Sharp R-750AM (serv.man2) Service Manual ▷ View online
8
750A -
29
R42
OUT
Magnetron high-voltage circuit driving signal.
To turn on and off the cook relay
(RY3). In 100% POWER opera-
tion, 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 rep-
etition according to the power
level.
(RY3). In 100% POWER opera-
tion, 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 rep-
etition according to the power
level.
30
R43
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.
31
R50
IN
Signal coming from touch key.
When any one of G-1 line keys on key matrix is touched, a corresponding signal from
R60, R61, R62, R63, R72 and R73 will be input into R50. When no key is touched,
the signal is held at "H" level.
When any one of G-1 line keys on key matrix is touched, a corresponding signal from
R60, R61, R62, R63, R72 and R73 will be input into R50. When no key is touched,
the signal is held at "H" level.
32
R51
IN
Signal similar to R50.
When any one of G-2 line keys on key matrix is touched, a corresponding signal will
be input into R51.
When any one of G-2 line keys on key matrix is touched, a corresponding signal will
be input into R51.
33
R52
IN
Signal similar to R50.
When any one of G-3 line keys on key matrix is touched, a corresponding signal will
be input into R52.
When any one of G-3 line keys on key matrix is touched, a corresponding signal will
be input into R52.
34
R53
IN
Signal similar to R50.
When any one of G-4 line keys on key matrix is touched, a corresponding signal will
be input into R53.
When any one of G-4 line keys on key matrix is touched, a corresponding signal will
be input into R53.
35
R60
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G5 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G5 line keys on key matrix is touched.
36
R61
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G6 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G6 line keys on key matrix is touched.
37
R62
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G7 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G7 line keys on key matrix is touched.
38
R63
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G8 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G8 line keys on key matrix is touched.
39-40
R70-R71
OUT
Terminal not used.
41
R72
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G10 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G10 line keys on key matrix is touched.
42
R73
OUT
Key strobe signal.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G9 line keys on key matrix is touched.
Signal applied to touch-key section. A pulse signal is input to R50 - R53 terminal
while one of G9 line keys on key matrix is touched.
Pin No.
Signal
I/O
Description
ON/OFF time ratio in
Micro cooking
(a. 48second time base)
Micro cooking
(a. 48second time base)
ON/OFF time ratio in
Micro cooking
(a. 32second time base)
Micro cooking
(a. 32second 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.
20.0 msec
During cooking
H : +5V
L : 0V
TOUCH CONTROL ASSEMBLY/ DESCRIPTION OF LSI
9
750A -
43-54
SEG0 -
OUT
Segment data signal.
SEG11
Connected to LCD.
The relation between signals are as follows:
The relation between signals are as follows:
LSI signal (Pin No.)
LCD (Pin No.)
LSI signal (Pin No.)
LCD (Pin No.)
SEG 0 (1) ............................. S12(4)
SEG 0 (1) ............................. S12(4)
SEG 6 (7) ......................... S6(10)
SEG 1 (2) ............................. S11(5)
SEG 7 (8) ......................... S5(11)
SEG 2 (3) ............................. S10(6)
SEG 8 (9) ......................... S4(12)
SEG 3 (4) ............................... S9(7)
SEG 9 (10) ....................... S3(13)
SEG 4 (5) ............................... S8(8)
SEG 10 (11) ..................... S2(14)
SEG 5 (6) ............................... S7(9)
SEG 11 (12) ..................... S1(15)
55-57
SEG12-
OUT
Terminal not used.
SEG14
58
VDD
IN
Power source voltage input terminal.
Connected to GND.
Connected to GND.
59-64
SEG15-
OUT
Terminal not used.
SEG20
Pin No.
Signal
I/O
Description
WARNING: Before carrying out any work carry out 3D checks
1) Disconnect the supply.
2) Door opened, and wedged open.
3) Discharge 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.
TOUCH CONTROL ASSEMBLY/ DESCRIPTION OF LSI
10
750A -
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
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.
containing them in aluminium foil.
2) When soldering, ground the technician as shown in
the figure and use grounded soldering iron and work
table.
table.
approx. 1M ohm
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.
E
C
B
Transistor
2SB1238
2SB1238
E
C B
Transistor
DTA123ES
KRA101M
KRA223M
KRC243M
DTA123ES
KRA101M
KRA223M
KRC243M
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).
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).
4. Servicing Tools
Tools required to service the touch control panel
assembly.
1) Soldering iron: 30W
assembly.
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.
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.
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.
SERVICING
TOUCH CONTROL ASSEMBLY
11
750A -
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
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.
Figure C-6. Door Replacement
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
COMPONENT REPLACEMENT AND ADJUSTMENT
Removal
1. Tear the door film from the door panel.
2. Now, the door film is free.
1. Tear the door film from the door panel.
2. Now, the door film is free.
Installation
1. Put the tab on the backing film of the door film as shown
1. Put 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
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