Sharp R1500 Service Manual

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SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2. COOKING TIME PROGRAMMED.
3. VARIABLE COOKING CONTROL "HIGH".
4. "START" BUTTON PRESSED.
Figure O-2. Oven Schematic-Cooking ConditionFigure O-1. Oven Schematic-Off Condition
SCHEMATIC
NOTE: CONDITION OF OVEN
1. DOOR CLOSED.
2.  CLOCK APPEARS ON DISPLAY.
NOTE: "    " indicates components with potential above 250V.
MAGNETRON 
TEMPERATURE FUSE
FUSE 
20A
TURNTABLE
MOTOR
FAN
MOTOR
MAGNETRON OVEN LAMP
MONITOR
SWITCHBLK WHT
POWER
TRANSFORMER
HIGH VOLTAGE
CAPACITOR
0.94µF/ AC2300V
HIGH VOLTAGE
RECTIFIER  COM. N.O.
COM. CONTROL UNIT
GND GRN
HOOD
MOTORA5
B5
B7
B9
Low High
A1 A3 B1 B3N.O.E1 E2DOOR
SENSING
SWITCH
PRIMARY
INTERLOCK
SWITCH 120 V AC.
60 Hz 
HOOD
LAMP
HL
RY1RY2
SECONDARY
INTERLOCK 
RELAY OVEN LAMP
RELAY
FMOLTTM
HOOD FAN
THERMAL
CUT OUT
HOOD
CAPACITORRY4
RY6
RY5 RY3
N.C.
CAVITY 
THERMAL CUT-OUT
HL
MAGNETRON 
TEMPERATURE FUSE
FUSE 
20A
TURNTABLE
MOTOR
FAN
MOTOR
MAGNETRON OVEN LAMP
MONITOR
SWITCHBLK WHT
POWER
TRANSFORMER
HIGH VOLTAGE
CAPACITOR
0.94µF/ AC2300V
HIGH VOLTAGE
RECTIFIER  COM. N.O.
COM. CONTROL UNIT
GND GRN
HOOD
MOTORA5
B5
B7
B9
Low High
A1 A3 B1 B3N.O.E1 E2DOOR
SENSING
SWITCH
PRIMARY
INTERLOCK
SWITCH 120 V AC.
60 Hz 
HOOD
LAMP
HL
RY1RY2
SECONDARY
INTERLOCK 
RELAY OVEN LAMP
RELAY
FMOLTTM
HOOD FAN
THERMAL
CUT OUT
HOOD
CAPACITORRY4
RY6
RY5 RY3
N.C.
CAVITY 
THERMAL CUT-OUT
HL 
						

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DESCRIPTION AND FUNCTION OF COMPONENTS
3. If the door is opened, and the secondary interlock relay
(RY2) and primary interlock 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 DOOR SENSING SWITCH,
SECONDARY INTERLOCK RELAY (RY2),
RELAY (RY1), PRIMARY INTERLOCK
SWITCH AND MONITOR SWITCH FOR
PROPER OPERATION. (REFER TO CHAP-
TER "TEST PROCEDURE").
NOTE: MONITOR FUSE AND SWITCH ARE REPLACED
AS AN ASSEMBLY
TEMPERATURE FUSE (MG)
The temperature fuse located on the fan duct assembly 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˚F
(150˚C) causing the oven to shut down.
NOTE: This is a fuse. It does not reset.
THERMAL CUT-OUT (HOOD )
This thermal cut-out located on the right base plate flange
(turntable motor side). 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˚F (60˚C) or higher, thus
removing this hot air from around microwave oven. When
the temperature around the thermal cut-out drops to 113˚F
(45˚C) or lower, the thermal cut-out shuts off the hood fan
motor.
THERMAL CUT-OUT (CAVITY )
This thermal cut-out is located on the bottom of the oven
cavity. It is designed to prevent damage to the oven unit if
the food in the oven catches fire due to overheating pro-
duced by improper setting of cooking time or failure of
control unit.
Under normal operation, the thermal cut-out  remains closed.
However, the thermal cut-out will open at 293˚F (145˚C)
causing the oven to shut down. The defective thermal cut-
out must be replaced with a new one.
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
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
DOOR SENSING AND PRIMARY INTERLOCK
SWITCHES
The primary interlock switch is mounted in the lower posi-
tion of the latch hook and the door sensing switch in the
secondary interlock system is mounted in the upper posi-
tion of the latch hook. They are activated by the latch heads
on the door. When the door is opened, the switches inter-
rupt the circuit to all components. A cook cycle cannot take
place until the door is firmly closed thereby activating both
interlock switches. The secondary interlock system con-
sists of the door sensing switch and secondary 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 relay (RY2) and primary interlock 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 (RY2)
and primary interlock switch are in the OFF condition
(contacts open) due to their being normally open contact
switches. And the contacts of relay (RY1) are in the ON
condition (contacts close).
2. As the door goes to a closed position, the monitor switch
contacts are first opened and then the door sensing
switch and the primary interlock switch contacts close.
(On opening the door, each of these switches operate
inversely.)
Latch hook
Door sensing
switch
Latch heads
Monitor switch
Primary interlock switch Open lever Door 
						

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TROUBLESHOOTING GUIDE
Never touch any part in the circuit with your hand or an uninsulated tool while the power supply is connected.
When troubleshooting the microwave oven, it is helpful to follow the Sequence of Operation in performing the checks. Many
of the possible causes of trouble will require that a specific test be performed. These tests are given a procedure letter which
will be found in the "Test Procedure "section.
IMPORTANT:If the oven becomes inoperative because of a blown  monitor fuse, check the monitor switch, relay (RY1)
secondary interlock relay (RY2), door sensing switch and primary interlock switch before replacing the
monitor fuse. If  monitor fuse is replaced, the monitor switch must also be replaced. Use part FFS-BA016/
KiT as an assembly.
IMPORTANT:Whenever troubleshooting is performed with the power supply cord disconnected. It may in, some cases,
be necessary to connect the power supply cord 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.
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.
HOOD LAMP
The hood lamps are mounted at the hood lamp angle on the
base cover. The hood lamps can be turned off and on by
touching the LIGHT HI/ LO button. And also the brightness
can be varied to high or low by touching the LIGHT HI/ LO
button. 
						

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CK = Check / RE = Replace
POSSIBLE CASE AND 
DEFECTIVE PARTS
PROBLEMTEST PROCEDURE
CONDITIONOFFCONDITIONIDLECONDITIONMICROWAVECOOKINGCONDITION
Home fuse blows when power cord is plugged into wall receptacle.
Monitor fuse blows when power cord is plugged into wall receptacle.
Display does not illuminate when power cord is first plugged into wall 
receptacle.
Display does not operate properly when STOP/CLEAR button is touched. 
(The time of day should appear on the display with beep sound during 
normal condition.)
Oven lamp does not light with door is opened.
Hood fan motor operates when power cord is first plugged into wall 
receptacle.
Temperature of oven base seems more than 140˚F (60˚C) because of\
 
operation of the range below. But hood fan motor does not turn on 
automatically. (Normally, food fan motor should be operating at low 
speed.)
Hood lights do not turn on when LIGHT HI/LO button is pressed.
Hood fan motor does not rotate at all with touched FAN HI/LO button.
Speed of the hood fan motor does not change when the FAN HI/LO button 
is touched for this function.
Oven lamp does not light in cook cycle. (But it does light when door is\
 
opened.)
Fan motor does not operate. (Oven lamp and turntable motor operate.)
Turntable motor does not operate (Oven lamp lights and fan motor 
operate.)
Oven does not go into cook cycle when START button is touched
Oven seems to be operating but little or no heat is produced in oven loa\
d. 
(Food incompletely cooked or not cooked at all at end of cook cycle.)
Oven goes into a cook cycle but extremely uneven heating is produced in \
oven load (food).
Variable cooking does not operate properly except Cooking Power 10 (P-
HI) mode.
Function of DEFROST CENTER does not operate properly.
Oven goes into DEFROST CENTER but food is not defrosted well.
CK LOW VOLTAGE
CK NO POWER AT OUTLET
RE
 SHORT IN POWER CORD
CK OPENED OR SHORTED WIRING
CK HOOD MOTOR CAPACITOR
RE HOOD LAMP OR SOCKET
RE TURNTABLE MOTOR
RE FAN MOTOR
RE OVEN LAMP OR SOCKET
P FOIL PATERN ON P.W.B.
O DEFROST   CENTER N RELAYS (RY-5), (TY6)
N RELAY (RY-4)
N RELAY (RY-3)
N RELAY (RY-2)
N RELAY (RY-1)
M KEY UNIT L CONTROL UNIT
K HOOD FAN MOTOR  J HOOD HERMAL CUT-OUT  I MONITOR FUSE 
H MONITOR SWITCH
GSECONDARY INTERLOCK SYSTEM
F PRIMARY INTERLOCK  SWITCH
ETEMPERATURE FUSE OR THERMAL CUT-OUT
D HIGH VOLTAGE CAPACITOR
C H.V. RECTIFIER  B POWER TRANSFORMER
A MAGNETRON 
						

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BPOWER TRANSFORMER TEST
TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT 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. To test for an open filament, isolate the magnetron from the high voltage circuit. 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. Reinstall the outer case (cabinet).
8. Reconnect the power supply cord after the outer case is installed.
9. Run the oven and check all functions.
MICROWAVE OUTPUT POWER
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted).
HIGH VOLTAGES ARE PRESENT DURING THE COOK CYCLE, SO EXTREME CAUTION SHOULD
BE OBSERVED.
Power output of the magnetron can be measured by performing a water temperature 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: silicon rectifier, high voltage capacitor and power transformer. This test will require
a 16 ounce (453cc) measuring cup and an accurate mercury thermometer or thermocouple type
temperature tester. For accurate results, the following procedure must be followed carefully:
1. Fill the measuring cup with 16 oz. (453cc) of tap water and measure the temperature 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 maximum temperature is recorded.
4. Subtract the cold water temperature from the hot water temperature. The normal result should be 29.2
to 54.2˚F(16.2 to 30.1˚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
temperature 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 cavity is clean.
AMAGNETRON ASSEMBLY 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 primary input terminals and measure the resistance of the transformer with an
ohmmeter. Check for continuity of the coils with an ohmmeter. 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
approximately 83 ohms; the resistance of the filament coil should be less than 1 ohm.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions. 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT 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. If the capacitor is open, no high voltage will be available to the magnetron. Disconnect input leads
and check for short or open between the terminals using an ohmmeter.
Checking with a high ohm scale, if the high voltage capacitor is normal, the meter will indicate
continuity for a short time and should indicate an open circuit once the capacitor is charged. If the
above is not the case, check the capacitor with an ohmmeter to see if it is shorted between either of
the terminals and case. If it is shorted, replace the capacitor.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
DHIGH VOLTAGE CAPACITOR TEST
ECAVITY THERMAL CUT-OUT 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. A continuity check across the thermal cut-out terminals should indicate a closed circuit unless the
temperature of the thermal cut-out reaches approximately 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. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
 MAGNETRON TEMPERATURE FUSE 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. A continuity check across the temperature fuse terminals should indicate a closed circuit. If the
temperature of the magnetron reaches approximately 302˚F(150˚C), the temperature fuse opens. An
open temperature fuse indicates overheating of the magnetron. Check for restricted air flow to the
magnetron, especially the cooling fan air guide.
5. Reconnect all leads removed from components during testing.
CHIGH VOLTAGE RECTIFIER 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. Isolate the rectifier from the circuit. Using the highest ohm scale of the meter, read the resistance
across the terminals and observe, reverse the leads to the rectifier terminals and observe meter
reading. If a short is indicated in both directions, or if an infinite resistance is read in both directions,
the rectifier is probably defective and should be replaced.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: Be sure to use an ohmmeter that will supply a forward bias voltage of more than 6.3 volts. (HIGH VOLTAGES ARE PRESENT AT THE HIGH VOLTAGE TERMINAL, SO DO NOT ATTEMPT TO
MEASURE THE FILAMENT AND HIGH VOLTAGE.) 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT 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. Before performing this test, make sure that the primary interlock switch and the secondary interlock
relay are operating properly, according to the above Switch and Interlock system Test Procedures.
Disconnect the wire lead from the monitor switch (COM) terminal. Check the monitor switch operation
by using the ohmmeter as follows. When the door 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
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
CAUTION: IF THE THERMAL CUT-OUT OR TEMPERATURE FUSE INDICATES AN OPEN CIRCUIT
AT ROOM TEMPERATURE, REPLACE THERMAL CUT-OUT OR TEMPERATURE FUSE.
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. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal
of the switch. The meter should indicate an open circuit with the door open and a closed circuit with
the door closed. If improper operation is indicated, replace the secondary interlock switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
FPRIMARY INTERLOCK SWITCH TEST
HMONITOR SWITCH TEST
GSECONDARY INTERLOCK SYSTEM TEST
DOOR SENSING SWITCH
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. Isolate the switch and connect the ohmmeter to the common (COM.) and normally open (NO) terminal
of the switch. The meter should indicate an open circuit with the door open and a closed circuit with
the door closed. If improper operation is indicated, replace the door sensing switch.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
NOTE: If the door sensing 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.
SECONDARY INTERLOCK RELAY (RY2)
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 two (2) wire leads from the male tab terminals of the Secondary Interlock Relay. Check
the state of the relay contacts using a ohmmeter. The relay contacts should be open. If the relay
contacts are closed, replace the circuit board entirely or the relay itself.
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions. 
						

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IBLOWN MONITOR FUSE TEST
TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT 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. If the monitor fuse is blown when the door is opened, check the secondary interlock relay, primary
interlock switch and monitor switch according to the "TEST PROCEDURE" for those switches before
replacing the blown monitor fuse.
CAUTION: BEFORE REPLACING A BLOWN MONITOR FUSE, TEST THE SECONDARY INTER-
LOCK RELAY, PRIMARY INTERLOCK SWITCH, DOOR SENSING SWITCH AND MONI-
TOR SWITCH FOR PROPER OPERATION.
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" part number FFS-BA016/KiT, 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. 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.plate of the oven cavity with the door 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. 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. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord
after the outer case is installed.
8. Run the oven and check all
functions.
JHOOD THERMAL CUT-OUT 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. A continuity check across the thermal cut-out terminals should indicate an open circuit unless the
temperature of the thermal cut-out reaches approximately 140˚F(60˚C) or more. At  that temperature,
the contacts will close. The thermal cut-out opens automatically at approximately 113˚F(45˚C).
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
KHOOD FAN MOTOR 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. If the motor does not turn, touch the FAN HI / LO button once (set hood fan motor power "HIGH") and
check voltage between pins "1" and "2" (Blue and Black wires) of the 6 pin connector. If 120 Volts
appear and the hood capacitor is good, replace the hood fan assembly. If 120 Volts does not appear,
check the motor circuit. The resistance values of motor terminals are as follows:
Primary
Interlock Switch
Monitor Switch
Screw Driver
Ohmmeter
RedWhite/ White 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
Resistance between;
BLU (1) AND YLW (4) = 0Ω(Shorted)
BLK (2) AND YLW (4) = 33Ω
BLU (1) AND BLK (2) = 33Ω
BLK (2) AND WHT (3) = 11Ω
WHT (3) AND RED (5) = 22Ω
6-PIN CONNECTOR
OF HOOD FAN MOTOR
5. Reconnect all leads removed from components during testing.
6. Reinstall the outer case (cabinet).
7. Reconnect the power supply cord after the outer case is installed.
8. Run the oven and check all functions.
LTOUCH 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 two units, Control
Unit and Key Unit, and also the Control Unit is divided into two units, LSI Unit and Power Unit, and
troubleshooting by unit replacement is described according to the symptoms indicated.
Before testing,
1) Disconnect the power supply cord, and then remove outer case. Refer to procedure of " HOOD
EXHAUST LOUVER REMOVAL ", " REMOVAL OF OVEN FROM WALL " and " OUTER CASE
REMOVAL ".
2) Open the door and block it open.
3) To discharge high voltage capacitor, wait for 60 seconds.
4) Remove two (2) screws holding the hood intake duct R to the ovencavity top plate and the base
plate R. And remove the hood intake duct R.
5) Disconnect the leads to the primary of the power transformer.
6) Ensure that these leads remain isolated from other components and oven chassis by using
insulation tape.
1. Key Unit.
NOTE ;
1) Check key unit ribbon connection before replacement.
2) Reconnect all leads removed from components during testing.
3) Re-install the hood intake duct R with two (2) screws.
4) Re-install the outer case (cabinet).
5) Reconnect the power supply cord after the outer case is installed.
6) Run the oven and check all functions.
The following symptoms indicate a defective key unit.
a) When touching the pads, a certain pad produces no signal at all.
b) When touching a number pad, two figures or more are displayed.
c) When touching the pads, sometimes a pad produces no signal.
If the key unit is defective.
1) Disconnect the power supply cord, and then remove outer case.
2) Open the door and block it open.
3) To discharge high voltage capacitor, wait for 60 seconds.
4) Replace the key unit.
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.
33 Ω
11 Ω 22 Ω HOOD FAN
CAPACITORYLW
REDBLU
BLK1
2
3
WHT
4
5
BLU BLK
YLW REDWHT12
45
3 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
8) Run the oven and check all functions.
2. Control Unit.
The following symptoms  indicate a defective control unit.  Before replacing the control unit, perform
the Key unit test (Procedure M) to determine if control unit is faulty.
2-1 In connection with pads.
a) When touching the pads, a certain group of pads do not produce a signal.
b) When touching the pads, no pads produce a signal.
2-2 In connection with indicators
a) At a certain digit, all or some segments do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.
2-3 Other possible problems caused by defective control unit.
a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.
When testing is completed,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) To discharge high voltage capacitor, wait for 60 seconds.
4) Reconnect all leads removed from components during testing.
5) Re-install the hood intake duct R.
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.
1. Disconnect the power supply cord.
2. Open the door and block it open.
3. To discharge high voltage capacitor, wait for 60 seconds.
4. Remove the control panel assembly.
5. If the display fails to clear when the STOP/CLEAR pad is depressed, first verify 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 door is closed and open when the door 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 door sensing switch is closed (either close the door 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 contact.
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.
6. Reconnect all leads
removed from components
during testing.
7. Re-install the control panel
assembly.
8. Reconnect the power
supply cord.
9. Run the oven and check all
functions.
MKEY UNIT TEST
G11
G12
G 9
G 8
KEY UNIT
POPCORN RICEREHEAT
CENTER
POULTRY
BONELESS
FROZEN
VEGETABLESFRESH
VEGETABLES
POWER
LEVELBAKED
POTATOESPOULTRY
BONE-INTIMER
CLOCK FROZEN
ENTREESHOT
WATERLIGHT
HI / LO
FAN
HI / LO
STEAKS /
CHOPS12
453
86
9
0 7
GROUND
MEAT
(DEFROST CENTER)GROUND
MEAT
(COOK CENTER)KEEP
WARM
G 7G 6G 5G 4G 3G 2G 1
G10
STOP
CLEAR
START
MINUTE
PLUS