R-24STM (serv.man6). Complete - Sharp Home Appliance Service Manual (repair manual). Page 9

R-24STM - 9

If the display fails to clear when the STOP/
CLEAR key is depressed, first verify the lead
wire harness is making good contact, verify that
the stop switch operates properly; that is the
contacts are closed when the door is closed
and open when the door is open. If the stop
switch is good, disconnect the lead wire har-
ness that connects the switch unit to the main
board and make sure the stop switch is closed
(either close the door or short the stop switch
connector). Use the Switch unit matrix indi-
cated on the switch unit circuit and place a
jumper wire between the pins that correspond
to the STOP/CLEAR key making momentary
contact. If the is assembly responds by clearing
with a beep the switch unit is faulty and must be
replaced. If the assembly does not respond,
the main board faulty and must be replaced. If
a specific key does not respond, the above
method may be used (after clearing the display
) to determine if the main board or switch unit is
at fault.

1

2

3

4

SW2

5

6

SW3

SW4

SW5

SW6

SW7

CN-G

SW1

START / AUTO MINUTE

POWER LEVEL

MEAT JOINT

MINCED MEAT

Express Cook 

WHOLE POULTRY

STOP / CLEAR

Do not touch the electrical parts and the printed wiring board to prevent an electric

shock. Because the control unit is " TRANSLESS CIRCUIT " and all electrical parts
are used at A.C. line voltage.

The touch control panel consists of circuits including semiconductors such as LSI, ICs, etc. Therefore,
unlike conventional microwave ovens, proper maintenance cannot be performed with only a voltmeter
and ohmmeter.
In this service manual, the touch control panel assembly is divided into two units, Control Unit and
Switch  Unit, and troubleshooting by unit replacement is described according to the symptoms
indicated.
1.  Switch Unit.        Note : Check switch unit lead wire harness connection before replacement.

The following symptoms indicate a defective switch unit. Replace the switch unit.
a) When touching the keys, a certain key produces no signal at all.
b) When touching a key, two figures or more are displayed.
c) When touching the keys, sometimes a key produces no signal.

2.  Control Unit

The following symptoms indicate a defective control unit. Before replacing the control unit
perform the Switch unit test (Procedure M) to determine if control unit is faulty.

2-1  In connection with keys.

a) When touching the keys, a certain group of keys do not produce a signal.
b) When touching the keys, no keys produce a signal.

2-2  In connection with indicators

a) At a certain digit, all or some dots do not light up.
b) At a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding dots of all digits do not light up; or they continue to light up.
e) Wrong figure appears.
f) A certain group of indicators do not light up.
g) The figure of all digits flicker.

2-3  Other possible problems caused by defective control unit.

a) Buzzer does not sound or continues to sound.
b) Clock does not operate properly.
c) Cooking is not possible.