Nagra III Instructions Manual

8/16/2019 Nagra III Instructions Manual

1/32

M

ay s

INSTRUCTIONS

MANUAL


2/32

Playb8ck Head

R_ r d l h a d

Accelerator Function

19

21

Neopilot

Head

for

Motion

Pic·

tu

Product.

20

24

1

Feed Spool

Speed

and

Shoulder

Modulation

Tape

equalization

Select

. Switch

Strap Button

Level

Meter

22

3

Bra

Head

Microphone

Tension

Battery

Microphone Input

i lot Signal

lutter

Level

Control

ndicator

ilters

8

9

Tak

lnchW

17

Une Input and

Playback Volume

Control

1

••

Reference Mon

Input·

Pulley

Indicator

Button Selector Switch

Signal Button Out


3/32

I


4/32

NAGRA I I I

T A P E

RECORDER

INSTR UCTIONS FOR USE

1 PRECAUTIONS TO BE TAKEN

When out of

use,

turn

the tape

t ransport

control to

its

mid posit ion. n the

"ON"

position,

when

not

running,

there

is danger of

producing a

flat on

the capstan rol ler The working surfaces

of

the fast rewind clutch may

also suffer.

II


5/32

Page 2

curve

is always excellent and varies l i t t le

from

tape to

tape.

At this

speed

the

tape

is

l i t t le affected by repeated play - backs. Another advantage

is

that

editing is

easy, and that a suitable machine operating at this speed can usua

be

found in

studios for play-

back of recordings.

19,05 cm/sec . 7. 5"/sec . CCIR Equalization Standard

This is

the

normal

speed

for

the

general

uses of the Nagra in

studios work

the CCIR standards.

Where this

is

not necessary, the following position wil

be

preferred:

19,05 cm/sec .

7.5"/sec.

Ampex Equalization Standard

This

is

a bet te r

standard, as

the

modulation noise,

medium range distortion

tape

backgr'ound

noise

are

reduced

considerably.

9,525

cm/sec . 3 .75"/sec .

This

speed is for use

where

high quality is not required and tape economy is

important .

One hour recording

t ime

can be obtained with

the use

of 5

reels

using extra thin tape or two hour's with 7" reels .

2) Tension

Pulley

This

pulley

is

movable

and

operates

a

brake

on

the spool,

ensur ing

constant

tape tension.

3) Microphone Input


6/32

Page 3

employing

this

speed, headphones

should

be

used

for monitoring. Then

when

t

battery voltage falls to a level unsatisfactory for recording

an

alarm signal

will be

heard

in

the phones.

t

is

well

to

remember ..that

bat ter ies

used

uninterruptedly for, say,

an

hour, will recupera te

when res ted for, say,

10

hours. Therefore exhausted bat ter ies may appear

acceptable

dur ing a

quick

tes t before recording, but

then

collapse

after a

few minutes

use.

To

recapitulate:

f

one

is

recording at 15 / sec. always use

monitoring

headphones

and

rea

the bat tery

mete r

pessimistically.

If

one

is recording

at

71

/2

or 3 3 /4

/ s ec

. for fairly shor t periods,

say

15 minutes, a battery test before s tar t ing should be sufficient. On the

other hand, if

the

recording s e ssion is of long duration, the bat ter ies

should be checked when changing reels

7)

Pilot

Signal Indicator

This is

an indicator on

which a white cross will appear

when

the Nagra is

receiving the pilot signal (N

eo

pilot Nagras only).

8) Accelera tor Button

By

press ing this

button

the motor

speed

is increased to i ts maximum. This ca


7/32

Page 4

The

automatic

record

position

is

useable

for

speech

but

not

for music.

The

automatic facil i ty only affects the

microphone

channel and not the line

input.

PLAYBACK

BATT. METER

to

the

left =

Play-back

on the internal

loudspeaker . In this position

the

meter indicates

the bat te ry

voltage. The

play-back level is varied by

the

"l ine

input

and playback"

volume

control .

The

headphones

are

fed

directly

from

the play-back amplifier

at

an

uncontrolled

level.

The quality through the loudspeaker

or

at the

l ine

outpu

is

not high. On

the

other hand

the

monitoring output for headphones is alwa

fed with a high quality signal.

HI-FI

PLAYBACK

= Normal high

quality

play-back.

The

loudspeaker is out of

circuit

and

the

signal output is fed at low level fo

headphones at the

monitoring

output

and

at high

level to the

l ine

output soc

The signal

fed

into the

l ine

i s measured by

the

meter . This output consis ts

not only

of the s ignal play-back from the tape

and

adjusted by the

control

"line input

and

play-back" but also a signal

from

the

microphone

can be

ad

for a commentary. The

level

of this

signal

is control led by the mike

input

potentiometer . When this facility is not required the mike input potentiom

must

be

turned

fully

anticlockwise

when

replaying a normally recorded tap

To play

back a normally recorded tape, the "l ine input and play- backll con

should

be turned to the

indication db. This will produce

a normal signal

the line. f i t

is

necessary

to

vary this

control

to have a normal signal to t


8/32

Page 5

The recordingampl i f ier when

on IITestingl1

The play-back

amplif ier

on

"Record" "Automatic

Record"

and

"Play-back

and Batt. Meter

".

The line amplif ier on Hi-Fi Play-back"

The normal output

level

is approximately 250 mY. One can use this

output

to

connectthe Nagra

to

an external power amplif ier .

A

1

a r m Signa

1 .

This s ignal

is in jected

between the lower

socket of

the

monitoring

output

and earth, when

the motor speed

s tabi l i ser

reaches the bot to

i ts r ang e , t ha t

i s , dur ing fas t

rewind

and in case of

exhaustion ofbat ter ies or

accidental brakingof

the

motor . I f one uses this

output for

connection to

a pow

amplif ier , the a la rm signal can

be

qui te annoying. In order

to

avoid this ,

one

connects

the

external ampl i f ier between the ear th on the l ine input on the

right

of

the apparatus , and the

upper socket

of the monitor ingoutput.

14) a. Line

Input

This input

is at high impedance and

one can connect i t

for

instance,

to

a

r

rece ive r

to record

a

t ransmiss ion . The

input

impedance is 100.000

ohms

a

the

normal

level 0,

5

volt .

b, Accessory Socket

The corresponding plug is a TuchelT. 3400. The connections are shown on

the

surrounding

label

as follows:


9/32

Page 6

Do not use this position for high quality feed to

another unit.

During

Hi-

Fi Play- back these sockets

car ry

the

normal l ine output signal.

15) Tension Pulley

This

pulley

is

movable and controls the take-up spool clutch. The normal

tape

tensions

are given in the speGification

of the

ins t rument .

16) Tape

Transpor t

Control

Turning

this control

which is marked on one

side

IIEn_Onlt clockwise, bring

the pinch

wheel

into contact with

the

capstan. Turning i t to the left disengag

it, and star ts rapid tape

rewinding.

This

occurs

when

the

selector switch

No.9) is turned to ei ther

play-back position, rewinding does

not

take

plac

when

the switch is

on Ilrecordlt, to diminish the possibi l i ty

of mistakes .

f re - spooling is required

when

the switch

is

at ItTestinglt

this

can be obtain

by depressing the accelerator

button

No.8) . When the equipment

is

not in

use,

this control must

be left in the

mid

position.

See page

1).

17) Pinch

Wheel

This rubber

rol ler

presses

the

tape against the capstan to drive the tape.


10/32

Page 7

is

not perfect . Variat ions of

0,5% are

quite common. The speeds

are

set

at

the

factory by

comparison with

a standard genera tor

driven

from a Quartz

crys ta l

clock.

Therefore

the

speed should

not be readjusted

if

the mains

frequency

is

not

known

to

be

accurate .

24) Feed Spool

The

tape

to

be

recorded

or reproduced

is placed

on this spool, with the

coating

(matte surface)

wound inwards.

25) Take Up

Spool

The

Battery

Box

compar tment is accessible

from

the

bottom

of

the

instrument.

A

normal set of bat ter ies consis ts of

12

1.5

volt

torch cells . When changing

cells, all should be changed together,

as

one

infer ior cell will

substrac t

from

the performanc e of the

good ones.

t is

very

important

not

to

make

any

mistake

over

the

polar i ty of

the bat te r ies ,

all

should

be

turned in

the same

direct ion as indicated by

the

diagram on

the

bottom of

the

box

.

t is

more convenient

to

put the end cells in

place

f irst ,

and

then

the cent re

cells . The

minimum voltage

below

which

a cell

cannot be

used

is 0.9

volt.

Usable battery types are:


11/32

Page

8

T H E S P E E D S T A B I L I S E R

The Nagra

III uses a new

technique

for

controlling

the speed of the motor

an

following notes

will

be helpful to

those who

need to service the machine.

1

Description

The block diagram herewith i l lustrates

the

principle

of the se rvo- c i rcu i t

which is used.

The motor

car r ies on

i ts spindle

a phonic wheel

as

well

as

the capstan, which

passes

in front

of

a

magnetic

head -

the

tachometer

hea

This

head

is

magnetised

and

the

rotation

of

the

phonic

wheel induces

an

alternating current, the frequency

of

which depends upon the speed of rotati

of

the

motor . This signal passes through the

tachometer

amplifier where

t

shaped

into

a square wave

of constant amplitude of

about 6

volts peak to

pea

This

output

is taken to

a

frequency

discr iminator .

This

opera tes the

servo

a

mplif ier which controls

the

motor speed. As the voltage at

the

servo

amplif ier

becomes increasingly

negative,

so

the motor

current

will increas

The

circuit

described

is not se lf -s ta r t ing. Therefore the

Nagra

includes a

star ter

which

applies

to

the

servo amplifier a large

negative voltage

when

one switches to

"play-back"

from

"stop" or

from "test" to

"record",

and al

when the connection between the socket"

stop"

on 14b and

ear th

is opened.

This

applied

voltage

causes

the

motor

to s tar t rapidly.


12/32

Page

9

b) Themotor

s tar ts

occasional ly

but

not always,

or

on turningby hand.

The

commutator may

be

di rty , c lean

it but do

not lubr icate

it.

c)

The

motor

s ta r t s

af ter press ing

accelerator

button and

comes

up

to

speed, but does not star t

on

i ts own. Fault in

s ta r te r .

Measure

the

voltage across the s tar t ing

condenser .

d) The

motor

s tar ts

well, passes

the normal sp

e

edand

then loses speed

and s tops . Thi s is

a typical

case where the servo ampl i f ier and the

s ta r te r are

funct ioning, but

the

discr iminator or the tachometer head

is

not

working.

Start themotor with the

accelerator button

with

a

drivingvoltage of

10

to

15

volts . The tachometer head

should develop

more

than

8

mill ivol ts .

f

the

head

i s

in

good

condition

inject

a

signal

of

3

mill ivol ts from

a

low

frequency

sourcecorrespondingto

the

speed

ofworking.

This

will

permit

t rac ingthe

signal

through the tachometer

amplif ier .

n case

of

t rouble of this sor t it

is good

to

t ry

s tra ight away whether

operat ion

is sat is factoryon other speeds.

t

is at

3

3/4" per

se

cond

that

one has most

difficulty

because

of

a weak tachometer

signal.

f

operat ion i s sa t i s factory at

3

3/4" , but

no t

at any other

speed,

examin

e carefully

the

wires

joining the speed switch

to the

speed

regu

inductances

etc.

e) Themotor s ta r t s but does not r each normal

speed . Disconnect

the


13/32

Page

10

Cause:

The servo- ampl i f ier

passes current to the motor even

when the

discr iminator does

not call for i t This

is

generally caused by

the rmal

current

in

the

t rans is tors

This

t rouble

will

ar i se

on every

equipment

if

the ambient

temperature is

sufficiently

high.

It

is

abnormal

below

40

0

centi

grade.

Two

possibil i t ies

must be considered:

Cl) The

motor has an abnormally high

consumption

which heats the servo

amplif ier . (See

"Faults

in

Motors").

b)

One or more t ransis tors of the servo amplif ier

have

deteriorated

(by over- heating,

for

exampl'e) and

thei r

standing

current

has

becom e

too high. Change

these

components , being careful not

to

over-heat

when

soldering.

This

fault will

disappear

when one

short circui ts

to

earth

the

bases of

the

suspected

t rans is tors

Each t rans is tor base

is

connected to

by

a res is tance .

The disconnection of such

res is tances is

sufficient to

increase

the fault. A

res is tance of

this

type is

also

contained in

the

discr iminator .

3)

Wow and

Flut ter

a)

Wow

at

the

frequency

of

rotation

of

the capstan.

Poss ible

source:

Mechanical or electrical

braking on the motor (see "faults in

motors") .

The

tachometer wheel is eccentr ic glVIng a signal

of

which

the


14/32

Page

MOTOR

The

motor of the Nagra is of

the permanent magnet electrodynamic

type

an

resembles

a d

Arsonval

galvanometer

with

centra l

magnet.

I t

may

be the

c

of

a

number

of difficulties

and

the following notes

are

intended

to

ass i s t

in

such cases:

I f

the r ecorder

refuses to

s tar t

occasionally, even when

one presse

accelera tor button, but in general s ta r t s

when

one turns it l ightly by

hand, the sur face of the

com

mutator

should be

examined

-

see

paragraph 5 .

I f the

r eco rde r

runs i r regular ly , see paragraph 5

and

subsequently

paragraph 6.

I f the

r ecorder

produces

a f lutter ,

check the smoothness of rotation

the motor . There

must

be nei ther rough spots nor perceptible play.

I f the motor shows speed

up

following excessive heating of the powe

t rans is tor

of the servo amplif ier , see first

paragraph 6, then 4

and

and finally

1 .

1.

Dismantling

and

de-magnetisat ion

The magnet is fixed in the

assembly

by a left hand

threaded

set screw. The

winding

surrounds

it.

To

remove

the rotor , af ter first having

unscrewed th


15/32

Page

12

2. Open Circuit of

Half

the Rotor

Below there

is

a schematic

of

the motor. t can be seen that the cur ren t passes

through

two

paths

in

paral le l .

Interruption

of one of

the paths

does

not

prevent

the motor

from functioning

but doubles

i ts res is tance

This

i s

indicated by

a

less

vigorous rewind

and part ly by

an

increase of the l imit ing

voltage

required for operation at 15 i p. s. One localize this fault

by

measur ing of the

rotor.

The

normal

value

is 21 ohm s

but

a rotor

half

open ci rcui ted

will

read

42 ohms.


16/32

Page 13

all t races of abrasive

powder

.

f

lhe fault cuntinues, the correspondingwire

of the

coi l

should be disconnected.

t

is then poss ible to ascer ta in if the faul

is in the

winding or

in the commuta to r .

f

the winding has shor t circui ted , a

new

ro to r

should be

ordered

f rom us.

On

the

other

hand,

it

is

often

possible

to repa i r the commuta to r by pass ing a

very

la rge cu r r en t through the shor t

circuit

to break

it down. The discharge of

a

100 microfarad

condenser char

to 300

vo l ts

will general ly be

sufficient.

4. Mechanical Fnc t ion

Mechanical

fr ict ion

of

the

ro tor inc reases both

th wow

and

the

power taken.

can dist inguish between elecl r ic braking,

such as is shown

in the

preceding

paragraph, because mechanical

fr ict ion

is constant , whereas the

e l e ~ t r i c

br

increases

quickly when

the

motor

speeds

up. Typical valuE's of the

consumpt

of

the motor

on

no load,

that

is without

tape

and with

the pinch wheel

not in

contact

with

the

caps tan

(but

not on

rapid

r e ~ w i n d

are given

below:

Speed

Normal no

load current

No load

current wi

two

segm ents

shor

circui ted

15 i . p . s . 26 ma

62

ma


17/32

Page 14

A misplacement cannot

happen except

by a

previous

care less

service work or b

unscrewing

or

dismantl ing of the

magnet. The

left

end thread

on the magnet

ensures that this cannot unscrew it

self

. On the other hand, it can happen

when

the

adjustment mentioned

above

has

been

made

and

the magnet insufficiently

well

secured. In practice, it

should

be

tightened

up securely

before re-adjustm

f

the difference is small , replace the brushes where they were because the

difference is probably an er ror in measurement .

Our factory-

ad

justment made

by

the

aid of a

special

machine is much

more

accurate

than

that made by

adjusting to minimum cur r ent.

PRECA

UTIONS

AGAINST

INTERNAL

NOISE

As

with

all tape

recorders ,

the Nagra III has some residual noise.

We

must

distinguish:

1 NOLse in

the

microphone preamplif i

er

2

Noise in the record amplif ier

(output amplifier)

3

Noise in recording

on the

magnetic

t rack

4

Noise

in

the

play

-

back

amplif ier

5 Noise

in

the switching

dlOdes of

the speed

standard

se lec tor

6

Noise in the

play-back

am

plif ier

7 For

the

second t ime noise in the

output

ampl i f ier


18/32

Page

15

residuals during recording

o r

play-back wlthout signal

o n til e other

two spee

The l eve l in

general will be

b

ettel ' thall

- 80

db.

Various forms

of

break-through

are

po ssible:

On play-back

induction

between the

motor

and the

replay

head, or

equa

induction

b e

tween the tachometer head and

the

wiring to

the

replay

hea

A

re-rout ing of these

wires

may reduce

the

t rouble. One can

diagnose

t rouble by

short circ1Jiting

the

wires

to the

head

on the

H F. f i l ter on

chassis. A s imi lar fault can be produced b y

damage to

the discr iminat

f i l te r or servo amplifier . t i s normal that there

should be

some break

through when the appara tus is working with

the

chass is

opened.

On record,

the

residual signal may

come through induction

into

the

microphone preampl i f ier

and

cable or by coupling to the input connecti

of the

power

amplif ier and cable

o r

finally, through the

power

leads

or

ear th

leads. These

residuals

are adjusted to be negligible before de l iv

of the recorder .

Should

they

a

ppear, it is likely

that

a

decoupling has

deter iorated, or a change in earthing, o r a

misplacem

ent of the

connections .

d)

Electrosta t ic

Discharge

This cons is ts of

short

sharp

crackl ings when the motor

is in op era tion, at

i r r egular

intervals . They

are

caus

e d

by an elect ros ta t ic char

ge on

the belt.


19/32

Page

6

Moto r spindle. T he motor

spindle

turns in a ball race indise

the

motor and

on a bear ing holder

und

erneath on

the end plate.

t can happen that a

film

of lubricat ing oil

and

on the bear ing holder

a l

ayer of aluminium oxide

which

protects

the

bearing

holder

and

the

ch ss is

from

corros ion

becomes

sufficiently

insulat ing

so

that

the spindle

is

no longer effectively earthed.

In this case

the

paras i t ic in

the

motor find

another

route to earth. The

p r s i t ics so passin g may in

t ruth

be

extremely smal l but

it

is

possible

that

this may

happen.

This trouble

can

be diagnosed when

it

is found

that

the noise

disappears

then the spindle is earthed

by

touching the capstan

with

a

wire to earth.

In

general it is

sufficient

to el iminate these

parasi t ics by

carefully

earthing the end

bearing

holder

and

removing

the

oxide on the

seat of the screw

holding the

bear ing holder but in

a

very

bad

case a

little

metal l ic

brush

on the back of the capstan is

obviously the most

certain

method.


20/32

-

L-

INSIDE VIEW

OF

BOX

/

I'

6'

I 5 ~

0

e ® c o r d ~ ~

rr=

Speed

s tabil izer

Coil

•

-,

t-.t:::j tJ

0

0 0

Speeds

Condensers

Speed

Commuta_

tor

C Frequency response

curve

correction

0

....

'C

....

>-3

'1

§

OJ

...

0

S

'1

0

....

'C

....

"2.

....

...

...

>-s

>-3

11

::

en

....

0

::l

UJ

....

PJ

tr

....

t::

en

'1

LJLJ

Motor Transistor

0

....

0

'1

UJ

0

I

"2.

....

...

...

n>

'1

correctin\g

Filteros

Play

Back

correcting

FilterS

0

"

, ~ I 911

' ,

' , ' ,

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Ampex

R = Play

Back Level

C = Correction for loss

in

head

R =

Recording Level

>-3

PJ

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Modulometer & Sensitivity

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21/32

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VIEW

OF

DECK

PLATE

Oscillator

t rans former

Premagnetization

P lay

back Bias

Frequency

i l t er

\

Take-up tensiometer

Take-up clutch

I

\

\

\

~ o t o r

Collector

Tachyrnetr ical Wheel

~

o

and

erase

oscil lator

o

Acceleration

Button

©

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22/32


23/32

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26/32

i


27/32

N G R

III

FIN L QU LITY CONTROL PROTOCOLE

DES

ESSAIS

INSPECTION REPORT ET MESURES DE SORTIE


28/32

See

at tached

explanations

Voir

expl ica t ions

ci-apres

*

*

DESCRIPTION

OF

TESTS

DESCRIPTION

DES CONTROLES

1)

Visual

and mechanical

1)

Contrale

visuel

e t

inspect ion

mecanique

2)

Pinch

wheel

pressure

2)

Pression de

contact

du

contre-cabestan

Feed tape

tension

of

the

Tension

de debit

du

tape

ruban

Take

up

tension

Tension

d'embobinage

~

3)

Tachometric

head

volt ge

3)

Tension

tachymetrique

at

3 ,75"/s

a 9,5

cm/s

4)CURRENT

CONSlft.IPT ION

* 4)

CONSOMMATION

DE

COURANT *"

TEST

TEST

PLAYBACK at 7,5"/5

PLAYBACK

a

19

cm/s

)

RECORD

a t

7,5"/5

(Beginning of

a 5"

reel)

RECORD

a 19

cm/s

(Debut de

bobine 5" )

5)

No

speed overshoot

of 5)

Pas

d'emballement

au

s t a r t e r

c i rcu i t

*

dema

rrage

*

6) SPEED

CONTROL

6) CONTROLE

DE

VITESSE

Absolute

speed

*

Vitesse

absolue

*


29/32

12)

OUTPUT AMPLIFIER

12) AMPLIFICATEUR

DE

SORTIE

Line input sens i t iv i ty

Sensib i l i te d 'ent ree

Accessory socket

input

sens i t iv i ty

Distorsion:

H

(at 0 db - 1000 cIs)

H3

Signal to

Noise ra t io

Line

output

level

Modulometer reading

13)

PLAYBACK CHAIN

Signal

to

Noise

ra t io

Tachometric signal

reject ion

14) Reproduce signal level at

o

db -

l5 / s

Monitoring PLAYBACK

Line

Hi-Fi

PLAYBACK

l igne

Sensib i l i te

d 'ent ree

accessoires

Distors ion

H

a 0 db -

1000

Hz) H3

Rapport

s ignal /bru i t

Niveau de

sor t ie

l igne

o

~

0

o

-

4

Indica t ion du modulomet re +

13) CHAINE DE

LECTURE

Rapport

s igna l /b ru i t

15

19 cm-CCIR

7,5

NAB

Residu

tachymetrique

14)

Niveau

de

l ecture

a

o

db -

38

cm/s

Monitoring

PLAYBACK

Ligne Hi-Fi

PLAYBACK

-

]


30/32

TECHNICAL COMMENTS ON THE TESTS

4) Current consumption

The

supply

voltage sha l l

be

18

v.

5) No speed overshoot

of s t a r t e r

ci rcui t

This

t e s t

shal l be carr ied out with a supply

voltage

of

24

v.

6)

Speed control

Average

speed s t ab i l i ty (or

absolute

speed ) .

N

ote:

This

measurement

can

be car r i

e d out

with

the aid of a standard t e s t tape and a

frequency

meter, or with the aid of the stroboscopes

which

are

found

on top of

the

f lu t t e r f te

rs .

A displacement

of one point in 10 seconds,

corresponds to a

speed

error of 0.1 %

I t is

well

to

remember tha t one

quar ter

of a

non-tempered

tone, corresponds to a

frequency

varia t ion of 3% Therefore, an error of 0.3 %

in

absolute

speed, corresponds to a pitch

variation

of 1/40 of

a

tone.

NOTICE: I t is imperative

to

use a crystal con

t ro l led

l igh source when checking

the s t robos

copes. The frequency

error

of

the mains,are in

general la rger than the

speed

error o f the

NAGRA. The reason for which

precis ion

of

th is

order

is

important, is the appl icat ion

of

the

NAGRA in telemetry.

In our t e s t

l aboratory, the

3 speeds of

15",

7

,5"

and

3,75"

are ajus ted by means of a

speed

standard

tes t

tape

on

which

a

s ignal of

1000

c is

!O, l % has been recorded, and our W M

speed

me-

/ .

COMMENTAIRES TECH N

IQUES

SUR LES

MES

4) Consommation

de courant

La t ens ion d 'a l imentat ion est de

5)

Pas

d'emballement

au

demarrage

On

procede

a cet essa i avec une

6)

Controle de vi tesse

Stabi l i te de la vi tesse moyenne

absolue ) . N

ote: Cette

mesure peu

avec

un ruban eta lon et un f

requ

discr iminateur , so i t a l a ide de

places

sur les guides

ro ta t i f s .

d'un

point

en 10

secondes

corresp

de vitesse de 0,1 %

Rappelons qu'un quart de

ton tem

a

une

varia t ion

de

frequence

de

de vi tesse absolue de

0, 3

% equiv

1/40 de

ton.

ATT ENTION: Pour des mesures prec

ut i l i se r une source de lumiere

p

par quar tz ;

les ecar ts de f reque

etant souvent superieurs a ceux

recherche d'une s i

grande precis

domaine

est

jus t i f iee

par l es ap

NAGRA en te lemesure.

Dans notre labora toire de

cont r6

ses de 38 ,1 cm,

19,05 e t

9,5 cm/

avec

une

bande

de

vi tesse-e ta lon

quence de 1000 :0 ,1 % a insi que


31/32

ter having a cal ibrated

discr iminator .

Drop of

speed

due to braking of

the capstan

This

t e s t

is carr ied

out by braking of the caps

tan

unt i l

the

motor

current

consumption

reaches

twice

the normal one. The

purpose

of this test

is to

chek

the

safe ty margin of

the se rvo-ampli

f ier .

7) Wow and Flutter

This

t e s t is carr ied out in PLAYBACK by

means of

a

standard

t e s t tape. The reading is taken on

our W M

instrument,

which

gives

the peak value

of

the weighted

wow and

f lu t ter

accord ing to the

DIN 4550

7

specif icat ions .

8)

Battery voltage l imi t

Recording and

playing

back simultaneously while

lower ing the power supply voltage. The l imi t

voltage is the

supply vOltage at which

the

alarme signal appears.

The

recorder should

function correct ly down to that voltage.

Test

conditions:

(worst case)

Speed: l5" /s

End

of

a 7" reel

Limit vOltage

of

Modulometre

I t is

that

supply vOltage which corresponds to

t h e r ed mark

on

the Modulometer. The reading

is

made in PLAYBACK.

This voltage is lower

than

12,5

V. I ts value is generally higher than the

l a t te r by 0,5 V. (worst case)

de mesure

W M

equipe d'un discr im

lonne.

Baisse

de

vitesse par f re inage

d

On

procede a cet te mesure

en f r e

tan

jusqu'a

ce que

la

consommatio

atteigne

le double de la valeur

a

pour

but de ver i f i e r la reserve

de

l 'asservissememt.

7) Pleurage e t sc int i l lement

Cette

mesure

es t f a i t e en PLAYBAC

d'une bande-etalon.

La valeur est mesuree

sur no tre

qui donne la valeur

de pointe

du

passage dans un

f i l t r e

de

ponder

la norme DIN 45507.

8)

Tension-limite

des

piles

Enregis t rer

et

l i r e

simultanemen

sant la tension

d 'a l imentat ion.

mite

est la

tension pour

l aque ll e

d'alarme

apparait.

L 'appa re i l do

correctement jusqu 'a cet te tensio

Conditions de mesure: (cas

le

plu

Vitesse:

38

cm/s

Fin

de

bobine 7"

Tension l imite du

Modulometre

C'est la t ens ion d 'a l imentat ion c

la marque

rouge au Modulometre. L

fa i t en

PLAYBACK.

Cette tension d

r ieure

a 12,5

V.

Sa

valeur est

ge

0,5 V

superieure

a la

tension

l im

dessus. (cas

le

plus defavorable)

~ ~


32/32

__________________________________________________________

9)

Reproduce

signal

level

The 0 db (= 4,4 V Line Output) correspond to a

r .m.s . value of the recorded f lux of 200 mil l i -

Maxwells

on

the tape. This

t e s t

is car r ied

by

means a level

t e s t

tape.

16) Erasure

e

guarantee an erasure of at least 75

db

for

a signal recorded on a

Scotch

tape

type

102 at

the l evel of 200 mMx

Measurement

An

800 cis

signal is recorded at 0 db, with a

tape speed of l5 / s ,

and then

erased using the

internal

f ac i l i t i es . The

r a t io

between

the

s i-

gnal, as

recorded

and the non-erased residue

gives

the

eff ic iency of the erasure.

Signal

to Noise rat io

The

measurement is performed

with

the

"A" wei

ghting

network

in

accordance

to I .E.C. s tandards

for Precision Sound

Level

Meters (Helsinki 1961)

The "A"

weighting network of the I .E.C. is

prac

t i ca l ly the

same

as the ASA

A

american

spec i f i -

cat ions .

In

our t e s t laboratory the reading

is

made

on

a

Bruel & Kjaer Audio Frequency Spectrometer

type

2112.

-

9)

Niveau de

lecture

Le niveau

0 db

(=

4,4 V

a l a sor

respond

la

valeur eff icace

d'un

milliMaxwells sur la

bande.

Cette

operee au moyen d'une

bande

etalo

16) Effacement

Nous

garantissons un

effacement

mieux d'un signal enregis t re

102 au niveau

de

200 mMx

Procede

de

mesure

On enregis t re au niveau 0 db

38

cm/s

puis

on efface avec

sur

un

l ' a

rapport entre le s ignal non effac

f i cac i te de l ' ef facement .

Rapport Signal /Brui t

La mesure es t f a i t e

avec le f i l t r

"A" prevu

par l es normes internat

C.E.I.

sur l es

mesures

acoustiqu

Le f i l t r e

"A" prevu

par

les

norm

pratiquement le meme que Ie

f i l t r

normes americaines.

Dans

notre

labora toire de control

real isee

au moyen de I 'analyseur

type

2112.

J

Nagra III Instructions Manual

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Transcript of Nagra III Instructions Manual