Sharp R-4A68, Service Manual

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14
R-4A68
The touch control section consists of the following units
as shown in the touch control panel circuit.
(1) Key Unit
(2) Control Unit
The principal functions of these units and the signals com-
municated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit through R51, R52, R53, R60,
R61, R62 and R63.
When a key pad is touched, a signal is completed through
the key unit and passed back to the LSI through R81, R82,
R83 and R90 to perform the function that was requested.
Control Unit
Control unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit and indicator
circuit.
1) LSI
This LSI controls the key strobe signal, relay driving signal
for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltages necessary in the control
unit.
Symbol Voltage Application
VC -5V LSI(IC1)
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
3) Synchronizing Signal Circuit
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.
4) ACL Circuit
A circuit to generate a signals which resets the LSI to the
initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
audible sounds (key touch sound and completion sound).
6) Door Sensing Switch
A switch to “tell” the LSI if the door is open or closed.
7) Relay Circuit
To drive the magnetron, fan motor, turntable motor and
light the oven lamp.
8) Indicator Circuit
Indicator element is a Light-emitting diode.
Basically, a Light-emitting diode is triode having a cathode
and an anode.
The Light-emitting diode has 4-digits, 9-segments are
used for displaying figures.