Ampex 400 Series User manual

AMPEx
SERIES 4b0
OPERATION AND
MAINTENANCE MANUAL
SERIES
400

MODELS
402
&
403
COP4SOIE
AMPEX
ELECTRIC
CORPORATION
REOW000
CITY
CALIFORNIA

MODELS
402
&
403
TWO
CASE
pORTABLE
AMPEX
ELECTRiC
CORPORATION
REDWOO0
CITV,CALIFORNIA

INSTRUCTION MANUAL
FOR
AMPEX MAGNETIC
TAcbE
RECORDER MODELS 400A,401,
402,403,404 and
405
TABLE CF CONTENTS
SECTION I Specifications
SECTION II Installation
SECTION 111 Operating Procedure
SECTION IV Operating Theory
SECTION
V Routine Maintenance
SECTION VI
Electronics Alignment
SECTION VII Mechanical
Service Guide
SECTION VIII Mechanical
Adjustments
SECTION IX Parts List
FIGURE 0
Reel Hold Down Knob
FIGURE 1
Single
Case
Portable Electronic Assembly Schematic
FIGURE 2 Rack, Console, Two Case Portable Electronic Assembly Schematic
FIGURE
3
Single Case Portable Power Supply Schematic
FIGURE 4
Rack, Console, Two Case Portable Power Supply Schematic
FIGURE 5
Control Circuit Schematic
FIGURE 6
Input
Transformer
Connections
FIGURE 7 Remote Control and
60 Cycle
Amplifier Connections
FIGURE 8 Playback Amplifier Equalization
FiGURE
9 Record Amplifier Equalization
FIGURE 10
Single
Case Portable Electronic
P
ssembly-Front View
FIGURE 11 Single Case Portable Electronic Pssembly -Top View
FIGURE
12
Single Case Portable Electronic ssemnbly -Bottom View
FIGURE 13
Rack, Console, Two Case Portable Electronic Assembly-Front View
FIGURE 14
Rack, Console, Two Case ‘ortable Elec.Ass’y.-Top & Rear View
FIGURE 15
Rack, Console, Two Case Portable Elec. Ass’y.-Bottom View
FIGURE 16
Mechanical Assembly-Top View
FIGURE 17 Mechanical Assembly-Bottom View
FIGURE 18 Mechanical Assembly-Rear View
FIGURE
19 Mechanical Assembly-Side View
FIGURE 20
Reel Idler
and
Flywheel
FIGURE 21 Console Cabinet
FIGURE 22
Mechanical Assembly Case
SERIES
400 INDEX

SECTION 1
SPECIFICATIONS-MODELS
400A,401A, 402
&
403
The Ampex Models 400A, 401A,
402 and 403
magnetic
tape recorders are
audio recorders utilizing the standard
1/4
inch wide tape. Models 400A
and 401P
are identical in every respect cept for the head assembly. Similarly,
the Models
401 and 403 are alike except for
head assemblies. The
main
difference between
these two groups is the former incorporates an Electronic Assembly designed for
single case portable mounting. The 400A and 402 incorporate half track erase,
record and playback heads. The 401A and 403 incorporate full track
erase record
and playback heads.
Half track heads are effective over
only one half
of the tape
width. Thus, a
machine having
a half track
record
head
can record two separate audio tracks on a
standard reel of tape. Machines having half track playback heads can reproduce
either full or half track recordings. Machines having full track playback heads can
only reproduce tapes
on
which
a single
track has been recorded. Head assemblies
incorporating full track record and erase heads and half track playback heads are
available on special order. This allows recording full track tapes and playing back
either full track or half track tapes. All of the models produce
a tape
frequency
characteristic which has been accepted as standard for
the
exchange of programs
by the National Association of Radio and Television Broadcasters.
TAPE SPEELt 15 inches per second and 7-1/2 inches per second, with motor
ipiea &hThjuind equalization switches conveniently located.
FREC’UENCY RESPONSE. Pt 15 inches
/
2db
30-15, 000 cycles
At
7-1/a inches
/
2db 40-10,
000
cycles
/4db 30-15,
000 cycles
SIGNAL-TO-NOISE RATIO . Over 65 db unweighted noise to maximum recording
levelT.
Over 55 db, asmaffied by NARTB standards. By NARTB definition, the
signal-to-noise ratio is the ratio of peak recording level to the total unweighted
playback noise when
erasing a signal of
peak recording
level and in the absence
of
a new signal. Thus, bias and erase noise are included,
as
well as playback ampli
fier noise. P.11 frequencies between 50 and 15, 000 cycles are measured. The peak
recording level is defined as that level at which the overall input to output total
RMS harmonic distortion does not exceed 3% when measured on a 400 cycle tone.
STARTING TIME. Instantaneous. When starting, the tape accelerates to full speed
in less than 1710 second
because the
capstan motor operates whenever the power is
on.
STOPPING TIME. When playing at 15 inches per second, the tape moves less than
two inches after the
stop button is
operated.
MODEL 400A, 401A, 402
&
403, SECTION
1,
Page 1
11/1/52

FLUTTER AND WOW.At
15 inches well under 2/10% RMS measuring all
fluTtooeitflThm 0
to 300 cycles using a tone of 3,000 cycles. At
7-1/a inches per second
under 1/4%.
PLAYBACK TIMING ACCURACY. 2/10% or /3.6 seconds
in a 30 minute re
cording.
PLAYING T1ME. 32 minutes at 15 inch
speed with
standard NARTB
reel; 64
minutes at
7-TR
inch
speed on each track. The standard RMA reel may also
be used on the tape supply turntable. The Models 400A and 402 Magnetic Tape
Recorders are designed to record on only one half of the standard 1/4 inch
wide tape in accordance with RMA standards. By turning the
reel over and re
cording on the other half, twice the amount of program can be
stored
on a single
reel, thereby affecting a 50% saving in tape.
REW1ND TIME.
Approximately one and a half minutes for the full 2, 400 foot
NARTB reel.
CONTROLS. Four buttons
control the functions
of Start Play, Fast Forward,
ewi5d inZ Stop. A separate record
button
energizes the record relay, which
drops
out
when the machine is stopped. Since
the functions are relay
operated,
the control buttons
may
be placed at
a
remote location.
COMPLETE LUG-IN HEAD HOUSING. Erase, record and playback heads are
contained in a single plug-in head housing.
SIMULTANEOUS MONITORING. Independent record and playback systems
allow thetape
to
be monitored while recording.
INUTJ switch allows the recorder to accommodate either microphone level
Fo’
{Iiipedance input or
to
bridge
600
ohms
plus 4 VU
line balanced or
un
balanced. Minus 70 dbm on microphone input
will produce recommended record
level.
PLAYBACK AMPLIFIER. Plus 4 VU output into 600 ohms balanced or un
balanced. Will feed higlflmpedance amplifier
directly with approximately one
volt.
METERING. A 4 inch VU
meter
is mounted on the front panel and provides for:
A. Direct monitor of record input signal before or during recording.
B.
Monitor of recorded output signal
from playback head while re
cording or during playback.
C. Reading bias
current.
D. Reading erase current.
MODEL 400A, 4OlA, 402 & 403, SECTION 1, Page 2
11/1/52

PHONE MONITORING. A
phone moniwr jack is provided for direct monitor of
eod1riuT iijhaT £fore or during reco.ding,
and
monitor of
recorded outut
signal ftom playback head while recording or during playback, .tn
4-B
switch
is incorporated in order that direct compat son can oe made aetneen the original
p1ogram and the recorded program while a recording is being u-4ade. The same
switch transfers the VU meter for level comparison 2nd monit’ring.
‘AOUNTINGS. Models 400A and 401P
are
available
as a single
case portable.
c4sdels 40l’nd 403 are available in a console cabinet, for rack mountings, or
as a two case portable.
POWER
INUT
REC’UIREMENTS.
115
Volts
AC
2
Amperes.
Recorders are avail
able Io iither 60 or 50 cycle
operation.
Sec
serial dumber plate before
operating.
DIMENSIONS.
Stngle
Ca5ctortable_
Complete recorder
in single case
Height - 13-3/4 inches
Width - 20 inches
Depth - 17-1/2 inches
Weight
- 83 pounds, approximately
Rack Mounting - Standard 1" wide panel-Commercial aoLching
Mechanica’ Unit-15-3/4" high panel
Electronic Unit-7" high panel
Power Supply-3-l/2" 3’igh panel
Studtj Console
- Complete recorder in cabinet
Height - 32 nches
Width - 23 inches
Depth - zs-i/z iri’hes
Two Case Portable
- Mechanical and electronic assemblies in
separate cases
Mechanic.l
Assembly:
7/idth-21 inches
Depth-iS inches
Height-iS inches
Weight-62 pounds
Electronic assembly in large
casehas
extrs
space for four-channel
mb:er or for
stow
age of cables and microphone
Width
- 21 inches
Depth - 13 inches
Height - 19 inches
Weight - less mixer-50 pounds
VIODEL 404, 401A, 402
& 403,
SEC
TION I, ?age
3
11/1/52

Electronic assembly in small case spzce
for power supply and
electronics cnly
no extra space
Width-21 inches
Depth - 13
inches
Height - 12 inches
Weight -45 pounds, approximately
ACCESSORY ITEMS.
All
recorders
in the 400 series are available with connectors ins ta.lei
in the Mechanical Assembly for "plug in" of remote controls, the Model
:75
Precision 60 cycle Power Supply, or the
Model
80
Speed
I
ock Equipme:.t.
The Model 375 Precision 60 Cycle power Supply is designed to pr’vide a
source of constant frequency to the capstan drive motor in localities whee the
available 60 cycle power Is not stable in
frequency.
The Model 380 Speed Lock Equipment is designed to automatically :ontrol
the playback speed of Series 400 recorders to synchronize with motion
r
cture
equipment.
P
remote
control box is available with five pushbuttons and two
i.it
i
cator lights mounted on a sloping panel
in
a
small wooden
case. Catalog ii
3766.
This unit is wired
and ready
to
ope.rate. . -
Piso available are remote controls on a flat plate for flush mounting in
st4dio control consoles. Catalog #3766-1. This unit is not wired. Wiring must
be done by the purchaser ta fit his installation.
A four channel high level Miser-Preamplifier
is. available for use with
Models 402 and 403
rack m--it aiid portable recorders. Catalog #3761,
An accessory pedestal is available for Model 402 and 403
Studio Con
soles to increase
their heir’c to 41 inches Catalog
#3795.
A set of casters is also
available for
the Studio Console.
Catalog 3963,
MODEL 400ft, 4011, 401 & ‘103, SECTION I, rage
4
11/1/52

SECTION Il
INSTALLATiON
IMPORT A NT:
Before operating the recorder, read the following sections on INSTLLA
TION and OPERATION.
CAUTION:
Do not attempt to lengthen the head cables. Additional cable capacity will
affect the frequency characteristics.
Console Models: Shipped in ready to operate condition. Connect the input, output,
inJ ACpr is follows: Remove the lower screen cover at rear of cabinet.
Pull
the
cables through bottom of cabinet and plug them into rear of Electronics
Assembly.
For
connection
instructions, see following paragraphs. Replace pro
tective screen covering to rear of cabinet.
IMPORTANT. The
console cabinet
must be spaced at least 4" from the wall in the rear
and at
least 3" between
a
wall or cabinet on either side, otherwise ventilation holes will be obstructed.
Two
Case
Portable
Models: The portable machine is shipped in a ready to operate
condition, except for the connection
of interconnecting cables.
To operate the recorder place the Mechanical Assembly Case to the left
of the Electronic Assembly Case.
Unlatch and remove the top cover and cable
access door on the right side of the Mechanical Assembly Case. Unlatch and re
move the front and rear doors on the Electronic Assembly Case.
Uncoil the interconnecting
cables from behind the cable access door and
plug them into mating
receptacle at
the
rear of the Electronic Assembly.
Connect the input, output, and
AC power to rear of Electronic Assembly.
Single Case Portable Models: These machines are shipped in a ready to operate
condition.
Remove
the
front panel cover and the top cover. All connections are
readily accessible from the front panel.
NOTE: Nhen storing the portable machines avoid setting the Mechanical Assembly
case on either of the handle ends. This will cause the Turntable Motor Tire to
rest on the Brake Drumand will
produce a flat in the tire if left in this position
any appreciable time.
Rack Mounted Models: The rack mounted machine should be mounted on a standard
T91nhrliiakw1th the Mechanical
unit above the main Electronic Panel. The
Electronic Power Supply Panel should be mounted directly above the Mechanical
/ ssembly
to
prevent
the possibility of 60 cycle field from entering the Electronic
Assembly.
SERIES 400 SECTiON 11, Page 1
ii/i/sz -

If
two
Series 400 Recorders are to be irounted on a standard rack,
the following placement is recommended starting at the top of the rack;
1. Install a spacer panel at the top of the rack if desired.
2.
Install below this panel the Mechanical Assembly for machine #1.
3. Install the Electronic Assembly for machine
#1.
4. Install a spacer panel.
5.
Install the
Mechanical
P ssembly for machine #2.
6. Install the Electronic Assembly for machine #2.
7. Install a spacer panel.
8. Install both Power Supply Panels at the bottom.
The cable on the power supply for the upper recorder will have
to be extended in length. Extension cable
#3814
is available for
this purpose,
The numbers
set off in parentheses in the following text are reference
numbers that refer to the Parts List Section IX and the figures in the rear of
this book.
I.
Connect the Power Cable,
catalog #2413, fom the AC Power Input Con
nector
J4092
on the Electronics Assembly
to a source of 115 Volt PC
power.
IMPORTPNT:Thts machine is available for either 50 or 60 cycle operation.
The power line frequency is indicated on the serial
number plate which
is lo
cated on the Power Supply Panel for rack mounted machines and
on
the exterior
of each case in the portable machine.
Ii. OlTT: Refer to Figure 1 or 2.
A.
For Studio
Line:
Plus 4 VU, 600 ohm line output,
balanced or unbalanced,
is available
across
Terminals 2 and 3 of the Line Out Connector,
.7404°,
Pin
1
is the
chassis ground,
if unbalanced output is desired; tie either side of the line to
ground.
It is necessary to supply 600 ohm termination to this output at all
times in order to
maintain
correct meter
calibration while recording or play
ing back. Therefore, if the output is not feeding a
terminated line or if the out
put is not connected, such as on remote pickups, the Line Output
Termination
Switch, 5404, must he switched to ON.
B. For Connection to
High
impedance
Amplifier Input:
Connect pin 3 of the Line Out Connector J404, to the high side of the
amplifier input. Strap pins 1 and 2 of the connector and connect to the ground
side of the amplifier input. The
Line Output Termination Switch S404, must
be left in the position designated ON at all times, as explained in A above.
SERIES 400, SECTION ii, Page 2
11/1/52

ill. iNPUT: Refer to Figures 1 or
2
and 6.
The following inputs are provided:
A. Microphones:
Any low impedance microphone, the nominal impedance
of which is in the
range of 30 to
250
ohms
can
be plugged in directly. Connect
the microphone to
pins 2 and 3
of
the Input
Connector,
3401S. Connect cable shield to pin 1.
Place the Input Transfer Switch, S40l, in the MIC position.
The microphone input
transformer
is strapped for
the optimum step up for
a 150 to 250 ohm source. In the case of microphones having 50 ohms or less im
pedance, 6 db additional gain can be obtained by strapping the input as shown in
Figure 6B. This is not usually necessary, however, and should not be
done unless
insufficient
gain is
found to exist. If the input is re-strapped,
serious frequency
discrimination will exist should the input be fed from a
source impedance greater
than 50 ohms. IMPORTANT. R402 and R403 will have to be
changed to 24 ohms
and P401 and P404 to 68, 000 ohms to
maintain a flat response on Balanced
Bridging when the
transformer
is
strapped for 50 ohm source impedance.
High impedance microphones are not recommended for use on this
equipment.
In general, the quality obtainable from high impedance
microphones is not sat
isfactory for professional work. In the event that it becomes necessary to connect
a high impedance microphone, the input circuit will have to be re-wired as shown
in Figure 6A.
B, Bridging a Balanced Studio Line:
Connect a
balanced line
to
pins 2 and 3 of the Input Connector, J4O1S.
Pin 1 is
ground. Place the Input Transfer Switch, S401, in
the
BALANCED
BRIDGE
position.
Input
levels of minus 10 to plus 10 VU
can
be
accommodated. The load
placed on the line is approximately 300, 000 ohms.
For bridging higher or lower level lines, an external bridge can
be wired
in the line to the machine. This would consist of
two resistors, the value of which
should be from 15, 000 to 30, 000 times the RMS
program voltage, in series with
each side of the line. A
24
ohm
/5% resistor should terminate each leg of the out
put
side of the two bridging resiiiors. The junction of the two 24 ohm resistors
should go to chassis ground. The output of the bridge must be
fed
to
the micro
phone input of the recorder. The input of the recorder may be connected
for
any impedance
from 50
to
250 ohm.
C. Bridging an Unbalanced Source:
Connect an unbalanced line, radio tuner, etc. , to pins
3 and
1
of the Input
Connector 340 iS. Pin 1 is the
ground side. Place the Input Transfer Switch,
5401, in the UNBALANCED BRiDGE position. This connection
provides a
60, 000 ohm bridging input
for any
RMS
program voltage greater than 1/2
volt.
SERIES 400, SECTION II,
Page 3
11/1/52

To increase the input impedance above 60, 000 ohms, a series resistance
of 330, 000 ohms can be wired into the input plug in series with pin 3 and
th- input cable. This will necessitate an input voltage of at least 2-1/2
voiè RMS. It is important that this resistor be physically placed in the
cable connector that plugs into the Recorder Input J4O1S in order that
the cable capacity be on the input side of the resistor.
IV, PHONES:
Any sensitive
head phones can be plugged in the Phone Jack J403S,
provided for monitoring the incoming line or playback output.
V. REMOTE CONTROL: Refer to Figure 7.
It is possible to remote
control the Start, Stop, Fast Forward, Rewind,
and
Record pushbuttons of this recorder, On standard recorders connect the
remote controls shown in Figure 7A to the Remote Control Terminal Strip
T5502 shown in Figure 18. i’ n eight
wire cable
is
required.
if
this tape recorder is equipped for "plug in" of remote controls,
connect a 10 pin male Jones plug Jones P-310-CCT-L,
MPEX
PL2O8P to
the 8 wire cable leading to the remote controls. Plug the
cable into the
Remote Control Connector in the
rear of the recorder.
If
remote control
should not be desired, Dummy lug #346 1 must be inserted
in this connector.
Jones P-3l0-CCT-L with 7
and
8
strapped.
Standard
recorders can be modified for the "plug in" of Remote Control
and 60
Cycle
Amplifier connections by the addition of an 8 and a 10 pin female
Jones
connector. These connectors can be mounted in the holes provided on
the Relay Mounting Bracket Ii in the rear
of
the Mechanical
Assembly. The
connectors
should
be
wired to Terminal Strips TSSO1 and T5502 as shown in
Figures
lB and 7D.
VI. 60 CYCLE MPL1FIER: For Drive Motor Power Refer to Figure 7.
Connections for AM?EX Model 375, 60 Cycle Amplifier,
or Model 380
Speed Lock Equipment are made on the 60 Cycle
Amplifier
Terminal
Strip
TSSO1
shown
in Figure 18, or at the 60 Cycle Amplifier
Connector, if the
recorder is so equipped. The
Control
Circuit Power Fuse F402 must be in
creased to 5 amperes when either of these units are used. Refer to Figure 7D
and the Model 375 or Model 380 instruction Book for the detailed installation
procedure.
NOTE:
If this recorder is equipped for "plug in" of the 60 Cycle Amplifier,
U TsThecessary to insert Dummy Plug #567 in the 60 Cycle Amplifier re
ceptacle when the 60 Cycle
Amplifier is not used.
SERIES 400, SECTION ii, °age 4
1 i/i/sz

Vu. CONVERSiON FRO
T
. B:
V
12 kICUNT:
if a portable or console c1er is convei ce! ‘o a rack mount machine,
the
Takeun Tension rm :ounterbalanc ring 6S r ii:jt re affded. This spring
is
supplied with th
recorder
and is hT&: to the eeL T rust 2racket 85.
See
Figure 17. To
instad, let ove
trcn
.r.E
bra cet ;r Jetween th lug
provided
on Safety
w’t
li 501 ard the . . : c’tdecoi the Takeup Ten
sion rrn
Collar
.
The ‘1 ‘e ro Tensior cm .
rxterbalanc
£pring 65 is
sho n instaLd c rack mounted
-eration on H. tien shipped as a
rack mount machine, the spring w.ii oe instaile. f tce conversion is to be perm
anerit,
the oiling cups ci the Turritabie toter 6, if ..i ped ith sI.eve bearings,
shoLid he
rotat3 tc be a .ie for otii
‘
. ccs ‘JNSrL.. Ni’
r:
PNlNG: $efore
01
en,.r; the ‘:csole or cci tae case:;, disconnect ‘C oower.
Complete accessibility
for
inspection
or
service
ii provided to the to
nd bottom
of the
Electronic Assembly and bottom of the viechanical Assemby.
Fig ie 21 for illustration of Cabinet opened for full accessibility.
Coening rocelLire
1. Remove
the four front parel screws
X, Figure
21, securing :lectronic
Assembly to cabinet.
2.
°uII
Electronics
P sserrbly forward in the position
illus trated in Figure
21.
3. For access
to undersic ofr lectronic ssencbly,
pivct it
back on the
hinge
protided at rear.
4. Hinge at
rear will
separate
for. torpiete
removal of chassis
from the
cabinet, if desired.
5. Toe Mechanical
Assembly can bF raised to a
450
positron removing
t’.o !ont
.1cc anical A sserv st-czs, Y
, Figire 21.
6. Use
siport red k’ to support Mechanical
Assembly.
7. The Hechanical
sse tbli may also be raised
to a vertical position
and wilt be s
upDuc’e: oy e chain stop.
IX. Cca:C
1IlvDR’iiDJ Cr *HANIC,"L AS3K3L?
s? TO CASL
ORT
S’;d
jechanical AssembLy Case on erd as shown
in Figure
22. Release
latches hal. I
‘
center
dirisions of case. Inen La
aporoximately
900.
Care must
be taker t:j insure that cabJes
*:an pass through cable compar.ment
into main
rabr’ce ft eely.
X. P OChC; TO UND.R SIDE CF
i’4
CH NIC
_
PSSEMBLY iN
SINGLE C! SE
PORTA LE,
SiLde the
Electronics Chassis out of the case.
Remove the head cable
SrIP1ES
400, SECTION II, Page
5
11/1/52

clamp
and disconnect
all cables from the Electronic
Chassis. Remove the
Mechanical Assembly
by lifting straight up.
It
may
be turned upside down
and placed on the
case for servicing. When returning
the assemblies to the
ca-se, make sure
the cables are properly clamped and threaded through the
cable guides so they
will not interfere with moving parts.
Xl, OVER/LL PERFORMANCE
CHECK: Bead Section 111. on OEBfrTiON
before making
these checks -
The following procedure is recommended
for checking the
performance
of this recorder
at
the
time
of
installation and as necessary thereafter.
. Overall Frequency
Response:
Thread a new reel of tape on the machine. Equalization curves
for the Record and Playback Amplifiers as shown in Figure 8 and
9
have been
established by use of Minnesota Mining and Manufacturing Company Type lii
Tape, Construction
BREA
or later. Slight deviations in performance can be
expected when using other tapes,but entirely satisfactory results can be ob
tained from any professional quality tane.
1. 7-1/2 Inch Response or 3-3/4 inch
ResnonseModels 404
&
405 only
DUE TC THE NATURE -OF THE RE-EMPHPSlS IN THE
RECCRD CIRCUIT, TAPE SATURATION WILL OCCUR AT
TH. HIGH
FRECUENCJES
UNLESS THE RES2ONSE CHECK
15 MADE PT LEAST
20
DB BELOW
NOR1vIAL
OPEASPTING
LLVEL.
Therefore, check the response with a sensitive meter
such
as a Hewlett-Packard 400C connected to
the
output. in
absence
of a
sensitive meter, a standard
VU
Metr preceded by a flat
amplifier with at least 20 db gain can be used. Response
will be within the limits indicated in the Specifications.
a. is Inch Response:
check approximately 10 db below operating
level to avoid
saturation
effects. Response will be within the
limits indicated in the Specifications.
B. Overall Noise Measurements:
Overall wide band noise should be measured with a Vacuum Tube
V ltmeter such as Hewlett-°ackard 400C wh eplaying
bark
a tape that
has
p:eviously been erased
on
the machine. First;
trase
the tape with the input
f Th E’rd amplifier shorted. Rewind and play this tape back. Pt the
7-1/2 inch and
15 inch speeds
the wide
band noise
should be at least 49 db
below onerat;.ng level point of approximately
1%
total harmonic distortion.
Pt the 3-3/4 inch speed for Models 404 and 405, the noise should be
at least
44 db
below operating level. No attempt should be made to measure wide band
SERiES 400, OCTION II, age 6
11/1/52

noise ‘vhdt stxz,ulLwus1y recording
and 1aying back
as
- -
;
of Ye flO 1C
ias irto he
play-ack
head may interL with t :C3S2 ‘c -
C. Listortion;
Dverall distortion can be treasured by connecting
any standard
distcrtion
rreasurenent
appatatus across the outpuL The readings from a wave
ana’yzer or
selective frequency distortion rr’eter will be more accurate than
those from
a null type instrument at lower distortion levels. Distortion read
ings are some-,vhat dependent
on tape. reading of l is
normal
at ooerating
level whi1 a reading of 3%
is
normal at
6 db above ooerating
level.
D. Flutter_and Vow:
Flutter
and
i1ow
are the change of
soeed over
a short time interval
in a Der1dic manner. They can be measured by means of a sta3dard flutter
bridge such as . F. Tatum Beverly Hills, California Model 2-- Flutter "1eter.
Variations in amplitude as indicated on level measurements do not constitute
flutter
and are entirely due to taoe coating variations. Readings will be well
‘1nder . 2%’c.
at
15 inch, . 25 at 7-1/2 inch and . 3
at
3-3/4 inch speed.
For more information on alignment or performance checking,
refer to STCTION VI - c ltgnment.
SERII3
400,
SECT1ON 11,
7-age 7
ii/i/sz

SLCTIOIr
III
OPLR4TING IROCEDUR
I, REEL SIZE:
The turntable
on the left side tape supply
is
equipped
to handle either
the NP-RTB io-i/z" reel
of tape or the smaller R. M. A. 5" and 7" sizes.
On
console or portable machines position
the small reels on the turntable engaging
the turntable-keys. For the large ia-i/a" reel,
use the black plastic Centering
Guide Catalog #976 that has been provided. On rack
mount machines, use the
Hold-Down
Knob Catalog #4402 wth both small and
large reels.
The #4402
reel Lold-down
knob works in the following manner.
A re
movable pin
in
the bottom surface
of the knob engages a corresponding hole in
the turntable.
A
coliet grips the turntable
shaft when the top of the knob is ro
tated. Two
spring
loaded
balls hold the reel to the turntable. A pin in the side
of
the knob
drives
the
reel. The knob should be positioned on the NPRTB reels
so
that
the
removable
pin engages one of the turntable holes and approximately
two thirds
of the
ball is exposed
above the
reel.
The knob should not be pushed
down all the way, but should stick up above the turntable. Once the knob
is po
sitioned correctly, the NARTB reels may be removed without removing the knobs.
When using the knob with the small RMA reels, unscrew the removable pin. The
knob is used only t9 prevent the reel from falling off the turntable, since three
keys in the turntable drive and center the reel. Lock the knob to the shaft,
avoid:
ing excess pressure on the reel which could distort the reel flanges.
The turntable on the right
side
Takeup Reel is
designed
to
handle only
the
NtRTB
10-1/2" reel. No
attempt should be made to use the small reel sizes
on this turntable
as
the
performance of
the
recorder
will
be seriously impaired.
U.
TA?E THREADING:
Thread the tape as indicated in Figure 16. All
new
factory
wound reels
should be unwound and inspected by running through at Fast
Forward before using
them
in the
?lay
mode of operation. New tapes are usually looped to the hub in
such a manner that the tape will not come free of the reel at the end of the reel.
This
will
prevent
the Safety Switch 5501 from disengaging the Capstan
Idler
50
from the Capstan A which results in a flat being
worn on the Rubber
:Capstan -
Idler Wheel. Any adhesive material accumulation on the
reel hub must be removed
with solvent for the same reason.
Ill. HALF-TRACK OPERATION:
The handling of half-track tape on
this machine
i
accomplished in the
following manner. The tape is threaded and operated as
described under T
Jii
THRLADING and
TAF-
MOTION.
However, only the upper half of the tape will
be used on the half-track machine. To utilize the lower half of the tape, the full
reel on
the
Takeup Turntable
should
be
removed, turned over and placed on the
SERIF 5
400 SECTION
III
Fage
1
1 i/i/sz

Tape Supply Turntable upside dow..
Place an empty reel
on the Takeup Turn
table. Repeat the operation
as performed on the first
track.
IV. POWER:
Power is supplied through Power
Switch S406, which
must be turned
on to operate the Electronic
and Mechanical Assemblies. The Mechanical
Assembly and
Electronic
Assembly
are individually fused by the 2 ampere Con
trol Circuit Fuse F402 and the
1 ampere Electronics Fuse F401,
V. SEED SWITCHES:
There are two switches associated with operating speed. Speed Switch
5502 governs the motor, and the Equalization Speed Switch 5402 corrects
the equalization in the amplifiers.
VI. TAPE
MOTION: -
The tape motion
is controlled by means
of
four pushbuttons labeled
Stop, Start, Fast
Forward, and Rewind.
1. Play or Record: The tape is set into Play motion at the speed selected
-by the Speed Switch when the Start Button 5507 is depressed. The
tape must be completely stopped before starting in this mode. To
change from Play mode to the Record mode with the tape in motion,
press the Record Button 5403.
2.
Stop: To
stop the tape motion vhile it is moving in any mode press the
- t&Button 5506. This will occur automatically if the tape should
break or run off either reel.
3. Fast Forward: If
the tape isin the
Dlay
or Record mode, press the
Fast Forward Button S504. If the tape is
stopped, first press the
Start Button,
then the Fast Forward Button or press both at the
same time. This
provides
a
Fast Forward speed which is used to
arrive rapidly at a point within a
reel.
4. Rewind: If the tape is in the Play or Record mode, press the
Rewind
Button S505. If the tape is stopped, press the Start
Button then
the
Rewind Button
or
press both at the
same time. This provides a fast
reverse to rewind a tape completely or to return to an earlier section.
In using either the Fast Forward or Rewind n-ode, it is desirable to
remove the tape from direct contact with the heads by opening the
gate
of the Head &ssembly. This
will
reduce wear on the heads and
prevent the oxide coating on the tape from depositing on the heads
and impairing their performance. it is not possible to switch from
Rewind
to
Fast Forward or vice versa unless the machine is re
turned to Stop. Interlocking
the
‘machine in
this manner provides the
least nossible wear on the Tape Transport system.
SERIES 400 SECTION AU - rage 2
i
1/1/52

Indexing the tape as in editing or
cueing or when anproaching
the end of
the
reel is simplified by holding down
a combination of buttons.
Hold down
the Stop and Fast Forward or
the Stop and
Rewind Buttons. Now press the
Start Button and control
the tape speed
with this button. CAUTION: Avoid
this operation
at high speeds, as it will result
in tape breakage if the wrong
combination of buttons
should be pushed. When the tape
is traveling at
high speed in the Rewind
or Fast Forward mode, the tane will
break if the
Stop and Start Buttons are pressed
in rapid sequence. This
is caused be
cause sufficient time is not allowed
for the brakes to -stop the tape
before
the Capstan Idler locks the tape to
the Capstan.
VII. PLAYBACK:
To
play back a previously recorded
tape, turn the Meter and Output Switch,
5405, to
the extreme left position designated
PLAYBACK. Then start the tape
in motion
as indicated under T?LAY.
For Single Case Portable Models. If the recording was
made at the correct
level, the
VU Meter will peak on 0 iiio. No attempt should be made
to
alter
the gain of the Playback Amplifier if the
meter does not peak on 0 zero. Other
wise, the calibration of this meter as
a record level indicator will be destroyed.
The playback gain
will be clcse
when playing
any tape recorded to NARTB specifi
cation s
For Rack, Console or Two Case ‘ortable Models * P Playback Level Con
trol
has
been
provided
on the front
panel
to adjust the tape level to plus 4 VU
output.
V1II.
RECORD:
To record a new program on prevtously recorded tape, or on blank tape,
turn the Meter and Output Switch 5405 to the second position from the left
which is designated RECORD-LEVEL. Turn the Record Level Control R409
clockwise until
the
level
reads
0
zero
on the VU Meter
on
the most intense
program peaks. The program can be
audibly monitored
through either
the
Phone
Jack J403S, or the Line Out Connector
J404’°
before the
tape is
in motion.
For correct meter calibration it is important that the Line Out be properly term
inated either external to the machine or by use of the Line Out Termination Switch
S404. This direct monitor feature allows the program to be set up through the
machine without actually recording
during
the set up period.
When the program level is properly set, start
the
tape
in
motion as indicated
under PLAY. Then push the Record Button, 5403. It is desirable that a delay
of at least i/i second occur before the Recc$rd Button is depressed, as the surge
from operating the Start Button may magnetize the record head, thereby increasng
the noise level on
the tape. The
Record
Indicator, NE4O1, next to the
Record
Button will now glow and the machine is recording.
It is desirable to check the record bias and
erase currents
occasionally.
In
order
to do this, re-position the Meter and Output Switch S405, to the po
SERIES 400 SECTION
LU,
‘°age 3
11/1/52 -

sitions designated
BIAS
and ERASE, respectively.
The
erase
is not critical
and should
read
approximately zero on the meter scale. The
bias should read
between -i/a and
/
1/2
on the VU scale. The
bias
is somewhat
critical
and
must
be
kept within
the
indicated range in
order to
record the higher fre
quencies at
the low
tape speed.
The bias is adjusted by means of the Bias Control, R449 located on
the
electronic chassis. The meter calibration for bias measurement can be
checked
as
indicated in SECTION VI.
SERIES 400 SECTION III,
Page 4
11/1/52

SEC LION IV
OPERATING THEOR Y
The purpose of this section is to explain the electrical and mechanical
functioning of the Recorder as the machine is operated. An understanding of
this functional operation will enable the operator to utilize fully the capa
bilities of the machine,
I. MECHANICAL ASSEMBLY: Refer to figures in rear of book for
circuits and
location of parts.
To understand the operation of the Tape Transport Mechanism it is necessary
to examine the following assemblies in the various modes of operation:
1. Capstan Drive Motor 24, Figure 18. The Capstan
Motor is
a
synchronous
motor whose extended shaft forms the Tape Drive Capstan
A Figure 16.
It has two sets of windings to provide the two
tape speeds.
2. Turntable Motor 6
Figure
19.
The Turntable Motor is an induction
motor
which drives
either the Tape Supply or Takeup Turntable by
means of a
Rubber-tired Pulley 7 on its shaft. The motor is positioned
to contact
either of
the turntable Brake Drums 34 and 35,
Figure 18, by the Tilt
Solenoids K503 and 1504.
3. Capstan Idler 50,
Figure 16. The Capstan
Idler is positioned by the
Capstan Solenoid 1501. In the Play mode
of operation the
Idler is
positioned against the Capstan A and
drives the tape at a
constant speed.
4. Stopping Brakes
36 and 39 Figure 17. The Stopping
Brakes are
solenoid
operated to stop the turntables whenever the machine
is stopped.
5. Reel Idler 69, Figure 20. The
Reel Idler is provided to
smooth out any
takeup speed variations in the
tape system.
6. Takeup Tension
Arm 62, Figure 16, The Takeup Tension
Arm provides
automatic
stop at the end of the reel of tape or
if the tape should br
eak*
7. Constant Tension
Brake 47, Figure 17. The Constant
Tension Brake is
mechanically
operated by the
Constant Tension Arm 44,
Figure 16. It
SERIES 400, SECTION
IV, Page 1
11/1/52