Wolf MWD30-2 User manual

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-2
#813632 - Revision B - December, 2009
TROUBLESHOOTING AND TECHNICAL DATA
This section of the manual Component Test Procedures.
NOTE: Before continuing, please take note of the WARNINGS and CAUTIONS below.
• TO AVOID ELECTRIC SHOCK DURING TROUBLESHOOTING, NEVER TOUCH ANY PART OF THE ELECTRI-
CAL CIRCUIT WITH HANDS OR UN-INSULATED TOOLS WHILE THE POWER IS CONNECTED.
• MICROWAVE OVENS CONTAIN CIRCUITRY CAPABLE OF PRODUCING VERY HIGH VOLTAGE AND CUR-
RENT. CONTACT WITH THE FOLLOWING COMPONENTS MAY RESULT IN SERIOUS PERSONAL INJURY OR
DEATH:
• TRANSFORMER • RECTIFIER • HIGH VOLTAGE HARNESS
• MAGNETRON • CAPACITOR
NOTE: THE CAPACITOR REMAINS CHARGED APPROXIMATELY 60 SECONDS AFTER THE OVEN IS
SWITCHED OFF. WAIT FOR 60 SECONDS, THEN SHORT THE CAPACITOR TO THE CHASSIS.
• BEFORE SERVICING THE MICROWAVE OVEN, THE CAPACITOR MUST BE DISCHARGED BY SHORTING
THE CONNECTING LEAD OF THE RECTIFIER AGAINST THE CHASSIS WITH AN INSULATED SCREWDRIV-
ER. FAILURE TO FOLLOW THIS STEP COULD RESULT IN SERIOUS PERSONAL INJURY OR DEATH.
• DO NOT OPERATE OR ALLOW THE OVEN TO BE OPERATED WITH THE DOOR OPEN.
Be careful when handling sheet metal parts - Edges may be sharp.
NOTE: When troubleshooting, it may be necessary in some cases to supply power to the unit with the outer cabinet
case removed (See CAUTION above).
In this event:
1. Disconnect the power supply cord, and then remove outer cabinet case.
2. Open the door and block it open.
3. Discharge high voltage capacitor (See WARNING above).
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. Only after performing the five steps listed above should the power supply cord be reconnected.
When the testing is completed:
1. Disconnect the power supply cord, 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 cabinet.
6. Reconnect the power supply cord after the outer case is installed.
7. Run the oven and check all functions.
NOTES:
• After performing any service to the Drawer Microwave, test to verify that there is no leakage of microwave ener-
gy (See next page).
• Make the following safety checks on all ovens to be serviced before activating the magnetron or other microwave
source, and make repairs as necessary:
• Interlock operation
• Proper drawer closing
• Seal and sealing surfaces (arcing, wear, and other damage)
• Evidence of dropping or abuse
• Before turning on microwave power for any service test or inspection within the microwave generating compart-
ments, check the magnetron, wave guide or transmission line, and cavity for proper alignment, integrity, and con-
nections.

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-3 #813632 - Revision B - December, 2009
MICROWAVE MEASUREMENT PROCEDURE
Requirements:
1. Microwave leakage limit (Power density limit): The power density of microwave radiation emitted by a microwave
oven should not exceed 1mW/cm2 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 switch shall prevent microwave radiation emission in excess of
the requirement as above mentioned. Secondary interlock relay and door sensing switch shall prevent
microwave radiation emission in excess of 5 mW/cm2 at any point 5cm or more from the external surface of the
oven.
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.
NOTES:
• Survey instruments that comply with the requirement for instrumentation as prescribed by the performance stan-
dard for microwave ovens, 21 CFR 1030.10(c)(3)(i), must be used for testing.
• Survey instruments that comply with the requirement for instrumentation as prescribed by CSA and NHW per-
formance standard for microwave ovens must be used for testing recommended instruments are, NARDA 8100
and NARDA 8200.
2. 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 non conductive 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.
3. Set the cooking control on Full Power Cooking Mode.
4. Close the drawer 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.
Leakage test:
Closed-drawer leakage test (microwave measurement):
1. Grasp the probe of the survey instrument and hold it perpendicular to the gap between the drawer 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 indica-
tion on the meter.
3. Check for leakage at the drawer 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 drawer, pull the drawer away from the front of the oven as far as is permit-
ted 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/cm2, and that the primary interlock switch/secondary interlock relay does turn the oven OFF before any
door movement.

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-4
#813632 - Revision B - December, 2009
TOUCH CONTROL PANEL ASSEMBLY TEST:
The touch control panel consists of circuits including semiconductors such as LSI,
ICs, etc. Therefore, unlike conventional microwave ovens, proper maintenance
cannot be performed with only a voltmeter and ohmmeter.
In this service manual, the touch control panel assembly is divided into three
units, Control Unit, Keyboard Unit and Power Unit, and troubleshooting by unit
replacement is described according to the symptoms indicated.
Before Testing:
1. Disconnect power supply cord, and then disassemble as per “Drawer
Microwave Disassembly” Section 4 Component Access Removal, Page 4-6.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the leads to the primary of the power transformer.
5. Ensure that these leads remain isolated from other components and oven
chassis by using insulation tape.
Keyboard Unit:
1. Check Keyboard unit connection before replacement.
2. Reconnect all leads removed from components during testing.
3. Re-install the covers.
4. Reconnect the power supply cord after the covers are installed.
5. Run the oven and check all functions.
The following symptoms indicate a defective keyboard unit:
• When touching the pads, a certain pad produces no signal at all.
• When touching a number pad, two figures or more are displayed.
• When touching the pads, sometimes a pad produces no signal.
If The Keyboard Unit is Defective:
1. Disconnect the power supply cord, and then remove covers.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Replace the Keyboard unit.
5. Reconnect all leads removed from components during testing.
6. Re-install the covers.
7. Reconnect the power supply cord after the covers are installed.
8. Run the oven and check all functions.
Control Unit:
The following symptoms indicate a defective control unit. Before replacing the
control unit, perform the Keyboard unit test (Procedure B) to determine if control
unit is faulty.
1. In connection with indicators
• At a certain digit, all or some segments do not light up.
• At a certain digit, brightness is low.
• Only one indicator does not light.
• The corresponding segments of all digits do not light up; or they continue
to light up.
• Wrong figure appears.
• A certain group of indicators do not light up.
• The figure of all digits flicker.
2. Other possible problems caused by defective control unit.
• Buzzer does not sound or continues to sound.
• Clock does not operate properly.
• Cooking is not possible.
COMPONENT TEST
TEST PROCEDURES
PROCEDURE LETTER
A
(This Section continues on the next page)

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-5 #813632 - Revision B - December, 2009
Power Unit or Touch Control Transformer:
1. Fan motor, stirrer motor, oven lamp or electrical parts do not turn on or do not
turn off.
2. Digital display on the control unit does not show anything.
When Testing is Completed:
1. Disconnect power supply cord, and then disassemble as per “Drawer
Microwave Disassembly” Section 4 Component Access Removal, Page 4-6.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Reconnect all leads removed from components during testing.
5. Re-install the covers.
6. Reconnect the power supply cord after the covers are installed.
7. Run the oven and check all functions.
COMPONENT TESTPROCEDURE LETTER
A
(Cont.)
KEY UNIT TEST:
1. Disconnect power supply cord, and then remover outer case.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. If the display fails to clear when the STOP/CLEAR pad is depressed, first veri-
fy the flat ribbon cable is making good contact, verify that the door sensing
switch (stop switch) operates properly; that
is the contacts are closed when the drawer
is closed and open when the drawer is open.
If the door sensing switch (stop switch) is
good, disconnect the flat ribbon cable that
connects the key unit to the control unit and
make sure the drawer sensing switch is
closed (either close the drawer or short the
door sensing switch connecter). Use the
Key unit matrix indicated on the control
panel schematic and place a jumper wire
between the pins that correspond to the
STOP/CLEAR pad making momentary con-
tact. If the control unit responds by clearing with a beep the key unit is faulty
and must be replaced. If the control unit does not respond, it is faulty and
must be replaced. If a specific pad does not respond, the above method may
be used (after clearing the control unit) to determine if the control unit or key
pad is at fault.
5. Reconnect all leads removed from components during testing.
6. Re-install the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
B
STOP/
CLEAR
REHEAT
6
START/
MINUTE
PLUS
1
2
7
SENSOR
COOK
SENSOR
REHEAT
DEFROST
9
8
3
4
OPEN
SENSOR
POPCORN
KEEP
WARM
TIMER
CLOCK
CLOSE
0
5
POWER
LEVEL
SET UP
CUSTOM HELP
CONTROL
LOCK
ON/OFF

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-6
#813632 - Revision B - December, 2009
CRELAY TEST:
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 these leads remain isolated from other components and oven
chassis by using insulation tape.
6. After that procedure, re-connect the power supply cord.
7. Remove the outer case and check voltage between Pin Nos. 5 and 7 of the 4
pin connector (CN-A) on the power unit with an A.C. voltmeter.
The meter should indicate 120 volts, if not check oven circuit.
RY, RY2, RY3 and RY4 Relay Test
These relays are operated by D.C. voltage
Check voltage at the relay coil with a D.C. voltmeter during the microwave
cooking operation.
• DC. voltage indicated Defective relay.
• DC. voltage not indicated Check diode which is connected to the relay
coil. If diode is good, control unit is defective.
COMPONENT TESTPROCEDURE LETTER
RELAY SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 26 vdc Oven lamp / Common
RY2 Approx. 25 vdc Power transformer
RY3 Approx. 26 vdc Stirred motor
RY4 Approx. 26 vdc Fan motor
RY5 Approx. 26 vdc Switching regulator or drawer motor
8. Disconnect the power supply cord, and then remove outer case.
9. Open the door and block it open.
10. Discharge high voltage capacitor.
11. Reconnect all leads removed from components during testing.
12. Re-install the outer case (cabinet).
13. Reconnect the power supply cord after the outer case is installed.
14. Run the oven and check all function.

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-7 #813632 - Revision B - December, 2009
DEFROST TEST:
D
COMPONENT TESTPROCEDURE LETTER
THE OVEN SHOULD BE FULLY ASSEMBLED BEFORE ATTEMPTING THE FOL-
LOWING PROCEDURE.
1. Place one cup of water in the center of the tray in the oven cavity.
2. Close the drawer, touch the Defrost pad. Then select Steaks/Chops by touch-
ing the number pad 2. And touch the number pad 5. (Now, weight 0.5lb is
set.) And then touch the start pad.
3. The oven is in Defrost cooking condition.
4. The oven will operate as follows:
WEIGHT 1ST STAGE 2ND STAGE 3RD STAGE
LEVEL TIME LEVEL TIME LEVEL TIME
0.5 lb 60% 20 sec. 40% 20 sec. 30% 45 sec.
5. If improper operation is indicated, the control unit is probably defective and
should be checked.

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-8
#813632 - Revision B - December, 2009
PROCEDURES TO BE TAKEN WHEN THE FUSE ON THE PRINTED WIRING
BOARD (PWB) IS OPEN:
To protect the electronic circuits, this model is provided with a fuse added to the
primary on the PWB.
1. Fuse check and repairs.
• Disconnect the power supply cord.
• Remove the outer case cabinet.
• Open the door and block it open.
• Discharge high voltage capacitor.
• If the Fuse is blown, replace power unit.
• Make a visual inspection of the varistor. Check for burned damage. If the
varistor has been burned, replace the power unit.
• Examine the touch control transformer with a tester for the presence of
layer short-circuit (check the primary coil resistance which is approximate-
ly 151.6? ± 10%). If any abnormal condition is detected, replace the
touch control transformer.
• Reconnect all leads removed from components during testing.
• Re-install the outer case (cabinet).
• Reconnect the power supply cord after the outer case is installed.
• Run the oven and check all functions.
2. Follow the troubleshooting guide given below, if indicator does not light up
after above check and repairs are finished.
• Disconnect the power supply cord.
• Remove the outer case cabinet.
• Open the door and block it open.
• Discharge high voltage capacitor.
• Disconnect the leads to the primary of the power transformer.
• Ensure that these leads remain isolated from other components and oven
chassis by using insulation tape.
• After that procedure, re-connect the power supply cord.
• Follow the troubleshooting guide given below for repair.
COMPONENT TESTPROCEDURE LETTER
E
STEPS OCCURRENCE CAUSE OR CORRECTION
1
The rated AC voltage is not present
between Pin Nos. 5 and 7 of the 4-
pin connector (CN-A).
Check supply voltage and oven
power cord.
2
The rated AC voltage is present at
primary side of touch control trans-
former.
Touch control transformer or sec-
ondary circuit defective.Check and
replace touch control transformer or
power unit.
• Disconnect the power supply cord, and then remove outer case.
• Open the door and block it open.
• Discharge high voltage capacitor.
• Reconnect all leads removed from components during testing.
• Re-install the outer case (cabinet).
• Reconnect the power supply cord after the outer case is installed.
• Run the oven and check all functions.

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-9 #813632 - Revision B - December, 2009
AH SENSOR TEST:
Checking the initial sensor cooking condition
COMPONENT TESTPROCEDURE LETTER
F
THE OVEN SHOULD BE FULLY ASSEMBLED BEFORE ATTEMPTING THE FOL-
LOWING PROCEDURE.
1. The oven should be plugged in at least two minutes before sensor cooking.
2. Room temperature should not exceed 95°F (35°C).
3. The unit should not be installed in any area where heat and steam are gener-
ated. The unit should not be installed, for example, next to a conventional
surface unit. Refer to the “INSTALLATION INSTRUCTIONS” of the operation
manual.
4. Exhaust vents are provided on the back of the unit for proper cooling and air
flow in the cavity. To permit adequate ventilation, be sure to install so as not
to block these vents. There should be some space for air circulation.
5. Be sure the exterior of the cooking container and the interior of the oven are
dry. Wipe off any moisture with a dry cloth or paper towel.
6. The Sensor works with food at normal storage temperature. For example,
chicken pieces would be at refrigerator temperature and canned soup at room
temperature.
7. Avoid using aerosol sprays or cleaning solvents near the oven while using
Sensor settings. The sensor will detect the vapor given of by the spray and
turn off before food is properly cooked.
8. If the sensor has not detected the vapor of the food, ERROR will appear and
the oven will shut off.
Water Load Cooking Test:
Make sure the oven has been plugged in at least two minutes before checking
sensor cook operation. The cabinet should be installed and screws tightened.
1. Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter meas-
uring cup.
2. Place the container on the center of tray in the oven cavity.
3. Close the drawer.
4. Touch the TIMER/CLOCK pad once, the POWER LEVEL pad twice and the
START pad once. And touch the number pads 1 once and the number pad 4
once. Now, the oven is in the sensor cooking condition, and “AH20” and “ON”
will appear in the display.
5. The oven will operate for the first 16 seconds, without generating microwave
energy.
NOTE: ERROR will appear if the door is opened or STOP/CLEAR pad is
touched during first stage of sensor cooking.
6. After approximately 16 seconds, microwave energy is produced. If ERROR is
displayed or the oven does not turn off, replace the AH sensor or check the
control unit, refer to explanation below. If the oven stops after 5 minutes and
no ERROR code is displayed, then the AH sensor is normal. Check other
parts except the AH sensor.
(This Section continues on the next page)

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-10
#813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
F
(Cont.)
TESTING METHOD FOR AH SENSOR AND/OR CONTROL UNIT:
To determine if the sensor is defective, the simplest method is to replace it with a
new replacement sensor.
1. Disconnect the power supply cord, and then disassemble as per “Drawer
Microwave Disassembly” Section 4 Component Access Removal, Page 4-6.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Remove the AH sensor.
5. Install the new AH sensor.
6. Reconnect all leads removed from components during testing.
7. Re-install the covers.
8. Reconnect the power supply cord after the covers are installed.
9. Reconnect the oven to the power supply and check the sensor cook operation
as follows:
• Fill approximately 200 milliliters (7.2 oz) of tap water in a 1000 milliliter
measuring cup.
• Place the container on the center of tray in the oven cavity.
• Close the drawer.
• Touch the TIMER/CLOCK pad once, the POWER LEVEL pad twice and
the START pad once. And touch the number pads 1 once and the num-
ber pad 4 once.
• The control panel is in automatic Sensor operation.
• The oven turns off automatically, and the time for detecting moisture will
be displayed.
If new sensor does not operate properly, the problem is with the control unit, and
refer to explanation be-low.
CHECKING CONTROL UNIT:
1. Disconnect the power supply cord, and then disassemble as per “Drawer
Microwave Disassembly” Section 4 Component Access Removal, Page 4-6.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the sensor connector that is mounted to control panel.
5. Then connect the dummy resistor circuit (see fig.) to the sensor connector of
control panel.
6. Disconnect the leads to the primary of the power transformer.
7. Ensure that these leads remain isolated from other components and oven
chassis by using insulation tape.
8. After that procedure, re-connect the power supply cord.
9. Check the sensor cook operation proceed as follows:
• Close the door. Touch the TIMER/CLOCK pad once, the POWER LEVEL
pad twice and the START pad once. And touch the number pads 1 once
and the number pad 4 once.
• The control panel is in the sensor cooking operation.
• After approximately 25 seconds, push plunger of select switch for more
than 3 seconds. This condition is same as judgement by AH sensor.
• After approximately 3 seconds, the display shows “ X X . X X “ which is
the time for detecting moisture. If the above is not the case, the control
unit is probably defective. If the above is proper, the AH sensor is proba-
bly defective. If the above is proper, the AH sensor is probably defective.
(This Section continues on the next page)

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-11 #813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
F
(Cont.)
10. Disconnect the power supply cord, and then remove covers.
11. Open the drawer and block it open.
12. Discharge high voltage capacitor.
13. Disconnect the dummy resistor circuit from the sensor connector of control
panel.
14. Carry out necessary repair.
15. Reconnect all leads removed from components during testing and repairing.
16. Re-install the covers.
17. Reconnect the power supply cord after the outer case is installed. Run the
oven and check all functions.
18. Carry out “Water load cooking test” again and ensure that the oven works
properly.
R1, R2 : 22 Ω ± 1% 1/2W
R3 : 4.3k Ω ± 5% 1/4W
R4 : 1M Ω ± 5% 1/4W
Plunger NC
NO
COM
COM NO
NC
R3 R4
R1
R2
1
2
3
F-1
F-2
F-3
To connector (F)
on Control Unit.
CONNECTOR
Refer to the Disassembly instructions found on page 16.
GMAGNETRON ASSEMBLY TEST:
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. To test for an open filament, isolate the magnetron from the high voltage cir-
cuit. A continuity check across the magnetron filament leads should indicate
less than 1 ohm.
5. To test for a shorted magnetron, connect the ohmmeter leads between the
magnetron filament leads and chassis ground. This test should indicate an
infinite resistance. If there is little or no resistance the magnetron is grounded
and must be replaced.
6. Reconnect all leads removed from components during testing.
7. Reassemble the unit.
8. Reconnect the power supply cord.
9. Run the oven and check all functions. (This Section continues on the next page)

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-12
#813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
G
(Cont.)
MICROWAVE OUTPUT POWER:
• THE OVEN SHOULD BE FULLY ASSEMBLED BEFORE ATTEMPTING THE
FOLLOWING PROCEDURE.
• HIGH VOLTAGES ARE PRESENT DURING COOK CYCLE, SO EXTREME CAU-
TION SHOULD BE OBSERVED.
Power output of the magnetron can be measured by performing a water tempera-
ture rise test. This test should only be used if above tests do not indicate a faulty
magnetron and there is no defect in the following components or wiring: This test
will require a 16 ounce (453cc) measuring cup and an accurate mercury ther-
mometer or thermocouple type temperature tester. For accurate results, the fol-
lowing procedure must be followed carefully:
1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the tem-
perature of the water with a thermometer or thermocouple temperature tester.
Stir the thermometer or thermocouple through the water until the temperature
stabilizes. Record the temperature of the water.
2. Place the cup of water in the oven. Operate oven at POWER 10(HIGH)
selecting more than 60 seconds cook time. Allow the water to heat for 60
seconds, measuring with a stop watch, second hand of a watch or the digital
read-out countdown.
3. Remove the cup from the oven and again measure the temperature, making
sure to stir the thermometer or thermocouple through the water until the maxi-
mum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature. The
normal result should be 28° to 54°F (16° to 30°C) rise in temperature. If the
water temperatures are accurately measured and tested for the required time
period the test results will indicate if the magnetron tube has low power output
(low rise in water temperature) which would extend cooking time or high
power output (high rise in water temperature) which would reduce cooking
time. Because cooking time can be adjusted to compensate for power output,
the magnetron tube assembly should be replaced only if the water tempera-
ture rise test indicates a power output well beyond the normal limits. The test
is only accurate if the power supply line voltage is 120 volts and the oven cav-
ity is clean.

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-13 #813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
HTHERMAL CUT-OUT TEST:
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. A continuity check across the thermal cut-out terminals should indicate a
closed circuit unless the temperature of the thermal cut-out reaches approxi-
mately 293°F(145°C). An open thermal cut-out indicates overheating of the
oven, exchange the oven thermal cut-out and check inside of oven cavity and
for improper setting of cooking time or operation of control unit. Check for
restricted air flow through the vent holes of the oven cavity, especially the
cooling fan and air guide.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the unit and check all functions.
If the thermal cut-out indicates an open circuit at room temperature, replace
thermal cut-out.
ISECONDARY INTERLOCK SWITCH TEST:
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Isolate the switch and connect the ohmmeter to the common (COM.) and nor-
mally open (NO) terminal of the switch. The meter should indicate an open
circuit with the drawer open and a closed circuit with the drawer closed. If
improper operation is indicated, replace the secondary interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
JSTOP SWITCH TEST:
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Isolate the switch and connect the ohmmeter to the common (COM.) and nor-
mally open (NO) terminal of the switch. The meter should indicate an open
circuit with the drawer open and a closed circuit with the drawer closed. If
improper operation is indicated, replace the stop switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
NOTE: If the stop switch contacts fail in the open position and the door is closed,
the cooling fan motor, stirrer motor and oven light will be activated by RY1.

Drawer Microwave (Models MWD24-2 / MWD30-2)
Troubleshooting Guide
5-14
#813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
KMONITOR SWITCH TEST:
1. Disconnect the power supply cord.
2. Open the drawer and keep it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Before performing this test, make sure that the secondary interlock switch,
according to the above Switch Test Procedure. Disconnect the wire lead from
the monitor switch (COM) terminal. Check the monitor switch operation by
using the ohmmeter as follows. When the drawer is open, the meter should
indicate a closed circuit. When the monitor switch actuator is pushed by a
screw driver through the lower latch hole on the front plate of the oven cavity
with the drawer opened (in this condition the plunger of the monitor switch is
pushed in), the meter should indicate an open circuit. If improper operation is
indicated, the switch may be defective and both the monitor switch, plus fuse
will need to be replaced. After testing the monitor switch, reconnect the wire
lead to the monitor switch (COM) terminal and check the continuity of the
monitor circuit.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
Ohmmeter
Monitor Switch
Secondary
Interlock Switch
Screwdriver
BRN,BLK
BRN,GRY
RED
BLK

Troubleshooting Guide
Drawer Microwave (Models MWD24-2 / MWD30-2)
5-15 #813632 - Revision B - December, 2009
COMPONENT TESTPROCEDURE LETTER
LBLOWN MONITOR FUSE TEST:
1. Disconnect the power supply cord.
2. Open the drawer and block it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. If the monitor fuse is blown when the drawer is opened, check the primary
interlock switch, secondary interlock switch and monitor switch according to
the “TEST PROCEDURE” for those switches before replacing the blown mon-
itor fuse.
Before replacing a blown monitor fuse, test the secondary interlock switch,
stop switch and monitor switch for proper operation.
HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO
NOT ATTEMPT TO MEASURE THE FILAMENT AND HIGH VOLTAGE.
If the monitor fuse is blown by improper switch operation, the monitor fuse and
monitor switch must be replaced with “monitor fuse and monitor switch assembly”
See Section 5, even if the monitor switch operates normally. The monitor fuse
and monitor switch assembly is comprised of a 20 ampere fuse and switch.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.
MPOWER TRANSFORMER TEST:
1. Disconnect the power supply cord.
2. Open the drawer and block it open.
3. Discharge high voltage capacitor.
4. Disconnect the primary input terminals and measure the resistance of the
transformer with an ohmmeter. Check for continuity of the coils with an ohm-
meter. On the R x 1 scale, the resistance of the primary coil should be less
than 1 ohm and the resistance of the high voltage coil should be approximate-
ly 90 ohms; the resistance of the filament coil should be less than 1 ohm.
5. Reconnect all leads removed from components during testing.
6. Reassemble the unit.
7. Reconnect the power supply cord.
8. Run the oven and check all functions.