Sharp R-820BK Service Manual Download Page 31

Page: 31 / 48

R-820BK
R-820BW

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 in

aluminium foil. Also wrap PW boards containing them in
aluminium foil.

2) When soldering, ground the technician as shown in the

figure and use grounded soldering iron and work 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.

(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 .

Therefore, before checking the performance of the touch
control panel,
1) Disconnect the power supply cord, and then remove

outer case.

2) Open the door and block it open.
3) Discharge high voltage capacitor.
4) Disconnect the leads to the primary of the power trans-

former.

5) Ensure that these leads remain isolated from other

components and oven chassis by using insulation tape.

6) After that procedure, re-connect the power supply cord.
After checking the performance of the touch control panel,
1) Disconnect the power supply cord.
2) Open the door and block it open.
3) Re-connect the leads to the primary of the power trans-

former.

4) Re-install the outer case (cabinet).

SERVICING

5) Re-connect the power supply cord after the outer case is

installed.

6) Run the oven and check all functions.

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.

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.

B. 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 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).

4. Servicing Tools

Tools required to service the touch control panel assembly.
1) Soldering iron: 30W

(It is recommended to use a soldering iron with a
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.

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