Metra Electronics DAT Combo Manual de usuario descargar pdf (Pagina 72)

TAPE

-SLIDE

Lit

and o/i

the

AC

to the shaded

-pole

induction

motor -which

normally

powers

the semi-

automatic

slide

changers.

By using

the

SCR

with

a diode bridge

circuit

both halves

of

the 60

-cycle

(Hz) power

are

passed

and

the

relay

can

be

eliminated. Another

way

to

eliminate

the

relay is

to use

two SCRs in

inverse

parallel

but

this is more

expensive.

Originally

this Tape -Slide

Synchronizer

was

used with

a

stereo

record -playback

tape

deck with

only

one

power amplifier

and

speaker

-for

the commentary

channel.

The

three -stage

transistor

amplifier oper-

ates

the

SCR circuit. It

provides plenty of

gain for use

with

the tape deck and

even a

small

crystal microphone

can be used

to

operate

the slide

changer and put

a

sync

signal on

the tape.

SCR -Diode Bridge

Switch. The heart

of

this unit is

the SCR -diode

bridge switch -

the basic

switch

circuit is

shown top

right.

The

SCR has high

resistance between

anode

(A)

and

cathode

(C) when

there

is no sig-

nal on

the

gate

(G),

and no AC

can flow

through the

diode bridge

to

power

the

motor

-it is off.

When

the gate of

SCR1 is made

positive

(by

a positive

-going signal between

gate and

cathode)

the resistance of

SCR1 becomes

very

low between anode

and cathode

(it

conducts) and

the

motor

runs.

Conduction of both halves

of the AC-

power

sine

wave

is brought about

as follows:

when

the AC cycle is

positive at W,

current

SCR

o

Mt

W

MOTOR

AC

LINE

c

DIODE

BRIDGE

Unique

basic circuit

is heart

of Slide Syn-

chronizer. Power

-line

AC flows through

motor

M1

but

DC

flows

through

SCR1 by way

of diode

bridge -simple

and

inexpensive.

flows

through motor

M1,

then

through

D5

from A

to B,

through SCR1

to

D2

(from D

to

C) back

to

the

other

side

of the

line

(Y).

When

the

positive cycle of

the

AC

line

is

at Y, current flows

through D3 (from

C

to B),

through SCR1 to D4 (from

D

to A),

then back

through motor M1

to the

other

side of

the line (W)

.

In like

manner, the

sync signal from the

output of

the tape recorder, when

rectified

and applied

as a positive

(

+) pulse

to the

gate of the

SCR

-diode bridge,

switches

the

slide-

changer motor.

Solid -State Synchronizer.

The

complete

schematic wiring

diagram, including

that for

the slide

changer, is shown

below. Re-

mote pushbutton

S2 is used

to operate

the

slide

changer.

An

Airquipt

(model

Y) semi-

automatic

slide changer

is used here.

How-

ever, practically

any

remote -pushbutton

operated

unit

could be used.

The

slide

changer

is shown

attached

to a TDC

LOW

INPUT

1 II

r

(

(

I

78

HIGH

INPUT J2

(TAPE

OUTPUT)

Fid

X

J

I

RI

5K

,

I

J

S1

1 .O1 M

F

*

1002

F '""

OUTPUT

PK522

AMPLIFIER

81k

Y

RADIO -TV EXPERIMENTER

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