Sharp R9h56 Service Manual

							R-9H56
9
Microwave Cooking:
Damper is in the open position, because a portion of cooling
air is channelled through the cavity to remove steam and
vapours given off from the heating foods.
It is then exhausted at the top of the oven cavity into a
condensation compartment.
Convection Cooking:
Damper is in the closed position, so that no hot air will be
allowed to leak out the oven cavity.
Damper Operation
1. When power supply cord is plugged in:
1-1. When power supply cord is plugged in, a signal is
sensed in the control unit, and operates shut-off relay
(RY4).
1-2. Contacts of shut-off relay (RY4) close, the damper
motor is energized, opening the damper door.
1-3. When the damper is moved to the open position by the
damper cam, damper switch is closed (ON position).
1-4. The signal of damper switch is re-sensed in the control
unit and shut-off relay (RY4) is turned off.
1-5. The 240 volts A.C. to the damper motor is stopped and
the motor turns off.
2. When oven is microwave cooking:
Damper is in the open position
3. When oven is convection cooking:
3-1 Damper motor is energized by touching the convection,
temperature and START pads.
3-2. When damper is in the closed position (damper switch
is OFF), its signal is sensed by the control unit, and
shut-off relay (RY4) is de-energized.
3-3. The damper is held in the closed position during the
convection cooking operation.3-4. At the end of the convection cooking, shut-off relay
(RY4) is energized, and the damper is returned to the
open position.
NOTE: If the damper door is not in the proper position,
closed during convection or open during microwave,
the control unit will stop oven operation after 1
minute.
Cooking Mode Operation of Damper
Microwave cooking OPEN
Convection cooking CLOSE
Sensor cooking OPEN
Automatic mix cooking CLOSE
Grill cooking CLOSE
Slow cooking CLOSE
DAMPER DUCT
DAMPER 
DAMPER CAM
DAMPER MOTORDAMPER SWITCH DAMPER SHAFT
Figure D-2. Damper Mechanism 
						

							R-9H56
10
 WARNING TO SERVICE PERSONNEL
Microwave ovens contain circuitry capable of producing very high voltage and current, contact with any part of the
high voltage circuit will result in electrocution. High voltage capacitor, Power transformer, Magnetron, High voltage
rectifier assembly, High voltage harness.
 REMEMBER TO CHECK 
3D
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge high voltage capacitor.
WARNING:AGAINST THE CHARGE OF THE
HIGH-VOLTAGE CAPACITOR
The high-voltage capacitor remains charged about
60 seconds after the oven has been switched off.
Wait for 60 seconds and then short-circuit the con-
nection of the high-voltage capacitor (that is, of the
connecting lead of the high-voltage rectifier) against
the chassis with the use of an insulated screwdriver.
Sharp recommend that wherever possible fault-finding
is carried out with the supply disconnected. It may in,
some cases, be necessary to connect the supply after
the outer case has been removed, in this event carry out
3D checks and then disconnect the leads to the primary
of the power transformer. Ensure that these leads re-
main isolated from other components and the oven
chassis. (Use insulation tape if necessary.) When the
testing is completed carry out 
3D checks and reconnect
the leads to the primary of the power transformer. REMEMBER TO CHECK 
4R
1) Reconnect all leads removed from components during
testing.
2) Replace the outer case (cabinet).
3) Reconnect the supply.
4) Run the oven. 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 microwave timer for two (2) minutes. Set the
power level to HIGH and push the START button. When
the two minutes has elapsed (timer at zero) carefully
check that the water is now hot. If the water remains cold
carry out 
3D checks and re-examine the connections 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 microwave leakage test carried out
SERVICING
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.
TROUBLESHOOTING GUIDE
IMPORTANT: If the oven becomes inoperative because of
a blown fuse M8A in the upper latch switch
- lower latch switch - monitor switch - moni-
tor resistor circuit, check the upper latch
switch, lower latch switch, monitor switch
and  monitor resistor before replacing the
fuse M8A. 
						

							R-9H56
11
MAGNETRONPOWER TRANSFORMERH.V. RECTIFIER ASSEMBLYHIGH VOLTAGE CAPACITORLATCH AND STOP SWITCHESMONITOR SWITCHDAMPER SWITCHMAIN FUSETEMPERATURE FUSE 150ûCTHERMAL CUT-OUTCONVECTION HEATERTHERMISTORFAN MOTORTURNTABLE MOTORCONVECTION MOTORDAMPER MOTORMONITOR RESISTORTOUCH CONTROL PANELKEY UNITRELAY (RY-1)RELAY (RY-2)RELAY (RY-3)RELAY (RY-4)RELAY (RY-5)RELAY (RY-6)FOIL PATERN ON P.W.B.AH. SENSOROVEN LAMP OR SOCKETOPENED OR SHORTED WIRE HARNESSWALL OUTLETLOW POWER SUPPLY VOLTAGE
SHORTED POWER CORD
Home fuse blows when power
supply cord is plugged into wall
outlet.
Fuse M8A blows when power
cord is plugged into wall outlet.
88:88 does not appear in display
when power cord is first plugged
into wall outlet.
Display does not operate prop-
erly when STOP/CLEAR pad is
touched. (The time of day should
appear on the display with beep
sound during normal condition.)
Oven lamp does not light with
door opened.
Oven lamp does not light at all
Oven lamp light, but turntable
motor does not operate.
Cooling fan motor does not oper-
ate.
The oven stops after1 minute
 Oven does not go into a cook
cycle, when START pad is
touched.
Low or no power is produced
during microwave cooking (The
food is heated incompletely or
not heated at all)
Extremely uneven heating is pro-
duced in oven load (food).
Function of variable cooking does
not operate properly except HIGH
power.
CONV indicator lights, but heat-
ing element does not heat.
Temperature in the oven cavity is
lower or higher than preset.
Convection cycle runs 1 minute
then the oven shuts down.
Convection cycle runs 3 minutes
then the oven shuts down.
Oven is in the sensor cooking con-
dition but AH sensor does not end
1st. stage or does not stop cooking
cycle or the oven stops 
soon.
CK = Check / RE = Replace
OFF
CONDITION
PROBLEM
TEST PROCEDURE
POSSIBLE CAUSE
AND
DEFECTIVE PARTSABC
DE E EFGGH I JJ J J K LMNNNNNNOPRE CKCK CK RE
CONDITION
COOKING
CONDITION
(MICROWAVE)
(CONVECTION)
(AH. SENSOR) 
						

							R-9H56
12 TEST PROCEDURES
PROCEDURE
LETTER
CARRY OUT 3D CHECK.
Isolate the magnetron from high voltage circuit by removing all leads connected to filament terminal.
To test for an open circuit filament use an ohmmeter to make a continuity test between the magnetron
filament terminals, the meter should show a reading of less than 1 ohm.
To test for short filament to anode condition, connect ohmmeter between one of the filament terminals
and the case of the magnetron (ground). This test should be indicated an infinite resistance. If a low or
zero resistance reading is obtained then the magnetron should be replaced.
MICROWAVE OUTPUT POWER (1 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (outer case fitted). Microwave output power from the magnetron can be measured by way of
IEC 705, i.e. it can be measured by using water load how much it can be absorbed by the water load.
To measure the microwave output power in the microwave oven, the relation of calorie and watt is used.
When P(W) heating works for t(second), approximately P x t/4.187 calorie is generated. On the other
hand, if the temperature of the water with V(ml) rises DT (°C) during this microwave heating period, the
calorie of the water is V x DT. NEVER TOUCH ANY PART IN THE CIRCUIT WITH YOUR HAND OR AN INSULATED TOOL
WHILE THE OVEN IS IN OPERATION.
AMAGNETRON TEST
The formula is as follows;
P x t / 4.187 = V x D T P (W) = 4.187 x V x DT / t
Our condition for water load is as follows:
Room temperature.........around 20°C Power supply Voltage....Rated voltage
Water load......1000 g Initial temperature......10±2°C Heating time......49 sec.
P = 85 x DT
COMPONENT TEST
Measuring condition:
1. Container
The water container must be a cylindrical borosilicate glass vessel having a maximum material
thickness of 3 mm and an outside diameter of approximately 190 mm.
2. Temperature of the oven and vessel
The oven and the empty vessel are at ambient temperature prior to the start the test.
3. Temperature of the water
The initial temperature of the water is (10±2)°C.
4. Select the initial and final water temperature so that the maximum difference between the final water
temperature and the ambient temperature is 5°C.
5. Select stirring devices and measuring instruments in order to minimize addition or removal of heat.
6. The graduation of the thermometer must be scaled by 0.1°C at minimum and accurate thermometer.
7. The water load must be (1000±5) g.
8. ÒtÓ is measured while the microwave generator is operating at full power. Magnetron filament heat-
up time is not included.
NOTE: The operation time of the microwave oven is Òt + 2Ó sec. 2 sec. is magnetron filament heat-up time.
Measuring method:
1. Measure the initial temperature of the water before the water is added to the vessel.
(Example: The initial temperature T1 = 11°C)
2. Add the 1 litre water to the vessel.
3. Place the load on the centre of the shelf.
4. Operate the microwave oven at HIGH for the temperature of the water rises by a value D T of
(10 ± 2)°C.
5. Stir the water to equalize temperature throughout the vessel. 
						

							R-9H56
13 TEST PROCEDURES
PROCEDURE
LETTER
COMPONENT TEST
6. Measure the final water temperature. (Example: The final temperature T2 = 21°C)
7. Calculate the microwave power output 
P in watts from above formula.
Initial temperature ...........................  T1 = 11°C
Temperature after (49 + 2) = 51 sec. ..............  T2 = 21°C
Temperature difference Cold-Warm ...............  DT1 = 10°C
Measured output power
The equation is ÒP = 85 x DTÓ .............. P = 85 x 10°C = 850 Watts
JUDGMENT: The measured output power should be at least ± 15 % of the rated output power.
CAUTION: 1°C CORRESPONDS TO 85 WATTS REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
1000g
1000g
1000g
T1˚C
T2˚C
Heat up for51 sec.
MICROWAVE OUTPUT POWER (2 Litre water load)
The following test procedure should be carried out with the microwave oven in a fully assembled
condition (with outer case fitted).
Microwave output power from the magnetron can be measured by way of substitution, i.e. it can be
measured by using a water load how much it can be absorbed by the water load. To measure the
microwave output power in the microwave oven, the relation of calorie and watt is used.
On the other hand, if the temperature of the water with V(ml) rises DT (ûC) during this microwave heating
period, the calorie of the water is V x DT.
The formula is as follows;
P  = 8330 x D T / t
Our condition for water load is as follows:
Room temperature.........23±2ûC Power supply Voltage.....240 volts.
Water load.....2000 ml Initial temperature......23±1ûC    Heating time . 1  min. 51sec.
P = 75 x DT
Measuring method:
A) The two water containers must be prepared.
The water container must be one (1) litre beaker made of Pyrex  glass and its diameter approximately
12cm.
B) Put the one (1) litre water into each beaker (Each beaker has one litre water). The initial temperature
of the water should be 23±1ûC.
C) Mark T1 on the one beaker and mark T2 on the other one. And stir the water and measure the
temperature of water the thermometer and note them. The graduation of the thermometer must be
scaled by 0.1ûC at minimum and an accurate mercury thermometer is recommended.
D) Place the two (2) beakers as touching each other in the centre of the oven cavity.
E) Set the timer to 2 minutes and 20 seconds, start the oven at 100% power.
F) The time must be measured with stopwatch or wristwatch.
G) After 1 minutes and 51 seconds, stop the oven by opening the door.
H) Put the two (2) beakers out of the oven cavity and measure the temperature of the water by stirring
the water with thermometer and note them. 
						

							R-9H56
14 TEST PROCEDURES (CONTD)
Example
Initial temperature ....................... T1 = 23ûC   T2 = 24ûC
Temperature after 1 min. 51 sec. ............ T1 = 33ûC   T2 = 34ûC
Temperature difference Cold-Warm ............DT1 = 10ûC  DT2 = 10ûC
Mean temperature rise DT .........DT  = (DT1 ± DT2) / 2 = (10ûC+10ûC) / 2 = 10ûC
Measured output power
The equation is P= 75 x DT .................. P= 75 x 10ûC = 750 Watts
NOTE: The measured output power should be at least 
± 15 % of the rated output power.
CAUTION: 1ûC CORRESPONDS TO 75 WATTS. REPEAT MEASUREMENT IF THE POWER IS
INSUFFICIENT.
COMPONENT TEST
PROCEDURE
LETTER
1 l 1 l
(T1  C)(T2  C)
1 l 1 l
(T1  C)(T2  C)
Heat up for 1min. 51 sec.
BPOWER TRANSFORMER TEST
WARNING: High voltages and large currents are present at the secondary winding and filament
winding of the power transformer. It is very dangerous to work near this part when
the oven is on. NEVER make any voltage measurements of the high-voltage circuits,
including the magnetron filament.
CARRY OUT 3D CHECKS.
Disconnect the leads to the primary winding of the power transformer. Disconnect the filament and
secondary winding connections from the rest of the HV circuitry. Using an ohmmeter, set on a low range,
it is possible to check the continuity of all three windings. The following readings should be obtained:
a. Primary winding ........... approx. 1.3 W
b. Secondary winding ....... approx. 72 W
c. Filament winding ........ less than 1W
If the reading obtained are not stated as above, then the power transformer is probably faulty and should
be replaced.
CARRY OUT 
4R CHECKS.
CHIGH VOLTAGE RECTIFIER ASSEMBLY TEST
HIGH VOLTAGE RECTIFIER TEST
CARRY OUT 
3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can be tested
using an ohmmeter set to its highest range. Connect the ohmmeter across the terminal B+C of the high
voltage rectifier and note the reading obtained. Reverse the meter leads and note this second reading.
The normal resistance is infinite in one direction and more
than 100 kW in the other direction.
CARRY OUT 4R  CHECKS.
AB
CD2 D1
ASYMMETRIC
RECTIFIER
HIGH VOLTAGE RECTIFIER 
						

							R-9H56
15 TEST PROCEDURES (CONTD)
PROCEDURE
LETTERCOMPONENT TEST
ASYMMETRIC RECTIFIER TEST
CARRY OUT 
3D CHECKS.
Isolate the high voltage rectifier assembly from the HV circuit. The asymmetric can be tested using an
ohmmeter set to its highest range across the terminals A+B of the asymmetric rectifier and note the
reading obtained. Reverse the meter leads and note this second reading. If an open circuit is indicated
in both direction then the asymmetric rectifier is good. If an asymmetric rectifier is shorted in either
direction, then the asymmetric rectifier is probably faulty and must be replaced with high voltage rectifier.
When the asymmetric rectifier is defective, check whether magnetron, high voltage rectifier, high voltage
wire or filament winding of the power transformer is shorted.
CARRY OUT 4R CHECKS.
NOTE: FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE BATTERIES OF THE
MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT LEAST 6 VOLTS, BECAUSE
OTHERWISE AN INFINITE RESISTANCE MIGHT BE SHOWN IN BOTH DIRECTIONS.
DHIGH VOLTAGE CAPACITOR TEST
CARRY OUT 3D CHECKS.
A. Isolate the high voltage capacitor from the circuit.
B. Continuity check must be carried out with measuring instrument which is set to the highest resistance
range.
C. A normal capacitor shows continuity for a short time (kick) and then a resistance of about 10MW after it has
been charged.
D. A short-circuited capacitor shows continuity all the time.
E. An open capacitor constantly shows a resistance about 10 MW because of its internal 10MW resistance.
F. When the internal wire is opened in the high voltage capacitor shows an infinite resistance.
G. The resistance across all the terminals and the chassis must be infinite when the capacitor is  normal.
If incorrect reading are obtained, the high voltage capacitor must be replaced.
CARRY OUT 
4R CHECKS.
ESWITCH TEST
CARRY OUT 3D CHECKS.
Isolate the switch to be tested and using an ohmmeter check between the terminals as described in the
following table.
Table: Terminal Connection of Switch
Plunger Operation COM to NO COM to NC
Released O.C. S.C.
Depressed S.C. O.C.
COM; Common terminal
NO;     Normally open terminal
NC;     Normally close terminal
S.C.;   Short circuit
O.C.;   Open circuit
If incorrect readings are obtained, make the necessary switch adjustment or replace the switch.
CARRY OUT 
4R CHECKS.
FBLOWN FUSE F M8A
CARRY OUT 
3D CHECKS.
1. If the fuse M8A is blown, there could be shorts or grounds in electrical parts or wire harness. Check
them and replace the defective parts or repair the wire harness.
2. If the fuse M8A is blown when the door is opened, check the upper latch switch, lower latch switch,
monitor switch and monitor resistor.
If the fuse M8A is blown by incorrect door switching, replace the defective switch(s) and the fuse M8A.
3. If the fuse M8A is blown, there could be short in the asymmetric rectifier or there is a ground in wire
harness. A short in the asymmetric rectifier may have occured due to short or ground in H.V. rectifier,
magnetron, power transformer or H.V. wire. Check them and replace the defective parts or repair the
wire harness.
CARRY OUT 
4R CHECKS.
CAUTION: Only replace fuse with the correct value replacement. 
						

							R-9H56
16
PROCEDURE
LETTERCOMPONENT TEST TEST PROCEDURES (CONTD)
GTEMPERATURE FUSE AND THERMAL CUT-OUT TEST
 CARRY OUT 
3D CHECKS.
 Disconnect the leads from the terminals of the temp. fuse or thermal cut-out. Then using an ohmmeter,
make a continuity test across the two terminals as described in the table below.
 CARRY OUT 
4R CHECKS.
Table: Temperature Fuse and Thermal cut-out Test
Temperature of ÒONÓ condition Temperature of  ÒOFFÓ condition Indication ofohmmeter
Parts Name (closed circuit) (ûC) (open circuit) (ûC) (When room temperature
 is approx. 20ûC)
Temp. fuse 150ûC This is not resetable type. Above 150 ûC Closed circuit
Thermal cut-out 150ûC Below 130ûC Above 150ûC Closed circuit.
Thermal cut-out 95ûC Below 75ûC Above 95ûC Closed circuit.
If incorrect readings are obtained, replace the temp. fuse or thermal cut-out.;
An open circuit temperature fuse 150ûC (MG) indicates that the magnetron has overheated, this may be
due to resistricted ventilation, cooling fan failure or a fault condition within the magnetron or HV circuit.
 An open circuit thermal cut-out 150ûC (OVEN) indicates that the convection motor has over heated, this
may be due to convection motor locked.
 An open circuit thermal cut-out 95ûC (FM) indicates that the fan motor winding has overheated, this may
be due to blocked ventilation or locked cooling fan.
CARRY OUT 3D CHECKS.
Before carring out the following tests make sure the heater is fully cool.
1. Resistance of heater
Disconnect the wire leads to the heater to be tested. Using ohmmeter with low resistance range.
Check the resistance across the terminals of the heater.
The resistance of heater is approximately 37.5 ohms.
2. Insulation resistance
Disconnect the wire leads to the heater to be tested. Check the insulation resistance between the
element and cavity using a 500V - 100Mohms insulation tester. The insulation resistance should be
more than 10Mohms  in the cold start.
If the results of above test 1 and/or 2 are out of above specifications, the heater is probably faulty and
should be replaced.
CARRY OUT 
4R CHECKS.
 HCONVECTION HEATER TEST
CARRY OUT 
3D CHECKS.
Disconnect connector-E from the CPU unit. Measure the resistance of the thermistor with an ohmmeter.
Connect the ohmmeter leads to Pin NoÕs E-3 and E-4 of the thermistor harness.
Room Temp. ........... 20ûC - 30ûC
Resistance ......... Approx. 350kW - 155kW
If the meter does not indicate above resistance, replace the thermistor.
CARRY OUT 
4R CHECKS.
ITHERMISTOR TEST
JMOTOR WINDING TEST
CARRY OUT 
3D CHECKS. 
						

							R-9H56
17 TEST PROCEDURES (CONTD)
PROCEDURE
LETTERCOMPONENT TEST
Disconnect the leads from the motor.
Using an ohmmeter, check the resistance between the two terminals as described in the table below.
Table: Resistance of Motor
Motors Resistance
Fan motor Approximately 295 W
Turntable motor Approximately 10.5 kW
Convection fan motor Approximately 210 W
Damper motor Approximately 11 kW
If incorrect readings are obtained, replace the motor.
CARRY OUT
 4R CHECKS.
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 troubleshooting by unit replacement is described according to the symptoms
indicated.
1. Key Unit.  Note: Check key unit ribbon connection before replacement.
The following symptoms indicate a defective key unit. Replace the 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.
2. Control Unit.
The following symptoms indicate a defective control unit. Replacethe control unit.
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 troubles 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.
d) Proper temperature measurement is not obtained.
LTOUCH CONTROL PANEL ASSEMBLY TEST
KMONITOR RESISTOR TEST
CARRY OUT 
3D CHECKS.
Disconnect the leads from the monitor resist. Using an ohmmeter and set on a low range. Check between
the terminals of the monitor resistor.
The resistance of monitor resistor is approx.  0.8 ohms.
If incorrect readings are obtained, replace the monitor resistor.
 CARRY OUT 
4R CHECKS. 
						

							R-9H56
18 TEST PROCEDURES (CONTD)
PROCEDURE
LETTERCOMPONENT TEST
MKEY UNIT TEST
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon 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 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 connector). 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 re-
spond, the above method may
be used (after clearing the con-
trol unit) to determine if the con-
trol unit or key pad is at fault.
G-11
G-12
G-3G-4G-5G-6
G-7
G-8G-9
G-10
G-2
G-1
KEY UNIT
123
4
5 67890
 STOP
CLEARAUTO STARTReheat
Pie
EASY
DEFROSTLESS
POWER
LEVEL
40˚C70˚C130˚C
150˚C
160˚C 180˚C200˚C220˚C 230˚C
250˚C
CLOCK
HIGH MIX LOW MIX CONVECGRILL
REHEAT
SENSORMULTI
COOKFrozen
Vegetables
Desserts
Fresh
Vegetables
Jacket
PotatoINSTANT COOKSTART
MORECasseroles
NRELAY TEST
emove the outer case and check voltage between Pin Nos. 7 and 9 of the 9-pin connector (A)  on the
control unit with an A.C. voltmeter. The meter should indicate 240 volts, if not check oven  circuit.
Shut-off, Cook and Heater 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 or
convection 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.
RELAY SYMBOLOPERATIONAL 
VOLTAGECONNECTED COMPONENTS
  RY1   Approx. 19.0 V.D.C.   Oven lamp/Turntable motor
  RY2(COOK)   Approx. 18.0 V.D.C.   Power transformer
  RY3(HEATER)   Approx. 18.0 V.D.C.   Heating element
  RY4   Approx. 19.0 V.D.C.   Damper motor
  RY5   Approx. 19.0V.D.C.   Convection motor
  RY6   Approx. 19.0 V.D.C.   Cooling fan motor
OPROCEDURES TO BE TAKEN WHEN THE FOIL PATTERN ON THE PRINTED WIRING BOARD
(PWB) IS OPEN.
To protect the electronic circuits, this model is provided with a fine foil pattern added to the primary on
the PWB, this foil pattern acts as a fuse. If the foil pattern is open, follow the troubleshooting guide given
below for repair.
STEPS OCCURANCE CAUSE OR CORRECTION
  1 The rated voltage is not applied to POWER 
terminal of CPU connector (CN-A)Check supply voltage and oven power cord.
  2  The rated voltage is applied to primary side of  
power transformer.Power transformer or secondary circuit  defective. Check 
and repair.
  3 Only pattern at a is broken. *Insert jumper wire J1 and solder. 
  4 Pattern at a and b are broken. *Insert the coil RCILF2003YAZZ between c and d.