Audio Circuits; Camera Control Circuits; Power Supply Circuits - Sony AV-3600 Service Manual

2-3.
AUDIO
CIRCUITS
2-4.
CAMERA CONTROL
CIRCUITS
Record
Audio input feeds through
C501
to preamplifiers
Q501 and Q502. The
gain of
Q502
is
automatically
controlled
by
AGC
amplifier
Q503
(FET).
R510
and
C506
provide negative feedback.
Output
of
Q502
is
applied to the
driver amplifier
Q504
and then to the
audio output
stage
Q505.
A
sample of the output
is
fed to the audio
level
detector
consisting
of
C528,
C535,
D501
and D502. The
output dc
voltage
of the
detector controls the conduction of
AGC
amplifier
Q503. Thus Q503,
in
the
feedback loop from
the
output
stage
Q505
to the input
Q501,
controls the
amount
of
feedback
current
and
the gain of
Q501.
R521
in
the source of
Q503
adjusts the
audio output
level.
Output from
Q505
is
applied to the audio record/
play head.
In addition,
rf
bias
produced
by
the
bias/
erase
oscillator
Q506
is
applied to the
head through
trimmer
capacitor
C532.
This
adjusts
the
bias signal
level
supplied to the head. Bias
trap
L502
and
C525
eliminates the high-frequency
bias signal
from
the
audio output
circuit.
L501 and
C512
in
the base of
Q504
and
L503
and
C519
in
the collector of
Q505
provide pre-emphasis.
Playback
In
playback,
the
feedback network
in
the
pre-
amplifier
is
altered to take the
path through R513,
R514,
and C510, This network changes
preamplifier
characteristics to
provide de-emphasis
and
equali-
zation. Preamplifier
output
appears across
R515,
which
sets
the drive to the
output
stage for playback.
The
driver
and output
stages,
Q504
and Q505,
func-
tion
in
the same
way
for
both
record
and playback.
The
bias/erase oscillator
Q506
is
not
energized as
B +
to this stage
is
switched
off in
playback.
The
sync
pulse
former on
the
SY3
Board
shapes
the 60-Hz
ac
sine
wave
into
vertical
sync
pulses to
lock
the horizontal deflection
oscillator in
the
camera.
The
sine
wave
signal
from
the
secondary
winding of
T001
is
supplied to C902.
Negative
peaks
are
clamped
to ground
by D901
and C902. The
clamped
signal
is
amplified
by Q901,
differentiated
by R905 and C904, and
supplied to the pulse ampli-
fiers
Q902
and Q903.
Q903
feeds negative
vertical
sync
pulses
through
the
CAMERA
connector
CN4
to the
camera.
2-5.
POWER
SUPPLY
CIRCUITS
The
ac
line voltage
is
stepped
down
by
the
power
transformer
T001
and supplied to
full
wave
recti-
fiers
D601
and D602.
Dc
output
from
the rectifiers
is
filtered
by C601
and
applied to the
series regulator
Q601,
Transistor
Q603
compares
a
sample
of
the
output
voltage, picked off
at
R604,
with
a reference
voltage supplied
by Zener diode D603.
A
change in
output
voltage, detected
by Q603,
results in a
change
in
conduction
of
Q602
and Q601
that offsets
the
original voltage
shift.
B+
for the
RF
adaptor
is
fed
through
a
simple
regulator consisting of
R005
and D001.
Sets bearing Serial
Number
12,201
and
higher
have
a
extra regulator for the
rf
adaptor
consisting
of
Q604
and Q605 on
an
R2
board. This regulator
operates the same
way
as
the
main
regulator.
2-6