R-353 (serv.man3). Complete (including Parts listing) - Sharp Home Appliance Service Manual (repair manual). Page 9

R353M - 9

OUTLINE OF TOUCH CONTROL PANEL

CARRY OUT 3D CHECKS.

Isolate the high voltage rectifier assembly from the HV circuit. The high voltage rectifier  can
be tested  using an ohmmeter set to its highest range. Connect the ohmmeter across the
terminal of the high voltage rectifier and note the reading obtained. Reverse the meter leads
and note this second reading.
The normal resistance is infinite in one direction and more than 100 k

Ω

 in the other direction.

CARRY OUT 4R CHECKS.

NOTE:

FOR MEASUREMENT OF THE RESISTANCE OF THE RECTIFIER, THE

BATTERIES OF THE MEASURING INSTRUMENT MUST HAVE A VOLTAGE AT
LEAST 6 VOLTS, BECAUSE OTHERWISE AN INFINITE RESISTANCE MIGHT BE
SHOWN IN BOTH DIRECTIONS.

The touch control section consists of the following
units.

(1) Key Unit
(2) Control Unit (The Control Unit consists of Power

Unit and CPU Unit).

The principal functions of these units and the
signals communicated among them are explained
below.

The key unit is composed of a matrix, signals
generated in the LSI are sent to the key unit
through P20, P21, P22, P23, P24, P25, P26 and
P27.
When a key pad is touched, a signal is completed
through the key unit and passed back to the LSI
through P43, P44, P45 and P46 to perform the
function that was requested.

Control unit consists of LSI, ACL circuit, indicator
circuit, power source circuit, relay circuit, buzzer
circuit, synchronizing signal circuit and back light
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.

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

Symbol

Voltage

Application

VC

-5.2V

LSI(IC1)

A circuit 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.

A circuit to drive the back light (Light emitting diodes
LD1- LD5).