Plug Grounded
Receptacle Box
Grounding Pin
3-Pronged Receptacle
14
8 9
7
12 13
1
59
324
6
11 310
TOUCH  CONTROL PANEL 
						

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OPERATION
DESCRIPTION OF OPERATING SEQUENCE
The following is a description of component functions during
oven operation.
OFF CONDITION
Closing the door activates the door sensing switch and second-
ary interlock switch. (In this condition, the monitor switch
contacts are opened.)
When oven is plugged in, 120 volts A.C. is supplied to the
control unit. (Figure O-1).
1. The display will show flashing 88:88.
To set any program or set the clock, you must first touch
the STOP/CLEAR pad. The display will clear, and   :   will
appear.
COOKING CONDITION
Program desired cooking time by touching the NUMBER pads.
Program the power level by touching the POWER LEVEL pad.
When the START pad is touched, the following operations
occur:
1.The contacts of relays are closed and components connected
to the relays are turned on as follows.
(For details, refer to Figure O-2)
RELAY CONNECTED COMPONENTS
RY-1 oven lamp/turntable motor/fan motor
RY-2 power transformer
2.120 volts A.C. is supplied to the primary winding of the
power transformer and is converted to about 3.3 volts A.C.
output on the filament winding, and approximately 2360
volts A.C. on the high voltage winding.
3. The filament winding voltage heats the magnetron filament
and the H.V. winding voltage is sent to a voltage doubler
circuit.
4.The microwave energy produced by the magnetron is
channelled through the waveguide into the cavity feed-box,
and then into the cavity where the food is placed to be
cooked.
5.Upon completion of the cooking time, the power transformer,
oven lamp, etc. are turned off, and the generation of
microwave energy is stopped. The oven will revert to the
OFF condition.
6. When the door is opened during a cook cycle, the monitor
switch, door sensing switch, secondary interlock switch,
relay (RY1) and primary interlock relay are activated with
the following results. The circuits to the turntable motor, the
cooling fan motor, and the high voltage components are de-
energized, the oven lamp remains on, and the digital read-
out displays the time still remaining in the cook cycle when
the door was opened.
7.The monitor switch electrically monitors the operation of the
secondary interlock switch and primary interlock relay and
is mechanically associated with the door so that it will
function in the following sequence.(1)When the door opens from the closed position, the primary
interlock relay (RY2) and secondary interlock switch open
their contacts. And contacts of the relay (RY1) remains
closed. Then the monitor switch contacts close.
(2)When the door is closed from the open position, the monitor
switch contacts open first. Then the contacts of the secondary
interlock switch and door sensing switch close. And contacts
of the relay (RY1) open.
If the secondary interlock switch and primary interlock relay
(RY2) fail with the contacts closed when the door is opened, the
closing of the monitor switch contacts will form a short circuit
through the C/T fuse, secondary interlock switch, relay (RY1)
and primary interlock relay (RY2), causing the C/T fuse to blow.
POWER LEVEL P-0 TO P-90 COOKING
When Variable Cooking Power is programmed, the 120 volts
A.C. is supplied to the power transformer intermittently through
the contacts of relay (RY-2) which is operated by the control
unit within a 32 second time base. Microwave power operation
is as follows:
VARI-MODE ON TIME OFF TIME
P-HI (100% power) 32 sec. 0 sec.
P-90 (approx. 90% power) 30 sec. 2 sec.
P-80 (approx. 80% power) 26 sec. 6 sec.
P-70 (approx. 70% power) 24 sec. 8 sec.
P-60 (approx. 60% power) 22 sec. 10 sec.
P-50 (approx. 50% power) 18 sec. 14 sec.
P-40 (approx. 40% power) 16 sec. 16 sec.
P-30 (approx. 30% power) 12 sec. 20 sec.
P-20 (approx. 20% power)  8 sec. 24 sec.
P-10 (approx. 10% power)  6 sec. 26 sec.
P-0 (approx. 0% power)  0 sec. 32 sec.
Note: The ON/OFF time ratio does not correspond with
the percentage of microwave power, because
approx. 3 seconds are needed for heating of the
magnetron filament.
POWER OUTPUT REDUCTION
If the oven is set for more than 20 minutes at 80, 90 or 100%
power level, after the first 20 minutes the power level will
automatically adjust itself to 70% power to avoid overcooking. 
						

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7 Figure O-1. Oven Schematic-Off Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. CLOCK APPEARS ON DISPLAY
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED
2. COOKING TIME PROGRAMMED
3. VARIABLE COOKING CONTROL P-HI (100%)
4. START PAD TOUCHED
Figure O-2. Oven Schematic-Cooking Condition
NOTE:     indicates components with potential above 250V.
120V AC
60 Hz
OVEN
LAMP
OVEN LAMP
RELAY
TURN-
TABLE
MOTORFAN 
MOTORPOWER 
TRANSFORMERMONITOR 
SWITCH
RECTIFIER
MAGNETRON
SECONDARY
INTERLOCK
SWITCHTTMOL
FM
C/T FUSEOR
N.O.
N.O.COM.
COM.
DOOR
SENSING
SWITCH
(RY1)(RY2)
CONTROL UNITPRIMARY
INTERLOCK
RELAY
GRNB2CAPACITOR
0.94µF
AC 2200V B1
120V AC
60 Hz
OVEN
LAMP
OVEN LAMP
RELAY
TURN-
TABLE
MOTORFAN 
MOTORPOWER 
TRANSFORMERMONITOR 
SWITCH
RECTIFIER
MAGNETRON
SECONDARY
INTERLOCK
SWITCHTTMOL
FM
C/T FUSE
N.O.
N.O.COM.
COM.
DOOR
SENSING
SWITCH
(RY1)(RY2)
CONTROL UNITPRIMARY
INTERLOCK
RELAY
GRNB2CAPACITOR
0.94µF
AC 2200V B1
OR 
						

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DESCRIPTION AND FUNCTION OF COMPONENTS
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.
Figure D-1. Door Open Mechanism
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 cannot 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.
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 C/T 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
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, PRIMARYINTERLOCK RELAY (RY2), SECONDARY IN-
TERLOCK SWITCH AND MONITOR SWITCH
FOR PROPER OPERATION. (REFER TO CHAP-
TER TEST PROCEDURE).
NOTE:C/T FUSE AND MONITOR SWITCH ARE
REPLACED AS AN ASSEMBLY.
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.
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 magnetron 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 cavity.
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 temperature fuse 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.
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.
C/T FUSE
 1.The C/T fuse blows when the contacts (COM-NO) of the
primary interlock relay (RY2) and 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 C/T fuse blows  to prevent an electric shock
or fire hazard.
3. The C/T fuse, located near the magnetron, is designed to
prevent damage to the magnetron. If an over heated condition
develops in the magnetron due to cooling fan failure,
obstructed air guide, dirty or blocked air intake, etc., the C/
T fuse will open.
Under normal operation, the C/T fuse remains closed. How-
ever, when abnormally high temperatures are reached within
the oven cavity, the C/T fuse will open at 302˚F (150˚C),
causing the oven to shut down or when the electric currents
beyond 20A flow, the C/T fuse will open.
Latch 
HeadsDoor
Switch Lever
Latch Hook
Door Sensing
Switch
Monitor Switch
Secondary
Interlock Switch