Sanyo PLUS T35 - Quartz Block Adjustment Details; VCO and Bias Adjustment; Tuning Meter Balance Adjustment; Tuning LED Lighting Test

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0404

is

a

buffer,

and

Q405

is

a

high

input

impedance

Meanwhile,

the

side

signal,

by

using

the

other

operational

circuit,

which

is

also

a

switching

circuit.

When

the

local

amplifier

of

Q408,

obtains

a

signal

as

shown

in

Fig.

5,

oscillation

frequency

approaches

within

+

several

kHz

of

and

controls

the

side

LED.

The

relation

between

signals

50

kHz,

each

circuit

functions,

and

Q405

is

turned

on.

and

frequencies

is

shown

in

Fig.

6.

At

the

same

time,

the

closed

loop

shown

in

Fig.

1

is

formed,

and

the

local

oscillatiage

frequency

is

locked.

Q406

is

a

device

comprising

two

operational

amplifiers:

one

forming

active

LPF

and

DC

AMP

and

the

other

forming

HPF

AMP.

Q406

(1)

terminal

receives

HPF

output,

which

is

rectified

and

smoothed

by

D412,

413

to

drive

0407.

When

the

beat

frequency

of

phase

comparator

output

nears

zero,

the

base

voltage

of

Q407

lowers

to

cut

it

off.

As

a

result,

Q404

(14)

becomes

high

level,

and

(15)

low

level.

On

the

other

hand,

S-curve

output

is

taken

from

the

tuner

section,which

is

amplified

by

0408

to

obtain

center

signal

and

side

signal.

Terminal

(7)

receives

the

center

signal

output,

and

becomes

low

level

within

+

20kHz

of

the

center

frequency

(Fig.

4).

In

con-

sequence,

0414

(9)

becomes

L

and

(10)

becomes

H.

Parallel

to

this,

by

switching

on

and

off

Q416

with

the

muting

output

obtained

from

SIGNAL

1,

Q414

(14),

(7),

(3)

and

Q417

are

controlled.

Also,

when

AM

signal

is

applied,

the

cathode

of

D404

is

pulled

to

L

side,

and

the

oscillation

of

Q411

is

stopped.

Q409

and

0413

are

the

circuits

to

maintain

within

the

broadcast

frequency

even

if

the

local

oscillation

fre-

quency

is

deviated

due

to

temperature

changes

when

the

power

source

is

turned

on

again

a

short

while

after

cutting

off

the

power

when

a

broadcast

had

been

being

received.

These

circuits

depend

on

charging

of

C426.

When

charging

of

C426

is

completed,

the

operation

is

designed

to

be

stopped

automatically.

0418

is

to

dis-

charge

C426.

t

1

!

1

i

1

{

Ae

(B)

50kHz

trigger

UUU

(A)

WAVEFORM

SHAPING

(B)

ee

ees

eae

Comparator

signal

(A)

Time

lag

due

to

C.R.

CONTINUOUS

WAVEFORM

(BEAT)

ot

10

—

20rs

:

{Beat

corresponding

to

frequency

deviation

of

(8)

PERFORMANCE

OF

GATE

2

focal

oscillation

and

reference

frequency

is

generated.)

240