Sharp R-741M (serv.man2) Service Manual ▷ View online
9
741M -
TOUCH CONTROL ASSEMBLY/ DESCRIPTION OF LSI
Pin No.
Signal
I/O
Description
20.0 msec
H : 0V
L : -5V
A
B
0.1 sec.
2 sec.
H : 0V
L: -5V
H : 0V
L: -5V
(Grill or dual)
ON
OFF
During
cooking
L : -5V
0V
H :
(Grill or dual)
ON
OFF
During
cooking
L : -5V
0V
H :
34
BZ
OUT
Signal to sound buzzer (2.0 kHz).
A: key touch sound.
B: Completion sound.
35
R00
OUT
Terminal not used.
36
R01
OUT
Grill heating element driving signal.
To turn on and off the grill heating element
relay (RY2). "L" level during grill cooking
or dual cooking; "H" level otherwise.
relay (RY2). "L" level during grill cooking
or dual cooking; "H" level otherwise.
37
R02
OUT
Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay
(RY3). In 100% POWER op-
eration, the signals hold "L"
level during microwave cooking
and "H" level while not cooking.
In other cooking modes (70%,
50%, 30%, 10%) the signal turns
to "H" level and "L" level in
repetition according to the power
level.
(RY3). In 100% POWER op-
eration, the signals hold "L"
level during microwave cooking
and "H" level while not cooking.
In other cooking modes (70%,
50%, 30%, 10%) the signal turns
to "H" level and "L" level in
repetition according to the power
level.
38
R03
OUT
Oven lamp, fan motor and turntable motor driving signal.
To turn on and off shut off relay (RY1). The
square waveform voltage is delivered to
the RY1 driving circuit.
square waveform voltage is delivered to
the RY1 driving circuit.
39
P20
IN
Signal coming from tact switch.
When either of tact switches SW64-SW66 is touched, a corresponding signal out
of SEG1, SEG2 and SEG3 will be input into P20. When no tact switch is touched,
the signal is held at "H" level.
of SEG1, SEG2 and SEG3 will be input into P20. When no tact switch is touched,
the signal is held at "H" level.
40-41
P21-P22
OUT
Terminal not used.
42
P23
IN
Signal coming from tact switch.
When either of tact switches SW60-SW62 is touched, a corresponding signal out
of SEG0, SEG1, SEG2 and SEG3 will be input into P23. When no tact switch is
touched, the signal is held at "H" level.
of SEG0, SEG1, SEG2 and SEG3 will be input into P23. When no tact switch is
touched, the signal is held at "H" level.
43
INT0
IN
Signal synchronized with commercial power source frequency.
This is the basic timing for time processing
of LSI.
of LSI.
44
INT1
IN
Connected to VC. (-5V)
45
K02
IN
Connected to VC. (-5V)
46
K03
IN
To input signal which communicates the door open/close information to LSI.
Door open "L" level signal (-5V). Door close "H" level (0V)
47
COM0
OUT
Common data signal: COM0.
Connected to LCD. (C1)
48
COM1
OUT
Common data signal: COM1.
Connected to LCD. (C2)
49
COM2
OUT
Common data signal: COM2.
Connected to LCD. (C3)
50
COM3
OUT
Terminal not used.
ON/OFF time ratio in Mi-
cro cooking
(a. 32second time base)
cro cooking
(a. 32second time base)
ON/OFF time ratio in Mi-
cro cooking
(a. 48second time base)
cro cooking
(a. 48second time base)
MICRO
ON
OFF
COOK
100%
100%
32sec.
0sec.
70%
24sec.
8sec.
50%
18sec.
14sec.
30%
12sec.
20sec.
10%
6sec.
26sec.
MICRO
ON
OFF
COOK
100%
100%
48sec.
0sec.
70%
36sec.
12sec.
50%
26sec.
22sec.
30%
16sec.
32sec.
10%
8sec.
40sec.
10
741M -
51
SEG0
OUT
Tact switch strobe signal.
Signal applied to tact switch section. A pulse signal is input to P23 terminal while the
tact switch SW60 is touched.
tact switch SW60 is touched.
52
SEG1
OUT
Tact switch strobe signal.
Signal applied to tact switch section. A pulse signal is input to P23 terminal while the
tact switch SW61 is touched. A pulse signal is input to P20 terminal while the tact
switch SW64 is touched.
tact switch SW61 is touched. A pulse signal is input to P20 terminal while the tact
switch SW64 is touched.
TOUCH CONTROL ASSEMBLY/ DESCRIPTION OF LSI
Pin No.
Signal
I/O
Description
53
SEG2
OUT
Tact switch strobe signal.
Signal applied to tact switch section. A pulse signal is input to P23 terminal while the
tact switch SW63 is touched. A pulse signal is input to P20 terminal while the tact
switch SW65 is touched.
tact switch SW63 is touched. A pulse signal is input to P20 terminal while the tact
switch SW65 is touched.
54
SEG3
OUT
Tact switch strobe signal.
Signal applied to tact switch section. A pulse signal is input to P23 terminal while the
tact switch SW62 is touched. A pulse signal is input to P20 terminal while the tact
switch SW66 is touched.
tact switch SW62 is touched. A pulse signal is input to P20 terminal while the tact
switch SW66 is touched.
55-58
SEG4-
OUT
Terminal not used.
SEG7
59-63
SEG8-
OUT
Segment data signal.
SEG12
Signal is similar to SEG13. Connected to LCD.
64
NC
No connection terminal.
WARNING:
Before carrying out any work carry out 3D checks
1)
D
isconnect the supply.
2)
D
oor opened, and wedged open.
3)
D
ischarge high voltage capacitor.
WIRING / RE-WIRING
RE-WIRING
Ensure the following:
1.
Wires must not touch:
a)
High voltage parts.
(Magnetron, high voltage transformer, high voltage capacitor and high voltage rectifier assembly)
(Magnetron, high voltage transformer, high voltage capacitor and high voltage rectifier assembly)
b)
Parts that become hot.
(Heating elements, oven lamp, oven cavity magnetron and high voltage transformer)
(Heating elements, oven lamp, oven cavity magnetron and high voltage transformer)
c)
Sharp edges.
(Bottom plates, oven cavity, waveguide flange, chassis support and other metallic parts)
(Bottom plates, oven cavity, waveguide flange, chassis support and other metallic parts)
d)
Movable parts.
(Fan blade, any motor, switch, switch lever and open button)
(Fan blade, any motor, switch, switch lever and open button)
2.
Positive lock connectors are fitted correctly. Ensure the locking pin is located correctly.
3.
Wires are connected correctly as per pictorial diagram.
4.
No wire leads are trapped by the outer wrap.
11
741M -
TOUCH CONTROL ASSEMBLY
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 itself 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 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 .
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 itself is so
short that the two can't be separated.
short that the two can't 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.
(sensor-related ones included) of the touch control
panel while keeping it connected to the oven.
SERVICING
B.
On some models, the power supply cord between
the touch control panel and the oven proper is so
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.
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).
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).
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.
approx. 1M ohm
Transistor
2SB1238
2SB1238
Transistor
DTA123ES
DTA143ES
DTB143ES
DTD143ES
DTA123ES
DTA143ES
DTB143ES
DTD143ES
E
C B
E
C
B
12
741M -
MONITORED LATCH SWITCH, STOP SWITCH
AND MONITOR SWITCH REMOVAL
AND MONITOR SWITCH REMOVAL
1. CARRY OUT 3D CHECKS.
2. Remove the control panel assembly referring to
2. Remove the control panel assembly referring to
“CONTROL PANEL REMOVAL”.
3. Disconnect the leads from all switches.
4. Remove the two (2) screws holding the latch hook to the
4. Remove the two (2) screws holding the latch hook to the
oven cavity.
5. Remove the latch hook.
6. Push the retaining tab slightly and remove the switch.
6. Push the retaining tab slightly and remove the switch.
9. Release door panel from eight (8) tabs of door frame by
sliding door panel downward.
10. Now, door panel is free.
11. Slide latch head upward and remove it from door frame
11. Slide latch head upward and remove it from door frame
by releasing latch spring from door frame and latch head.
12. Now, latch head and latch spring are free.
13. Remove the two (2) screws holding the glass stopper to
13. Remove the two (2) screws holding the glass stopper to
the door frame.
14. Remove the glass stopper from the door frame.
15. Slide the front door glass leftwards and then slide
15. Slide the front door glass leftwards and then slide
upwards to release the tabs holding it.
16. Now, the front door glass is free
RE-INSTALL
1. Re-install the front door glass to the door frame as
follows.
1) Insert the upper edge of the front door glass into the six
(6) tabs of the door frame.
2) Slide the front door glass downwards and insert the
lower edge of the front door glass into the six (6) tabs of
the door frame.
the door frame.
3) Slide the front door glass rightwards and insert the right
edge of the front door glass into the one (1) tab of the
door frame.
door frame.
2. Re-install the glass stopper to the door frame as follows.
1) Re-install the glass stopper to the door frame so that the
1) Re-install the glass stopper to the door frame so that the
two (2) holes of the glass stopper meet the two (2) pins
of the door frame.
of the door frame.
2) Hold the glass stopper to the door frame with the two (2)
screws.
3. Re-install the latch spring to the latch head. Re-install
the latch spring to the door frame. Re-install latch head
to door frame.
to door frame.
4. Re-install door panel to door frame by fitting eight (8)
tabs of door frame to eight (8) holes of door panel.
5. Fit the door panel to the door frame with four (4) screws.
6. Inserttwo (2) pins of door panel on two (2) hole of upper
6. Inserttwo (2) pins of door panel on two (2) hole of upper
and lower oven hinges.
7. Re-install choke cover to door panel .
Note: After any service to the door;
Make sure that door sensing switch and monitored
latch switch are operating properly.
latch switch are operating properly.
MONITOR
SWITCH
SWITCH
MONITORED
LATCH
SWITCH
LATCH
SWITCH
TAB
TAB
STOP
SWITCH
Figure C-4. Switches
DOOR REPLACEMENT
REMOVAL
1. CARRY OUT 3D CHECKS.
2. Push the open button and open the door slightly.
3. Insert a putty knife (thickness of about 0.5mm) into the
2. Push the open button and open the door slightly.
3. Insert a putty knife (thickness of about 0.5mm) into the
gap between the choke cover and door frame as shown
in Figure C-5 to free engaging parts.
in Figure C-5 to free engaging parts.
4. Release choke cover from door panel.
5. Now choke cover is free.
5. Now choke cover is free.
CHOKE COVER
PUTTY KNIFE
DOOR FRAME
Figure C-5. Door Disassembly
6. Release two (2) pins of door panel from two (2) holes of
upper and lower oven hinges by lifting up.
7. Now, door sub assembly is free from oven cavity.
8. Remove the four (4) screws holding the door panel to the
8. Remove the four (4) screws holding the door panel to the
door frame.
DOOR FILM
Removal
1. Tear the door film from the door panel.
2. Now, the door film is free.
2. Now, the door film is free.
Installation
1. Pull the tab on the backing film of the door film as shown
in Fig. 7.
2. Tear the backing film by pulling the tab.
3. Put the pasted side of the door film on the door panel.
3. Put the pasted side of the door film on the door panel.
Door film
Backing Film
Figure C-7. Door film
COMPONENT REPLACEMENT AND ADJUSTMENT
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