Sharp R-4P58 - Page 20

TEST PROCEDURES (CONT'D)
SOOO
OE
Eee
SSS
ees
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PROCEDURE
LETTER
NOTE:
*At
the
time
of
these
repairs,
make
a
visual
inspection
of
the
varistor
for
burning
damage
and
examine
the
transformer
with
tester
for
the
presence
of
layer
short
circuit
(check
primary coil resistance).
if any abnormal condition is detected, re-
place the defective parts.
CARRY OUT 4R CHECKS.
COMPONENT TEST
TOUCH
CONTROL
PANEL
ASSEMBLY
OUTLINE OF TOUCH CONTROL PANEL
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
signals
commu-
nicated
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
P23
-
P27.
When
a
key
pad
is
touched,
a
signal
is
completed
through
the
key
unit
and
passed
back
to
the
LSI
through
P74
-
P77
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,
tempera-
ture
measurement
circuit,
indicator
circuit,
encoder
circuit,
and
back
light
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
voltage
necessary
in
the
control
unit.
Symbol Voltage
VC -5.2V
Application
LSKIC1)
18
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
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).
eel
6
eet
Door Sensing Switch (Stop Switch)
A
switch
to
"tell"
the
LSI
if
the
door
is
open
or
closed.
7) Relay Circuit
To
drive
the
magnetron,
heating
element,
fan
motor,
turntable motor and light the oven lamp.
8) Encoder
The
encoder
converts
the
signal
generated
by
LS!
into
the
pulse
signal,
and
the
pulse
signal
is
returned
to
the
LSI.
AL fo tap ew
9) Back Light Circuit
A
circuit
to
drive
the
back
light
(Light
emitting
diodes
LD1 - LDS).
10) indicator Circuit
This
circuit
consists
of
4-digits,
30-segments
and
3-
common
electrodes
using
a
Liquid
Crystal
Display.