Sharp R-4G75M (serv.man7) Service Manual ▷ View online
19
R-4G75(W)M
R-4G75(B)M
R-4G75(B)M
Pin No.
Signal
I/O
Description
27
RESET
IN
Auto clear terminal.
Signal is input to reset the LSI to the initial state when power is applied. Set to “L” level
the moment power is applied, at this time the LSI is reset. Thereafter set at “H” level.
Signal is input to reset the LSI to the initial state when power is applied. Set to “L” level
the moment power is applied, at this time the LSI is reset. Thereafter set at “H” level.
28/29
P71/P70
IN/OUT
Terminal not used.
30
XIN
IN
Internal clock oscillation frequency setting input.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit with
respect to XOUT terminal.
The internal clock frequency is set by inserting the ceramic filter oscillation circuit with
respect to XOUT terminal.
31
XOUT
OUT
Internal clock oscillation frequency control output.
Output to control oscillation input of XIN.
Output to control oscillation input of XIN.
32
VSS
IN
Power source voltage:-5V.
VC voltage of power source circuit input.
VC voltage of power source circuit input.
33
P27
IN
Signal coming from touch key.
When any one of G-12 line keys on key matrix is touched, a corresponding signal from
P14,P12,P10,P07,P06 and P05 will be input into P27. When no key is touched, the
signal is held at "L" level.
When any one of G-12 line keys on key matrix is touched, a corresponding signal from
P14,P12,P10,P07,P06 and P05 will be input into P27. When no key is touched, the
signal is held at "L" level.
34
P26
IN
Signal similar to P27.
When any one of G-11 line keys on key matrix is touched, a corresponding signal will
be input into P26.
When any one of G-11 line keys on key matrix is touched, a corresponding signal will
be input into P26.
35
P25
IN
Signal similar to P27.
When any one of G-10 line keys on key matrix is touched, a corresponding signal will
be input into P25.
When any one of G-10 line keys on key matrix is touched, a corresponding signal will
be input into P25.
36
P24
IN
Signal similar to P27.
When any one of G-9 line keys on key matrix is touched, a corresponding signal will
be input into P24.
When any one of G-9 line keys on key matrix is touched, a corresponding signal will
be input into P24.
37
P23
OUT
Segment data signals.
The relationship between signals and indicators are as follows:
Signal
The relationship between signals and indicators are as follows:
Signal
Segment
Signal
Segment
P23 ............... LB
P07 .................... f
P01 ............... UB
P10 .................... e
P02 .................. k
P11 .................... d
P03 ................... j
P12 .................... c
P04 ................... i
P13 .................... b
P05 .................. h
P14 .................... a
P06 .................. g
Refer to the touch control panel circuit for the relationship between signals and
indicators. Normally, one pulse is output in every synchronized signal (ß) period, and
input to the anode of the Fluorescent Display.
indicators. Normally, one pulse is output in every synchronized signal (ß) period, and
input to the anode of the Fluorescent Display.
38-43
P15-P22
OUT
Digit selection signal.
The relation between digit signal and digit are as follows:
Digit signal
The relation between digit signal and digit are as follows:
Digit signal
digi
P15 ........................................... 1st.
P16 .......................................... 2nd.
P17 ........................................... 3rd.
P20 ........................................... 4th.
P21 ........................................... 5th.
P22 ........................................... 6th.
P16 .......................................... 2nd.
P17 ........................................... 3rd.
P20 ........................................... 4th.
P21 ........................................... 5th.
P22 ........................................... 6th.
Normally, one pulse is output in every ß
period, and input to the Fluorescent Dis-
play.
period, and input to the Fluorescent Dis-
play.
44
R14
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-1 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-1 line keys on key matrix is touched.
ß(50Hz)
GND
VP
H
L
GND
VP
ß(50Hz)
P15
P16
P17
P20
P21
P22
GND
VP
20
R-4G75(W)M
R-4G75(B)M
R-4G75(B)M
45
P13
OUT
Segment data signal.
Signal similar to P23.
Signal similar to P23.
46
R12
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-3 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-3 line keys on key matrix is touched.
47
R11
OUT
Segment data signal.
Signal similar to P23.
Signal similar to P23.
48
R10
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-5 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-5 line keys on key matrix is touched.
49
R07
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-6 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-6 line keys on key matrix is touched.
50
R06
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-7 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-7 line keys on key matrix is touched.
51
R05
OUT
Segment data signal.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-8 line keys on key matrix is touched.
Signal similar to P23.
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while
one of G-8 line keys on key matrix is touched.
52-55
P04-P01
OUT
Segment data signal.
Signal similar to P23.
Signal similar to P23.
56
P00
OUT
Terminal not used.
57-59
P37-P35
OUT
Terminal not used.
60-64
P34-P30
OUT
Used for initial balancing of the bridge circuit (absolute humidity sensor).
Pin No.
Signal
I/O
Description
21
R-4G75(W)M
R-4G75(B)M
R-4G75(B)M
ABSOLUTE HUMIDITY SENSOR CIRCUIT
(1) Structure of Absolute Humidity Sensor
The absolute humidity sensor includes two thermistors
as shown in the illustration. One thermistor is housed in
the closed vessel filled with dry air while another is in the
open vessel. Each sensor is provided with the protective
cover made of metal mesh to be protected from the
external airflow.
as shown in the illustration. One thermistor is housed in
the closed vessel filled with dry air while another is in the
open vessel. Each sensor is provided with the protective
cover made of metal mesh to be protected from the
external airflow.
(2) Operational Principle of Absolute Humidity Sensor
The figure below shows the basic structure of an absolute
humidity sensor. A bridge circuit is formed by two
thermistors and two resistors (R1 and R2).
The output of the bridge circuit is to be amplified by the
operational amplifier.
Each thermistor is supplied with a current to keep itself
heated at about 150˚C (302˚F) and the resultant heat is
dissipated in the air and if the two thermistors are placed
in different humidity conditions they show different
degrees of heat conductivity leading to a potential
difference between them causing an output voltage
from the bridge circuit, the intensity of which is increased
as the absolute humidity of the air increases. Since the
output is very minute, it will be amplified by the operational
amplifier.
humidity sensor. A bridge circuit is formed by two
thermistors and two resistors (R1 and R2).
The output of the bridge circuit is to be amplified by the
operational amplifier.
Each thermistor is supplied with a current to keep itself
heated at about 150˚C (302˚F) and the resultant heat is
dissipated in the air and if the two thermistors are placed
in different humidity conditions they show different
degrees of heat conductivity leading to a potential
difference between them causing an output voltage
from the bridge circuit, the intensity of which is increased
as the absolute humidity of the air increases. Since the
output is very minute, it will be amplified by the operational
amplifier.
(3) Detector Circuit of Absolute Humidity Sensor
This detector circuit is used to detect the output voltage
of the absolute humidity circuit to allow the LSI to control
sensor cooking of the unit.
When the unit is set in the sensor cooking mode, 16
seconds later the detector circuit starts to function and
the LSI observes the initial voltage available at its P66
terminal. With this voltage given, the switches SW1 to
SW5 in the LSI are turned on in such a way as to change
the resistance values in parallel with R-1.
of the absolute humidity circuit to allow the LSI to control
sensor cooking of the unit.
When the unit is set in the sensor cooking mode, 16
seconds later the detector circuit starts to function and
the LSI observes the initial voltage available at its P66
terminal. With this voltage given, the switches SW1 to
SW5 in the LSI are turned on in such a way as to change
the resistance values in parallel with R-1.
Changing the resistance values results in that there is
the same potential at both F-3 terminal of the absolute
humidity sensor and P67 terminal of the LSI. The
voltage of P66 terminal will indicate about -2.5V. This
initial balancing is set up about 16 seconds after the unit
is put in the Sensor Cooking mode.
As the sensor cooking proceeds, the food is heated to
generate moisture by which the resistance balance of
the bridge circuit is deviated to increase the voltage
available at P66 terminal of the LSI. Then the LSI
observes that voltage at P66 terminal and compares it
with its initial value, and when the comparison rate
reaches the preset value (fixed for each menu to be
cooked), the LSI causes the unit to stop sensor cooking;
thereafter, the unit get in the next necessary operation
automatically.
When the LSI starts to detect the initial voltage at P66
terminal 16 seconds after the unit has been put in the
Sensor Cooking mode, if it is impossible to take a
balance of the bridge circuit due to disconnection of the
absolute humidity sensor, ERROR will appear on the
display and the cooking is stopped.
the same potential at both F-3 terminal of the absolute
humidity sensor and P67 terminal of the LSI. The
voltage of P66 terminal will indicate about -2.5V. This
initial balancing is set up about 16 seconds after the unit
is put in the Sensor Cooking mode.
As the sensor cooking proceeds, the food is heated to
generate moisture by which the resistance balance of
the bridge circuit is deviated to increase the voltage
available at P66 terminal of the LSI. Then the LSI
observes that voltage at P66 terminal and compares it
with its initial value, and when the comparison rate
reaches the preset value (fixed for each menu to be
cooked), the LSI causes the unit to stop sensor cooking;
thereafter, the unit get in the next necessary operation
automatically.
When the LSI starts to detect the initial voltage at P66
terminal 16 seconds after the unit has been put in the
Sensor Cooking mode, if it is impossible to take a
balance of the bridge circuit due to disconnection of the
absolute humidity sensor, ERROR will appear on the
display and the cooking is stopped.
Absolute humidity sensor circuit
Sensing part
(Open vessel)
(Open vessel)
Sensing part
(Closed vessel)
(Closed vessel)
Metal
mesh
mesh
C
S
R3
R1
R2
+
-
Operational
amplifier
amplifier
Output
voltage
voltage
S : Thermistor
open vessel
open vessel
C : Thermistor
closed vessel
closed vessel
2
Absolute humidity (g/m )
Output voltage
Absolute humidity vs,
output voltage characterist
output voltage characterist
SW1
SW2
SW4
SW3
SW5
P30
P31
P32
P33
P34
VA : -15V
VA : -15V
VC : -5V
LSI
(IC1)
(IC1)
+
-
D
D
C
C
C
R
R
R
R
F-1
F-2
F-3
R3
R4
R5
R6
R7
R8
P67
P66
R1
R2
64
63
62
61
60
4
5
6
R51
10
11
7
8
1
4
C
S
12
C. Thermistor in
closed vessel
S. Thermistor in
open vessel
closed vessel
S. Thermistor in
open vessel
3
5
2
6
22
R-4G75(W)M
R-4G75(B)M
R-4G75(B)M
SERVICING
1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the
circuits. When handling these parts, the following pre-
cautions should be strictly followed. CMOS LSI have
extremely high impedance at its input and output termi-
nals. For this reason, it is easily influenced by the sur-
rounding 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.
circuits. When handling these parts, the following pre-
cautions should be strictly followed. CMOS LSI have
extremely high impedance at its input and output termi-
nals. For this reason, it is easily influenced by the sur-
rounding 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 all PW boards containing them
in aluminium foil.
in aluminium foil.
2) When soldering, ground the technician as shown in the
figure and use grounded soldering iron and work 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
cautions you must considre when doing so. To carry the
servicing, power supply to the touch control panel is
available either from the power line of the oven proper
itself of from an external power source.
touch control panel of the microwave oven and the
cautions you must considre when doing so. To carry the
servicing, power supply to the touch control panel is
available either from the power line of the oven proper
itself of from an external power source.
(1) Servicing the touch control panel with power supply
from the oven proper:
CAUTION:
THE HIGH VOLTAGE TRANSFORMER OF THE MI-
CROWAVE OVEN IS STILL ALIVE TO GIVE YOU
DANGER DURING SERVICING.
Therefore, when checking the performance of the touch
control panel, put the outer cabinet on the oven proper to
keep from touching the high voltage transformer, or
unplug the primary terminal (connector) of the high
voltage transformer to turn it off; and the end of such
connector shall be insulated with an insulating tape. After
servicing, be sure to replace the leads to their original
locations.
CAUTION:
THE HIGH VOLTAGE TRANSFORMER OF THE MI-
CROWAVE OVEN IS STILL ALIVE TO GIVE YOU
DANGER DURING SERVICING.
Therefore, when checking the performance of the touch
control panel, put the outer cabinet on the oven proper to
keep from touching the high voltage transformer, or
unplug the primary terminal (connector) of the high
voltage transformer to turn it off; and the end of such
connector shall 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 proper is so short that
they can’t be separated from each other. For those
models, therefore,check and repair all the controls (with
they can’t be separated from each other. For those
models, therefore,check and repair all the controls (with
approx. 1M ohm
E
C B
Transistor
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Transistor
2SB793
2SB793
the sensor-related ones included) of the touch control
panel while keeping it in contact with the oven proper.
panel while keeping it in contact with the oven proper.
B. On some models, on the other hand, the power supply
cord between the touch control panel and the oven
proper is so long that they may be separated from each
other. For those models, therefore, it is allowed 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 stop switch (on PWB) of the
touch control panel with a jumper, which brings about an
operational state that is equivalent to the with the oven
door being closed. As to the sensor-related controls of
the touch control panel, their checking is allowed if the
dummy resistor(s) whose resistance is equal to that of
those controls are used.
proper is so long that they may be separated from each
other. For those models, therefore, it is allowed 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 stop switch (on PWB) of the
touch control panel with a jumper, which brings about an
operational state that is equivalent to the with the oven
door being closed. As to the sensor-related controls of
the touch control panel, their checking is allowed if the
dummy resistor(s) whose resistance is equal to that of
those 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 stop switch (on
PWB) of the touch control panel,which brings about an
operational state that is equivalent with the oven door
being closed. And connect an external power source to
the power input terminal of the touch control panel, and
then it is allowed to check and repair the controls of the
touch control panel; as in the case of (1)-B above, it is
here 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 proper,and short both ends of the stop switch (on
PWB) of the touch control panel,which brings about an
operational state that is equivalent with the oven door
being closed. And connect an external power source to
the power input terminal of the touch control panel, and
then it is allowed to check and repair the controls of the
touch control panel; as in the case of (1)-B above, it is
here also possible to check the sensor-related controls of
the touch control panel by using the dummy resistor(s).
4. Servicing Tools
Tools required when servicing the touch control panel
assembly.
assembly.
1) Soldering iron: 30W
(To prevent leaking current, it is recommended to use a
soldering iron with a grounding terminal.)
soldering iron with a 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,
1) Before turning on the power source of the control unit,
remove the aluminium foil applied for preventing static
electricity.
electricity.
2) Connect the connectors of the indicator and key unit to
the control unit taking care that the lead wires are not
twisted.
twisted.
3) After aluminium foil is removed, take extra care that
abnormal voltage due to static electricity etc. is not
applied to the input or output terminals.
applied to the input or output terminals.
4) Attach connectors, electrolytic capacitors, etc. to PWB,
taking care that all connections are tight.
5) Be sure to use specified components where high preci-
sion is required.
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