Sanyo PLUS T35 - Quartz and Digital Counter Alignment; Quartz Alignment Procedures; Digital Counter Frequency Display Alignment

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DEGITAL

COUNTER

BLOCK

1.

FM

frequency

fine

adjustment

(1)

Set

FM

SG

to

98.000

MHz,

1

kHz,

75

kHz

dev.

(100%

modulation),

and

feed

this

signal

into

FM

ANT

terminal

(300-ohm)

of

the

set.

(2)

Tune

in

by

tuning

the

tuning

knob,

and

turn

on

quartz

switch

(locked).

(3)

Tip

IF

OFFSET

to

FM

side.

That

is,

short-circuit

by

connecting

the

tip

of

R023

connected

to

FM/AM

terminal

(pin

No.

12)

of

IC

002

to

the

earth.

Then

the

second

place

from

the

bottom

(digit

2)

flickers.

(4)

Turn

SVR

RO39

(10K

ohms,

balanced)

and

adjust

until

the

display

becomes

98.000

and

digit

2

stops

flickering.

FM

FREQUENCY

FINE

FM-SG

O00

000

O00

EEE

O]

Cha)

2.

AM

frequency

fine

adjustment

(1)

Produce

signals

of

1000

kHz

with

AM

SG

and

4,000

Hz,

30%

modulation

at

the

external

modulation

terminal,

and

apply

the

signals

into

AM

ANT

terminal.

(2)

Tune

in

by

turning

the

tuning

knob,

and

stop

where

the

output

reaches

the

lowest

level.

(See

waveform.)

(3)

Tip

IF

OFFSET

to

AM

side.

That

is,

short-circuit

by

connecting

the

tip

of

R023

connected

to

FM/AM

terminal

(pin

No.

12)

of

IC

002

to

V,,

(+9.4

V).

Then

the

second

place

from

the

bottom

(digit

2)

flickers.

(4)

Turn

SVR

R040

(10K

ohms,

balanced)

and

adjust

until

the

display

becomes

1000

and

digit

2

stops

flickering.

AM

FREQUENCY

FINE

AF

OSC

AM-SG

QUARTZ

SAMPLING

LOCK

1.

Principle

The

quartz

sampling

lock

(OSL)

is

designed

to

compare

the

phase

of

FM

loca!

oscillation

frequency

with

the

reference

frequency

generated

by

crystal

oscillator,

convert

the

fluctuations

of

local

oscillation

into

DC

voltage

and

apply

it

to

a

variable

capacity

diode

(vari-

cap

diode)

in

order

to

control

the

local

oscillation.

The

crystal

fundamental

oscillation

frequency

is

6.4

MHz,

which

is

divided

to

1/128,

so

that

the

local

oscillation

can

be

locked

at

50

kHz

intervals

using

the

50

kHz

fre-

quency

as

the

reference

frequency.

2.

Circuit

description

Part

of

local

oscillation

is

taken

out

from

FM

_

locat

oscillation

through

buffer

Q106,

and

is

amplified

in

0401.

On

the

other

hand,

fundamental

oscillation

(6.4

MHz)

and

frequency

dividing

are

performed

by

Q411

{a

frequency

divider

built

in

oscillation

circuit),

and

a

square

wave

output

of

50

kHz

is

obtained.

Next,

the

waveform

is

shaped

by

0410

(TTL

NAND

gate)

(see

Fig.

1),

and

high

speed

pulse

of

50

kHz

is

obtained

in

the

output.

By

switching

Q403

with

high

speed

pulse,

Q402

operates

when

0403

is

ON.

Therefore,

since

the

previous

RF

AMP

output

is

impressed

to

the

base

of

Q402,

the

phase

of

the

local

oscillation

when

Q402

is

ON

can

be

detected.

C4648P

is

a

charge

pump,

and

holds

the

output

after

phase

detection

until

a

next

pulse

(Fig.

3).

LOCAL

OSG

Xtal

-

OSC

DIVIDER

WAVE

FORM

PHASE

COM.

OSC

SCOPE

ij

TUNING

POINT