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Sharp GF-9090H - APSS FUNCTIONALITY; APSS INDICATOR CIRCUIT; MUTING CIRCUIT; APSS DETECTION CIRCUIT

Sharp GF-9090H
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DESCRIPTION
OF
APSS
APSS
is
the
abbreviation
of
Automatic
Program
Search
System
that
permits
advancing
the
tape
past
an
unwanted
selection
to
the
beginning
of
the
next
program
automati-
cally
with
one
push
of
a
key.
In
this
machine,
the
APSS
in
the
reverse
direction
is
also
realized
besides
that
in
the
forward
play.
That
is
to
say,
this
unit
is
equipped
FWD.-
APSS
key
(
<q
)
and
REV.-APSS
key
(
p>
).
In
playback
mode
when
the
FWD.-APSS
key
is
depressed
the
tape
is
fed
at
a
high
speed
and
is
slowed
down
to
a
regular
play
speed
at
the
beginning
of
the
next
selection.
Or,
when
the
REV.-APSS
key
is
depressed
the
tape
is
rewound
at
a
high
speed
and
is
set
to
regular
playback
mode
at
the
beginning
of
the
selected
program.
The
following
explana-
tion
refers
to
the
function
of
the
APSS.
FUNCTION
OF
APSS
When
the
FWD.-APSS
key
is
depressed
in
playback
mode
of
the
tape,
the
pinch
roller
is
cleared
from
the
flywheel
shaft
and
the
roller
assembly
meshes
with
the
gear
of
the
take-up
turntable
permitting
the
tape
to
advance
at
a
normal
fast
forward
speed.
On
the
other
hand,
when
the
@)
APSS
INDICATOR
CIRCUIT
(Refer
to
Figures
8,
9,
10
and
11)
With
the
APSS
indicator
circuit
being
given
+12V
power,
the
multi-vibrator
(Q502
and
Q501)
starts
to
oscillate
to
n
Hz
(about
2
Hz)
and
output
of
the
multi-vibrator
will
be
applied
to
the
flip-flop
circuit
(Q503
and
Q504)
to
be
1/2
divided
into
1/2n
Hz
(about
1
Hz).
These
outputs
of
the
multi-vibrator
and
flip-flop
circuit
are
to
light
up
the
light
emitting
diodes
DS13,
D512
and
D511
through
the
logical
circuit
(D501
to
D506).
Figure
10
is
a
timing
chart
concerning
the
above
operation.
In
Figure
10,
1)
and
2)
are
output
waveformes
of
the
multi-vibrator
(Q502
and
Q501),
and
3)
and
4)
are
those
of
the
flip-flop
circuit
(Q503
and
Q504).
Using
these
four
(4)
waveforms,
the
logical
circuit
is
to
further
create
waveforms
5),
6)
and
7)
to
have
the
light
emitting
diodes
light
up.
The
horizontal
axis
shown
in
Figure
10
refers
to
a
time
axis:
the
light
emitting
diodes
D513,
D512
and
D511
light
up
in
this
order
one
after
another,
respectively
at
the
periods
a,
b
and
c.
Meanwhile,
at
the
period
d,
all
the
light
emitting
diodes
are
kept
off.
The
periods
a
to
d
are
considered
one
cycle
of
the
light-up
operation
and
this
cycle
is
repeated:
the
light-up
operation
looks
as
if
it
moved
from
right
to
left.
Q505
and
Q506
are
switching
transistors.
When
the
FWD.-APSS
key
is
depressed,
the
Q505
will
be
turned
“ON”
while
the
Q506
will
do
so
when
the
REV.-APSS
key
is
depressed.
As
for
the
REV.-APSS
operation
mode,
the
light
emitting
diodes
D511,
D512
and
D513
light
up
in
this
order
one
after
another,
respectively
at
the
periods
a,
b
and
c
---
the
light-up
operation
looks
as
if
it
moved
from
left
to
right.
FWD.-APSS
key
is
depressed,
the
FWD.-APSS
switch
(SWSO1)
is
turned
“ON”
so
that
+12V
power
be
applied,
via
D509,
to
the
APSS
indicator
circuit
1)
,
muting
circuit
(2)
and
APSS
detection
circuit
@.
Playback
key
Record
key
Fast
forward
Rewind/
/Cue
key
mm.
Review
key
Pause
key
Eject
key
Forward
Reverse
APSS
key
APSS
key
(FWD-APSS)
(REV-APSS}
Stop
key
Figure
8
FUNCTION
KEY
LAYOUT
Q501~9506
ascassic)
ALY
APSS
INOKATOR,
Figure9
APSS
INDICATOR
CIRCUIT
APSS
INDICATOR
PERIOD
jee
NUE
PLLA
[
a
|
r
1
3)
$03
COLLECTOR
|
4).
0604
COLLECTOR
2)
@502
COLLECTOR
[]
I,
Sl
ie
oe
[ee
a
ce
ie
T
Telolelalelelelalalvlel
Tale
le {time
0511,0512
and
D513
OFF
Period
O5I1
ON
Period
OSI2
ON
Period
‘$13.
ON
Period
5)
D511
ANODE
Zam
pee
te
t
6)
0512
ANODE
7)
DS5t3
|
ANODE
ota
|
1
OOHOHORY
LEFT
RIGHT
Figure
10
FWD-APSS
IND.
TIMING
CHART
(2)
MUTING
CIRCUIT
(Refer
to
Figure
12)
The
current
fed
to
the
muting
circuit
turns
“ON”
the
muting
transistor
(Q302
and
Q305)
and
attenuates
the
signal
from
head
to
hold
back
the
monitor
noise.
APSS
DETECTION
CIRCUIT
(Refer
to
Figures
13,
14
and
15)
The
current
fed
to
the
APSS
detection
circuit
drives
the
tape
playback
signal
given
from
the
record/playback
head
into
the
APSS
pre-amp
(IC401)
through
the
equalizer
amp
(Q201
to
Q204)
and
APSS
mixer
(Q205),
turning
“ON”
the
Q401,
and
now
the
signal
is
amplified
to
exceed
VBE
(voltage
between
base
and
emitter)
and
charges
the
C406
up
to
+12
volts.
Next,
when
the
Q402
is
turned
“ON”,
the
Q403
is
turned
“OFF”,
and
the
potential
of
the
Q403
collector
stabi-
lizes
at
+12
volts.
Therefore
the
Q404
is
not
turned
“ON”,
in
consequence,
neither
is
the
Q405.
As
a
result,
the
plunger
is
not
actuated.
In
other
words,
as
far
as
the
tape
carries
signals
the
plunger
does
not
work,
that
is,
the
tape
is
continuously
fast
forwarded
according
to
the
mechanism
of
the
APSS.
Meanwhile,
when
there
is
no
signal
on
the
tape,
the
potential,
even
if
amplified
by
the
equalizer
amp
(Q201
to
Q204)
and
APSS
pre-amp
(IC401),
becomes
lower
than
VBE
of
Q401,
which,
therefore,
is
turned
“OFF”,
and
the
electric
charge
of
C406
(determined
by
the
value
of
R405
and
C406)
is
discharged
at
the
time
constant.
When
the
potential
of
C406
is
discharged
to
be
below
VBE
of
Q402,
the
Q402
is
turned
“OFF”
and
the
Q403
is
activated.
Therefore,
the
collector
potential
of
Q403
becomes
zero
(0)
volt
and,
consequently,
the
+12-
volt
voltage
passes
through
the
R412,
allowing
a
discharge
current
to
flow
towards
the
C407.
By
this
discharge
current
the
potential
of
the
Q404
base
drops
momentarily
to
zero
(0)
volt,
and
the
Q404
is
turned
“ON”.
tees
REV-APSS
APSS
INDICATOR
PERIOD
an
h
+)
Q501
COLLECTOR
|
MULTI-VIBRATOR]
rer
2)
0502
COLLECTOR
LI
LU
[|
padi
oe
ty
=
3)
9803
COLLECTOR
LL
—j
LN
FLIP-FLOP.
m
r
4)
Q504
COLLECTOR
_
To
5)
DSi!
ANODE
]
[|
sa
6)
D512
ANODE
|
[
]
—4$
7)
DSI3
ANODE
[|
‘|
i
F
4h;
[
Tololelalalefelatalele!
lalele|
time
--4a-,
|
|
DSI1,DSI2
ond
DSIS
OFF
Period
Gb)
REV)
D513
ON
Period
LEFT
RIGHT
DSI2
ON
Period
DSII
ON
Period
Figure
11
REV-APSS
IND.
TIMING
CHART
Q301,Q304
2S8C373
DIN
AMP
Q302,Q305
2SC372(Y)
MUTING
Roch
C302
R308
10/16V
wK
BUFFER
PRE.
AMP.
ae
AMP.
APSS
DET.
CIRCUIT
GROUND
°
V
V
V
R/P
SWITCH
(SW2OI-K,1)
Figure
12
MUTING
CIRCUIT
{L602)
Q201,Q203
2SCIG82IGR)
EQ
AMR:
Ra);
0202,0204
te,
>
gurren
RECORD/PLAY
BACK
Seat
HEAD
c204
APSS
DET.
CIRCUIT
28C373
MIXER
{>
BUFFER
AMP.
DOIN
SOCKET
(so202)
{L603}
Ae
Figure
13
EQ
AMP.

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