R-247. Complete - Sharp Home Appliance Service Manual (repair manual). Page 14

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The touch control section consists of the following units as
shown in the touch control panel circuit.

(1) Key Unit (Membrane switch)
(2) Control Unit

The principal functions of these units and their related
signals are explained below.

Key Unit (Membrane switch)
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit through P24, P25, P26,
P31, P32 and P33.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through P50 - P53
to perform the function that was requested.

Control Unit
Control unit consists of LSI, reset circuit, indicator circuit,
power source circuit, relay circuit, buzzer circuit and
synchronizing signal circuit.

This circuit generates a signal which resets the LSI to
the initial state when power is supplied.

This circuit consists of 4-digits, 12-segments and 3-
common electrodes using a Liquid Crystal Display.

OUTLINE OF TOUCH CONTROL PANEL

This circuit generates voltage necessary in the control
unit from the AC line voltage. In addition, the synchro-
nizing signal is available in order to compose a basic
standard time in the clock circuit.

Symbol

Voltage

Application

VSS

-5V

LSI(IC1)

To drive the magnetron, fan motor, turntable motor and
light the oven lamp.

The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion
sound).

The power source synchronizing signal is available in
order to compose a basic standard time in the clock
circuit. It accompanies a very small error because it
works on commercial frequency.

A switch to “tell” the LSI if the door is open or closed.

T1

(J1)

VRS1

RY2

RY1

CN-A

1

3

Problem: POWER ON, indicator does not light up.

CARRY OUT 3D CHECKS.

STEPS

OCCURRENCE

CAUSE OR CORRECTION

The rated voltage is not applied between Pin

1

No. 3 of the 2 pin connector (A) and the

Check supply voltage and oven power cord.

normal open terminal of the relay RY2.

2

The rated voltage is applied to primary side

Low voltage transformer or secondary circuit defective.

of low voltage transformer.

Check and replace control unit.

3

Only pattern at "a" is broken.

*Insert jumper wire J1 and solder.

4

Pattern at "a" and "b" are broken.

*Insert the coil RCILF2003YAZZ between "c" and "d".

NOTE: At the time of making these repairs, make

a visual inspection of the varistor. Check
for burned damage and examine the trans-
former with tester for the presence of
layer short-circuit (check primary coil re-
sistance). If any abnormal condition is
detected, replace the defective parts.

CARRY OUT 4R CHECKS.