Leader LAV-191 User manual

MODEL

LAV

191

AUDIO.

TESTER

INSTRUCTION

MANUAL

LEADER

ELECTRONICS

CORP.

CONTENTS

SECTION PAGE

DESCRIPTION

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

CONTROLS

AND

CONNECTORS

3.1 AC Millivoltmeter

Section

3.2

Signal

Generator

Section

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

3.3

Rear

Connections

..........

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

OPERATION

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

4.1 Initial Checks . 5

4.2

Signal

Generator

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

4.3

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

4.4

Typical

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

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

·-

...

.....

1. DESCRIPTION

The

LAV-191 is a

combination

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

lMHz

and

the

output

is controllable

from

-120dB

ldB

steps

into

a 600!2 load.

The

millivoltmeter covers a voltage range from

150J1V

SOOVrms

in the 10Hz

lMHz

range.

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

and

RIGHT

-are

provided

for

stereo circuit measurements. A separate decibel scales,

OdB

0.775Vrms

and

0 dB =1 Vrms can

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

over 3Vrms.

Attenuator:

120dB in 1dB steps

600fl;

40dBX2,

20dB,

lOdB, 1dB X 10 accuracy

within±

1.5%.

Frequency

Characteristics:

Accuracy

range

Frequency

± O.SdB

0-60

500kHz

60-

120

150kHz

2dB

0-60

to 1 MHz

± 6dB

60-

120

500kHz

± 10dB

60-

120

1 MHz

Output:

Over 3 Vp-p

into

600!2

Rise Time

Sag

6oon

10%

200

ns.

50Hz

Input

Impedance:

Approx

Control

range: ± 1%/V

......

.....

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

pin plug

Lead, spade

tip

pin plug

Option,

separate order:

l.SmV

(O.lSmV min.)

500Vrms full scale in

ranges.

-80

+55dB

(OdB

0.775V)

-80

+54

dB=

1V)

ranges.

Within ±2%

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

full scale

RCA

jack

Less

than

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.

CONTROLS

AND

CONNECTORS

3.1.

Millivoltmeter Section, see Fig. 3-1.

Meter: With scales calibrated for Volts, rms,

and

decibels.

® Mechanical zero

adjuster

for

the

meter.

® SIGNAL SENSITIVITY: When

the

knob

set

the

position

CAL, this

unit

can

used

AC millivoltmeter calibrated

the

value

the

range used in

the

same

manner

that

ordinary

AC millivoltmeter. When the

knob

is set

other

than

CAL, this

unit

set

the

level

incoming signal

OdB

and

compare signal against

standard

signal

making

measurement

ratio,

etc.

RANGE switch: Selects the

input

voltage and

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

stereo

input.

@ INPUT

SELECTOR

switch: Selects

the

LEFT

RIGHT

signal

stereo

input.

Input

jack

for

RIGHT

signal

stereo

input

......

3.2

Signal

Generator

Section,

see Fig. 3-1.

ATTENUATION

switches:

For

attenuating

the

output

signal; range

llOdB.

Q3)

Attenuator

switch: Adjusts the

output

signal

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

output

signal

(connected

in parallel

with

jack

(]7

FREQ.

RANGE

switches: Five

pushbuttons

for

selecting

the

range

the

output

frequency.

Frequency

dial, Hz:

Calibrated

from

10Hz;

actual

output

frequency

depends

the

ra'hge setting.

~Q>

OUTPUT

LEVEL

control:

For

continous

adjustment

output.

~~·

Switch

for

output

waveform

selection,

~sine

square,

marked.

G?t

Pilot

lamp:

Indicates

when the AC

power

on.

Gi}

POWER

switch:

Push

the

power.

3.3

Rear

Connections,

see Fig. 3-2.

<24.

SYNC terminals:

For

connection

external

frequency

control

source;

black

terminal

for

ground.

(25.

Shorting-link:

Normally

connected

across

the

SYNC

terminals

when

the

synchronizing

input

signal

not

used.

(2(\

Number

plate.

(27

Amplifier

output

terminal

Approx.

1V rms

output

voltage will be available

from

this

terminal

when

meter

indication

fuii scaH.

By using

output

from

this

terminal,

monitering

the

waveform

under

test

oscilloscope

available.

!2_$

Puts

the

accessory cable

and

others.

Gi.9i

Fuseholder

for the AC line.

(i)Q;

inlet.

AC receptacle:

Outlet

for

direct

power

connection

auxiliary

equipment,

independent

power

switch

and

line

fuse;

indicated

current

rating

not

exceeded.

Note:

AC lOOV

250V

max.

Power

voltage selection

switch.

Cord

winder.

.....

......

Fig. 3-1

Front

panel

controls

and

connectors~

Fig.

3-2

Rear

panel

controls.

OPERATION

4.1 Initial Checks

Check

the

pointer

setting

the

meter.

not

zeroed

the

left

end

the

scale,

adjust

the

zero-set screw

the

panel

below

the

meter.

(See Fig. 3-1.)

4.2

Signal

Generator

4.2.1 PRECAUTIONS

The

output

should

not

connected

circuit

which

voltage

over

12Vrms,

present

prevent

damage

the

attenuator

system.

IfD

C voltage is

present,

connect

through

capacitor

eliminate

D C voltage.

······ 5 ······

Output

connection

leads

should

short

as possible.

Long

leads are liable

pick

noise

when

used

low

output

levels.

Using a

shielded

cable

the

output

will

affect

the

output

high frequencies

into

high

impedance

loads due

the

shunt

capacitance effect.

4.2.2

CONTROL

ADJUSTMENTS

4.2.3

Set

the POWER switch

ON. Allow

about

seconds

for

warm-up.

Frequency

setting:

The

output

frequency

set

with the

frequency

diai

and

the

FREQ.

RANGE

switches.

FREQ.

RANGE

SETTING

(Multiplier)

Connections

XlO

X100

X1K

X10K

lOOK

Ground

lead

the

black

OUTPUT

terminal.

OUTPUT

FREQUENCY

RANGE

10-

100Hz

100-

1000Hz (1kHz)

10kHz

10-

100kHz

100-

1000kHz

(1l\.1Hz)

"Hot"

lead

the red

OUTPUT

terminal,

plug

the

jack

(both

outputs

are in

parallel).

Output

leads

the

input

the test circuit.

Output

Level

Setting:

The

OUTPUT

LEVEL

control

normally

used

set

the

reference

output

level.

The

attenuators

-push

buttons

and

the

rotary

switch

-are

set

required.

The

signal

attenuation

the

sum

the

markings

the

attenuators.

The

marking

the

attenuator

referred

the

600Q

load.

Example:

Pushbuttons

and

Rotary

switch

Total

attenuation=

+ 6 =

36dB

Square

Wave

Output

Square

wave signals are useful in the rough

determination

response characteristics

amplifiers

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

the amplifier

output

for

different

responses.

······ 6 ......

Waveshape· Amplifier Response

Condition

RECTANGULAR t

n_ru

' SATISFACTORY

FLAT

DROOPING

LOW

PRIMARY INDUCTANCE

OUTPUT

TRANSFORMER:

INCORRECT VALUES

THE

DEFICIENT

LOW

FREQUENCIES COUPLING ELEMENTS

PEAKED HIGH LEAKAGE INDUCTANCE

(U\

IN OUTPUT

TRANSFORMER

HIGH DISTRIBUTED

DEFICIENT

HIGH FREQUENCIES CAPACITANCE IN CIRCUIT

RIPPLE MALADJUSTMENT IN

THE

llJl

NEGATIVE FEEDBACK

CIRCUIT; INCORRECT

RINGING AT HIGH FREQUENCY CONSTANTS; INSTABILITY

For

amplifier

with

good

characteristics, the response will be flat

about

the

11th

harmonic

the

input

fundamental.

example.

a 1kHz square wave

reproduced

without

distortion,

the

amplifier response is flat

about

11kHz.

NOTES: 1.

Output

voltage settings are initially

made

with

the

OUTPUT

LEVEL

adjustments

and

the

waveform switch set

the

sine

wave

position.

The

indicated

value

the

scope will

equal

the

peak-to-peak

output

voltages.

The

waveform

selector

switch

then

set

the

square wave

position.

Disregard

the

voltmeter

reading.

doubt,

check

the p-p

output

voltage

with

calibrated

scope.

advisable

check

the

input

waveform

scope

before

application.

Connection

from

the

SYNC

output

terminal

the

scope

sync

input

will

make

adjustments

easier

when

displaying waveforms.

The

low

frequency

response will

start

fall

off

about

1/11

the

fundamental

when

there

is a sag,

droop,

the

displayed waveform.

4.2.4

Use

SYNC

Connections

General

The

sync

connections,

the rear

panel,

can be used in several

applications

as described

below.

The

"input"

"output"

impedance

approximately

10k.Q.

Output

Frequency

Control

The

oscillator

frequency

can

synchronized

with

accurate

source

over a range

±1%

per

rms

volt

input,

see Fig. 4-1.

For

example,

when

the

oscillator

set

some

point

between

990

and

1010Hz,

and

......

.....

signal

exactly

1000Hz

applied, the oscillator will

automatically

lock

1000Hz.

Thus,

high

accuracy

can be achieved

with

the

use

a precision

frequency

standard.

another

application,

distorted

waveform

can

"purified",

filtered,

passing it

through

the

oscillator.

1\/\../

~OUTPL"fj

EXTERNAL

JSYNCJ

SOURCE

"/\fV

LAV-191

Fig. 4-1 Use

the

SYNC terminals.

C. SYNC

Output

Application

The

sync

output

voltage,

approximately

2.5Vrms,

should be

sufficient

synchronize

trigger

the

sweep

scope

operate

a frequency

counter.

This voltage is

not

affected

the

setting

the

OUTPUT

LEVEL

control.

4.3

Millivoltmeter

4.3.1.

PRECAUTIONS

4.3.2

Maximum

input

voltages:

prevent

damage

the

input

circuit,

application

excessive

voltages

must

avoided.

peak

600V

Low

voltage

measurements:

When

measuring

voltages in

the

millivolt ranges,

the

RANGE

switch

should

set

a high range

and

lowered

required.

the

input

leads

are

the

open,

"free"

condition,

the

meter

pointer

may

off

scale;

always

set

the

RANGE

switch

a high range.

Due

the

high

input

impedance,

stray

voltage

picked

cause

this

effect.

The

RANGE

switch

should

be set

where

the

readings can be

taken

above

1/3

full scale

length

(except

the

lowest

range).

This

will result in higher

accuracy

the

readout.

PREPARATION

Set

the

RANGE

switch

SOOV

and

turn

the

POWER

switch.

2. When the

power

rurned

(or

off),

the

meter

pointer

may

fluctuate;

this

normal

condition.

The

miiiivoltmeter

ready

for

use

soon

the

pointer

comes

rest.

Connect

the

input

leads

the

terminals,

black

for

the

low

potential

and

the

red

for

the

"high"

side.

When

stereo

outputs

are

under

measurement,

connect

the

signal

inputs

the

LEFT

and

RIGHT

jack

respectively;

set

the

INPUT

SELECTOR

switch

required.

······

.....

4.3.3 VOLTAGE MEASUREMENTS

1. Connect the

input

lead tips to the test

point

the

output

the test circuit.

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

1/3

full scale. This

will result in higher accuracy

the readout.

3. The voltage range

the different settings

the RANGE switch

given in the following

table.

RANGE VOLTAGE RANGE, SCALE SCALE V

mV,

SWITCH V

ormV

MULTIPLIER

PER

DIV.

500

0-500

0-5

100 10

150

0-150

1.5 100 5

0-5

1.5 10 0.5

0-5

1 0.1

1.5

1.5 1

0.05

4.3.4

(DECIBEL) MEASUREMENTS

The dB scale

calibrated with reference

OdB

0.775Vrms

(1mW)

into

600D.

The dB range at the different settings

the RANGE switch

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

-20

-20~+

-10

-30

-3o~-

-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.

_,.,.

.JU

The

range

the

algebraic sum

the RANGE

marking and the scale reading.

......

······

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