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8/16/2019 Nagra III Instructions Manual
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M
ay s
INSTRUCTIONS
MANUAL
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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
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I
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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
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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
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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
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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
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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:
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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.
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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:
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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.
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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
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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
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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
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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.
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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
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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
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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.
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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.
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-
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
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§
OJ
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S
'1
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11
::
en
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::l
UJ
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tr
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en
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Motor Transistor
0
....
0
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UJ
0
I
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n>
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correctin\g
Filteros
Play
Back
correcting
FilterS
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CCIR
Ampex
R = Play
Back Level
C = Correction for loss
in
head
R =
Recording Level
>-3
PJ
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:Y
Modulometer & Sensitivity
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8/16/2019 Nagra III Instructions Manual
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BOTTOM
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
©
o
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MODULATION
METER &
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MICROPHONE PRE
-
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LINE AMPLIFIER
OUTPUT TRANSFORMER
AUTOMATIC
LEVEL
CONTROL
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K
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Recording -
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Back
n r ~ g i s t r e m e n t
- Lecture
PAGE 2
7, 5
/ s
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i
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N G R
III
FIN L QU LITY CONTROL PROTOCOLE
DES
ESSAIS
INSPECTION REPORT ET MESURES DE SORTIE
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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
*
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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
-
]
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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
8/16/2019 Nagra III Instructions Manual
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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)
~ ~
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__________________________________________________________
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