Sharp R-3S68, Service Manual

Page: 16 / 36

14
R-3S68
Control Unit
Control unit consists of tact switches, LSI, power source
circuit, synchronizing signal circuit, ACL circuit, buzzer
circuit and indicator circuit.
1) Tact Switches
The tact switches are composed of a matrix, signals
generated in the LSI are sent to the tact switches through
R61-R63. When a tact switches is touched, a signal is
completed through the tact switches and passed back to
the LSI through R81-R83 to perform the function that
was requested.
2) LSI
This LSI controls the key strobe signal, relay driving
signal for oven function and indicator signal.
3) Power Source Circuit
This circuit generates voltages necessary in the control
unit.
Symbol Voltage Application
VC -5V LSI(IC1)
4) 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.
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
5) ACL Circuit
A circuit to generate a signals which resets the LSI to the
initial state when power is supplied.
6) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit
noticing sounds (key touch sound and completion sound).
7) Door Sensing Switch
A switch to “tell” the LSI if the door is open or closed.
8) Relay Circuit
To drive the magnetron, fan motor, turntable motor and
light the oven lamp.
9) 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.