Leader Lav-191 User manual

MODEL

LAV

..

191

AUDIO.

TESTER

INSTRUCTION

MANUAL

LEADER

ELECTRONICS

CORP.

CONTENTS

SECTION PAGE

1

DESCRIPTION

2

2 SPECIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

3

CONTROLS

AND

CONNECTORS

3

3.1 AC Millivoltmeter

Section

3

3.2

AF

Signal

Generator

Section

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3.3

Rear

Connections

..........

, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4

OPERATION

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.1 Initial Checks . 5

4.2

AF

Signal

Generator

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4.3

AC Miiiivoitmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

4.4

Typical

Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

10

5 MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

12

-

·-

...

1

.....

.

1. DESCRIPTION

The

LAV-191 is a

combination

of

a wideband audio generator and a wide-range AC millivolt-

meter.

This

instrument

is specially useful in testing and servicing audio circuits, monaural and stereo,

for frequency response and gain characteristics.

The

generator frequency range is 10Hz

to

lMHz

and

the

output

is controllable

from

0

to

-120dB

in

ldB

steps

into

a 600!2 load.

The

AC

millivoltmeter covers a voltage range from

150J1V

to

SOOVrms

in the 10Hz

to

lMHz

range.

In

addition to the direct input, two swi.tchable input -LEFT

and

RIGHT

-are

provided

for

stereo circuit measurements. A separate decibel scales,

at

OdB

=

0.775Vrms

and

0 dB =1 Vrms can

be

used

when

comparing signal levels.

Audio

Generator

Section

Frequency Range

Calibration Accuracy

Output

Characteristics

Sine Wave

Impedance

Control

Square Wave

Output

Impedance

SYNC Signal

Terminal

2. SPECIFICATIONS

10Hz-

lMHz

in five decade ranges.

± (3%+1Hz).

Voltage: over

3Vrms

into

600!2

Responce:

Flat

within

±O.SdB.

Distortion,

maximum:

500Hz~

20kHz 0.05%

50Hz~

200kHz 0.4%

20Hz

~

500kHz 0.8%

10Hz....,

lMHz

1.5%

600fl

Internal load

and

external

load

change-over system.

Variable: 0

to

over 3Vrms.

Attenuator:

120dB in 1dB steps

at

600fl;

40dBX2,

20dB,

lOdB, 1dB X 10 accuracy

within±

1.5%.

Frequency

Characteristics:

Accuracy

dB

range

Frequency

± O.SdB

0-60

to

500kHz

60-

120

to

150kHz

±

2dB

0-60

to 1 MHz

± 6dB

60-

120

to

500kHz

± 10dB

60-

120

to

1 MHz

Output:

Over 3 Vp-p

into

600!2

Rise Time

Sag

6oon

±

10%

200

ns.

5%

at

50Hz

Input

Impedance:

Approx

10

kn

Control

range: ± 1%/V

......

2

.....

.

J

AC

Millivoltmeter Section

Voltage Range

Decibel Range

Accuracy

Frequency

Range

Input

Impedance

Input

Selection

Amplifier

Output

Voltage

Output

Terminal

Distortion

Output

Frequency

Responce

Power Supply

Size and Weight

Accessories, supplied -

Lead, clip

to

pin plug

Lead, spade

tip

to

pin plug

Option,

on

separate order:

l.SmV

(O.lSmV min.)

to

500Vrms full scale in

12

ranges.

-80

to

+55dB

(OdB

=

0.775V)

-80

to

+54

dB

(0

dB=

1V)

in

12

ranges.

Within ±2%

of

full scale.

20Hz-100kHz

within

±2% ref:

1kHz.

10Hz-1MHz within ±10%

10Mf2; less than SOpF: 1.5-SOOmV range

less

than

35pF:

1.5-SOOV range

LEFT

and

RIGHT, switchable.

Approx.

1V rms

at

full scale

RCA

jack

Less

than

2%

at

1kHz,

full scale

10Hz-500kHz,

-3dB

(Connected

input

resistor

·10Mf2.

and

capacitor

50pFto

output

terminal)

100,117,200,234V

50/60Hz;

approx. 8VA.

215(H)

x 300(W) X 160(D)

mm;

4kg.

2ea.

2 ea.

Carrying case with strap.

3.

CONTROLS

AND

CONNECTORS

3.1.

AC

Millivoltmeter Section, see Fig. 3-1.

CD

Meter: With scales calibrated for Volts, rms,

and

decibels.

® Mechanical zero

adjuster

for

the

meter.

® SIGNAL SENSITIVITY: When

the

knob

is

set

at

the

position

of

CAL, this

unit

can

be

used

as

AC millivoltmeter calibrated

at

the

value

of

the

range used in

the

same

manner

as

that

of

ordinary

AC millivoltmeter. When the

knob

is set

at

other

than

CAL, this

unit

is

to

set

the

level

of

incoming signal

at

OdB

and

compare signal against

standard

signal

in

making

measurement

of

SN

ratio,

etc.

@)

RANGE switch: Selects the

input

voltage and

dB

level ranges.

® ® INPUT terminal (red):

For

the

high

potential

side.

®LEFT,

®

Klunl.

®@

INPUT terminal (black):

For

the

low

potential

side; this is

"floated"

from

the chassis

with

a 0.22t,tF

capacitor,

@

LEFT,

@ RIGHT.

(j)

Input

jack

for

LEFT

signal

of

stereo

input.

@ INPUT

SELECTOR

switch: Selects

the

LEFT

or

RIGHT

signal

of

stereo

input.

®

Input

jack

for

RIGHT

signal

of

stereo

input

.

......

3

......

3.2

AF

Signal

Generator

Section,

see Fig. 3-1.

©

ATTENUATION

dB

switches:

For

attenuating

the

AF

output

signal; range

is

0

to

llOdB.

Q3)

Attenuator

switch: Adjusts the

AF

output

signal

in

ldB

steps.

(j])

OUTPUT

IMPEDANCE switch: Selects

the

output

load

impedance;

600ft

(f~

OUTPUT

jack:

For

use

with

the

pin plug lead.

@;

Ground

terminal

(chassis

connection).

Q1)

OUTPUT

terminal:

For

the

AF

output

signal

(connected

in parallel

with

jack

(]7

@l

FREQ.

RANGE

switches: Five

pushbuttons

for

selecting

the

range

of

the

output

frequency.

@;

Frequency

dial, Hz:

Calibrated

from

1

to

10Hz;

actual

output

frequency

depends

on

the

ra'hge setting.

~Q>

OUTPUT

LEVEL

control:

For

continous

adjustment

of

output.

~~·

Switch

for

output

waveform

selection,

~sine

or

square,

as

marked.

G?t

Pilot

lamp:

Indicates

when the AC

power

is

on.

Gi}

POWER

switch:

Push

on

the

AC

power.

3.3

Rear

Connections,

see Fig. 3-2.

<24.

SYNC terminals:

For

connection

to

an

external

frequency

control

source;

black

terminal

is

for

ground.

(25.

Shorting-link:

Normally

connected

across

the

SYNC

terminals

when

the

synchronizing

input

signal

is

not

used.

(2(\

Number

plate.

(27

Amplifier

output

terminal

Approx.

1V rms

output

voltage will be available

from

this

terminal

when

meter

indication

is

fuii scaH.

By using

output

from

this

terminal,

monitering

of

the

waveform

under

test

on

oscilloscope

is

available.

!2_$

Puts

in

the

accessory cable

and

others.

Gi.9i

Fuseholder

for the AC line.

(i)Q;

AC

inlet.

@)

AC receptacle:

Outlet

for

direct

power

connection

to

auxiliary

equipment,

independent

power

switch

and

line

fuse;

indicated

current

rating

not

to

be

exceeded.

Note:

AC lOOV

6A

or

AC

250V

2A

max.

®

Power

voltage selection

switch.

®

Cord

winder.

.

.....

4

......

Fig. 3-1

Front

panel

controls

and

connectors~

Fig.

3-2

Rear

panel

controls.

4.

OPERATION

4.1 Initial Checks

Check

the

0

pointer

setting

on

the

meter.

If

not

zeroed

at

the

left

end

of

the

scale,

adjust

the

zero-set screw

on

the

panel

below

the

meter.

(See Fig. 3-1.)

4.2

AF

Signal

Generator

4.2.1 PRECAUTIONS

1.

The

output

should

not

be

connected

to

a

circuit

in

which

voltage

over

12Vrms,

is

present

to

prevent

damage

to

the

attenuator

system.

IfD

C voltage is

present,

connect

it

through

a

capacitor

to

eliminate

D C voltage.

······ 5 ······

2.

Output

connection

leads

should

be

as

short

as possible.

Long

leads are liable

to

pick

up

noise

when

used

at

low

output

levels.

Using a

shielded

cable

at

the

output

will

affect

the

output

at

high frequencies

into

high

impedance

loads due

to

the

shunt

capacitance effect.

4.2.2

CONTROL

ADJUSTMENTS

4.2.3

1.

Set

the POWER switch

at

ON. Allow

about

30

seconds

for

warm-up.

2.

Frequency

setting:

The

output

frequency

is

set

with the

frequency

diai

and

the

FREQ.

RANGE

switches.

FREQ.

RANGE

SETTING

(Multiplier)

3.

Connections

XlO

X100

X1K

X10K

X

lOOK

a.

Ground

lead

to

the

black

OUTPUT

terminal.

OUTPUT

FREQUENCY

RANGE

10-

100Hz

100-

1000Hz (1kHz)

1-

10kHz

10-

100kHz

100-

1000kHz

(1l\.1Hz)

1

b.

"Hot"

lead

to

the red

OUTPUT

terminal,

or

plug

to

the

jack

(both

outputs

are in

parallel).

c.

Output

leads

to

the

input

of

the test circuit.

4.

Output

Level

Setting:

The

OUTPUT

LEVEL

control

is

normally

used

to

set

the

reference

output

level.

The

attenuators

-push

buttons

and

the

rotary

switch

-are

set

as

required.

The

signal

attenuation

is

the

sum

of

the

markings

on

the

attenuators.

The

marking

on

the

attenuator

is

referred

to

the

600Q

load.

Example:

Pushbuttons

at

20

and

10

Rotary

switch

at

6

Total

attenuation=

20

+

10

+ 6 =

36dB

Square

Wave

Output

Square

wave signals are useful in the rough

determination

of

response characteristics

of

amplifiers

at

high

and

low frequency.

The

interconnections

are identical with those

for

sine wave

operation,

see Fig. 4-1.

The

scope for waveform observation

should

have fast rise

time

characteristics.

The

chart

given below shows the waveforms

at

the amplifier

output

for

different

responses.

······ 6 ......

Waveshape· Amplifier Response

Condition

RECTANGULAR t

n_ru

' SATISFACTORY

FLAT

DROOPING

LOW

PRIMARY INDUCTANCE

I~

~

IN

OUTPUT

TRANSFORMER:

INCORRECT VALUES

OF

THE

DEFICIENT

LOW

FREQUENCIES COUPLING ELEMENTS

PEAKED HIGH LEAKAGE INDUCTANCE

I~

(U\

IN OUTPUT

TRANSFORMER

OR

HIGH DISTRIBUTED

DEFICIENT

HIGH FREQUENCIES CAPACITANCE IN CIRCUIT

RIPPLE MALADJUSTMENT IN

THE

I~

llJl

NEGATIVE FEEDBACK

CIRCUIT; INCORRECT

RINGING AT HIGH FREQUENCY CONSTANTS; INSTABILITY

For

an

amplifier

with

good

characteristics, the response will be flat

up

to

about

the

11th

harmonic

of

the

input

fundamental.

As

an

example.

If

a 1kHz square wave

is

reproduced

without

distortion,

the

amplifier response is flat

to

about

11kHz.

NOTES: 1.

Output

voltage settings are initially

made

with

the

OUTPUT

LEVEL

adjustments

and

the

waveform switch set

at

the

sine

wave

position.

The

indicated

value

on

the

scope will

be

equal

to

the

peak-to-peak

output

voltages.

The

waveform

selector

switch

is

then

set

at

the

square wave

position.

Disregard

the

voltmeter

reading.

If

in

doubt,

check

the p-p

output

voltage

with

a

calibrated

scope.

2.

It

is

advisable

to

check

the

input

waveform

on

a

scope

before

application.

3.

Connection

from

the

SYNC

output

terminal

to

the

scope

sync

input

will

make

adjustments

easier

when

displaying waveforms.

The

low

frequency

response will

start

to

fall

off

at

about

1/11

of

the

fundamental

when

there

is a sag,

or

droop,

in

the

displayed waveform.

4.2.4

Use

of

SYNC

Connections

A.

General

The

sync

connections,

on

the rear

panel,

can be used in several

applications

as described

below.

The

"input"

or

"output"

impedance

is

approximately

10k.Q.

B.

Output

Frequency

Control

The

oscillator

frequency

can

be

synchronized

with

an

accurate

source

over a range

of

±1%

per

rms

volt

input,

see Fig. 4-1.

For

example,

when

the

oscillator

is

set

at

some

point

between

990

and

1010Hz,

and

a

......

7

.....

.

signal

of

exactly

1000Hz

is

applied, the oscillator will

automatically

lock

in

at

1000Hz.

Thus,

high

accuracy

can be achieved

with

the

use

of

a precision

frequency

standard.

In

another

application,

a

distorted

waveform

can

be

"purified",

or

filtered,

by

passing it

through

the

oscillator.

1\/\../

~OUTPL"fj

EXTERNAL

JSYNCJ

SOURCE

I

"/\fV

LAV-191

Fig. 4-1 Use

of

the

SYNC terminals.

C. SYNC

Output

Application

The

sync

output

voltage,

approximately

2.5Vrms,

should be

sufficient

to

synchronize

or

trigger

the

sweep

in

a

scope

or

to

operate

a frequency

counter.

This voltage is

not

affected

by

the

setting

of

the

OUTPUT

LEVEL

control.

4.3

AC

Millivoltmeter

4.3.1.

PRECAUTIONS

4.3.2

1.

Maximum

input

voltages:

To

prevent

damage

to

the

input

circuit,

application

of

excessive

voltages

must

be

avoided.

AC

peak

+

DC

=

600V

2.

Low

voltage

measurements:

When

measuring

voltages in

the

millivolt ranges,

the

RANGE

switch

should

be

set

at

a high range

and

lowered

as

required.

If

the

input

leads

are

at

the

open,

or

"free"

condition,

the

meter

pointer

may

go

off

scale;

always

set

the

RANGE

switch

at

a high range.

Due

to

the

high

input

impedance,

stray

voltage

picked

up

cause

this

effect.

3.

The

RANGE

switch

should

be set

where

the

readings can be

taken

above

1/3

of

full scale

length

(except

on

the

lowest

range).

This

will result in higher

accuracy

of

the

readout.

PREPARATION

1.

Set

the

RANGE

switch

at

SOOV

and

turn

on

the

POWER

switch.

2. When the

power

is

rurned

on

(or

off),

the

meter

pointer

may

fluctuate;

this

is

a

normal

condition.

The

miiiivoltmeter

is

ready

for

use

as

soon

as

the

pointer

comes

to

rest.

3.

Connect

the

input

leads

to

the

terminals,

black

for

the

low

potential

and

the

red

for

the

"high"

side.

When

stereo

outputs

are

under

measurement,

connect

the

signal

inputs

to

the

LEFT

and

RIGHT

jack

respectively;

set

the

INPUT

SELECTOR

switch

as

required.

······

8

.....

.

4.3.3 VOLTAGE MEASUREMENTS

1. Connect the

input

lead tips to the test

point

or

the

output

of

the test circuit.

2.

The RANGE switch should be set where the readings can be taken above

1/3

of

full scale. This

will result in higher accuracy

of

the readout.

3. The voltage range

at

the different settings

of

the RANGE switch

is

given in the following

table.

RANGE VOLTAGE RANGE, SCALE SCALE V

or

mV,

SWITCH V

ormV

MULTIPLIER

PER

DIV.

500

0-500

0-5

100 10

150

0-150

0-

1.5 100 5

50

0-

50

0-5

10

1

15

0-

15

0-

1.5 10 0.5

5

0-

5

0-5

1 0.1

1.5

0-

1.5

0-

1.5 1

0.05

4.3.4

dB

(DECIBEL) MEASUREMENTS

The dB scale

is

calibrated with reference

to

OdB

=

0.775Vrms

(1mW)

into

600D.

The dB range at the different settings

of

the RANGE switch

is

given in

the

following table.

RANGE

SETTING dBm dBV

+50

+30

~+56

+30

~+54

+40

+20

~+46

+20"'

+44

+30 +10

~

+36

+10~+34

+20

o~+26 o~+24

+10

-10~+16

-10"'

+14

0

-20

~+

6

-20~+

4

-10

-30

~-

4

-3o~-

6

-20

-40

~

-14

-4o~

-16

-30

-so""

-24

-50"'-26

-40

-60

"'-34

-60~-36

-50

-70"'

-44

-70""

-46

-J::f\

-01\

l"'o.J

_r:A

_of\~_r:.L.

_,.,.

uv

.JU

*

The

dB

range

is

the

algebraic sum

of

the RANGE

marking and the scale reading.

......

9

······

4.3.5

Use

of

SIGNAL SENSITIVITY (S/N MEASUREMENTS)

A. This SIGNAL SENSITIVITY shall

be

used

with

its

knob

® usually set at

the

position

of

CAL.

B. By utilizing this

knob,

measurement

of

SN ratio, level measurement against standard

signal (e.g. measurement

of

crosstalk characteristics), etc. can

be

easily performed.

An

example

of

SN ratio measurement

by

means

of

this

instrument

is

now

describe<!

as

follow:

C. Example

of

SN ratio measurement

An

amplifier (A)

of

which

maximum

output

is 2V is

now

assumed

to

be measured

by

this

instrument

for

its SN ratio

at

the

maximum

output.

Arrange wiring

between

this

instrument

and

the

amplifier as

shown

in

the

drawing,

set

the

millivolt

meter

at

SV

range and set

the

butput

of

amplifier (A)

at

2V based

on

indicated value

on

the

meter.

(At

this

time,

gain

of

(A) is

set

at

maximum.)

Next,

rotate

the

knob

of

SIGNAL SENSITIVITY counterclockwise

to

its

extreme

end

{at this time the

meter

indicates 0.6V.) and set

the

range

at

l.SV

(OdB

range) one

step lower.

Next,

adust

the

indicator needle

of

dBV or dBm scale

to

OdB

by

means

of

SIGNAL

SENSITIVITY knob.

At

this

point,

change-over

the

switch shown in the drawing

toN

side.

Rotate

the

range change-over switch

@)

counterclockwise

to

cause

the

meter

needle

to

sway.

If

the

meter

indicates

-3dB

in the

-50dB

range

when

the scale

of

dBm range is set

at

OdB

and

the

switch is set

at

N side, its SN ratio'will

be

53dB

by

the following formula:

(0)-

(-50)-

(-3)

=53

CJ~@~

0 0 0 0

0 ()

ocooCaooQ

0

LA

V-191

LOAD

Fig. 4-2

4.4

Typical Applications

4.4.1

USE

OF

THE

ATTENUATORS

The

output

impedance

of

the

attenuator

system is designed

to

match

the

600il

load.

The

correct

attenuation,

or

sum

of

the marked settings, holds only

for

the

600il

condition.

When

other

load

impedances are used, there will be a mismatch in which the actual voltage

attenuation

depends on the load.

For

example, when working

into

an

open

circuit,

or

a high impedance,

the

output

voltage will

be

6dB

above the

600il

condition. Thus, this value must be

subtracted

from

the

marked

settings.

......

10

.....

.

L

In

other

words,

if

the

voltage is initially

set

at

1V, say

at

OdB,

into

600U,

then

at

open

circuit,

the voltage will

be

2V,

or

6dB

higher.

Under

this

condition,

the

attenuation

will be

-6dB

and

must

be

accounted

for.

The

table

below

shows

the

number

of

dB

for

voltage

to

be

subtracted

from

the

settings

at

different

load

impedances.

Example:

NUMBER

OF

dB

TO

BE

SUBTRACTED

0

1.9

3.7

5.0

5.5

5.9

6.0

Attenuator

setting

Load

impedance

Actual

attenuation

LOAD

IN OHMS

35dB

2000U

600

1000

2000

5000

30k

60k

00

(open)

35-

3.7 = 31.3 dB

If

in

doubt,

the

output

voltage

at

each

attenuation

step

can be

measured

with

the

voltmeter.

4.4.2.

INPUT/OUTPUT

CHARACTERISTIC

Generator

settings:

Frequency

at

400

or

1000Hz.

Attenuators

at

OdB

(pushbuttons

at

out

and

rotary

switch

at

0).

Connect

the

voltmeter

to

the

OUTPUT.

Adjust

the

OUTPUT

LEVEL

control

for

the

meter

reading

at,

say 1V

and

do

not

touch

the

control

during

the

measurements.

Remove

the

connection.

Set

the

pushbutton

for

60dB

attenuation.

Connections:

Generator

output

to

the

amplifier

input.

Voltmeter

input

across

the

load

at

the

amplifi~r

output,

see Fig. 4-3.

LAV-191

D @ AMPLIFIER

INPUT OUTPUT UNDER TEST LOAD

......

Q

""IN

OUTQ

,...

91--

Q

:::::::

'-J

v

rv

61

~

I

Fig.

4-3.

Amplifier

measurement

......

11

.....

.

Adjustments:

Note

the

voltmeter

reading

as

the

attenuation

is

lowered

(increase

in

the

input

voltage).

The

"overload"

point

will be

reached

when

any

increase in

the

input

voltage will

produce

no

further

increase

in

the

output.

Normally

the

"undistorted"

output

is

taken

at

some

point

on

the

linear

portion

of

the

plotted

input/output

curve.

The

output

power

at

this

point

is calculated from

the

relation -

(VOLTS)2

p

output

=

---------

watts.

LOAD

INn

4.4.3

FREQUENCY

RESPONSE

Using the same

connections

shown

in Fig. 4-3, a

frequency

run

is

made

on

the

amplifier.

The

method

most

commonly

used

-

constant

input

VS.

output

level (voltage) -will be

described.

The

input

to

the

amplifier

is set

at

a voltage well

below

the

overload

point.

The

generator

frequency

is

varied over

the

desired range

and

the

amplifier

output

voltage

is

plotted

against

the

frequency.

The

generator

output

is flat for

practical

purposes

and

generally

there will be

no

need

to

adjust

the

output

at

each

test

frequency.

When

plotting

the

response in dB,

it

will be

convenient

to

initially

set

the

generator

output

so

that

the

voltmeter

reading

is OdB

at

400

or

1000Hz. "rhen

by

varying

the

frequency

and

noting

the

dB

scale reading,

the

relative response VS.

frequency

can be

plotted

on

a semi-log

paper.

5.

MAINTENANCE

5.1

Power

voltage

Voltage

of

power

supplied

to

this

Audio

Tester

is

indicated

by

the

switch

fixing

plate

on

the

rear

panel.

To

set

desired

power

line voltage, insert

the

voltage switching

plug

with

guide

plate

into

its

socket

so

that

the

arrow

marked

on

the

plug

is

directed

to

one

of

power

line voltages

marked

on

the

socket

as

shown

in

the

following figure.

For

lOOV

For

220V

For

240V

240V:::t_~

~c

!__j§ffi

l 220V

_;

L.lOOV

J

For

117V

240V-,

,-117V

~L

• m

0.r.:;

+

~.···

l

nov

-J~~L

ioo~:;·.,

..

J

......

12

......

5.2 Fuse

Fuses

of

this

Tester

are

rated

as

shown

in

the

Table.

If

a fuse is

broken

off,

find

its cause.

Replace

the

fuse

after

safety

was

confirmed.

Power

voltage

Fuse

rating

100, 117V 0.5 A

220! 240V 0.3 A

......

13

······

"'

'

oc

> w

-<

,.,

-'

iJ)

w

,_

0

~

"

...... 14 ······

Leader LAV-191 User manual

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