Sharp R-9570 Service Manual page 22

R-9570
SERVICING
1. Precautions for Handing Electronic Components
This unit uses PMOS LSI in the integral part of the circuits.
When handing these parts, the following precautions
should be strictly followed.
PMOS 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 elec-
tricity charged in clothes, etc, and sometimes
it
is not fully
protected by the built-in protection circuit.
In order to protect PMOS LSI.
1)
2)
When storing and transporting, throughly wrap them
in aluminum foil.
Also wrap PW boards containing them in aluminium
foil.
When soldering, ground the technician as shown in
the figure and use grounded soldering iron and work
table.
a~prox 1 MR
2. Shapes of Electronic Components
@
EC
0
Transistor
DTAI 43EA, DTCI 14EA
2SC2021,2S~937OQ,288851
2SD 1228M
Transistor
Resistor Block
2SB953
R50
3. Servicing of Touch Control Panel
We describe the procedures to permit servicing the touch
control panel of the microwave oven and the cautions you
must consider 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 HI.GH VOLTAGE TRANSFORMER OF THE
MICROWAVE OVEN IS STILL ALIVE TO GIVE YOU
DANGER DURING SERVICING.
Therefqre, when checking the performance of the
touch control panel, put the outer cabinet on the oven
proper to keep you from touching the high voltage
transformer, or unplug the primary terminal (connec-
tor) of the high voltage transform& to turn it off; and
the en! of such connector shall be insulated with an
insulating tape. After servicing, be sure to replace the
leads to their original locations.
4
A.
B.
(2)
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 the sensor-related ones included) of the
touch control panel while keeping it in contact with
the oven proper.
On some models, on the other hand, the power sup-
ply 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 whiie 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 equiva-
lent to that with the oven door being closed.
As to the sensor-related controls of the touch control
panel, their checking is allowed if the dummy resis-
tor(s) whose resistance is equal to that of those con-
trols is used.
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 such an operational state that is equiva-
lent to that with the oven door being closed. And con-
nect an external power source to the power input
terminal of the touch control panel, and then it is al-
lowed to check and repair the controls of the touch
control panel; as in the case of (11-B above, it is here
also possible to check the sensor-related controls of
the touch control panel by using the dummy
resistor(s).
'.
Sevicing Tools
Tools required when servicing the touch control panel as-
sem bly.
1) Soldering: 30W
(To prevent leaking current, it is recommended to use
a soldering iron with grounding terminal.)
2) Oscilloscope: Single beam, frequency range: DC -
10MHz type or more advanced model
3) Others: Other tools
-e
5. Other Precautions
1)
2)
3)
4)
5)
When turning on the power source of the control unit,
remove the aluminum foil applied for preventing stat-
ic electricity.
Connect the connectors of the indicator and key units
to the control unit taking care that the lead wires are
not twisted.
After aluminum foil is removed, take extra care that
abnormal voltage due to static electricity etc. is not
applied to the input or output terminals.
Attach connectors, electrolytic capacitors, etc. to PW
board, taking care that all connections are tight.
Be sure to use specified components where high pre-
cision is required.
20