Sharp R-8740 (serv.man17) Service Manual ▷ View online
R-8740M - 25
Pin No.
Signal
I/O
Description
41
P17
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G5 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G5 line keys on matrix is touched.
42
P16
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G6 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G6 line keys on matrix is touched.
43
P15
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P207 - P23
terminal while one of G7 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P207 - P23
terminal while one of G7 line keys on matrix is touched.
44
P14
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G8 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G8 line keys on matrix is touched.
45
P13
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G9 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G9 line keys on matrix is touched.
46
P12
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G10 line keys on matrix is touched.
Signal applied to touch-key section. A pulse signal is input to P20 - P23
terminal while one of G10 line keys on matrix is touched.
47-48
P11-P10
IN
Terminal not used.
49
P07
OUT
Cooking mode indicator driving signal.
To turn on and off the light emitting diode LD9.
To turn on and off the light emitting diode LD9.
50
P06
OUT
Cooking mode indicator driving signal.
To turn on and off the light emitting diode LD8.
To turn on and off the light emitting diode LD8.
51
P05
OUT
Cooking mode indicator driving signal.
To turn on and off the light emitting diode LD6.
To turn on and off the light emitting diode LD6.
52
P04
OUT
Cooking mode indicator driving signal.
To turn on and off the light emitting diode LD7.
To turn on and off the light emitting diode LD7.
53-56
P03-P00
OUT
Terminal not used.
57-60
P37-P34
OUT
Terminal not used.
61-72
SEG11-SEG0
OUT
Segment data signal.
Connected to LCD.
The relation between signals are as follows:
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 (72) .............................. S1
SEG 6 (66) ............................ S7
SEG 1 (71) .............................. S2
SEG 7 (65) ............................ S8
SEG 2 (70) .............................. S3
SEG 8 (64) ............................ S9
SEG 3 (69) .............................. S4
SEG 9 (63) .......................... S10
SEG 4 (68) .............................. S5
SEG10 (62) ......................... S11
SEG 5 (67) .............................. S6
SEG11 (61) ......................... S12
73/74
VCC/VREF
IN/IN
Connected to GND.
75
AVSS
IN
Connected to VC.
76
COM3
OUT
Terminal not used.
77
COM2
OUT
Common data signal: COM3.
Connected to LCD (Pin No. 3).
Connected to LCD (Pin No. 3).
78
COM1
OUT
Common data signal: COM2.
Connected to LCD (Pin No. 2).
Connected to LCD (Pin No. 2).
79
COM0
OUT
Common data signal: COM1.
Connected to LCD (Pin No. 1).
Connected to LCD (Pin No. 1).
80
VL3
IN
Power source voltage input terminal.
Standard voltage for LCD.
Standard voltage for LCD.
DESCRIPTION OF LSI
LSI(IX091DR)
The I/O signal of the LSI(IX091DR) are detailed in the following table.
The I/O signal of the LSI(IX091DR) are detailed in the following table.
R-8740M - 26
I-2 is a 2K-bit, serial memory, enabling CMOS to be erased/written electrically. This memory is constructed with
256 registers x 8bits, enabling individual access, read and write operations to be performed. Details of input/
output signal for I-2 are as shown in the following diagram.
256 registers x 8bits, enabling individual access, read and write operations to be performed. Details of input/
output signal for I-2 are as shown in the following diagram.
Table 2. Relation between Pin Nos, and Signals
Pin No.
Signal
I/O
Description
1-3
A0-A2
IN
Connected to +5V.
4
VSS
IN
Connected to GND.
5
SDA
IN/OUT
Serial data input/output : input/outputs data to I-1.
6
SCL
IN
Clock signal input : input/outputs serial data at every one pulse.
7
TEST
IN
Connected to GND.
8
VCC
IN
Connected to +5V.
Memory IC (I-2)
R-8740M - 27
SERVICING
Transistor
2SB1238
2SB1238
Transistor
DTA123ES
DTA143ES
DTD143ES
DTA123ES
DTA143ES
DTD143ES
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.
(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 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; 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.
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; 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, 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).
Disconnect the touch control panel completely from
the oven, 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).
4. Servicing Tools
Tools required to service the touch control panel assembly.
1) Soldering iron: 30W
1) Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)
grounding terminal.)
2) Oscilloscope: Single beam, frequency range: DC -
10MHz type or more advanced model.
3) Others: Hand tools
5. Other Precautions
1) Before turning on the power source of the control unit,
remove the aluminium foil applied for preventing static
electricity.
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.
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.
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
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.
them in aluminium foil.
2) When soldering, ground the technician as shown in
the figure and use grounded soldering iron and work
table.
table.
2. Shapes of Electronic Components
3. 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 or from
an external power source.
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 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 .
THE HIGH VOLTAGE TRANSFORMER OF THE
MICROWAVE OVEN IS STILL LIVE DURING SERV-
ICING AND PRESENTS A HAZARD .
Therefore, when checking the performance of the
touch control panel, put the outer cabinet on the oven
to avoid touching the high voltage transformer, or
unplug the primary terminal (connector) of the high
voltage transformer to turn it off; the end of such
connector must be insulated with an insulating tape.
After servicing, be sure to replace the leads to their
original locations.
touch control panel, put the outer cabinet on the oven
to avoid touching the high voltage transformer, or
unplug the primary terminal (connector) of the high
voltage transformer to turn it off; the end of such
connector must be insulated with an insulating tape.
After servicing, be sure to replace the leads to their
original locations.
A. On some models, the power supply cord between
the touch control panel and the oven is so short that
the two can't be separated.
the two can't be separated.
approx. 1M ohm
E
C B
E
C
B
R-8740M - 28
WARNING: Avoid possible exposure to microwave energy. Please follow the instructions below before
operating the oven.
1. CARRY OUT 3D CHECKS.
2. Make sure that a definite” click” can be heard when the
2. Make sure that a definite” click” can be heard when the
microwave oven door is unlatched. (Hold the door in a
closed position with one hand, then push the door open
button with the other, this causes the latch leads to rise,
it is then possible to hear a “click’ as the door switches
operate.)
closed position with one hand, then push the door open
button with the other, this causes the latch leads to rise,
it is then possible to hear a “click’ as the door switches
operate.)
3. Visually check the door and cavity face plate for damage
(dents, cracks, signs of arcing etc.).
Carry out any remedial work that is necessary before oper-
ating the oven.
Do not operate the oven if any of the following conditions
exist;
ating the oven.
Do not operate the oven if any of the following conditions
exist;
1. Door does not close firmly.
2. Door hinge, support or latch hook is damaged.
3. The door gasket or seal is damaged.
4. The door is bent or warped.
5. There are defective parts in the door interlock system.
6. There are defective parts in the microwave generating
2. Door hinge, support or latch hook is damaged.
3. The door gasket or seal is damaged.
4. The door is bent or warped.
5. There are defective parts in the door interlock system.
6. There are defective parts in the microwave generating
and transmission assembly.
7. There is visible damage to the oven.
Do not operate the oven:
1. Without the RF gasket (Magnetron).
2. If the wave guide or oven cavity are not intact.
3. If the door is not closed.
4. If the outer case (cabinet) is not fitted.
1. Without the RF gasket (Magnetron).
2. If the wave guide or oven cavity are not intact.
3. If the door is not closed.
4. If the outer case (cabinet) is not fitted.
Please refer to ‘OVEN PARTS, CABINET PARTS, DOOR PARTS’, when carrying out any of the following removal
procedures:
procedures:
OUTER CASE REMOVAL
6. Lift the entire case from the oven.
To remove the outer case proceed as follows.
1. Disconnect oven from power supply.
2. Open the oven door and wedge it open.
3. Remove backplate.
4. Remove the screws from rear and along the side edge of
1. Disconnect oven from power supply.
2. Open the oven door and wedge it open.
3. Remove backplate.
4. Remove the screws from rear and along the side edge of
case.
5. Slide the entire case back about 3cm to free it from
retaining clips on the cavity face plate.
CONTROL PANEL REMOVAL
1. CARRY OUT 3D CHECKS
2. Remove outer wrap.
3. Disconnect wiring panel.
2. Remove outer wrap.
3. Disconnect wiring panel.
4. Lift up the control panel assembly and pull it forward. Now
the control panel assembly is free.
HIGH VOLTAGE TRANSFORMER REMOVAL
1. CARRY OUT 3D CHECKS
2. Disconnect the filament leads of high voltage transformer
2. Disconnect the filament leads of high voltage transformer
from high voltage capacitor and the magnetron.
3. Disconnect the H.V. wire A from the high voltage
transformer.
4. Disconnect the main wire harness from the high voltage
transformer.
5. Remove the two (2) screws and one (1) washer holding
the transformer to base plate.
6. Remove the transformer.
7. Now the high voltage transformer is free.
7. Now the high voltage transformer is free.
7. Discharge the H.V. capacitor before carrying out any
further work.
8. Do not operate the oven with the outer case removed.
N.B.; Step 1, 2 and 6 form the basis of the 3D checks.
CAUTION:
N.B.; Step 1, 2 and 6 form the basis of the 3D checks.
CAUTION:
DISCHARGE HIGH VOLTAGE CAPACITOR
BEFORE TOUCHING ANY OVEN COMPONENT OR
WIRING.
WIRING.
HIGH VOLTAGE COMPONENTS REMOVAL
(HIGH VOLTAGE CAPACITOR AND HIGH VOLTAGE RECTIFIER ASSEMBLY)
To remove the components, proceed as follows.
1. CARRY OUT 3D CHECKS
2. Disconnect all the leads and terminals of high voltage
1. CARRY OUT 3D CHECKS
2. Disconnect all the leads and terminals of high voltage
rectifier assembly from the high voltage capacitor.
3. Remove one (1) screw holding earth side terminal of high
voltage rectifier assembly and remove capacitor holder.
4. Remove one (1) screw holding capacitor holder to oven
cavity.
5. Release the capacitor holder from the duct.
CAUTION: WHEN REPLACING HIGH VOLTAGE
RECTIFIER ASSEMBLY, ENSURE THAT
THE CATHODE (EARTH) CONNECTION IS
SECURELY FIXED TO THE CAPACITOR
HOLDER WITH AN EARTHING SCREW.
THE CATHODE (EARTH) CONNECTION IS
SECURELY FIXED TO THE CAPACITOR
HOLDER WITH AN EARTHING SCREW.
6. Remove the capacitor from the capacitor holder.
7. Now high voltage rectifier assembly and capacitor should
7. Now high voltage rectifier assembly and capacitor should
be free.
COMPONENT REPLACEMENT AND ADJUSTMENT PROCEDURE
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