TANDBERG TCD 310 Service Manual

4.
MOTOR
AND
SOLENOID
CIRCUITS
4.1
ASHORT
EXPLANATION
OF
THE
SOLENOID
OPERATING
CIRCUIT
(0305,
0306)
Operation
of
the
pinch
roller
(start)
solenoid
should
be
slightly
delayed,
to
give
the
reel
motors
time
to
remove
any
slack
in
the
tape,
before
the
pinch
rollers
are
pulled
in.
When
both
PLAY
and
RECORD
buttons
are
re-
leased,
C316
has
no
voltage
and
Q307
(PNP)
is
cut-
off.
Q306
(NPN)
has
a
base
voltage
of
0
V
and
is
also
cut-off.
When
the
PLAY
or
RECORD
button
is
depressed
the
following
sequence
is
started:
1.
12
START / STOP
CIR cu
DO
AR 2068
13.5
V
is
connected
to
the
+side
of
C316.
The
voltage
drop
over
R326
gives
Q307
an
emitter
voltage
of
about
11
V.
The
transistor
requires
a
base
voltage
which
is
0.7
V
more
negative
than
the
emitter
to
start
conducting.
The
transistor
|
will
therefore
still
be
in
cut-off
state.
Jcsirare
te
Solenoid
operating
circuit
.
C316
is
charged
through
R328/R333.
The
posi-
tive
voltage
at
point
A
is
connected
via
C315
to
the
base
of
Q307.
This
voltage
is
gradually
reduced
as
C316
is
charged.
.
After
a
little
while,
the
voltage
at
point
A
has
been
reduced
so
much
that
the
base
of
Q307
drops
lower
than
10.3
V,
and
the
transistor
starts
conducting.
.
When
Q307
starts
conducting,
the
collector
voltage
increases,
driving
Q306
into
conducting
state.
Point
B
is
connected
to
ground,
current
passes
through
the
activate”
coil
(Ly)
of
the
start
solenoid
and
the
pinch
rollers
operate.
.
When
Q306
is
conducting,
the
current
to
C316
passes
through
R332
and
Q306,
C316
will
there-
fore
be
fully
charged
in
a
very
short
time.
.
When
C316
is
fully
charged,
there
will
be
no
voltage
at
point
A,
and
C315
is
charged
through
R325,
The
current
through
R325
will
keep
Q307
in
conducting
state.
.
After
a
little
while
the
current
to
C315
has
been
reduced
so
much
that
Q307
goes
cut-off.
Q306
also
goes
cut-off,
stopping
the
current
through the
activate”
coil.
START
Ty SOLENDIC

TANDBERG TCD 310 Specifications

General

Weight	7.5kg
Track System	4-track, 2-channel stereo
Tape Speed	4.76 cm/s
Heads	1 x record/playback, 1 x erase
Type	Cassette Deck
Frequency Response	30 Hz to 16 kHz (Chrome tape)
Signal to Noise Ratio	58dB
Wow and Flutter	0.07 %
Motor	DC servo motor
Tape Type	CrO2
Power Supply	220V
Input	Line In