R-24AT (serv.man2). Complete - Sharp Home Appliance Service Manual (repair manual). Page 17

15

Switches Terminals

Released

Depressed

SW1

F1 - F4

O.C.

S.C.

SW2

F1 - F5

O.C.

S.C.

SW3

F2 - F4

O.C.

S.C.

SW4

F2 - F5

O.C.

S.C.

SW5

F3 - F4

O.C.

S.C.

CARRY OUT 3D CHECKS.
If the display fails to clear when the STOP/CLEAR pad is depressed, first verify the flat ribbon cable is
making good contact, verify that the door sensing switch (stop switch ) operates properly; that is the
contacts are closed when the door is closed and open when the door is open. If the door sensing switch
(stop switch ) is good, disconnect the flat ribbon cable that connects the key unit to the control unit and make
sure the door sensing switch is closed (either close the door or short the stop switch connector ). Use the
key unit matrix indicated on the control panel schematic and place a jumper wire between the pins that
correspond to the STOP/CLEAR pad making momentary contact. If the control unit responds by clearing
with a beep, the key unit is faulty and must
be replaced. If the control unit does not
respond, it is faulty and must be replaced.
If a specific pad does not respond, the
above method may be used (after clearing
the control unit ) to determine if the control
unit or key pad is at fault.

CARRY OUT 4R CHECKS.

1. CARRY OUT 3D CHECKS.
2. Remove the switch unit from the control panel, referring to control panel removal.
3. To test the switches (SW1-SW5) on the switch unit, check between the terminals of the connector

CN-F as described in the following table by using ohmmeter when the switches are released and
depressed.

4. If incorrect readings are obtained, replace the

defective switch.

5. CARRY OUT 4R CHECKS.

a) When rotating the encoder, the cooking time can not be entered.

3. Control Unit

The following symptoms may indicate a defective control unit. Replacing the control unit. Before
replacing the control unit, perform the switch unit test (Procedure P) to determine if control unit is faulty.

3-1 Programming problems.

a) When touching the buttons, a certain group of buttons do not produce a signal.

3-2 Display problems.

a) For a certain digit, all or some segments do not light up.
b) For a certain digit, brightness is low.
c) Only one indicator does not light.
d) The corresponding segments 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.

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

a) Buzzer does not sound or continues to sound.
b) Cooking is not possible.

O.C. : Open Circuit / S.C. : Short Circuit

SET

3

4

5

6

7

8

9

0

2

CHECK

VOLUME

START

STOP /
CLEAR

1

11

12

13

14

15

16

19

20

17

18

DOUBLE

QUANTITY

EXPRESS
DEFROST

MANUAL /

REPEAT

POWER

LEVEL

G12

G11

G10

G 9

G 8

G 7

G 6

G 5

G 4

G 3

G 2

CARRY OUT 3D CHECKS.

Remove the outer case and  check voltage between Pin Nos. 5 and 7 of the  connector (A) on the control
unit with an A.C. voltmeter. The meter should indicate 230~240 volts, if not check control unit circuity.

RY1, RY3 and RY4 Relay Test For R-24AT / R-22AT
These relays are operated by D.C. voltage.