4-10.
VOLTAGE
SUPPLIES
Separate secondary windings
on
the
power
transformer provide
30
VDC
through
J1
to diode bridge
rectifiers
CR1
and
CR2.
The
low
current
for
the
amplifiers
is
supplied
by
CR1.
Diodes
CR16
and
CR17
provide reverse
voltage
protection
to
regulator
mounted
on
the outside of the
rear
panel.
The
regulator
provides
+24
VDC
controlled
within
24
mV
with
internal
current
and
thermal overload
protection.
Voltage
for
the logic
and
solenoid are
supplied
directly
from
the output
of
CR2.
Capacitor
C5
provides
filtering
for
this
high
current
source.
4-11.
SOLENOID
CONTROL
When
the logic
is
in the stop
mode,
the base of
Q5
is
grounded to
the
flip-flop
on
the Playback/Logic board.
The
voltage
on
Q5
collector
is
high
and
zener diode
CR20
conducts
which
delivers
current
to
Pin
2 of
IC1.
With
this
current
present,
IC1
shuts
off
base drive to the
2N3055
solenoid
driver
located
on
the
rear
panel.
The
solenoid remains in the deenergized
positon.
In
this
mode,
pin
13
of
IC1
is
pulled
low
which
turns
on
FET
Q3.
FET
Q3
allows
C9
to charge to a higher voltage than
is
present with
R20.
When
the logic changes to the
run
mode,
the base of
Q5
goes
high to turn
Q5
on.
The
run
lamp
and
the record logic ground to
Q5
through
CR12
and
CR13.
Diode
CR20
stops conducting
and
IC1
delivers
base drive to the solenoid
driver.
The
voltage across the 3.3
Ohm
resistor
located
on
the inside
rear
panel
(current
through the solenoid)
is
inputed to
IC1
at
pin 4.
IC1
will
deliver
base drive to
keep
the voltage
at
Pin
4 equal to the voltage
at
Pin
5.
When
the
START
mode
is
first
initiated,
the voltage
on
IC1
Pin
5
is
high
due
to
C9
being charged
by
Q3.
IC1
delivers
enough
base drive to the
solenoid
driver
to
saturate
this
device. This places the
full
30
volt
supply
(less
2N3055
and
3.3
Ohm
drop) across the solenoid to assure
fast
accurate
pull
in.
Pin
13
of
IC1
goes
high
and
Q3
turns
off.
Capacitor
C9
discharges
to a
new
voltage determined
by
R20.
IC1
lowers the solenoid drive base
drive
until
the voltage
at
IC1
Pin
4 equals
that
at
Pin
5. This loop insures
a constant voltage across the 3.3
Ohm
resistor
(constant solenoid
current).
In
the
STOP
mode,
the base of
Q?
goes
high
from
the
flip-flop
on
the playback board.
Transistor
Q?
turns
on
to provide a
ground
for
the stop
lamps
and
the record logic through
CR13
and
CR15.
(The
front
panel stop
switch
lamp
+24
VDC
supply
is
connected through the
deck
microswitch
so
that
this
lamp
lights
only in the
STOP
mode
when
a
cartridge
is
loaded).
4-12.
FAST
FORWARD
AND
Q-TRIP
RELAYS
The
ac
voltage
for
the drive motor
is
supplied
from
the
power
transformer primary through
Jl
and
J2.
When
equipped
for
either
manual
or
automatic
fast
forward, relay
K1
is
installed
to switch
power
to the
normal
or high speed windings as required. Capacitors
C1, C2, C3,
and
C4
provide
arc suppression during switching.
16
To Next Page
Loading...