Sharp R-530BK Service Manual page 27

R-530BK
R-530BW
SERVICING
Precautions for Handling Electronic
Components
This unit uses CMOS LSI in the integral part of the cir-
cuits. When handling these parts, the following precau-
tions should be strictly followed:
CMOS LSI have extremely high impedance at its input
and output terminals. For this reason, it is easily in-
fluenced by surrounding high voltage power sources,
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, practice the following
guidelines:
1. When storing and transporting LSI, thoroughly wrap
them in aluminum foil.
Also wrap all PW boards in aluminum foil.
2. When soldering, the technician should use a ground-
ing strap as shown in the figure and use a grounded
soldering iron and work table.
n
Approx. 1 MQ
/
Shapes of Electronic Components
P
C
B
E
Transistor
2SB1238
Transistor
KRC243M
Servicing of Touch Control Panel
We describe the procedures to permit servicing of the
touch control panel of the microwave oven and the pre-
cautions you must take when doing so.
To perform the servicing, power to the touch control pan-
el is available either from the power line of the oven itself
or from an external power source.
Servicing The Touch Control Panel With
The Oven Power Supply
The high voltage transformer of the microwave oven
is still live during servicing and presents a hazard.
When checking the performance of the touch control
panel, put the outer cabinet on the oven to avoid touch-
ing 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 re-
connect the leads to their original locations.
1. On some models, the power supply co rd be tween the
touch control panel and the oven itself is so short that
2
the two can't be separated. For those models, check
and repair all the controls (sensor-related ones in-
cluded) of the touch control panel while keeping it
connected to the oven.
On some models, the power supply cord between the
touch control panel and the oven proper 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 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 dummy resistor(s)
with resistance equal to that of the controls are used.
Servicing The Touch Control Panel With An
External Power Supply
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 acti-
vates 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 sen-
sor-related controls of the touch control panel by using
the dummy resistor (s).
Servicing Tools
Tools required to service the touch control panel assem-
bly.
1. Soldering iron: 30W
(It is recommended to use a soldering iron with a
grounding terminal.)
2. Oscilloscope: Single beam, frequency range:
DC-IOMHz type or more advanced model.
3. Hand tools.
Other Precautions
1.
2.
3.
4.
5.
Before turning on the power source of the control unit,
remove the aluminum foil applied for preventing static
electricity.
Connect the connector of the key unit to the control
unit being sure that the lead wires are not twisted.
After aluminum foil is removed, be careful that abnor-
mal voltage due to static electricity etc. is not applied
to the input or output terminals.
Attach connectors, electrolytic capacitors, etc. to
PWB, making sure that all connections are tight.
Be sure to use specified components where high pre-
cision is required.
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