Sharp R820jsf Service Manual

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The following test procedure should be carried out with the microwave oven is a fully assembled
condition (outer case fitted).
It is difficult to measure the exact temperature in the convection oven. An accurate thermocouple type
temperature tester must be used. A low priced bi-metal type thermometer is not reliable or accurate.
The temperature should be checked with outer case cabinet installed, approx. 5 minutes after preheat
temperature is reached (audible signal sounds four times). The temperature experienced may be
approx. 30˚F more or less than indicated on the display, however, in most cases the food cooking results
will be satisfactory.
Difference in power supply voltage will also affect the oven temperature. The Household power supply
voltage may sometimes become lower than the rated voltage (120 V) and cause under-cooking. If the
power supply voltage is 10% lower than the rated voltage, longer cooking time is required by 10% to 20%.
TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
KCHECKING TEMPERATURE IN THE CONVECTION MODE
10.Reconnect the power supply cord after the outer case is installed.
11.Run the oven and check all functions.
JTHERMISTOR 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 connector-D from the control unit. Measure the resistance of the thermistor with an
ohmmeter. Connect the ohmmeter leads to Pin No’s D1 and D3.
Room Temperature Resistance
68˚F(20˚C) - 86˚F(30˚C) Approx. 293kΩ - 184KΩ
5. If the meter does not indicate above resistance, replace the thermistor
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.
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, CPU 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.
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.
1.  Key Unit.
NOTE ;
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) Check key unit ribbon connection before replacement.
5) Reconnect all leads removed from components during testing. 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
MKEY UNIT 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 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. 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.
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) Discharge high voltage capacitor.
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.
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.
d) Proper temperature measurement is not obtained.
When 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 all leads removed from components during testing.
5) Re-install the outer case (cabinet).
6) Reconnect the power supply cord after the outer case is installed.
7) Run the oven and check all functions. 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
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.
NRELAY 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 No. 1 of the 3 pin connector (A) and the
common terminal of the relay RY6 on the control unit with an A.C. voltmeter.
The meter should indicate 120 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, grill
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 SYMBOL OPERATIONAL VOLTAGE CONNECTED COMPONENTS
RY1 Approx. 25.0V D.C. Convection motor
RY2 Approx. 24.0V D.C. Power transformer
RY3 Approx. 24.0V D.C. Grill heaters (Top)
RY4 Approx. 24.0V D.C. Bottom heater
RY5 Approx. 25.0V D.C. Fan motor
RY6 Approx. 25.0V D.C. Oven lamp / Turntable 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 functions.
G6
G9
G10
G12
G11
G8G7G1G2G3G4G5
5
04
93
82
71
6
START
TOUCH ONPOWER
LEVEL
CLOCKROAST
MINUTE
PLUSREHEATROAST
DEFROSTGRILL
PIZZA
GRILL
KITCHEN
TIMERBAKE
COOK
CONVEC
POPCORNCUSTOM
HELP
STOP
CLEAR(AUTO)
(AUTO)(AUTO)
(AUTO)(AUTO)
(AUTO)
OAUTO DEFROST TEST
WARNING : The oven should be fully assembled before following procedure.
(1) Place one cup of water in the center of the turntable tray in the oven cavity. 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
(2)Close the door, touch the Auto Defrost pad once and touch the Number pad 1, and touch the
Number pad 5. And then touch the START pad.
(3) The oven is in Auto Defrost cooking condition.
(4) The oven will operate as follows
WEIGHT1ST STAGE 2ND STAGE 3RD STAGE 4TH STAGE
(Ground meat)LEVEL TIME LEVEL TIME LEVEL TIME LEVEL TIME
0.5lb 70% 50sec. 0% 1min. 50% 35sec. 30% 45sec.
(5) If improper operation is indicated, the control unit is probably defective and should be checked.
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.
1. Foil pattern check and repairs.
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) Follow the troubleshooting guide given below for repair.
STEPS OCCURRENCE CAUSE OR CORRECTION
1Only pattern at a is broken. *Insert jumper wire J1 and solder.
2Pattern at a and b are broken. *Insert the coil RCILF2003YAZZ between c and d.
5)Make a visual inspection of the varistor.
Check for burned damage and examine
the transformer with a tester for the
presence of layer short-circuit (check
the primary coil resistance which is
approximately 176Ω ± 10%). If any
abnormal condition is detected, replace
the control unit.
6)Reconnect all leads removed from
components during testing.
7) Re-install the outer case (cabinet).
8) Reconnect the power supply cord after the outer case is installed.
9) 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.
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) Follow the troubleshooting guide given below for repair.
STEPS OCCURRENCE CAUSE OR CORRECTION
The rated AC voltage is not present between
1Pin No. 1 of the 3-pin connector (A) and the Check supply voltage and oven power cord.
common terminal of the relay RY6.
2The rated AC voltage is present at primary Low voltage transformer or secondary circuit defective.
side of low voltage transformer. Check and replace the control unit.
8) Disconnect the power supply cord, and then remove outer case.
PFOIL PATTERN ON THE PRINTED WIRING BOARD TEST
CN - A  AC 
a
bd c
VRS1
1
FAN
(J1)5 
						

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TEST PROCEDURES
PROCEDURE
LETTERCOMPONENT TEST
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 functions.
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.
4) Reset Circuit
A circuit to generate a signal which resets the LSI to the
initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion sound).
6) Door Sensing Switch (Stop Switch)
A switch to tell the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, grill heaters, bottom heater,
convection motor, fan motor, turntable motor and  light
the oven lamp.
8) Back Light Circuit
A circuit to drive the back light (Light emitting diodes LD1
- LD10).
9)  Indicator Circuit
This circuit consists of 2line, 7-digits, 45-segments and
5-common electrodes using a Liquid Crystal Display.
10)Temperature Measurement Circuit : (OVEN THER-
MISTOR)
The temperature in the oven cavity is sensed by the
thermistor. The variation of resistance according to sensed
temperature is detected by the temperature measurement
circuit and the result applied to LSI. The LSI uses this
information to control the relay and display units. The touch control section consists of the following units as
shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit (The Control unit consists of Power unit and
CPU unit.)
The principal functions of these units and signals communi-
cated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit from P24, P25, P26, P27,
P44, P45, P46 and P47.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through P70 - P73
to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, reset circuit, buzzer circuit, relay circuit,
temperature measurement circuit, indicator circuit and back
light circuit.
1) LSI
This LSI controls the temperature measurement signal,
key strobe signal, relay driving signal for oven function
and indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control
unit.
Symbol Voltage Application
VC -5.2V LSI(IC1) 
						

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DESCRIPTION OF LSI
LSI
The I/O signal of the LSI are detailed in the following table.
Pin No. Signal I/O Description
1C1INTerminal not used.
2VL1 IN
Power source voltage input terminal.
Standard voltage for LCD.
3-6 AN7-AN4 INHeating constant compensation terminal.
7AN3 IN
Temperature measurement input: OVEN THERMISTOR.
By inputting DC voltage corresponding to the temperature detected by the thermistor,
this input is converted into temperature by the A/D converter built into the LSI.
8AN2 IN
Input signal which communicates the door open/close information to LSI.
Door closed; H level signal.
Door opened; L level signal.
9-10 AN1-AN0 IN Terminal not used.
11 P57 OUT
Timing signal output terminal for temperature measurement(OVEN THERMIS-
TOR).
H level (GND) : Thermistor OPEN timing.
L level (-5V) : Temperature measuring timing. (Convection cooking)
12 P56 IN Terminal not used.
13 P55 OUT
Timing signal output terminal for temperature measurement(OVEN THERMIS-
TOR).
H level (GND) : Thermistor OPEN timing.
L level (-5V) : Temperature measuring timing. (Convection cooking)
14-18 P54-P50 IN/OUT Terminal not used.
19 P47 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G8 line key on matrix is touched.
20 P46 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G7 line key on matrix is touched.
21 P45 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G6 line key on matrix is touched.
22 P44 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G5 line key on matrix is touched.
23 P43 OUT
Signal to sound buzzer.
A: key touch sound.
B: Completion sound.
C: When the temperature of the oven cav-
ity reaches the preset temperature in
the preheating mode, or when the
preheating hold time (30 minutes) is
elapsed.
24 INT2 IN
Signal to synchronized LSI with commercial power source frequency(60Hz).
This is basic timing for time processing of LSI.
25 P41 OUTOven lamp and turntable motor driving signal(Square Waveform : 60Hz).
To turn on and off shut-off relay (RY6). The
square waveform voltage is delivered to
the relay (RY6) driving circuit.
A
B
C
H: GND
L 0.1 sec
2.0 sec
1.0 sec
1.0 sec
16.7 msec.H : GND
L (-5V)
During cookingL
H16.7 msec. 
						

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Pin No. Signal I/O Description
26 P40 OUT
Bottom heater driving signal.
To turn on and off the bottom relay (RY4).
L level during grill (TOP AND BOTTOM)
cooking, Convection cooking or Roast
cooking, H level otherwise.
The heater relay turns on and off within a
48 second time base in accordance with
the special program in LSI.
27 P77 OUTConvection motor driving signal.
To turn on and off shut-off relay(RY1). L
level during CONVECTION; H level oth-
erwise. (Relay RY1 does not turn on at
preheating mode.)
28 P76 OUT
Fan motor driving signal.
To turn on and off the fan motor relay RY5.  L
level during cooking, or for 5 minutes after grill
cooking or for a while after convection or roust
cooking. H level otherwise.
29 P75 OUTGrill heaters (TOP HEATER) driving signal.
To turn on and off the grill heaters relay
(RY3). L level during grill (TOP  GRILL,
TOP AND BOTTOM) cooking, Con-
vection cooking or Roast cooking, H
level otherwise.
The heater relay turns on and off within
a 48 second time base in accordance
with the special program in LSI.
30 P74 OUTMagnetron high-voltage circuit driving signal.
To turn on and off the cook relay
(RY2). In HIGH POWER operation,
the signals hold L level during mi-
crowave cooking and H level while
not cooking. In other cooking modes
(90%,  80%, 70%, 60%, 50%, 40%,
30%, 20%, 10%, 0%) the signal
turns to H level and L level in
repetition according to the power
level.
31 P73 INSignal coming from touch key.
When any one of G12 line keys on key matrix is touched, a corresponding signal from
P24, P25, P26, P27, P44, P45, P46 and P47 will be input into P73. When no key is
touched, the signal is held at L level.
32 P72 IN
Signal similar to P73.
When any one of G11 line keys on key matrix is touched, a corresponding signal will
be input into P72.
33 P71 IN
Signal similar to P73.
When any one of G10 line keys on key matrix is touched, a corresponding signal will
be input into P71.
34 P70 IN
Signal similar to P73.
When any one of G9 line keys on key matrix is touched, a corresponding signal will
be input into P70.
Power output ON time OFF time
100 % 48 sec. 0 sec.
90 % 44 sec. 4 sec.
80 % 40 sec. 8 sec.
70 % 36 sec. 12 sec.
60 % 32 sec. 16 sec.
50 % 26 sec. 22 sec.
40 % 22 sec. 26 sec.
30 % 16 sec. 32 sec.
20 % 12 sec. 36 sec.
10 % 8 sec. 40 sec.
VARI ON TIME OFF TIME
HIGH POWER 32 sec. 0 sec.90% 30 sec. 2 sec.80% 26 sec. 6 sec.70% 24 sec. 8 sec.60% 22 sec. 10 sec.50% 18 sec. 14 sec.40% 16 sec. 16 sec.30% 12 sec. 20 sec.20% 8 sec. 24 sec.10% 6 sec. 26 sec.0% 0 sec. 32 sec.Power output ON time OFF time
100 % 48 sec. 0 sec.
90 % 44 sec. 4 sec.
80 % 40 sec. 8 sec.
70 % 36 sec. 12 sec.
60 % 32 sec. 16 sec.
50 % 26 sec. 22 sec.
40 % 22 sec. 26 sec.
30 % 16 sec. 32 sec.
20 % 12 sec. 36 sec.
10 % 8 sec. 40 sec.
ONOFF During
cooking
LGND H.(Convection)
ONOFF
For 5 minutes after grill, or for a 
while after convection or roust. LGND H. 
						

							R-820JS
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Pin No. Signal I/O Description
35 RESET IN
Auto clear terminal.
Signal is input to reset the LSI to the initial state when power is applied. Temporarily
set to L level the moment power is applied, at this time the LSI is reset. Thereafter
set at H level.
36 XCIN IN Terminal not used.
37 XOUT IN Terminal not used.
38 XIN IN
Internal clock oscillation frequency input setting.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit with
respect to OUT terminal.
39 XOUT OUT
Internal clock oscillation frequency control output.
Output to control oscillation input of XIN.
40 VSS IN
Power source voltage: -5V.
VC voltage of power source circuit input.
41 P27 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G4 line key on matrix is touched.
42 P26 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G3 line key on matrix is touched.
43 P25 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G2 line key on matrix is touched.
44 P24 OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P70 - P73 terminal while
one of G1 line key on matrix is touched.
45 P23 OUT
Common data signal: COM5.
Connected to LCD (Pin No. 37)
46-50 P22 - P16 OUT
Segment data signal.
Connected to LCD.
The relation between signals are as follows:
LSI signal (Pin No.) LCD (Pin No.) LSI signal (Pin No.) LCD (Pin No.)
SEG 0 (90) ............... SEG45 (51) SEG23 (67) ............ SEG17 (17)
SEG 1 (89) ............... SEG44 (50) SEG24 (66) ............ SEG16 (16)
SEG 2 (88) ............... SEG43 (49) SEG25 (65) ............ SEG15 (15)
SEG 3 (87) ............... SEG42 (48) SEG25 (65) ............ SEG15 (32)
SEG 4 (86) ............... SEG41 (47) SEG26 (64) ............ SEG14 (14)
SEG 5 (85) ............... SEG40 (46) SEG27 (63) ............ SEG13 (13)
SEG 6 (84) ............... SEG39 (45) SEG28 (62) ............ SEG12 (12)
SEG 7 (83) ............... SEG38 (44) SEG29 (61) ............ SEG11 (11)
SEG 8 (82) ............... SEG37 (43) SEG30 (60) ............ SEG10 (10)
SEG 9 (81) ............... SEG31 (31) SEG31 (59) .............. SEG 9 ( 9)
SEG10 (80) .............. SEG30 (30) SEG32 (58) .............. SEG 8 ( 8)
SEG11 (79) .............. SEG29 (29) SEG33 (57) .............. SEG 7 ( 7)
SEG12 (78) .............. SEG28 (28) SEG34 (56) .............. SEG 6 ( 6)
SEG13 (77) .............. SEG27 (27) SEG35 (55) .............. SEG 5 ( 5)
SEG14 (76) .............. SEG26 (26) SEG36 (54) .............. SEG 4 ( 4)
SEG15 (75) .............. SEG25 (25) SEG37 (53) .............. SEG 3 ( 3)
SEG16 (74) .............. SEG24 (24) SEG38 (52) .............. SEG 2 ( 2)
SEG17 (73) .............. SEG23 (23) SEG39 (51) .............. SEG 1 ( 1)
SEG18 (72) .............. SEG22 (22) P16 (50) ................. SEG32 (38)
SEG19 (71) .............. SEG21 (21) P17 (49) ................. SEG33 (39)
SEG20 (70) .............. SEG20 (20) P20 (48) ................. SEG34 (40)
SEG21 (69) .............. SEG19 (19) P21 (47) ................. SEG35 (41)
SEG22 (68) .............. SEG18 (18) P22 (46) ................. SEG36 (42) 
						

							R-820JS
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Pin No. Signal I/O Description
51-90
SEG39-SEG0OUTSegment data signal.
Connected to LCD. No connection in LCD.
91 VCC IN Connected to GND.
92 VREF IN Connected to GND.
93 AVSS IN Connected to VC.
94 COM3 OUT
Common data signal: COM4.
Connected to LCD (Pin No. 36).
95 COM2 OUT
Common data signal: COM3.
Connected to LCD (Pin No. 35).
96 COM1 OUT
Common data signal: COM2.
Connected to LCD (Pin No. 34).
97 COM0 OUT
Common data signal: COM1.
Connected to LCD (Pin No. 33).
98-99 VL3-VL2 IN
Power source voltage input terminal.
Standard voltage for LCD.
100 C2 IN Terminal not used. 
						

							R-820JS
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1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the circuits.
When handling these parts, the following precautions should
be strictly followed. CMOS LSI have extremely high
impedance at its input and output terminals. For this reason,
it is easily influenced by the surrounding high voltage power
source, static electricity charge in clothes, etc., and
sometimes it is not fully protected by the built-in protection
circuit.
In order to protect CMOS LSI.
1)When storing and transporting, thoroughly wrap them in
aluminium foil. Also wrap PW boards containing them in
aluminium foil.
2)When soldering, ground the technician as shown in the
figure and use grounded soldering iron and work table.
2. Servicing of Touch Control Panel
We describe the procedures to permit servicing of the touch
control panel of the microwave oven and the precautions
you must take when doing so.
To perform the servicing, power to the touch control panel
is available either from the power line of the oven itself or
from an external power source.
(1)Servicing the touch control panel with power
supply of the oven :
CAUTION:
THE HIGH VOLTAGE TRANSFORMER OF THE
MICROWAVE OVEN IS STILL LIVE DURING SERV-
ICING AND PRESENTS A HAZARD .
T
herefore, before checking the performance of the touch
control panel,
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 trans-
former.
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.
After checking the performance of the touch control panel,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) Re-connect the leads to the primary of the power trans-
former.
4) Re-install the outer case (cabinet).
5) Re-connect the power supply cord after the outer case is
installed.
6) Run the oven and check all functions.
SERVICING
A. On some models, the power supply cord between the
touch control panel and the oven itself is so short that the
two cant be separated.
For those models, check and repair all the controls
(sensor-related ones included) of the touch control panel
while keeping it  connected to the oven.
B. On some models, the power supply cord between the
touch control panel and the oven proper is long enough
that they may be separated from each other. For those
models, therefore, it is possible to check and repair the
controls of the touch control panel while keeping it apart
from the oven proper; in this case you must short both
ends of the door sensing switch (on PWB) of the touch
control panel with a jumper, which brings about an
operational state that is equivalent to the oven door being
closed. As for the sensor-related controls of the touch
control panel, checking them is possible if the dummy
resistor(s) with resistance equal to that of the controls are
used.
(2)Servicing the touch control panel with power
supply from an external power source:
Disconnect the touch control panel completely from the
oven proper, and short both ends of the door sensing
switch (on PWB) of the touch control panel, which brings
about an operational state that is equivalent to the oven
door being closed. Connect an external power source to
the power input terminal of the touch control panel, then
it is possible to check and repair the controls of the touch
control panel; it is also possible to check the sensor-
related controls of the touch control panel by using the
dummy resistor(s).
3. Servicing Tools
Tools required to service the touch control panel assembly.
1) Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)
2)Oscilloscope: Single beam, frequency range: DC -
10MHz type or more advanced model.
3) Others: Hand tools
4. Other Precautions
1) Before turning on the power source of the control unit,
remove the aluminium foil applied for preventing static
electricity.
2)Connect the connector of the key unit to the control unit
being sure that the lead wires are not twisted.
3)After aluminium foil is removed, be careful that abnormal
voltage due to static electricity etc. is not applied to the
input or output terminals.
4) Attach connectors, electrolytic capacitors, etc. to PWB,
making sure that all connections are tight.
5)Be sure to use specified components where high
precision is required.
approx. 1M ohm