Tandy CM-8 User Manual

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3.

Vertical Deflection Circuit

The

vertical

sync.

signal

with

positive

polarity

is ap-

plied

to

pin

0of

the

vertical

and

horizontal

IC

(IC601

).

Pin @

of

IC601 is

connected

to

the

internal

vertical

oscillator

circuit.

The

frequency

of

the

oscillator

can

be

controlled

by

the

voltage

of

pin @

which

can

be

varied

by

V.HOLD VR (R514).

The

sawtooth

signal

is

obtained

by

the

integrating

circuit

which

is

connected

between

pin @

and

pin @ . . . . .

The

oscillator

output

is

fed

to

the

vertical

drive

c1rcu1t

through

a

buffer

circuit.

Its

output,

derived

from

pin

0 , is

applied

to

the

vertical

output

circuit

(IC 501

).

The

sawtooth

wave

is

applied

to

pin@

of

IC601

as

an

AC

feedba

ck

signal.

The

output

circuit

of

IC

501

is

controlled

by

V-S IZE VR

(R

507)

to

vary

the

vertical

size

of

the

raster

.

The

verti

cal

linearity

control

(R

526)

is

part

of

an in-

tegrating

circuit

which

controls

the

line

arity

of

the

sawtooth

waveform

.

4.

Horizontal Oscillator, AFC and Drive Circuit

The

horizontal

sync.

signal

with

positive

polarity

is ap-

plied

to

pin @

of

IC601

.

The

output

from

the

flyback

transformer

(T602)

is in -

tegrated

and

connected

to

pin @

of

IC601

as

part

of

the

automatic

frequency

control

circuit.

H.

CENT

control

(R623)

determines

the

relative

posi

-

tion

of

the

raster

and

picture.

The

horizontal

oscillation

frequ

ency

can be.

controlled

by H. HOLD VR

(R607)

connected

to

pin @

of

IC601.

The

horizontal

frequency

is

obtained

from

pin @

of

IC601

,

and

is

fed

to

the

next

horizontal

drive

circuit.

From

Pin. @

of

IC601

C609 l

0601

HOR

IZ

. DR

IVE

The

pulse

-

switching

mode

of

the

driver

and

output

stage

is a reverse

polarity

type;

that

is,

when

the

driver

transistor

0601

is ON ,

the

output

transistor

0602

is

OFF.

5. Horizontal Output and

HV

Rectifier

(Figs.

3-5)

The

horizontal

dirve signal,

developed

at

pin @

of

the

deflection

processor

integrated

circuit

(IC601

),

is

am-

plified

through

the

horizontal

drive

stage

(0601)

and

coupled

to

the

base

of

the

horizontal

output

circuit

via

the

horizontal

drive

transformer

(T601

).

Refer

to

Fig. 3.

The

horizontal

output

circuit

generates

the

horizontal

scanning

signal

and a

high

voltage

to

be

applied

to

the

picture

tube

.

The

function

of

the

horizontal

output

stage

(0602)

is

to

serve as a

switch

for

the

horizontal

output

circuit.

Refer

to

Fig. 4.

During

the

horizontal

scanning

period,

0

operates

(S

1

is

closed,

S2

is

open)

and

the

current

is

applied

in one

direction

through

the

horizontal

coils

of

the

deflection

yoke

(LY)

and

the

capacitor

(C).

During

retrace

time

,

O is

inoperati

ve

(S

1 is

open,

S2

is

closed)

and

the

cur

-

rent

is

applied

in

the

opposite

direction

through

the

damper

diode

(D) ,

the

horizontal

coils

of

the

deflection

yoke

(LY) and

the

capacitor

(C).

The

high

voltage

applied

to

the

anode

of

the

picture

tube

is

generated

by

boosting

the

pulse

from

the

col-

lector

of

0602

through

T60

2

during

the

flyback

(re

-

trace) period and

applying

this

boosted

pulse

to

a series

of

silicon

rectifiers

.

Refer

to

Figure

5.

High

voltage

regulation

is

accomplished

internally

in

T602.

C611

R614

T60

1

HORIZ

.

DRIVE

R613

To

BASE

of

0602

Figure 3. Horizontal Drive Circuit

7

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Tandy CM-8 Specifications

General

Brand	Tandy
Model	CM-8
Category	Monitor
Language	English

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