Sharp R-753 (serv.man3) Service Manual ▷ View online
12
753M -
SERVICING
approx. 1M ohm
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.
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.
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
SERVICING AND PRESENTS A HAZARD .
THE HIGH VOLTAGE TRANSFORMER OF THE
MICROWAVE OVEN IS STILL LIVE DURING
SERVICING 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.
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
so long enough that they may be separated from
each other.
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
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.
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).
3. 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
4. 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.
13
753M -
MICROWAVE MEASUREMENT
After any repair, the microwave oven must be checked for microwave leakage to ensure continued safe operation. BS EN
60335-2-25 specifies that the maximum permitted leakage with a load of 275 ml is 50 W/m
60335-2-25 specifies that the maximum permitted leakage with a load of 275 ml is 50 W/m
2
(equivalent to 5 mW/cm
2)
at
a distance of 5 cm from the oven.
PREPARATION
The following items are required to carry out this test:-
1. A low form of 600 ml beaker made from an electrically non-conductive material, such as glass or plastic, with an inside
1. A low form of 600 ml beaker made from an electrically non-conductive material, such as glass or plastic, with an inside
diameter of approximately 8.5 cm. This must contain 275
±
15 ml of water, at an initial temperature of 20
±
2˚C.
2. A leakage detector which has been calibrated within the preceding 12 months to a standard whose accuracy can be
traced to National Physical Laboratory Standards.
Recommended instruments are:
Apollo “XI”
Celtec “A100”
Celtec “A100”
Before commencing the test, check that the leakage detector is functioning and adjusted according to the manufacturer’s
instructions, and any spacers are fitted to ensure that measurement is taken 5cm from the surface of the oven.
instructions, and any spacers are fitted to ensure that measurement is taken 5cm from the surface of the oven.
PROCEDURE
1. Place the beaker containing the water load in the oven cavity at the centre of the turntable. The placing of this standard
load in the oven is important, not only to protect the oven, but also to ensure that any leakage it is not disguised by too
large a load absorbing energy.
large a load absorbing energy.
2. Close the oven door, and with the power level set to FULL, turn the oven ON with the timer set for a few minutes
operation. Should the water begin to boil before the test has been completed, it should be replaced.
3. As shown in the diagram below, move the probe slowly (not faster than 2.5 cm/sec.);-
a) around the edge of the door following the gap
b) across the face of the door
c) across any vents in the oven’s sides, rear or top
a) around the edge of the door following the gap
b) across the face of the door
c) across any vents in the oven’s sides, rear or top
Dotted line indicates the path by the leakage detector.
Whilst the maximum leakage permitted in BS60335 2-25 is 50 /W/m
2
(equivalent to 5 W/cm
2
),it is not normal to detect any
significant leakage, and therefore any detected leakage should be investigated.
14
753M -
SCHEMATIC DIAGRAM
230-240V 50Hz
SW
F8A
SW3:
FUSE
F
*
H.V.
NO
NO
NC
OVEN LAMP
FAN MOTOR
TURN TABLE
MOTOR
MONITOR
MONIT’D
LATCH
SWITCH
SWITCH
SWITCH
SW1
SW2
COM.
NO.
RY3
COM.
NO.
COM.
NO.
OL
FM
M
T
T
A1
RY1
RY2
CONTROL UNIT
A3
125 C
CUT OUT
THERMAL
MAG
160 C
CUT OUT
THERMAL
OVEN
STOP
B2
B1
GRILL HEATER
15A
0.0047 /250V
0.0047 /250V
680K/0.5W
10M/0.5W
NOISE SUPPRESSION COIL
/250V
0.22
FUSE
G-Y/15
/15
/15
BRN
BLU
L
N
EARTH
DIAGRAM
SCHEMATIC
*
MAGNETRON
RECTIFIER
*
POWER TRANSFORMER
*
H.V.
CAPACITOR
ASYMMETRIC
RECTIFIER
2100VAC
1.02
R-753( )M
*
*INDICATES PARTS WITH POTENTIALS OVER 240V
15
753M -
WIRING DIAGRAM
(REFERENCE ONLY)
FUSE
F2:
*
H.V.
F
*
MONITORED
SWITCH
MONITOR
LATCH
SWITCH
SW3
F8A
230-240V 50 H
Z
*
INDICATES PARTS WITH POTENTIALS OVER 240V
F1:
1.02
2100VAC
RECTIFIER
ASYMMETRIC
CAPACITOR
*
H.V.
*
POWER TRANSFORMER
RECTIFIER
*
MAGNETRON
H.V.
H.V.
15A
0.0047 F/250V
0.0047 F/250V
680K/0.5W
10M/0.5W
NOISE SUPPRESSION COIL
F/250V
0.22
FUSE
G-Y/15
/15
/15
BRN
BLU
L
N
EARTH
BLU
GRILL HEATER
FM
OL
TTM
RED
SW1:
SW2:
A5
B1
B2
A3
CONTROL UNIT
RY2
RY1
A1
NO.
COM.
NO.
COM.
RY3
NO.
COM.
/20
WHT
BLK
/20
BRN
WHT
20
20
ORG
/18
/18
BLK
BLU
RED
/18
/18
WHT
BLK
/18
RED
/18
WHT
BLU
BRN
/20
BLU
/18
BLU
/20
GRY
STOP
MAG
THERMAL
CUT OUT
CUT OUT
125 C
WHT
160 C
CUT OUT
THERMAL
OVEN
RED
SWITCH
**
Click on the first or last page to see other R-753 (serv.man3) service manuals if exist.