Audio Technology NAGRA-D User manual

SERVICE MANUAL
NAGRA-D/DII
20 01002 253
• ~ ~~ AUDIO
TECHNOLOGY
SWITZERLAND C

CHAPTER I
CHAPTER II
CHAPTER III
CHAPTER IV
CHAPTER V
CHAPTER VI
CHAPTER VII
CHAPTER VIII
INTRODUCTION
MECHANICAL SECTION
CALIBRATION
TIME CODE
TECHNICAL INFORMATIONS
ACCESSORIES
SCHEMATICS

CHAPTER I
1.0 INTRODUCTION
1.0.1 Page numbering
1.1 IMPORTANT NOTES
1. 1.1 . Electrostatic discharge
1. 1.2 Tape care / handling
1.1.3 Output connection
to a mixer
1.2 NAGRA-D FORMAT
1.2.1 Definitions
1.2.2 Error code format
1.2.3 Track format
1.2.4 Sector format
June 1994

1.0 INTRODUCTION
The concept
of the NAGRA-D was to build a truly professional format that is reliable, will last
for many years and lends itself well
to archiving. The arguments regarding the format, choice
of tape etc. are not covered here.
The NAGRA-D is a four channel--digital audio recorder having 24 bits- per sample recording
on 6.35mm metal oxide tape, on either 5" or 7" reels,
of the tape type as used by the DASH
or PRODIGI formats.
It accommodates the sampling frequencies of 32 kHz, 44.1 kHz and 48
kHz rendering it suitable for all types of professional recording applications. The NAGRA-D
is transparent to the AES bus giving connection possibilities to a wide range of external digital
equipment.
The sound
on the NAGRA-D is recorded on helical track, by means of a rotary head (scanner)
containing 4 separate VHS heads
(2 for recording and 2 for playback), allowing read after
write (off tape monitoring) which can be heard through the two, level adjustable, headphone
outputs. The recorded tracks have a width of70 ttm and a pitch
of 80.7ttm. At the longitudinal
tape speed
of 99.25 mm/s, the scanner makes 62.5 revolutions per second (3750 r.p.m.) for
a sampling frequency
of 48 kHz.
Three longitudinal tracks (Control, Cue and Time code) are also recorded on the tape. The
control track is used to synchronize the tape transport during playback. The CUE track can
record a mix
of the four digital inputs, for search features, or alternatively it can record an
external cue microphone for commentary applications. This track can be monitored at high
speed,
in either direction, allowing rapid sequence location audibly. (Please refer to the
instruction manual for the "footprint"
of the format). The third longitudinal track is the
SMPTE/EBU time code track. The specifications of the format can be seen at the beginning
of chapter IV "Time code"
The format
of the NAGRA-D allows 4.608 x 10
6 bits per second to be recorded, meaning that
on a 5" reel of tape 16.03 x 10
9 bits (16 giga bits). The combination
of selected tape speed and
number
of channels to be recorded gives tape durations to satisfy almost all applications.
Apart from the two AES digital inputs, four analog inputs are available for either line
or
microphone input sources. When in microphone operation each of the four inputs is switchable
between "T" powering, + 12V phantom and
+48V phantom. The signal levels are adjusted
using the input potentiometers, and the levels are indicated on the four microprocessor
controlled meters. Microprocessor control
of the entire machine gives almost limitless
possibilities, not only as far
as the digital recording is concerned, but also for external control,
editing, fault diagnosis etc.
NOTE:
June 1994
The NAGRA-D has
no user selections I switches inside all mode selections etc.
are made via
an external PC or by the MENU mode.
I 1

1.0.1 PAGE NUMBERING
The page numbering
in this manual is done in such a way so that update or replacement pages
may be added at any time. Each page number starts with the number
of the chapter (in Roman
numerals) followed by the page number.
EXAMPLE III -4 This indicates Chapter III page 4
If a page were to be added after this page but before page 5 then the number on the additional
page would
be III 4. 1
Each
page is also marked with the date in the bottom left corner. If a new page is received
then the page with the old date should be discarded. Update pages for this manual will
be sent
out according to the return of the service manual registration form at the beginning of this
manual.
June 1994 I 2

1.1 IMPORTANT NOTES
1.1.1 ELECTROSTATIC DISCHARGE
The Nagra-
D's electronic circuits are all SMD devices using CMOS and MECL technology,
which renders them very susceptible to electrostatic discharge. These circuits are fully
protected while installed
in the machine, however if any of the circuits are to be disconnected
and/or removed from the machine then the operator must at all times be connected to ground
via a wrist bracelet and the circuits must only
be placed on a conductive mat also connected
to ground. The circuits are printed with the international sign indicating the danger.
1.1.2
TAPE CARE / HANDLING
Although scissor editing is technically possible on the NAGRA-D, it is not recommended to
touch the tape unless absolutely necessary. Cotton gloves are recommended for this, in order
to prevent moisture (finger prints) from the skin affecting the tape.
Due to the fact that the tape
of the NAGRA-D is not protected by a cassette, it is
recommended to spool tapes at a slower than maximum speed for storage purposes (see
instruction manual
"MENU's"). If the tape is rewound at high speed, the trapped air during
rewind causes the tape to wind unevenly on the reel, meaning that the edges
of the tape stand
proud.
If the plastic reel is now handled, there is a risk of physically damaging the edges of
the tape. On the lower edge of the tape in the format of the NAGRA-D are the time code and
Control track (see "footprint"
in the instruction manual) which will cause problems for playing
back the tape
if the edges of the tape are damaged.
June 1994 I 3

1.1.3 OUTPUT CONNECTIONS TO A MIXER
The NAGRA-D does not have transfonners on its audio outputs. This means that
if the outputs
are to be connected to the inputs
of a mixing console so that the four channels can be mixed
down to two, then
be sure that the inputs to the mixer are set to the line position. If they are
set to the Phantom
+48 position for example then the output OP-Amps of the NAGRA-D may
be damaged.
June 1994 I 4

1.2 THE NAGRA-D FORMAT
1.2.1 DEFINITIONS
Scanner rotational frequency
1 rotation
of the scanner
Wrap angle 88°
1.2.2 ERROR CODE FORMAT:
Type
of coding:
Sample size:
N°
of samples in an ECC block
N°
of audio samples / rotation
N°
of ECC blocks / rotation
N°
of ECC blocks / track
N°
of ID samples / track
N°
of ID samples per block
: FS
/768
= REC1 + PLAYI + REC2 + PLAY2
Reed-Solomon on a Gallois field 256
(8 bit
words), interlaced coding Inner
Cl(38,34,5) and
outer
C2(l2,9,4)
24 bits
9 x
11 = 99
768 x
4= 3072
3072/99= 31.03 (=32 blocks)
32/2= 16
16
x 99 -1536 = 48
48/16=3
11 samples of 24 bits (data or ID)
33 columns of C2 coding
CNTl DATA DATA DATA DATA DATA DATA DATA ECCl E CC 1 ECCl ECC1
---- -
CNT2 DATA DATA DATA DATA
DATA
DATA DATA ECC1 ECC1 ECC1 ECC1
----
CNT3 DATA DATA
DATA DATA DATA DATA DATA ECC1 ECC1 ECCl ECC1
-----
CNT4
DATA DATA DATA DATA DATA DATA DATA ECC1 ECC1 ECC1 ECC1
-----
CNT5
DATA DATA DATA DATA DATA DATA DATA
ECC'
ECC1
ECC' ECC'
- ---
CNT6 DATA
DATA DATA DATA DATA DATA DATA
ECC' ECC' ECC' ECC'
--- --
CNT7 DATA DATA DATA
DATA
10 10 10
ECC1 ECC1 ECCl
ECC'
-----
CNT8 DATA DATA DATA
DATA 10 10 10 ECC1 ECC1 ECC1
ECC'
----
CNT9
DATA DATA DATA DATA 10 10 10 ECC1
ECC'
ECC1
ECC'
-----
CNT'C
ECC2
ECC2 ECC2 ECC2 ECC2 ECC2 ECC2
ECC1
ECC'
ECC1
ECC'
-----
CNT"
ECC2
ECC2 ECC2 ECC2 ECC2 ECC2 ECC2
ECC' ECC' ECC' ECC'
----
CNT1 ECC2 ECC2 ECC2 ECC2 ECC2 ECC2 ECC2
ECCl
ECC'
ECC'
ECC1
June 1994 I 5

1.2.3 TRACK FORMAT
12 : 192 Sectors
1= Preamble (for mechanical stability and
pH start up) = 128 symbols
2= Sectors
3= Postamble (for mechanical stability)
1.2.4 SECTOR FORMAT:
1= Sync
8/9
2= CNT (Counter) 4 Symbols
1 Symbol
1 ECC 1
3= One line
of ECC block 37 Symbols =
33 data + 4 ECC Inner
Size
of 1 symbol = 8 bits for the DSP
Length
of a sector
Number
of sectors per track
Number
of data bits per track
9 bits on the tape.
42 symbols
16 x 12 = 192
192 x 42 x 9 = 72576
Total bits without sectors 2 x 128 x 9 = 2304 bits
Total number
of bits per track 72576 + 2304 = 74880 bits
Minimum bit rate = (FSI768) x (360/88) x 74880 Fs x 398.9
The bit rate must be a multiple
of the sampling frequency:
Bit rate Fs x 400 = 19.2 Mbits/sec for Fs 48 kHz
= 17.64 Mbits/secforFs44.1 kHz
= 12.8 Mbits/sec for Fs 32 kHz
Number
of bits per track = 400 x 768/(360/88) = 75093 bits.
June 1994 I 6

Fuses inside the NAGRA-D
Inside the NAGRA-D there are five important fuses, the location and type
of which needs to
be explained for easier diagnostics.
Open the top deck
of the machine by loosening the two deck fastening screws on the front of
the deck plate.
On the power input and protection circuit A-
15 located at the back- of the machine mounted
vertically behind the internal battery there are two fuses,
Fl and F2. Both of these fuses are
wire ended soldered fuses located on the right-hand side
of the circuit. Fl is a 5A fuse and is
connected
in series with the internal battery. F2 is a SA fuse and is connected between the
external
jX)wer socket and the jX)wer circuits of the machine. (on early machines this was a 3A
fuse but should be replaced by a 5A)
Remove the bottom
of the machine by removing the six screws that hold the lower plate on.
On the power converter circuit A23 which runs the full width
of the rear of the machine there
are three more wire ended fuses,
Fl, 2 and 3.
Fl is a SA and protects the +5V logic supply for the entire machine.
F2 is a 2A fuse and protects the power supply to the loading motor circuitry only.
F3 is a O.5A fuse and protects the unregulated supply which among other things supplies all
the meter lamps/leds and the all the indication leds.
If the machine is fitted with the ND-AP auto jX)wering option then there is an additionnal fuse
located on the ND-AP circuit board.
June 1994 I 7

CHAPTER II
MECHANICAL SECTION
DIS-ASSEMBLY AND RE-ASSEMBLY
June 1994
1.0 Removing the plexi glass cover.
1.1 Removing the dust cover.
1.1.2 Removing the outer tape roller.
1.1.3 Removing the tension rollers.
1.1.4 Removing the rotary tape guide.
1.1.5 Removing the scanner entry and exit guides.
1.1.6 Removing the pinchroller.
1.1.7 Removing the reel-holders.
1.2 Removing the longitudinal headblock.
1.3 Removing the pinchwheel and guide carriage.
1.4 Removing the reel motors.
1.4.1 Re-fitting the reel motors.
1.5 Removing the parking brake arms.
1.5.1 Re-fitting the parking brake arms.
1.6 Removing the complete scanner.
1.6.1 Removing the scanner rotor.
1.6.2 Re-assembly of the scanner.
1.7 Removing the capstan motor.
1.7.1 Re-fitting the capstan motor.
1.8 Removing the cam motor.
1.8.1 Re-fitting the cam motor.
1.9 Tension arms.
1.9.1 Re-mounting the tension arms.
2.0 Replacing the pinchwheel and guide carriage
2.1 Tape path height alignment
2.2 Mechanical spare parts list
2.3 List of special tools

BE SURE TO READ EACH PROCEDURE THOROUGHLY BEFORE COMMENCING
A list
of mechanical parts can be found at the end of this chapter. The list contains all the parts
mentioned
in the text and is split up into sections according to the part of the machine being
worked on. Some
of the parts are sub-assemblies and must be replaced as a complete item.
When ordering parts be sure to use the full ten digit number as well as the description so
as
to avoid any confusion.
1.0 REMOVING
THE PLEXI-GLASS COVER
Before attempting any work on the mechanics
of the NAGRA-D the plexi-glass cover should
be removed. This is firstly to allow easier access, and secondly to protect it from getting
scratched. Open the cover and hold it vertically, hold the two corners nearest to the hinges,
and move the cover about 4mm to the left and it will come away from the machine.
If the NAGRA-D is fitted with the ND-SET 7" reels cover, then this must be removed as the
deck plate
of the machine cannot be lifted with this option fitted.
June 1994 II 1

1.1 REMOVING THE DECK PLATE DUST COVER
In order
to have access to the mechanics of the NAGRA-D it is necessary to remove the deck
plate dust cover, which is on the top of the machine and is held in place by 5 screws. This
need not be removed unless access to the following parts is needed:
Pinchwheel and guide carriage assembly
Tension arm supports
or their differential'transformers
Cam motor and drive mechanism and its differential transformer
Reel motor parking brakes.
If access to any of the above is needed then proceed through the rest of section 1 of this
chapter in the order that it is written which will cover all the steps necessary before the dust
cover can be removed.
1.1.1 REMOVING
THE OUTER TAPE ROLLER
To remove the deck plate dust cover of the machine, it is necessary to remove several
mechanical parts. Using a small jewelers screwdriver, as shown in Figure·1, unscrew the top
cap
of the rotary tape guide Oocated directly behind the supply tension roller), and be sure not
to loose the small Mylar washer located under the cap, as well as the height adjustment
washer(s) located under the roller itself (if fitted).
June 1994
I2

1.1.2 REMOVING THE TENSION ROLLERS
Before removing the tension rollers, put a small pencil mark on the deck plate indicating their
position while in PLAYBACK. Next slightly loosen the screw in the bottom
of each tension
roller (max
1,4 of a turn) and remove the roller. The fixation screws are also indicated in figure
1 below.
Note: On machines up to"serial number 1000520 the"left tension roller is slightly thinner than
the right one (approx. 19/100mm). The thinner one is recognized by a single groove
around the top of the roller. On machines carrying serial numbers greater than 1000520
both rollers are
of the new thinner type. It is important not to mix up the two types as
the counter roller will not count correctly
if the two rollers are swapped over.
Outer tape guide roller fixing screw -
Left tension roller fixing screw
---
Figure 1:
June 1994
Showing where to unscrew the ourer rape roller guide and left
tension roller. The right rension roller pulley is removed in the
same manner.
II3

1.1.3 REMOVING THE ROTARY TAPE GUIDE (beside the longitudinal headblock)
It is now necessary to remove the rotary guide located immediately to the right of the
longitudinal headblock.
DO NOT move the positioning screw located in the right-hand side
of the guide, as this adjusts the mechanical position of the control track (covered in the
electrical calibration section
of this manual), or the small screw in the front lower edge of the
guide (painted red)
as this will affect the wrap of the tape on the scanner (this is factory
calibrated and 'should NEVER be'touched): SimplY'femove the
main central rear screw holding
the
guide to the deck plate, using a screwdriver, taking care not to loose its washer.
Figure 2:
Rotary outer tape guide, showing the rear fixing screw.
June 1994
II4

1.1.4 REMOVING THE SCANNER ENTRY AND EXIT GUIDES
The entry and exit guides to the scanner are very critical parts of the transport, and should be
treated carefully. Any mechanical damage to these parts will mean that the machine cannot be
re-aligned correctly. These two guides must be removed before the deck plate cover can be
removed. This is done by inserting a special driver into the black cut-away screw in the top
of the guide to be removed. Unscrew the guide, using the special tool number 01 90901 089
(the whole guide will turn):'Carefully remove the guide aiong with its support mounting.
NOTE:
The coloured scanner guide is the entry guide and sits on the left of the
scannner.
In the drawing below the guide screw is indicated with a normal screwdriver,
however the special tool mentioned above must be used for removing, replacing
and adjusting
of these guides.
Do not touch the small screw that is painted red in the front
of these guides as this is used for
the alignment -covered later under ELECTRICAL CALIBRATION, and ensure that when
refitting the guides that the red screw is in front as before.
Figure 3:
Unscrewing the scanner exit guide.
June 1994
IIS

1.1.5 REMOVING THE PINCHROLLER
The pinchroller assembly must also be removed, before the cover can come off. To do this
proceed as follows:
Insert a screwdriver as shown
in the diagram below and loosen the fixing screw about a quarter
of a turn. Insert a flat screwdriver (acting as a lever) on the front edge slightly to the right of
the main securing screw and use -this as ·a lever to slight!y'open -the·support to release the
pressure, and lift the pinchroller assembly vertically, making sure not to loose the nylon
spacer. Be careful not to loose the pinchroller assembly pressure spring, as the assembly may
come apart once
it has been removed from the deck.
Figure 4: Indication of the pinch roller assembly with the screwdriver.
NOTE: This screw replaces the Allen screw that was fitted to the earlier machines.
June 1994
II6

1.1.6 REMOVING THE REEL MOTOR SPOOL HOLDERS
In order that the reel motor dust covers
do not inhibit the removal of the deck plate cover
remove each
of them by removing the central Allen screw (2.5mm driver) and lifting the
whole reel holder clear. Remove the dust cover from each reel motor by removing the three
screws from each.
NOTE: -On some machines there
may be a-shim below the -reel-holders,-which is for the
height adjustment, and this should be kept and re-installed when it is refitted.
Once all these mechanical parts have been removed then the 5 screws holding the dust cover
onto the deck can be removed and then the cover itself can be removed, giving access to the
mechanics
of the machine. When lifting off the dust cover be sure that it does not catch the
front
of the scanner.
This plate may be cleaned with alcohol
if necessary.
June 1994
II7

1.2 REMOVING THE LONGITUDINAL HEADBLOCK
Removing of the longitudinal headblock may be necessary if either of the longitudinal heads
(Erase, time code/cue/control track) are
to be replaced, but it will definitely be necessary if
the pinchwheel and guide carriage is to be removed as the headblock covers the carriage's
fixing screws.
The longitudinal headblock isheltl in"place with three M2;5 x 8 screws fitted with washers.
Carefully remove these screws, and lift the headblock up. The headblock is fixed to the
machine with
an 8 pin rigid connector as well as a three pin wire connector which is fitted with
a small plastic connector. When the headblock
is loose, lift it up slightly and use a small
screwdriver to remove the three pin connector from its underside. NEVER pull directly on the
wires to remove this connector as they are fragile and will break easily.
Figure 5: Longitudinal headblock
June 1994
1I8

1.3 REMOVING THE PINCHWHEEL AND GUIDE CARRIAGE
In the top center
of Figure 5 the pinchwheel and guide carriage is attached to the cam
engagement gear via the linkage arm. This link is made with a small pin. This pin is removed
by unscrewing the screw
of the small spring bracket and removing both the bracket and the pin
below it. Once this has been removed the linking arm can be pulled out
of the arm and then
the arm pushed out
of the way. The pinchwheel and guide carriage is fixed to the deck plate
in three places. Each
of the -fixation points-is -held down with two -screws of M 2.5 x 6mm.
Two are located next to the rail on the left-hand side
of the carriage, and one adjacent to the
rail on the right-hand side. Remove all six screws, along with their washers. Pull the carriage
towards the front
of the machine to avoid the reel motors, then slightly lift the rear end of the
carriage and remove
it from the machine, making sure that it does not catch the lower edge
of the front panel, or the scanner. Once this is removed, be careful not to loose the right-hand
slider, as this is not secured to the carriage, it is simply pushed on.
r-
I
Fixing
screws
Figure 6:
June 1994
Fixing
screw
--.J
Faalion of the pinchwheel and guide carriage. (longitudinal headblock
has been removed)
119