Ampex 400 Manual Grayscale

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User Manual: Ampex-400 manual grayscale

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AMPEx
SERIES 4b0

OPERATION AND
MAINTENANCE MANUAL

SERIES 400

MODELS 402 & 403
COP4SOIE
AMPEX ELECTRIC CORPORATION
CALIFORNIA
REOW000 CITY

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

INSTRUCTION MANUAL
FOR
AMPEX MAGNETIC TAcbE RECORDER MODELS 400A,401,
402,403,404 and 405

TABLE CF CONTENTS

SECTION
SECTION
SECTION
SECTION
SECTION
SECTION
SECTION
SECTION
SECTION
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FiGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE
FIGURE

I
II
111
IV
V
VI
VII
VIII
IX

0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22

Specifications
Installation
Operating Procedure
Operating Theory
Routine Maintenance
Electronics Alignment
Mechanical Service Guide
Mechanical Adjustments
Parts List
Reel Hold Down Knob
Single Case Portable Electronic Assembly Schematic
Rack, Console, Two Case Portable Electronic Assembly Schematic
Single Case Portable Power Supply Schematic
Rack, Console, Two Case Portable Power Supply Schematic
Control Circuit Schematic
Input Transformer Connections
Remote Control and 60 Cycle Amplifier Connections
Playback Amplifier Equalization
Record Amplifier Equalization
View
Single Case Portable Electronic P ssembly-Front
Single Case Portable Electronic Pssembly -Top View
Single Case Portable Electronic ssemnbly -Bottom View
Rack, Console, Two Case Portable Electronic Assembly-Front View
Rack, Console, Two Case ‘ortable Elec.Ass’y.-Top & Rear View
Rack, Console, Two Case Portable Elec. Ass’y.-Bottom View
Mechanical Assembly-Top View
Mechanical Assembly-Bottom View
Mechanical Assembly-Rear View
Mechanical Assembly-Side View
Reel Idler and Flywheel
Console Cabinet
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
The main difference between
401 and 403 are alike except for head assemblies.
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
By NARTB definition, the
levelT. Over 55 db, asmaffied by NARTB standards.
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
ewi5d
inZ Stop.
drops out when the
the control buttons

buttons control the functions of Start Play, Fast Forward,
A separate record button energizes the record relay, which
machine is stopped. Since the functions are relay operated,
may be placed at a remote location.

COMPLETE
LUG-IN HEAD HOUSING. Erase,
contained in a single plug-in head housing.

record and playback heads are

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.
B.
C.
D.

Direct monitor of record input signal before or during recording.
Monitor of recorded output signal from playback head while re
cording or during playback.
Reading bias current.
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
Height
Width
Depth

Weight
Rack Mounting

Studtj Console

in single case

13-3/4 inches
20 inches

17-1/2 inches
83 pounds, approximately

Standard 1" wide panel-Commercial
Mechanica’ Unit-15-3/4" high panel
Electronic Unit-7" high panel
Power Supply-3-l/2" 3’igh panel

aoLching

Complete recorder in cabinet
Height
32 nches
-

Width
Depth

Two Case Portable

23 inches
zs-i/z iri’hes

Mechanical and electronic
separate cases

assemblies

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.
is. available for use with
A four channel high level Miser-Preamplifier
rack
m--it
aiid
portable
recorders.
Catalog #3761,
Models 402 and 403
An accessory pedestal is available for Model 402 and 403 Studio Con
Catalog #3795.
soles to increase their heir’c to 41 inches
A set of casters is also available for the Studio Console. Catalog

MODEL 400ft, 4011, 401 & ‘103, SECTION I, rage 4
11/1/52

3963,

SECTION Il
INSTALLATiON
IMPORT A NT:
Before operating the recorder,
TION and OPERATION.

read the following sections on INSTLLA

CAUTION:
Do not attempt to lengthen the head cables.
affect the frequency characteristics.

Additional cable capacity will

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.
the
Pull
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.
2.
3.
4.
5.
6.
7.
8.

Install a spacer panel at the top of the rack if desired.
Install below this panel the Mechanical Assembly for machine #1.
Install the Electronic Assembly for machine #1.
Install a spacer panel.
Install the Mechanical P ssembly for machine #2.
Install the Electronic Assembly for machine #2.
Install a spacer panel.
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:
A.

Refer to Figure 1 or 2.

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
the value of which
in the line to the machine. This would consist of two resistors,
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
The junction of the two 24 ohm resistors
put side of the two bridging resiiiors.
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,
Record
pushbuttons of this recorder, On standard recorders connect the
and
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,
MPEX PL2O8P to
connect a 10 pin male Jones plug Jones P-310-CCT-L,
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

i/i/sz

ii, °age 4

Vu. CONVERSiON
if a portable

FRO

B:
.

or console

c1er

kICUNT:

convei ce! ‘o a rack mount machine,
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
rxterbalanc
The
‘1
‘e
ro
Tensior
cm
£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

the Takeun Tension

rm :ounterbalanc

‘

ccs

‘JNSrL..

PNlNG:

$efore

Ni’

en,.r; the ‘:csole

Complete accessibility
nd bottom of the Electronic

or cci tae

case:;, disconnect

‘C oower.

for inspection or service ii provided to the to
Assembly and bottom of the viechanical Assemby.

Fig ie 21 for illustration of Cabinet opened for full accessibility.
Coening
1.
2.

3.
4.
5.
6.
7.

IX.

rocelLire

Remove the four front parel screws X, Figure 21, securing :lectronic
Assembly to cabinet.
°uII Electronics P sserrbly forward in the position illus trated in Figure 21.
ofr lectronic
ssencbly, pivct it back on the
For access to undersic
hinge protided at rear.
removal of chassis from the
Hinge at rear will separate for. torpiete
cabinet, if desired.
removing
Toe Mechanical Assembly can bF raised to a 450 positron
.1cc anical A sserv
st-czs, Y , Figire 21.
t’.o !ont
red k’ to support Mechanical Assembly.
Use siport
sse tbli may also be raised to a vertical position
The Hechanical
and wilt be s upDuc’e: oy e chain stop.
1IlvDR’iiDJ

Cca:C

latches
be taker
rabr’ce

*HANIC,"L

AS3K3L?

s? TO

CASL

ORT

jechanical AssembLy Case on erd as shown in Figure 22. Release
S’;d
hal. I
center dirisions of case. Inen La aporoximately 900. Care must
into main
t:j insure that cabJes *:an pass through cable compar.ment
ft eely.
‘

X. P OChC; TO UND.R SIDE CF i’4
PORTA LE,
SiLde the Electronics

CH NIC

Chassis

PSSEMBLY

out of the case.

iN SINGLE C! SE

Remove

the head cable

SrIP1ES 400, SECTION
11/1/52

II, Page

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
405 only

404 &

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

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

V ltmeter

SERiES 400,

OCTION II,
11/1/52

age 6

noise ‘vhdt stxz,ulLwus1y
ias

irto he play-ack
C.

recording

head may interL

and

1aying
with t

back as
:C3S2

‘c

;

of Ye flO 1C

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.
.

refer

For more
to STCTION VI
-

information
c ltgnment.

on alignment

SERII3

or performance

checking,

400, SECT1ON 11,

ii/i/sz

7-age 7

SLCTIOIr III

OPLR4TING IROCEDUR

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.

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
New tapes are usually looped to the hub in
them in the ?lay mode of operation.
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
TAFTHRLADING and
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
1 i/i/sz

Fage

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
This will reduce wear on the heads and
gate of the Head &ssembly.
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
i 1/1/52

rage 2

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,
to the extreme left position designated PLAYBACK.
Then start the tape
in motion as indicated under T?LAY.

5405,

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
has
trol
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 meter calibration for bias measurement can be
the electronic chassis.
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.

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.

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.

Stopping Brakes 36 and 39 Figure 17. The Stopping Brakes are solenoid
operated to stop the turntables whenever the machine is stopped.

Reel Idler 69, Figure 20. The Reel Idler is provided to smooth out any
takeup speed variations in the tape system.

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*

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

provides

constant hold-back

tension to the Tape Supply Turntable

27,

regardless of the amount of tape on the reel or its size.
When the Power "On-Off’ Switch 5406 is thrown, AC voltage is
applied to the Electronics Assembly and to the Capstan Motor. Therefore, the
Capstan is turning whenever the recorder is turned on, which makes possible the
fast start feature. When the tape is threaded the Safety Switch S501 is actuated
by the Takeup Tension Arm 62.
This energizes the DC Power Supply which in
turn provides power to operate the solenoids and relays.
START: When the Start Button S507 is pressed the Start Relay
1505 will be energized. It is held energized through its own contacts and the
normally closed Stop Button 5506.
The Start Relay, through appropriate inter
locks, performs the following functions:
1.

Energizes the Brake Solenoid 1502

thus releasing the Stopping Brakes

36 and 39.

Energizes the Forward Tilt Solenoid 1504
table Motor in the takeup position.

thus positioning the Turn

Applies AC power through the Takeup Torque Switch S503 to the Turn
table Motor.

Energizes the Capstan Solenoid 1501. which positions the Capstan Idler
50 to contact the tape and the Capstan.

The Capstan Solenoid when energized mechanically opens the Takeup
Torque Switch which inserts a resistor P503 in series with the Turntable Motor.
This allows the high starting torque to be reduced to a more suitable value for
operating conditions. Full power is utilized in Fast Forward or Rewind. The
recorder is now operating in the Play mode of operation with the tape moving at
the speed selected by the Speed Switch S502.
FAST FORWARD: If the Fast Forward Button 5504 is pressed and
the machine is in the Play mode of operation, the Fast Forward Relay 1506 will
be energized.
The relay performs the following functions:
1.

It interlocks the Rewind Relay 1507

so it can not be energized.

It breaks the circuit to the Capstan Solenoid.

When the Capstan Solenoid is de-energized the Takeup Torque Switch
closes, thus applying full power to the Turntable Motor. Since the Forward Solenoid
is still energized the machine is now operating in the Fast Forward mode of opera
tion. If the Rewind Button is pressed nothing will happen and it is necessary to re

SERIES 400, SECTION IV ?age a
11/1/52

turn to Stop before the mode of operation can again be changed. This interlocking
prevents scuffing the Turntable Motor Tire on the Brake Drums.
REWIND:
If the Rewind Button 5505 is pressed and the machine is
in the Play mode, the Rewind Relay 1507 will be energized.
The relay performs
the following functions:
1.

It interlocks the Fast Forward Relay 1506

It breaks the circuit to the Capstan Solenoid 1501
Solenoid 1504.

It energizes the Rewind Tilt Solenoid 1503
table Motor in the Rewind position.

It reverses the polarity on one winding of the Turntable Motor thus re
versing its direction.

so it can not be energized.
and the Forward Tilt

thus positioning the Turn

When the Capstan Solenoid is de-energized the Takeup Torque Switch
closes applying full power to the Turntable Motor. The machine is now operating
in the Rewind mode of operation.
If the Fast Forward Button is pressed nothing
will happen and it is necessary to return to Stop before the mode of operation can
again be changed.
Nhen the Stop Button is pressed during any mode of operation,
STOP:
the Start Relay will be de-energized.
This in turn breaks the circuits to the Rewind
and Fast Forward Relays and to the circuits described in the paragraph on START.
The Stopping Brakes will be applied to both turntables.
In addition it applies DC
power through a series resistor R502 to the condenser winding of the Turntable
Motor. This brakes the motor and prevents throwing a tape loop when the tape
direction is changed.

SERIES 400,

SECTION IV Eage 3
11/1/52

Ii.

HEAD ASSEMBLYY

The Head Housing is a die cast assembly which contains the three
heads used in the recording process.
The heads are respectively Erase,
Record and Playback as viewed from left to right when facing the machine.
The gate on the housing holds the Playback and Record Shield Covers and the
Tape-lifting Fingers.
The function of the Tape-lifting Fingers is to re
move the tape from the heads when the gate is open during Rewind or Fast
Forward position.
This reduces head wear considerably.
The tape may
leave a deposit on the heads if allowed to contact them at high speeds. Such
a deposit will seriously

be guarded
lf a deposit
a soft rag.
gate should

impair

against by always
is left, it may be
Never use metal
never be allowed

the performance

of the machine and should

opening the gate on Fast Forward or Rewind.
easily removed with carbon tetrachloride on
of any kind to touch the head surfaces.
The
to spring shut but should be closed gently.

The Model 400A, 402, and 404 Recorders incorporate half-track
Erase, Record, and Playback Heads. These heads function on the upper
half of the tape only. In order to use the remaining half of the tape the
reels must be turned over as explained in Section Ill-UI. The Head Assembly
of the Model 4OlA, 403 and 405 Recorders incorporate full track Erase,
Record, and Playback Heads.
This affords maximum performance from the
full width of the tape and permits complete interchangeability of tapes re
corded on the Models 300, 201 and other full track recorders.

SERIES 400 SECTION IV,

11/1/52

Page 4

in.

£LCfRONlC54sSEhrBLY:

The OlecTr.;nc
..sembiy of the Series 400 sccrder3
consists of
a Record
a
layback
mnlifier
and
an
En
e
4td
Bias
Oscillator
mtslifier,
on one chassis and a
ower Supply on a separate chas. is.
The Record
mçlifier is a four stage, high gain annrlifier that
feeds ëhe Record Head through the Noi0e Balance Circuit and Record Relay
F401.
The Record Belay is ener2ized by the Record Button :403
through
contacts of the Start Relay V.505 in the energized çosition and contacts of
the Fast Fcrwa-cd Relay L506 and the flewind P.elay 1<537 in dc-energized
*.ositions.
TherefDre,
tte taecord mode of operation can cnly be realized when
the tare is traveling at the
t:iy
henever the Fast Forward,
Rewind
‘,‘eeds.
or Aol. Euttons are &e ressed,
the Record Relay will be de-energized.
Three
ut
low
in
irnf.edctnca
cn be elected by the Input Transfer Switch 5401;
itt
edance microphone,
balanced brid;’e and unbaianced bridge.
Ehe Pecorci
mp
also
.irovides
se:arate
high
ft
quency
pre-emphasis
for
each
seed.
lifier
This change in ecualization is made by he qualization
5’sead Switch 340?
iccated on the ft rt 2aneI.
Ti-e Record C,sin :ontrol p409 is located on the
front ‘anel.
-

The
layback
mç.lifier Is a three staze amplifier which ,srovides a
plus 4 TTJ 60. ohm output at the Line C’u :onnec tot J404: .
The Flayback
equalization is the 5aoe mr the 7- /a and 13 inch :.eeds arsd is adjusted to
the .tandatd curve Fig.
Lv R43Z, located on too cf the Electronic chassis.
but is
The 3-3/4 inch
tayhack eoualiation
conforms to the curve in ‘i*.
ih’
not adjustable.
ia hack gain on single case portaUe models is ccntrolled
fiice
driver
by a
d screw
adjustment P437 which should nc be varied in the
normal opera Lion of the n-’achine,
On all other models the gain rosy be adjusted
the
Level
P437
located on the front panel. An output term
by
-layback
Control
ination is prvjdr
by thi line C-at Termination Switch S404.
--

3ionitoring ts provided by a VU Meter and a hone Jack which is
connected to the layback
I mplifier output.
The Meter and Outlut Switch
S405 provides four monitoring checks: Playback Level, Record Level,
Bias Current, Erase Current.
In the Erase position the VU meter is con
nected across the 7 ohm resistor P448 to read erase current,
in the Bias
osition the meter is connected across the adjustable 500 ohm resistor R450
to read bias current.
ic both the Record and Playback Level positions the
meter is connected across the Elayback
mlifier
o ttout.
In the Playback
position the Playback t mpiifier functions normally and the output of the tape
is monitored.
In the Record position the last two stages of the playback
P mplifier are disconnected from the first stage and bridged across the Record
Amplifier before 9re-emphasis
through the Record Level Meter Calibration
Control R413.
The Calibration Control is factory adjusted so that the de
sired record level will be effected on the tape.
The rase

and Bias oscillator

provides

the 100 KC erase

and bias

SERIES 400 SECTION IV, Page 5
11/1/52

frequency. It feeds the erase head through the Erase Trimmer C435
and the record head through the Record Bias Control R449. The Power
Supply provides the 6.3 Volt AC heater power, the 12. 6 Volt DC heater
power through a full wave selenium rectifier SR6OJ and the plate supply
through the 5Y3G Full Wave Rectifier V60l.

SERIES 400 SECTION IV,

1 i/i/sz

Page 6

SECTION V
ROUTINE

MAINTENANCE

CLEANING:

The Tape Transport Mechanism should at all timec be kept clears and dry.
The following parts should be inspected daily before the use of the recorder arid
cleaned with a soft rag and carbon tetrachloride or alcohol, if necessary Refer
to Figure 16.
1.

Head surfaces contacted by tape.

Capstan A.

Capstan Idler so.
Cleaning is required only if fregn
should adhere to the rubber.

Capstan Tape Guide 89.

II,

matter

Constant Tension Arm Tape Guide 45.

Reel Idler Pulley 71.

Takeup Tension Arm Tape Guide J.

HEAD DEMAGNETIZATION:

Occasionally the heads may become magnetized through an electrical fault
in the amplifiers, improper use of the machine, or by the heads coming in contact
with a magnetized object. This will result in an increase of noise level frorr 5 to
10 db. It is especially important that the heads be free of magnetization if you are
to realize the dynamic range of the machine. It should be remembered that any
phenomena that tends to put an unbalanced pulse through the Record Head will inag
netize it, Such pulses can appear in the form of signal or power line pulses.
If the following precautions

are observed,

no difficulty

should be experienced:

Do not remove any tube from the Record Amplifier while the machine
is recording.

Do not connect or disconnect input leads or head leads while recording.

Do not depress the Record Button until after depressing the Start
Button, In other words, allow the transient caused by switching the
motors and solenoids to die out before the record head is connected.
A one-half second pause is sufficient.

SERIES 400, SECTION Vt Page 1
l1/1/5

Do not saturate

the Record Amplifier with an abnormally high
signal,
input
Such a signal would he 10 db greater than tape sat
uration or approximately 30 db greattr than normal operating

level,
5.

Do not test continuity

in the heads with an ohm meter.

Should the heads become magnetized,
they can be demagneized
with an AMPEX Head IJernagnetizer Catalog #704. The following Demagneti
zation Procedure should be performed:
Bring the tip of the Derragneizer
in
direct contact or close proximity to the head core stack, Run the tip of the
Demagnetizer up and down the entire height of the core stack three or four
times, Remove the demagnetizer very slowly, allowing the AC field to die
off gradually.
Repeat this operation on Record and Playback Heads only, as
the Erase Head will demagnetize itself. In the event demagnetization
is not
effected, repeat the process several times.
IV,

LUBRICATION:

The following places require lubrication
ing upon the amount of usage of the machine:

once or twice a year depend

Capstan Drive Motor 24 and Turntable Motor 6.
recommend the followin lubr1cants for
The motor manufacturers
their respective motors;
Eastern Air Devices-Saccny
Vacuum Oil Company. S,A.E,20
Bodine Zlectric Comoany ‘Gulf Oil & Refining Comany-Gulfcrest
P
Standard Oil Co,of Indiari-Stanoil
#l8oi
Sacony Vacuum Oil Co.
argoyle D, I, E.
Light
If equivalent oils are to be used, ar epresentative of the oil corrpany thould be
contacted to ascertain that the equivalent is miscible with the lul ricants listed
-

above. Otherwise,

sludging may result.

requirer
Capstan Drive Motor, The Uop-’ Sleeve Bearing on this muto
lubrication.
Pry off the Capste.i Dust Cap 26 shown in Figur 16. T:e
oil hole on the motor is located near the outside edge of the cutout arid
in some cases tray be partially cbscured.
Lubricate with 10 drops of
the recommended lubricant,
preferahiy using an oil can with flexible
spout.

Turntable
4otcr,
The rec ord r may be equipped with different tyiI5
of turntable motors, If the tir tahle rrctor has oil cups o oiling heR
Raise c r rencve
requires 10 drops of the recor.rznded
lubricant.
Tape Transport Top Plate to C pose the oil holes. Refer o Section J
for access into the console ca net or portable case. If U e motor is
ubricatior i
supplied with ball bearings frio oil cups or oiling holes,
not required.

SERIES 400, SECTICN V, Page 2

11/1/52

Reel Idler Upper Bearing 72. Refer to Figure 20. Remove the Plug
Button 74 and lubricate with one drop of SAE 20 motor oil.

The following places have been lubricated at the factory with Dow-Corning
DC-44 Silicone Grease light consistency. No further lubrication should be
necessary unless the grease becomes contaminated with dirt in which case the
part should be cleaned and re-lubricated.
1.
2.
3.
4.
5.

Capstan Idler Arm Bushing 4,
Figure 19.
Constant Tension Arm Bushing 5, Figure 19,
Capstan Solenoid Eye Bolt 54, Figure 17.
Reel Idler Thrust Bearing 86, Figure 20.
Safety Switch Level Ssoi, Figure 17.

The Takeup Tension Arm Bushing 3, Figure 17, has been lubricated at
the factory with Dow-Corning DC-ZOO oil. No further lubrication should be neces
sary unless the oil becomes contaminated with dirt in which case the part should
be cleaned and re-lubricated.
If DC-ZOO oil is not available, SAE 20 motor oil
can be used,
The following places require no lubricationand
1.
2.
3.
4.

should be left dry:

Brake Shoe pivot on the Constant Tension Brake 47,
The armatures of all solenoids,
Brake Solenoid Link 13, Figure 18.
Tilt Solenoid Spade Bolts 14, Figure 18.

Figure 17.

V. BRAKE LINING:
Periodic inspection should be made of the Brake Linings on the Stopping
Brakes, 36 and 39, Constant Tension Brake 47 and the Hold Pack Brake 22,
as worn linings will result in damage to the surface of the Brake Drums. These
linings are made of high grade felt but they may require replacement after long
service. The linings are supplied by the factory cut to size. For ordering in
formation, see Parts List, Section IX.
The recommended method of applying Brake Lining is described below:
1.

Remove both Brake Drums 34 and 35 as described in Section VIII -4.

Remove old lining and scrape the shoe clean. It is not necessary to
remove the brakes to do this.

Spread a liberal amount of DuPont Household Cement or equivalent on
the brake shoe; excessive cement should be avoided as it will soak
through the Brake Lining.

SERIES 400, SECTION V, Page 3

11/1/52

Position the felt carefully so it lines up with the outside edges of the
shoe and allow at least 30 minutes for cement to dry.
CAUTION: Be sure that cement is not allowed to remain on working
surfaces.

Replace the Brake Drums and adjust the turntable and Brake Drum
height as described in Section VIII-4. A number of stops may be neces
sary to bring the stopping energy of the brakes up to normal, Sanding
the Brake Drums as described in Section VIII-Z will hasten this pro
cess. Do not touch the surface of the Brake Drum after sanding.

In an emergency any good quality ioO% wool felt may be cut to
size and used as linings. They should, however, be replaced as soon as poss
ible with factory linings. If a felt containing nylon should be used, a brown
residue will be deposited on the drums. This should be removed with sand
paper as explained in Section VIII-Z when factory linings are applied.

SERIES 400, SECTION V, Page 4
11/1/52

SECTiON VI

ELECTRONIC ALiGNMENT

Alignment is the necessary adjustments required to have the Electric
Assembly of the tape recorder perform properly.
A machine "out of alignment"
may be characterized by poor frequency response, high noise, low output, or
high distortion.
It should not be necessary to align the recorder when it comes
to you from the factory.
The procedures described on the following pages have
been performed at the factor prior to shipment. Further adjustments are not
required except as found necessary in routine maintenance.
Alignment consists of the following steps:

Head Alignment
ii Playback Circuit Alignment
ILl Record Circuit Alignment
1. Bias Adjustment
2. Record Level Meter Calibration
3. Record Equalization
A. 15 inch per second
B. 7-1/2 inch per second
4.
Noise Balance
IV Erase Adjustment
lt
Standard Alignment Tape #4494 is available for alignment purposes.
is recorded at 15 inches per second, 10 db below 15 inch operating level. It
contains a 15 XC tone for head azimuth check, a reference tone for level adjust
ment, and a series of tones for a playback response check. IMPORTANT: Before
playing the standard tape, demagnetize the heads with the AMPEX Head Demag
netizer, Catalog #704. Magnetized heads will cause a partial erasure of the high
frequencies on the standard tape.

MODEL 400A, 401A, 402 & 403,SECTION Vi, Page 1
11/1/52

HEAD ALIGNMENT:

The high frequency response of the recorder depends on the correct
head alignment.
If tapes are to be interchangeable from one machine to another
the heads of all machines must have the same azimuth setting, This is accom
Tape Ca talo’g #94
plished by using a Stad
, for aligning the heads
of all machines.
Head alignment is independent of tape speed; however, it is rec
ommended that the heads be aligned at 15 inches per second since the standard tape
is recorded at this speed.
Remove the top cover from the Head Housing by removing the two
screws from the top and pulling cover gently back and up. Looking at the Head
Housing from the front the three heads from left to right are: Erase, Record, and
Playback.
The azimuth angle of the erase head is not adjustable.
The Record and Playback Heads should be aligned only after reading
and fully understanding

the procedure

under PLAYBACK AND RECORD CIRCUIT

Al IGNMENT.
The actual physical alignment of the Record and Playback Heads con
sists of placing a 1/4" spintite socket wrench on the left hand elastic stop nut in
each head and adjusting back and forth until the proper azimuth angle is arrived at.
First adjust the Playback Head azimuth by playing the standard tape
at 15 inches per second and adjusting the stop nut for the maximum output of the
15 kc tone first
tone that appears on the standard tape.
The Record Head azimuth is then aligned with the Playback Head by
recording a 15, 000 cycle signal from an audio oscillator on a blank tape and ad
justing the record stop nut for maximum playback output.

MODELS 400A, 4014,402 & 403, SECTION Vi, °age 2

i i/i/sz

II.

ALIGNMENT
1.

OF PLAYBACK CIRCUiT:

Refer to Figure

Position the Electronic Assembly so that adjustments
the controls located on the top of the chassis.

2. Set the Tape Speed Switch S502
to 15 inches per second.

1 or 2.
can be made on

and Equalization Speed Switch S402

3. Set the meter and Output switch S405 to the PLAYBACK-LEVEL p0S ition.
4. Terminate the line output either by means of the Line Out Termination
Switch 5404 or by external termination of 600 ohms.
5. Connect an amplifier and loudspeaker to the output or plug in a pair
of high impedance head phones so that voice announcements on the
standard tape can be heard.
6. Thread the standard tape on the machine and set the tape in motion in
the Play mode of operation.
7. Adjust the playback head azimuth as discussed under HEAD ALIGNMENT.
8.

The second tone on the standard tape is used to adjust the playback gain.
Adjust the Playback

Level Control

R437

for a reading of -10 on the VU

meter. On the Model 400A and 401A, R437 is a screw driver control,
which should be locked after this adjustment.
On the Model 402 and 403,
R437 is a front panel control. IMPORTANT:
Retain this setting until
the Record Level Meter Calibration has been adjusted.
9. PLAYBACK EQUALIZATiON: The Playback Amplifier is factory equal
ized by means of the High Frequency Playback Equalizer R432 Figure

11 or 14, in accordance with the standard voltage curve shown in Figure
8. The recommended method for adjusting the Playback Amplifier re
sponse is to connect an audio oscillator and vacuum tube voltmeter to the
Playback Amplifier as shown in Figure 8. Adjust the Playback Equal
izer R432 to give the frequency response of the standard 50 micro
second curve. Deviation from this curve is not recommended.
Check
the playback level setting with a standard tape if any change is made in
the Equalizer.
The above will properly align the playback

circuit for operation at both

speeds.
The 15 inch standard tape will play back within / 2 db to 15, 000 cycles when
the Playback Amplifier is adjusted to the standard curvi.
Failure for the standard
tape to play back vithin these tolerances after the Playback Amplifier has been aligned
indicates one of the following:
a. Trouble in the Head Assembly such as worn heads.
b. A faulty Standard Tape which has been partially erased af
high frequencies by passing over magnetized heads, etc.
MODEL 400A, 401A, 402 & 403, SECTION Vi, Page 3

ii/i/sz

An overall frequency response check will isolate the trouble. Good
overall response indicates a faulty Standard Tape. Poor Overall response
indicates one of the following:
a.

b.
c.

Faulty Heads
Tape deficiency
Record or Playback Amplifier improperly equalized.
incorrect bias

Alignment of the Record Circuits as described in the next sub-section
will further aid in isolating trouble.
Iii, ALIGNMENT OF THE RECORD CIRCUITS: Refer to Figure 1 or 2.
The 7-i/a inch and 15 inch per second record alingment should not
be attempted until the playback is properly aligned.
Perform the following in order indicated:
1.

Bias Adjustment: The record bias current is factory adjusted for opti
mum overall response and low frequency distortion.
However, the
optimum value of bias current will vary with different types of tape.
The record equalization characteristics on this equipment have been
determined for peak bias at 1000 cycles at 15 inch per second tape
speed, Peak bias means that the bias current is adjusted so that the
1000 cycle signal is recorded at its maximum level. Adjust the bias
in the following manner:
a.

Thread a blank tape on the machine.

Terminate the playback am

plifier as in Playback Alignment. Set the Speed Switches S402 and S502
to 15" per second. Set the meter and Output Switch S405 to the Playback
Level position.
b. Connect an audio oscillator to the Input Connector J4OIS,
set the
input Transfer Switch S401 for unbalanced bridging input and adjust
the frequency to 1000 cycles per second.
c.

Start the machine

d. Adjust the Record
imately 0 zero.

in the record

mode of operation.

Level Control R409

so the meter

reads

approx

e. Adjust Bias Control R449 for maximum playback level of 1000
cycle tone while recording the playing back simultaneously.
it is de
sirable to be within 1/2 db of the maximum efficiency point in order to
achieve wide frequency range recording at 7-1/2" per second,
f. The Bias Meter Calibration is adjusted as follows: After the bias
is adjusted, meter the bias in the normal fashion and adjust the Meter
Shunt R450 for 0 zero
reading on the VU scale of the meter.
MODEL 400A,

401A, 402 & 403, SECTION Vi, Page 4

ii/i/sz

Record Level Meter Calibration: The Record Level Meter Calibration
Control R41 3, Figure 11 or 14, is adjusted so that the program level
as read on the VU meter is the same as monitored from the Dlayback
Head or the incoming line. This is accomplished by recording a 250
cycle tone or program in the absence of an audio oscillator at 0
zero on the VU meter with the Meter and Output Switch in the PLAY
BACK-LEVEL position.
Then switch the Meter and Output Switch to
the RECORD-LEVEL position and adjust the Record Level Meter Cal
ibration Control for 0 zero on the VU meter.
IMPORTANT:
The
Playback Level Control R437 must be set as described in Playback
Alignment before making this adjustment.

Record Equalization:
The 7-1/2 inch and 15 inch record equalization
circuits have been factory adjusted to the curves shown in Figure 9.
These curves have been found to produce flat overall response, when
recording on Minnesota Mining and Manufacturing Company type ill
tape, construction SR BA, or later.
Other tapes may require resetting
or equalization and Bias Control.
Badly worn tapes may produce loss
in high frequency response at the i-i/a inch speed and should not be
used.

The adjustment

procedure

for flat overall

15 inch Record Equalization

Set up the

Start the machine

response

on any tape is as follows:

Adjustment

machine as described
in the record

under

Bias Adjustment.

mode of operation

at the 15 inch tape

speed.
3. Reset the audio oscillator to 15,000 cycles and adjust the record head
azimuth as described under Head Alignment. NOTE: All frequency checks
at the 15 inch tape speed should be made 10 db below operating level
-10 on the VU meter monitoring record to avoid saturation effects
On the Model 402 and 403 the
caused by the high frequency preemphasis.
front panel Playback Level Control may be set for increased gain so the
following adjustments can be made in a more sensitive meter range.
4. Reset oscillator to 250 cycles and adjust the Record Level Control
R409 so the VU Meter monitoring playback reads -10.

5. Reset oscillator to 8,000 cycles and adjust the 15 inch Record Equal
izer so the VU meter monitoring playback reads -10.
6.

Frequency response should be

2 db 30 to 15, 000 cycles.

MODEL 400P, 4OlA, 402 & 403, SECTION Vi, Page 5
11/1/52

7-1/a Inch Record Equalization Adjustment
1. With the machine set up as above, change the Speed Switches
5402 and 5502 to the 7-l/z inch position.
2. Reset oscillator to 250 cycles and adjust the Record Level Control
so the VU meter monitoring playback reads -10.
3.
Reset oscillator to 8,000 cycles and adjust the 7-1/2 inch Record
Equalizer so the VU meter monitoring playback reads -10.
4. Frequency response should be p1 2 db from 40 to 8,000 cycles. Due
to tape saturation, frequency checks can not be made at this level
beyond 8,000 cycles. To run response checks beyond 8,000 cycles
refer to Overall Performance Check, Section Ii-Xi.

Noise Balance: A noise balance control is provided to eliminate excessive
low frequency noise and null second harmonic distortion.
The noise bal
ance should not be touched unless all heads have been thoroughly demag
netized with an AMPEX Head Demagnetizer or equivalent See Section V.
If noise of a crackling nature is still found to exist in the output of the
connect a 1 MFD condenser across the output of the machine
machine,
and adjust the Noise Balance Control R424, Figure 11 or 14, for mini
mum record noise as read on a sensitive meter or heard in a loudspeaker
connected to the machine output through a power amplifier.

IV. ERASE ADJUSTMENT: The erase current is factory adjusted and no
further adjustment should be necessary unless the Erase Head is replaced.
Should this happen, the following procedure must be followed:
a.
b.
c.
d.

Set the Meter and Output Switch S405 in the Erase
position and press the Record Button S403.
Back off the Erase Trimmer C435, Figure 11 or 14,
to a minimum capacity clockwise direction.
Increase the capacity until the meter reads 0 zero.
Check the bias current after making this adjustment
since a ch ange in erase current will produce a change
in bias current.

MODEL 400A, 401A, 402 & 403, SECTION Vi, Page 6
11/1/52

SECTION
MECHNICP

This

VII

SERVICE

section is a guide to locating

GUIDE

irregularities

in the operation

of the Tape Transport Mechanism of this r e cc r d c r. Sources of irregularities
in the Electronic Assembly have not been included in this book since standard elec
tronic maintenance techniques apply. This section is divided into the following
four parts:

Failure to Start.

II.

Irregularities

in Play Mode.

III.

Irregularities

in Rewind or Fast Forward Mode.

IV.

Miscellaneous.

To use this section first decide into which of the above groups the
trouble lies. Check the list of symptoms in the group to further localize the
trouble. Investigate each of the parts listed under the appropriate symptoms
to detect incorrect adjustments or possible defects.
Refer to Section VIII for
The numbers in parentheses are
the correct mechanical adjustment procedures.
reference numbers which refer to the figures in the rear of the book.
I.

FAILURE TO START.

Capstan

Drive Motor inoperative

at one or both speeds.

Check the following:

AC Power to the recorder.
a.

Control Circuit

Fuse

F402.

Power Cable from Mechanical Assembly to Elec
tronic Assembly.

d.
e.

Capstan Drive Motor Connector J502P.
Speed Change Switch S502.
Jumpers from 1 to 2 and 3 to 4 on 60 Cycle Ampli
fier Terminal Strip TSSO1.
NOTE: Machines
equipped for Trplug in" of 60 Cycle Amplifier must
have properly jumpered Dummy Plug catalog #567
inserted in the 60 Cycle Amplifier Connector J703S
in absence of the 60 Cycle Amplifier.

Head cables interfering

with Drive Motor Flywheel.

SERIES

4C0, SECTION

11-1- 52

VII Page 1

Capstan Drive Motor 24
or shorted winding.

Drive Motor Capacitor 0508.

for binding of shaft,

open

Machine does not operate or trips itself off when St?rt Button
is depressed.
NOTE:
Before making these checks read Sec
tion Ill-Il on Tape Threading.
Check the following:
1.

Switches
a.

Safety Switch 5501.

VIII- 10.
Stop Button 3506.

c.
d.

See Section

For adjustment,

see

Supply.

Selenium Rectifier SR5Ol.
Resistor RSOl.
Electrolytic Condenser C50Z.

Relays.
a.
b.
c.

Start Button 5507.
Takeup Torque Switch S503.
Section VIIl-7.

DC Relay and Solenoid Power
a.
b.
c.

For adjustment,

Start Relay 1505.
Rewind Relay 1507.
Fast Forward Relay 1506.

Solenoids.
a.
b.
c.

Capstan Solenoid 1501.
For adjustment,
see
Section VIII-l.
Forward Tilt Solenoid 1504.
For adjustment,
see
Section VIII-8.
Brake Solenoid K50Z.
For adjustment,
see Section
VIII-2.

Play Resistor

Jumper from Terminal 7 to 8 on the Remote Control Ter
minal Strip T3502.
NOTE: Machines equipped for plug
in" of Remote Control must have the properly jumpe red
Dummy Plug catalog #3461 inserted in the Remote Con
trol Connector J7OIS in absence of a Remote Control
System.

SERIES 400, SECTION VII Page 2
11/1/52

R503 for an open circuit.

II.

Binding of Turntable

Iotor

Cables interfering

Counterbalance Spring 65 in rack mount position
‘-‘ortable machines.
See Section lI-Vu.

Unsatisfactory

and 19.

with the Brake Drums 34

IRRYGUT ARITIES IN LAY
P.

ivots

starting

MODE.
in lay

Mode.

Check the followng:

Takeup Torque Switch S303 for adjustment.
opening too early.
See Section VIII-7.

and 35.

May be

Binding of Turntable Motor I ivots 18 and 19 may
cause late engagement

of Turntable

Motor.

Solenoids 1533 and 1504 if misadjusted can cause
sliipage or late engagement of Turntable Motor B50a.
See Section VIII-8.

Insufficient takeup torque in the P’ay mode.

Tilt

a.
-

Play Resistor R503

See Section VIII-9.

with Takeup Brake Drum 35.

Cable interfering

Stopping Brakes

set too high.

and 39.

Dragging

brakes.

Brake Clearance adjustment too great so that brakes
are slow in releasing.
See Section VIII-2.

Capstan Idler pressure adjustment.

Takeup Tension

Constant Tension

Arm 62

See Section VIII-1.

sluggish.

Brake 47

adjustment.

See Section

VIII-3.

Low relay and solenoid

supply voltage which would slow

down the relay and solenoid operation time.
B.

High flutter. The low flutter specifications on this equipment
are rigidly met. Any noticeable flutter can probably be traced
to one of the following:

SERIES 400 ,

SECTION VII ?age 3
11/1/52

Cable dragging on
Takeup Brake Drum 35.
Reel Idler Flywheel 78.
Capstan Drive iv4otor Flywheel.

a.
b.
c.

2. Foreign material

such as deposit left by the tape on

a. Capstan A, Figure 16.
b. Reel Idler Pulley 71, Figure ZO.
c. Capstan Idler 50, Figure 16.
.d. Turntable Motor Tire 7, Figure 19.
e. Takeup Brake Drum 35, Figure 18.
f. Head Surfaces.
Figure 16.
g. Tape Guides 45, 89, and j,
-

3. Excessive

drag in Reel Idler
turns freely, it is not likely
should not be disassembled.
freely or is noisy, check the

a.
b.

69. If Reel Idler is quiet and
to contribute to the flutter and
If the Reel Idler will not turn
following. Refer tp Figure 20.

Reel Idler Adjustment. See Section VIII-6.
Top Bearing 72 insufficiently lubricated. See Section
V-IV.

c.
d.

Thrust Bearing 86 worn.
Foreign material in Lower Bearing 75.
-

4. Capstan Drive Motor 24.
a.

Top Bearing insufficiently lubricated. Do not over-lubricate.
See Section V-IV.
Bent Capstan A.
Motor windings partiaUy open or shorted.
-

b.
-

5. Capstan Idler 50 defective.

T.akeup Torque Switch 5503 not opening.
for adjustment.

Bad Tape worn,

8..

Recorder subjected to excessive external vibration.

See Section VIII-7

ragged, or of poor quality.

Recorder fails to shut off when tape runs out. Check the following:

SERIES 400,

SECTION VII, Page
11/1/52

Takeup Tension Arm 62
a.
b.
c.

sluggish due to:

Dirt between Takeup Tension Arm 62 and Bushing 3.
Takeup Tension Arm Return Spring -64 ‘diiconne-c-ted
or broken.
Safety Switch S501 inoperative or out of adjustment.
See Section VUI-lO.
Safety Switch Condenser C501 shorted.
-

d.
D.

III.

Instability of Tape on Capstan.
1.

Oil on Capstan A or Capstan Idler 50.

Takeup Torque Switch S503 not opening causing excessive
takeup tension. See Section VIII-7 for adjustment.

Capstan Idler Pressure

Adjustment.

Capstan Solenoid 1501

not seating.

Constant Tension Brake Spring 49 disconnected or broken.

Constant Tension Arm 44 binding in Bushing 5.

Bad Tape stretched

See Section VuIl-l.

edges or bad splices.

Recorder goes into Fast Forward Mode when Start Button is
depressed.
Check the following:
1.

Capstan Idler Pressure

Adjustment.

Capstan Solenoid 1501

for defect.

IRREGULARITIES
A.

Check the following:

See Section VIII-1.

IN FAST FORWARD OR REWIND MODE.

Recorder stops when Fast Forward or Rewind Buttons are
depressed.
Check the following:
1.

Fast Forward Button S504.

Rewind Button S505.

Fast Forward Relay 1506.

Rewind Relay 1507.

Rewind Tilt Solenoid 1503.
VIII-8.

For adjustment,

see Section

SERIES 400, SECTION VII Page 5
11-1 -52

________
B.

Recorder sluggish in Fast Forward or Rewind. Check
the following:
--

1. Takeup Torque Switch S503 stays open.
Section VIII-7 for adjustment.

See

2. Cable Dragging on either Brake Drum 34 or 35.
3. Stopping Brakes 3o and 39.
-

a. Dragging Brakes.
b. Brake Solenoid 1502
Section VIII-2,

lone or inoperative.

3cc

4. Turntable Motor 6 for insufficient lub’ication.
Section V-IV.
5. Slippage between Turntable Motor Tire 7
Drums 34 or 35.

and Brace

a. Tilt Solenoid 1503 and K504. For Ec’ustrflent ee
*
Section VIII-8.
b. Oil on Brake Drums 34 or 35 or Tur table AoL.
Tire 7.
c. Binding of Turntable Motor Pivots 13 and 19;.
IV, MISCELLANEOUS IRUEGULARITIES
tape.

A. Braking too severe causing breaking or delorrnatior
*

Binding of Brake P rm Pivot, Figure
See Section V1II-2A for adjustment.

Brake Solenoid Stop 67 deformed.

17 r oint G

See Si- -tion

ILl.

B. Braking insufficient causing tape slack to be throwi w en the
machine is stopped.
1.

Brake Drum contaminated with oil or gr a
Section VIIIZF, for cleaning procedure

e. Se

Braking rotationally uneven.
1.

Brake Drum contaminated with oil or gr-ea:
Section VIll-2F for cleaning procedure.

3LRIES 400, SZCTION V1I,

I 1/1/52

Page 6

See

SECTION VIII
MECHANICAL

ADJUSTMENTS

The mechanical adjustments described below have been made at the factory
prior to shipment of the machine. No further adjustments should be necessary ex
cept as required by routine maintenance if irregularities should occur in the oper
ation of the machine.
CAUTION: When returning the Mechanical Assembly to the
portable case after making adjustments, make sure the cables do not interfere with
moving parts.
-

The following mechanical adjustments are described:
1.

Capstan Idler Pressure Adjustment

Adjustment of Braking System.

Constant Tension Brake Adjustment.

Turntable and Brake Drum Height.

Rewind Holdback Brake Adjustment.

Reel Idler Adjustment.

Takeup Torque Switch Adjustment.

Forward and Rewind Tilt Solenoids Adjustment

Play Takeup Torque Adjustment.

10.

Safety Switch Adjustment.

The numbers in the parentheses
figures in the rear of the book.
1.

are reference

numbers and refer to the

Capstan Idler Pressure Adjustment.
The Capstan Idler 50 is positioned to contact the Capstan A
by the Capstan Solenoid 1501. The pressure is adjusted by a lock
See Point B, Figure 17.
nut on the Capstan Solenoid Eye Bolt 54.
Tightening this nut causes greater pressure until a point is reached
where the Capstan Solenoid will not seat or bottom. At this point
the pressure is very low and the nut must be backed off. Excessive
pressure should also be avoided as it throws unnecessary load on
the Upper Drive Motor Bearing.

SERIES 400, SECTION VIII, Page 1
11/1/52

The recommended method for adjusting this solenoid is to take up on
the adjusting nut B until the Capstan Idler 50 just touches the Capstan
A when the Capstan Solenoid 1501 isbottomed. Then turn the nut an
additional z-i/z turns. CAUTION: Make sure the solenoid will bottom
after this adjustment. If not, the solenoid or linkage is defective. When
adjusted as above, sufficient drive force exists under all operating con
ditions to prevent tape slippage unless the Capstan Idler should become
contaminated with oil or foreign matter.
2.

Adjustment of Braking System.
The braking system in this machine is designed to retain its adjust
ments over extremely long periods of time. The following explanation
and adjustment information will be of value if it becomes necessary to
replace parts in the braking system or to clean the Brake Drums.
It is necessary that each reel have considerably more braking
force in one direction than the other. This is often referred to as
"Brake Differential". The braking force can be easily measured by
attaching a piece of string about 30 inches long to the hub of the NARTB
reel, the other end being attached to a spring scale 0 to 64 oz. preferred
Wind the string around the hub and pull the scale evenly. Take the read
ing only while the turntable shaft is in steady motion as the force re
quired to overcome the static friction of the system will be considerably
higher than that of the actual braking force. Most scales when operated
in the horizontal plane will show a zero setting different from the norm
al scale zero. The scale readings should be corrected accordingly. In
measuring forces on the Tape Supply Reel, hold the Constant Tension
Arm 44 firmly in the direction of the Capstan A as this is also a
brake and should not be included in the reading of Tape Supply braking
force.
The following braking forces are optimum:
Tape Supply Reel with Constant Tension Arm held "off"
Clockwise
3 oz. p1 1 oz.
Counterclockwise
18 oz. 7 2 oz.
Takeup Reel
Clockwise
Counterclockwise

28 oz.
8 oz.

/3
71

oz.
oz.

The following adjustments should be performed in the sequence indicated
if a part in the braking system is replaced.

SERIES 400, SECTION VIII, Page 2
11/1/52

Rrake A rm °ivoL
I he

if rake Arm Pivots

art adjusted

by a lork nut,

.U
-

so the Brake Arms 3c and 39 will siide freely n t *tr s:cs.
Jonsiderable vertical play can be tolerated at the end of ‘-e Brake
"rm. Tighten the lock nut down until it bottoms on the Arm,
Then back off i/s turn or more as required to eliminate any drag
or bind in the Brake Arm. An excessivley high brake differential
can us-4aliy be traced to this adjustment.
T..-e Su’nly Brake Shoe Clearance.
ane or fasten the [akeup Tension Arm 62 in the onerating pa
siUo,. ae
the "fechanical Assembly in a position so that the
Brake ..oes -anbe observed and start the recorder.
2,

Loosen ftc --c sc -ews that secure the Brake Solenoid 1502 to
ftc ioienoid --ounting Bracket. See Figure 18, Point C. Slide
L-e Sclenod

tn the required

direction

to establish

a cle arance

i/o4 to 1/ 32 inch between the P-rake Lining and the Brake Drum.
Tighten the Solenoid screws securely when the adjustment is

correct.

As Erake Lirnngs wear the clearance

slightly,

but this will not affect the performance

will increase

of the machine.

TakeuD Brake Shoe Clearance,
The Takeup Brake Clearance is adjusted by the Brake Roe’ Adjust
ing Clamo 43 to provide a clearance f 1/64 to 1/32 inch between
the Brake Lining and the Brake Drum when the Brakes are released
Brake Solenoid energized. Tighten the set screw 43 securely.
Ihe btake Rod Retaining Ring 100 is placed on the Brake Rod to
prevent the Rod being detached from the Brake. Be sure there is
at least 5/32 inch clearance between this Ring and the Brake Arm.

F rake Pivot Spring

Position.

Three holes are located in each Brake Arm to anchor the Brake Pivot
Spring 98. Anchoring this spring in the middle hole will normally
provide the optimum braking forces previously listed. If this is not the
case, move the spring to the hole required to produce the correct
braking forces. If the forces should be considerably lower than the
optimum values and do not change when the Pivot Spring is moved,
contamination ,of the Brake Drums or Brake Linings is indicated.
Clean the Drums as described on the next page under F.

SERIES 400, SECTION VIII, Pae 3
1 i/i/sz

Brake Solenoid Stop 67.
The clearance between the end of the Brake Solenoid plunger
and the Stop shouii be 3/16 inch when the plunger is bottomed.
Adjustment is accomplished by beraif.g the Stop Bracket 67
to provide the aforementioned clearance. Be sure that the Stop
catches the plunger of theSolenoid but does not drag on the
linkage. Improper adjustment will result in excess braking
differential.

Prake Drum Cleaning Procedure.
In servicing the recorder the :rake Drums 34 and 35
may become contaminated by handling, or by oil or grease
getting on them. evlild cases of contamination will soon dis
appear through the normal operation of the machine, The Brake
Shoe may chatter until the contamination wears off. In such cases
cleaning is not necessary if the recorder handles the tape satis
factorily. If operation is unsatisfarory,
clean both brake drums
as follows:
1.
2.

Hold a piece of #320 wet-or-dry sandpaper firmly against
the braking surf-ace of the Brake Drum.
Rotate the Brake Drum four or five revolutions by turning
the turntable. It is not necessary to release the brakes for
this operation. Shift the sandpaper to a clean spot frequently
to avoid contamination of the paper.
If this does not cure the condition, the Brake Linings have
become contaminated and should be replaced. See Section V-V.

Constant Tension Brake Adjustment:
The Constant Tension Brake 47 is adjusted for minimum clearance be
tween the Constant Tension Brake Lining 48 and the Tape Supply Brake
Drum 34 when the Brake is released. T-.e adjustment is made by the
P-rake Stop, a set screw and lock nut shown in Figure 17, Point D. As the
Brake Lining wears, readjustment of the Stop is desirable.
a.
-

b.
c.

Loosen the lock nut. -Vith both the Stopping Brakes and Constant
Tension Brakes released, screw in the set screw until a slight
drag is noticed on the Brake Drum.
Back off the set screw until the drag just disappears.
Tighten the lock nut and re-check for drag. The drum should
spin freely with both Brakes reeased, The Constant Tension Arm
44 should have a very short travel
approximately 1/8 inch at
the end of the arm.
-

SERIiS 400, SECTION VIII, Page 4
ll/1/5?

NOTE: It is important that the force applied to the Constant 1 ensio;
Brake 47 by the Constant Tension Brake Soring 4
be in the corr.ct
direction; otherwise the Brake I wing may wear anevenly and tEe Brake
may oscillate or chatter causing high flutter, This should not be con
fused with the normal motion of the arm to compensate for dtscontinui
ties in the reels. If the Spring is attached to the Takeup Torque Switch
5503 with a solder lug, this lug should be positioned at right angles
to the edge of the Switch. See Figure 17,
4.

Turntable and Brake Drum Height.
The height of both the Turntables 27 or 28 and their respective
Brake Drums 34 and 35 must be carefully adjusted whenever they are
removed. Their removal should be avoided unless absolutely necessary.
When removing Brake Drums, first loosen the Turntable Set Screws,
Figure 17, Point E. Loosen the Brake Drum set screws, Figure 13,
Point F, backing them off far enough to prevent galling of the Turntable
Shaft. Lift the Turntable from the Brake Drum, Carefully mark the
Brake Drums so they will be returned to the same shafts. If it is neces
sary to replace either a Brake Drum or a Turntable, they must be re
placed as a pair.
Hhen replacing Brake Drums, place a little oil on the Turntable
Shaft and work the Drum on the shaft, Adjust the Turntable Height so
that the top surface of the Turntable Pad 30 Figure 19, is 0. 635 inches
from the surface of the Mechanical top plate. Be sure to tighten the set
screws.
After the correct Turntable Height is set, adjust the Brake Drum
height so that the lower spoke side of the Brake Drum lines up with the
Turntable Motor Tire. Approximately 1/32 inch of the Drum should
show below the tire. Tighten the set screws, being sure that they line
u- with the flats on the Turntable Shaft. Clean the braking surface of
the Brake Drum thoroughly as explained in Section VIII-ZF as it will
become contaminated by handling.

Rewind Holdback Brake Adjustment.
The Rewind l-loldback Brake 22 is adjusted to give a slight tension
during rewind. It should only require adjustment if it is accidentally
bent, With the Takeup Brake Drum 35 removed, the lining of the Holdback Brake should assume a position 2-5/8 inches from the edge of the
Takeup Turntable Shaft.

Reel Idler Adjustment.
Should the Reel Idler 69 be removed, it must be reassembled as
shown in Figure 20. Vertical play in the Reel Idler Pulley and Shaft
Assembly 71 is provided by the Reel Idler Thrust Bearing 86.
SERIES 400,

SECTION VIII, Page 5

11/1/52

Assemble the Re el Idler Housing 70 to the Mechanical Top Plate
as shown in Figure 20.
b. Place a spacer 1/16 inch thick between the top of the Reel Idler
Pulley 71 and the Reel Idler Housing
c. Make sure that the Reel Idler -aIi Bea --g is in place. Si e the
Peel Idler Spacer 84 on the shaft. HoL3rg the Reel Idler Ely
heel 78 by the Sauare Hub, oottom it against the Spacer and
fall Bearing. Then tighten the set scre
,
-’>’

P1=1
j.0OS

A POWEl JT
"ReaP

‘1

40Cr,

-11

METER SOUTPUT
SWITCH

45117

IOO

3,5v

*444

*5%

CAPACITiES

C430

IIIJj
H>’

*5%

I’
C 439
.0002
500W

IO0-

ERASE
TRIMMER

ELECTRONICS
MODEL - 400A

AMPEW ELECTRIC cORPORATION
RED*000 CITY, CALIPNIA

StAG

CIS.
.001

7402
*445

M1CROPAPACS

‘t

t*A

C433

395W

CONTROL

4711

2-F015 50 S SO 014115. IACPOPHONE
SEE IHS?ILL AVON
hALL VOLTAGES MEAMIO WITH 20,000 OHMS PER VOLT "ICIER WITH
II? V AC UNC VOLTAIC ALL PlACING EXCEPT V409 OSCILATOP
VOLTAGES TAKEN WITH P404 0E-EHERGIZEO.

7403

-zsv

-25w

*450
5000
‘AlA
SIAS CALISPATION

P452

1123

.44075
I TOW PLATE POWER

11401

P442
22001

-an

TES:

hALL

C 427
25
25W

*440
11116.

V409

fP_r0..0.1___

‘S

47P

+355W

lollilTItiol

rf1’

I$HORTNG

L’f01x18 I+I&I

444:
I ItO

*439

PLAY0AN
LEVEL

I-

S
S

27OOs

"on-

-H
¶

I
IV SAC
EQ UA L IlL

Itt

2000

P433

TRANSFC*MEP
MUST

SMPEOAIICE

JUSTEO

CONNECTiONS‘OUTPUT

IMPIDAN:E

500 ‘*400
335

OHMS
OhMS

CONNECT
CONNECT

TO
TO

I S 4,
I 5 5*

JOIN
JOIN

3 10 4
S TO 4

20045250
1251.150
50

01111$
OHMS
OHMS

CONNECT
CONNECT
CONNECT

TO
TO
TO

255,
44,
2*4.

JOIN
R
JOIlI

3 TO 4
I TO354’TO6
2 TOSS 4305

_______________
___________ ________I
___________

TPANSFEP
6401 SWITCH

IIUT
MIC
*401

SAL

NOTE -1

SEE

v4OI
125.4?

TSOI

____________
_____-

75’,

*442

V402
125.47

1526

+I203j

P400
*40

p407

4O3

1%
-

330N

-If411
OS
400+

SWIICH

£40

T I

4
‘Ti,o+

400+

2211
7W
-

N427400G

lOON

00I?1p

#419
4/OR

‘olt:

‘ISV

P404

*406.
1200 *
A

4711

25 - =
256
-

‘

£40?
000I

*411

£401
25
400

P413
lOOK

I
V405

47111

±5%

I’s" ¶

25V

£410
ID I

400W

*416
2200’>

33011

V4061
fl,?
I’ELFCII

£414

s
6454
P428
MEG

*IMEG

1%
I, V

____

I
I

PLAYBACK HEAO

C4SBI,
-013

235

I’"l
"

C4JL

11%
-

200+

P434

0416 4

t5%T

200W

P437

P435
44 0

*456
630K

04SF’7

.....V

4340V

LINE
TERMINATION
SWITCH 5404

P461
2211

PHONES

403’

_,,,j
-

AMPLIFIER

4330+

+406
6C5/6J5

4003’

LINE OJTI

-$t

C437

£41
25
25i

ISlE
OW
£445
25

ION

IF
I’
£423

V407
2 3j7

P426

4445

C424
.0025

I"J,

*430
2200

]

MEG
PLAyBACK 4553
LEVEL
*

400V

20Mh

4220+

005

L401

ts-I t

40I

C400"F

T41

#4,9
2200

401SF
B4.ANCE

IAn

25+

470+

AflAAAU

ISO’,

25
4444

1503

*420
470
t153

*41?

‘39K

*433

003/ V*IS0

C409

H ECL30Lf

1C404
+

‘P415

EOUALI2EPS

*405
N 410
2200-’>.

:t1201
-

________

+421

t70v

400

V4O4
6C5/6J5

lOOK

INPUT

__-

£412

V403
25.47

±5%

_____
__

P432

-‘-F’ I 1.

C 421
4
450W

L_02

rn-A
600W

P444
I MEO

*455
470’>
.5%

*434
2700’>

412W

C427
25

1*-

PL At S AC N
tOO AL I? E

P442
2200’>

M 40’

3600’>
63W
AC
Xxv

+ 1%

263
DC

‘I

±4
I

20001

C OP TAC T SI

HHf

C429 I
_i.P457
20

92iL1::,
I23!

IA
SLO’SLO

: ‘-f-fl
:
I

U00

FsI

1403

A C P0*63 INPUt
.44095

...tff

Vt’
r

4711

-3--%-4
47

L_’
-25W

£450

I
I

004

0004

P444

E5%

!5%

395+

.44075

.4 405P
PECOPO HEAD

*449

004

I
ERASE
TPIMMER

A’
-

C 436
0002
500+

J406P
ERASE HEAL

CA35
0Oh

ITOP PLATE POWERI
£435
450W

‘ALL CAPACITIES APE IN MICROFAPADS
so 5 50 OHMS

BIAS
CON TPOL

BIALIBRATI0N

-NOTES

2-FOP

,I
P430
Soon

,±cr-

LU
J4045

400’>

63N7
40W::_

METEP S OUTPUT
S WITCH

-n
p

MICROPHONE SEE INSTALLATIONS

S-ALL VOLTAGES *IEAS4J*EO WITH 20,000 OHMS PEP VOLT *ETJ* WITH
Ills AC LINE WOLTASE - ALL READING EXCEPT +405 O$C-LATON
VOLTAGES TANEN WITN 1401 D4-ENEPGIZEO

AMPEX

ELECTRONIt S
MODEL 402-403
ELECTRIC CORPORATION
REDWOOD CITY CALIFORNIA

T402 TPAPSFORMEP IMPEOANCE CONNECTIONS
P443 MUST SE ADJUSTED FOP OUTPUT IMPEDANCE
500 TO 400 OHMS CONNECT TO I 5 4 - JOIN 3 TO 4
333 OHMS CONNECT TO I 6 3. JOIN 3 TO 4
200 TO 250 OHMS CONNECT TO 255. JOIN 3 TO 4
125 TO ISO OHMS CONNECT TO 64, JOIN I TO 364
50 01111$ CONNECT TO 264, JOIN 2T036 4105

TOG
J

TURRET
SEE
PIN

KET

PICTORIAL VIEW F
IIUMBEPS OPIENTATIGII

0
C
J 604 P

N-

C
N

Ii
C
0

NETWAY

SLOT
IIOTE1

N
0

‘P
TURRET

Eli

SCOUT

POWER

SUPPLY

-I.
C

U
N

C
‘I

SERIES 400 SINGLE CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REDWOOD CITY.CALIFORNIA

ALL VOLTAGES MEASURED WITH
20,000 OHMS PER VOLT METER WITH
lIly AC POWER INPUT JGOIP IS
C0I**CTEO TO THE ELECTRIICS WITH
THE RECORD PELAY 01-ENERGIZED

- -

IS
PIN

POWER CABLE

PICTORIAL VIEW FOR
NUMBERS ORIENTATI

J 6OIP

‘I"

ICEYWAY

SLOT
NOTE

TI
111?

TURRET

SOCNET

SUPPLY
SERIES 400
AMPEX ELECTRIC CORPORATION
POWER

REDWOOD

CITY.CALIFORNIA

1
ALL VOLTAGES MEASURED WITH
20.000 OHMS PER VOLT METER WITH
lIlY AC POWER INPUT J6OIP IS
COIMIECTED TO THE ELECTRONICS WITH
THE RECORD RELAY 01-ENERGIZED

FIG 6A

INPUT FOR HIGH IMPEDANCE MICROPHONE
SEE
INSTALLITION
401
$

LOW

CAPACITY

CACLE

TO GRIO
V4OI

S MEG

PLATE
V40’

P409

D
GROUND

BUSS

FIG 62

INPUT TRJNSFORMER CONNECTION FOR
30 & 50 OHMS MICROPHONES
SEE INSTALLATION

-‘1

-J

SERIE 400
AMPEX ELECTRIC CORPORAT!ON
REDWOOD CT% CALIFOVNIA

FIG 6

_________________________

___________________________________

______

__________
______________
_____

FIG 76

FIG lA
REMOTE CONTROL CIRCUITS

REMOTE CONTROL CIRCUIT
PLUG IN
I
REMOTE CONTROL
TERMINALSTRWI
TI-SOt
REMOVESTRAP
SETWEENTEMRNM.
I
7SSANOCOINT*CT
I
ASSIOWM
0-701 IIWO-SOOV

REMOTE CONTROL
TERMINAL STRIP
TS- 502

RUT
FORYRO SUTTON
S-TO’

$
I

S-lOS

REMnCONTROLI
NOT iato INSERT
*SYFtUSNO.S4
OR STRAP 7 TO S

I
I

REMOVE STRAP RETWEEJI
ITEIWSNAI.S7$$AIIDCOISIECT
ITOREMOTE1CI4ASSISCONII NECTOR J70I5 AS SHORN

I
I

STOP SUTTON

RECORD SUTTON
5-705

2
I

i
I

REMOTE CONTROL
JONES 0+05545 COWECTOR

IIIIIIIII!
I

START SUTTON
1-704
IQTE CONTRa.

JOltS CABLE CONNECTOR
J702P
-

CONNECT REMOTE CONTROL CIROAT AS SHOWN IN
FIG 5A TO TERMINAL I TOS OF J-702P,
0 PIN MALE JONES CONNECTOR

TAPE MOTION LIQ’T
A-tOt

FIG 7C
60i/’ AMPLiFIER CONNECTIONS

FIG 70

60*/’ AP*UFIER CONNECTIONS

SEE NOTE

SO.PAIIUF%E%
TERMPNAI. STRIP

PLUG IN
4

REMOVE STRAP
*1SETWEENTEM

LII 1111
*
-

*sAND4ANDflIECT
AS SHOWN

II
-

5
I

ONJNMYPLUSIIO
SITORSTEAP ITO
NOTUSEDIMERT[
2

I
I

WHEN 6OP AMP

flaIR

3
4

SLACK

2
I

*
I
I

II
I

I
I

I J

STRAP
* REMOVE
ETWEEN TEIWSIIIJ
I344C06tn
TO
CIaSS.

J
-

SOIlS

WINECTOAJ-TOWS

AS SeWN

CALL
SOI1’ Alt

*1411

JONES Ca*4ECTOR
ON NO, 77 POWER

I
I

LCAt
II?? R
FUflIIsHED WITh
SI- -f’

60,1’ AItSER
TERAV4ALSTRIP
T3’SOI

40.1’ At JONES
0+03515 CONIECTOW
4-703S

II
I

44T

sorspCONNECTOR
an

CABLE

I I I

__________

RED

d----

‘-

nfl

WHITE

CAt NO. IIfl POWER
CABLE FURNISHED
WITH SO’1A1L$ER

JONES COllECTOR

044

Na 1177 PORER
CAStE
I

NOTE:

THE SOIlS AMPLIFIER IS A SUPPLY OF
IISY 10.1’ FOR OPERATING THE ORIVE
MOTOR WHEN THE POWER LINE
FREGUENCY STASILITY IS INADECJATE.

REMOTE CONTROL & 6OJ’
AMPLIFIER CONNECTIONS
- SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITY, CALIFORNIA

FIG.

3’tT-SZ

EPS4TS

rut

-H
I

ru;
m
rrT-r -It
1-1-f m

:1:1
:

t-l-

tj4±t
,T
4FH

j,:f

£I

E-

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Eli

- --

iv::
-

viit

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*1 I

-I,,,,.,:,,I,,,TrrrrI-rrr-tT-ttrTttI,f

‘iF--

S
-T

p144

- H

U] I, -[
I

14II
1I
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ItL1I-i’

a
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F-

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a---,
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CO

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414
6
20

I
zOO

67891

3
3000

FREQUENCY IN CYCLES PER SECOND

--l’i

---4--

4567

9 I
10000

2
20000

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asI

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::::-

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-4
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:
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67891

2
1000

FREQUENCY IN CYCLES PER SECOND

ElI

67897

2
10000
-

*0000

P401

P402

14401

NE4OI

S4O5

5402

RECORD

TOP PLATE FUSE
-

‘S

7-5

‘5

PLAY -

LEVELS

,BIAS

ncr LEVEL

CHASSIS FUSE

AMPIEX
ELECTRIC

RECORD

CHASSIS POWER
EQUALIZATION

-a

0
/

RECORD GAIN

PHONES

RECORD
BIAS

LINE

OUT

LINE OUT

C
0

J 405S

R449

INPUT TRANSFER SWITCH

SAL.

J4O3S

INPUT

TERMINATION

AOJ.

5406

METER & OUTPUT SWITCH

SPEED SWITCH

CORPORATION

J4b4P

S404

44015

ELECTRONICS-FRONT PANEL
SERIES 400 SINGLE CASE PORTABLE
AMPEX ELECTRIC coRPORATION
REDWOOD CITY,CALIFORNIA

BRIDGE

MIC
I ,UNSAL,
BI1IDCE

$403

P409

LU
-I

wO
-

wQ.gz
VoO

I-uO
C

ERASE

435

u-I
Cn_J

‘

‘-I

2oo

zzfl
o

cflUo

ir
I-0ui2

oO
WuJ

-Jv-,O

FACTORY

FIG 11

C429

C428
V401

J408S

J407S
1401
1402
1401

T403

C41 2

K401
V408

C414
V40 4
R437
C41 1

V409

C406

J406P

R41 3

C425

V403

.1407
J405P

C435

C4O5
V405
R432
V406

V402

J402P
5401

R424
C413

-t

J4015

R409

ELECTRONIC ASSEMBLY

- BOTTOM

VIEW

SERIES 400 SINGLE CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

FIG

ELECTRONIC
‘1

FRONT

ASSEMBLY
PANEL

C
‘I,

SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITYCALIFORNIA

V406

ELECTRONIC ASSEMBLY
TOP & REAR VIEWS
AMPEX

SERIES 400
ELECTRIC CORPORATION
REDWOOD CITY.CALIFORNIA

PIG

PLAYBACK
INPUT

PLAYBACK
OUTPUT

RECORD
INPUT

R 432
V 405-

V406

R437

-s

ELECTRONIC
BOTTOM
‘I

C
LA

ASSEMBLY
VIEW

SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITYICALIFORNIA

R4I3 REC
OUT

TAPE SUPPLY TURNTABLE

CAPSTAN IDLER ARM-

CONSTANT TENSION ARM -

45 TAPE GUIDE
TAPE GUIDE HOOK

CAPSTAN TAPE GUIDE

90
91

SPACER
SHIM

CAPSTAN IDLER

CAPSTAN DUST CAP

______

MECHANICAL ASSEMBLY
-II

0
0-

TOP VIEW

SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

REEL IDLE
REEL IDLER A

________

23
32
3!

G
REWIND

BRAKE

SSOT
98

SAFETY

BRAKE

PIVOT

42
43

BRAKE

ADJUSTING

TAKEUP

BRAKE LINING
SPRING

TURNTABLE

SUBASSEMBLY

BRAKE
LINING

SWITCH
SPRING

BRAKE

BRA

BALL BEARING

WASHER

HOLDEACIC

ERTAINING SING
BEARING HOUSING

-S

ROD

CLAMP

BRAKE

LINK

4!
BRAKE SPRING
BRAKE ROD RETAINING BIB

lOG

RETURN

TAKEUP

COLLAR

RUSHING

SPRING

TENSION ARM

5502

ANCHOR

R302
S504

COUNTER BALANCE SPRING
SHOWN CONNECTED POR
RACK MOUNT OPERATION
SSDb

C508
70

REEL

IDLER

FLY WHEEL

BEEt IDLER THRUST IRACK ET

MECHANICAL ASSEMBLY-BOTTOM VIEW
BRAKE DRUMS REMOVED

SERIES 400
AMPEX ELECTRIC CORPORATION

REDWOOD CITYICALIFORNIA

FAN

K504

FORWARD TILT SOLENOID

SOLENOID BRACKET

CAPSTAN DRIVE MOTOR

MOTOR ARM & PIVOT
FELT WASHER

F
VIS

34 TAPE SUPPLY BRAKE DRUM

TAPE SUPPLY BRAKE

TAPE SUPPLY BRAKE SPRING

C509
CS 10

42
67

a
a

BRAKE ROD

BRAKE SOLENOID STOP

LINK’

/K5 02 BRAKE SOLENOID

TOP PLATE - REAR VIEW
SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

C51 I

HOUSING

PLUG BUTTON

FELT WASHER
UPPER BEARING
BEARING ADAPTER

REEL IDLER

ASSEMBLY

RUBBER BEARING
HOUSING
BALL BEARING
FACING PLATE

SPACER

BALL BEARING
RETAINING RING

REEL IDLER
FLYWHEEL ASSEMBLY

THRUST BALL
LIMIT STOP
THRUST BEARING
THRUST BRACKET

1/2-20 JAM NUT

HUB & DAMPENER

REEL IDLER 8 FLYWHEEL
SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

FIG

KSO6

TOP PLATE CASTING

PACING PLATE

/
MECHANICAL ASSEMBLY-SIDE VIEW
BRAKE DRUMS REMOVED

‘I

SERIES 400
AMPEX ELECTRIC CORPORATION

REDWOOD CITLCALIFORNIA

‘0

MECHAN1

Y
-

AS5EMSLY

HOLDDOWN SCREWS

-_----____

ELEVAfl

qØO

MECHANICAL ASSEMBLY
LEVELING AWIJSTMENT

ELECTRONIC ASSEMBLY
HOLD-DO’ SCREWS

CONSOLE CABINET
MODELS 402 &403
AMPEX ELECTRIC CORPORATION
CALIFORNSA
REDWOOD CITY,

fIG

MECHANICAL ASSEMBLY CASE
SERIES 400
TWO CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REDWOOD CITY.CALIFORNIA

FIG

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