Ampex 400 Manual 200dpi 1bit

User Manual: Ampex-400 manual-200dpi 1bit

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AMPEx
SERIES 4b0

OPERATION AND
MAINTENANCE MANUAL

SERIES 400

MODE1S 402 & 403
COt4SOLE
CORPORATION
AMPEX EECTRIC
CLII CA1FORN’’
REDWOOD

-7
II
‘I-

MODES 402 & 403
TWO CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

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-Il 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
?iuTtooeitflThm
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
ewind
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 recoding, 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
p:-ogram 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-A 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 icture
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.
-

Plso 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 mounted 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, S401, 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 Pmplifier re
ceptacle when the 60 Cycle Amplifier is not used.

SERIES 400, SECTION 11, °age 4
1 i/i/sz

Vu. CONVERSiON

FRO

B: V 12
.

kICUNT:

If a portable or console
c1er is convei ce! ‘o a rack mount machine,
the Takeun Tension
rm :ounterbalanc
ring 6S r ii:jt re affded. This spring
is supplied with th recorder and is hT&:
to the
eeL
T rust 2racket 85.
See Figure 17. To instad, let ove trcn .r.E bra cet ;r
Jetween th lug
provided on Safety
w’t li 501
ard the
:
c’tdecoi
the Takeup Ten
sion
rrn Collar
i.
riterbalanc
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 tie conversion
is to be perm
anerit, the oiling cups ci the Turritabie
toter 6, if
..i ped ith sI.eve bearings,
sboLld he rotat3 tc be a
.ie for otii
.

‘

cc.s

‘iNS

PNlNG:

$efore

rL..
01

Ni’

en,.r; the ‘:csole

or cci tae

case:;, disconnect

‘C oower.

Complete accessibility for inspection or service ii provided to the to
nd bottom of the Electronic Assembly and bottom of the viechanical Assemby.
Fig ie 21 for illustration of Cabinet opened for full accessibility.
Coening
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
Use s.iioort red k’ to support Mechanical Assembly.
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?

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.

XI, 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 SRBA 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.

404 &
7-1/2 Inch Response or 3-3/4 inch ResnonseModels
405 only
DUE TC THE NATURE -OF THE RE-EMPHPS1S
IN THE
RECCRD CIRCUIT, TAPE SATURATION WILL OCCUR AT
TH. HIGH FRECUENCIES 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:
Make theesporise 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
ltmeter such as Hewlett-°ackard
400C wh
.playing bark a tape that has
.

p:eviously been erased on the machine. First; trase the tape with the input
f Th Erd
amplifier shorted. Rewind and play this tape back.
t the
7-1/2 inch and 15 inch speeds the wide band noise should be at least 49 db
below onerat;.ng

level point

of approximately

1% total harmonic

distortion.

Pt the 3-3/4 inch speed for Models 404 and 405, the noise should be at least
44 db below operating level. No attempt should be made to measure wide band
SERiES 400,

OCTION Ii,
11/1/52

age 6

noise

ias

‘vhdt stxz,ulLwus1y
recording and 1aying
into he play-ack head may interL
with t

back as
-ias

;

of Ye flO 1C

Listortion;

Dverall distortion can be rreasured by connecting any standard
distcrtion r-i-easurenent appatatus across the outpuL The readings from a wave
ana’yzer or selective frequency distortion meter 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 I is normal at ooerating
level whi1 a reading of 3% is normal at 6 db above ooerating level.

Flutter and

Vow:

Flutter and i1ow are the change of soeed over a short time interval
in a Der1-dic manner.
They can be measured by means of a sta3dard flutter
bridge such as
. F. Tatum
Beverly Hills, California Model 2-- Flutter r’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

or performance

checking,

SERII3 400, SECTiON 11, 7-age 7

ii/i/sz

SLCTIOIr III

OPLR4TING

ROCEDUR

REEL SIZE:

The turntable on the left side tape supply is equipped to handle either
the NP-RTB 10-1/2" 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.
movable pin in the bottom

surface of the knob engages a corresponding

A re
hole in

the turntable.
A collet 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

them
such
This
from
Idler
with

in the ?lay mode of operation.
New tapes are usually looped to the hub in
a manner that the tape will not come free of the reel at the end of the reel.
will prevent the Safety Switch 5501 from disengaging the Capstan Idler 50
the Capstan A which results in a flat being worn on the Rubber :Capstan
Wheel. Any adhesive material accumulation on the reel hub must be removed
solvent for the same reason.

In.

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
T-’.FTHRLADING 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
turned over and placed on the
reel on the Takeup Turntable should be removed,

SERIF 5 400 SECTION III

11/1/52

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
3502 governs the motor, and the Equalization Speed Switch 5402 corrects
the equalization in the amplifiers.

VI.

TAPE MOTION:

The tape motion is controlled

Stop, Start,

Fast Forward,

by means of four pushbuttons

labeled

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
or
Rewind Button
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 returned 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.

Viii.

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/a 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
In order

to do this,

re-position

occasionally.

the Meter and Output Switch S405,
-

SERIES 400

to the po

SECTION LU, ‘°age 3
11/1/52
-

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

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

SEC LION IV

OPERATING THEOR Y

The purpose of this section is to explain the electrical and mechanical
functioning of the Recorder as the machine is operated. An understanding of
this functional operation will enable the operator to utilize fully the capa
bilities of the machine,
I. MECHANICAL ASSEMBLY: Refer to figures in rear of book for circuits and
location of parts.
To understand the operation of the Tape Transport Mechanism it is necessary
to examine the following assemblies in the various modes of operation:
1.

Capstan Drive Motor 24, Figure 18. The Capstan Motor is a synchronous
motor whose extended shaft forms the Tape Drive Capstan A Figure 16.
It has two sets of windings to provide the two tape speeds.

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 1<503 and 1<504.

Capstan Idler 50, Figure 16. The Capstan Idler is positioned by the
Capstan Solenoid 1<501. 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 break.

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
1<505 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 1<502 thus releasing the Stopping Brakes
36 and 39.

Energizes the Forward Tilt Solenoid 1<504 thus positioning the Turn
table Motor in the takeup position.

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

Energizes the Capstan Solenoid K50l. 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 1<506 will
be energized.
The relay performs the following functions:
1.

It interlocks the Rewind Relay 1<507 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 2
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 1<507 will be energized.
The relay performs
the following functions:
1.

It interlocks the Fast Forward Relay 1<506

It breaks the circuit to the Capstan Solenoid 1<501 and the Forward Tilt
Solenoid 1<504.

It energizes the Rewind Tilt Solenoid 1<503 thus positioning the Turn

so it can not be energized.

table Motor in the Rewind position.
4.

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

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 P502 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

HEAD ASSEMBIJYY

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 impair the performance of the machine and should
be guarded against by always opening the gate on Fast Forward or Rewind.

lf a deposit is left, it may be easily removed with carbon tetrachloride

The
a soft rag. Never use metal of any kind to touch the head surfaces.
gate should never be allowed 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 111-111. 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, Page 4
11/1/52

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
n-içlifier 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 Fcrward Relay L506 and the El-ewind Relay 1<537 in dc-energized
*-ositions.
Therefore,
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 unbalanced bridge.
Ehe Pecorci
mp
also
.irovides
se:arate
high
ft
quency
pre-emphasis
for
each
seed.
lifier
This change in esualization is made by he qualization
5’ead 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 -amelifier 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 to? cf the Electronic
chassis.
but is
The 3-3/4 inch
tayhack eoualiation
conforms to the curve in ‘i*.
ih’ --ia hack gain on single case portaUe models is ccntrolled
not adjustable.
fiice
by a
d screw driver 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 orovide- Lv 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 mpltfier 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
molifier 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 R4l3.
The Calibration Control is factory adjusted
sired record level will be effected on the tape.
The rase

and Bias oscillator

provides

the

so that the de

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 V601.

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.

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,

matte-c

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 from 5 to
10 db. It is especially important that the heads be free of magnetization if you are
to realize

that any
phenomena that tends to put an unbalanced pulse through the Record Head will inag
the dynamic

range of the machine.

It should be remembered

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:
1.

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
ll/l/5

Do not saturate the Record Amplifier with an abnormally high
input signal, Such a signal would he 10 db greater than tape sat
uration or approximately 30 db greattr than normal operating
level,

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,

Demagnetizer up and down the entire height of
times, Remove the demagnetizer very slowly,
off gradually. Repeat this operation on Record
the Erase Head will demagnetize itself. In the
effected, repeat the process several times.

Run the tip of the

the core stack three or four
allowing the AC field to die
and Playback Heads only, as
event demagnetization is not

IV, LUBRICATION:
The following places require lubrication once or twice a year depend
ing upon the amount of usage of the machine:
I.

Capstan

Drive Motor

and Turntable

The motor manufacturers

Motor

recommend the followin

lubr1cants for

their respective motors;
Eastern Air Devices-Sacdny Vacuum Oil Company. S,A.E,20
Bodine Electric Company--Gulf Oil & Refining Com-any-Gulfcrest
P
Standard Oil Co,of Indiari-Stanoil
#18 ci
Sacony Vacuum Oil Co. - argoyle D, I, E.
Light
If equivalent oils are to be used, ar epresentative of the oil corr-pany thould be
contacted to ascertain that the equivalent is miscible with the llil 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 obscured.
Lubricate with 10 drops of
the recommended lubricant, preferahiy using an oil can with flexible
spout.

victor.
Turntable
The rec orth r may be equipped with different tyi’-5
of turntable motors, If the tir tahle ntctor has oil cups o oiling hole
requires 10 drops of the recor.rznded lubricant. Raise c r renc-ve
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
ubricalior i
supplied with ball bearings fric 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 lubrication-and
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:

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

ii/i/sz

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 100% 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.
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.
is recorded

MODEL 400A, 4OlA, 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 Standard
, 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 400,4014,402 & 403, SECTION VI, °age 2
1 i/i/sz

II.

ALIGNMENT OF ?LPYBACK CIRCUIT:

Refer to Figure

1 or 2.

1. Position the Electronic Assembly so that adjustments
the controls

located

2. Set the Tape Speed Switch S502 and Equalization
to 15 inches

can be made on

on the top of the chassis.
Speed Switch

S402

per second.

3. Set the meter and Output switch S405 to the PLAYBACK-LEVEL p05 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
11/1/52

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.

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 7-1/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.
plifier
to 15"
Level
b.

Thread a blank tape on the machine. Terminate the playback am
as in Playback Alignment. Set the Speed Switches S402 and S502
per second. Set the meter and Output Switch S405 to the Playback
position.
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 in the record mode of operation.

d. Adjust the Record Level Control R409
imately 0 zero.

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 i/a 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
11/1/52

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 111
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 response on any tape is as follows:
15 Inch Record Equalization

Adjustment

Set up the machine as described under Bias Adjustment.

2. Start the machine in the record 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
-to 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

7-1/2 Inch Record Equalization Adjustment
1. With the machine set up as above, change the Speed Switches
5402 and S501 to the i-i/a inch position.

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.
4.

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 a.djusted 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.

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, 4OlA, 402 & 403, SECTION VI, Page 6

u/i/si

SECTION
MECHNICP

VII

SERVICE

GUIDE

This section is a guide to locating 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.
A.

Capstan Drive Motor inoperative at one or both speeds.
Check the following:
1.

AC Power to the recorder.
a.
b.
c.
d.
e.

Control Circuit Fuse F402,
Power Cable from Mechanical Assembly to Elec
tronic Assembly.
Capstan Drive Motor Connector J502P.
Speed Change Switch S50Z.
Jumpers from 1 to 2 and 3 to 4 on 60 Cycle Ampli
fier Terminal Strip TS50l.
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 J7035
in absence of the 60 Cycle Amplifier.

Head cables interfering with Drive Motor Flywheel.

SERIES 4C0, SECTION VII Page 1
11-1-52

Capstan Drive Motor 24
or shorted winding.

Drive Motor Capacitor 0508.

fer 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.

Start Button S507.

Takeup Torque Switch 5503.
Section VIII-7.

DC Belay and Solenoid Power
a.
b.
c.

See Section

For adjustment,

see

Supply.

Selenium Rectifier SR5O1.
Resister RSOl.
Electrolytic Condenser C5oZ.

Belays.
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 K502.
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 Iplug
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

P503 for an open circuit.

Binding of Turntable

Thbles interfering

Counterbalance

ivots

and 19.

with the Brake Drums 34

Spring 65

"ortable machines.
II.

Iotor

and 35.

in rack mount position

See Section Il-Vil.

IRRYGUT ARITIES IN LAY MODE.
P.

Unsatisfactory

starting in lay

Mode.

Check the fol1owng:

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

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

Tilt Solenoids 1533 and 1504 if misadjusted can cause
sliipage or late engagement of Turntable Motor B502.
See Section VIII-8.

Insufficient takeup torque in the P’ay mode.

a.
b.

May be

Play Resistor P503 set too high. See Section VIII-9.
Cable interfering with Takeup Brake Drum 35.

Stopping Brakes 36 and 39.
a.
b.

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

Capstan Idler pressure adjustment.

Takeup Tension Arm 62

Constant Tension Brake 47
VIII-3.

Low relay and solenoid

See Section VIII-l.

sluggish.
adjustment.

See Section

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

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

Capstan A,

Reel Idler Pulley 71,

Capstan Idler 50,

Turntable

Takeup Brake Drum 35,

Head Surfaces.

Figure 16.

Motor

Figure

Tire 7,

Tape Guides 45,

89,

Figure

19.

Figure 18.

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.

ZO.

Figure 16.

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.

Thrust Bearing 86

Foreign

material

worn.

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

defective.

T.akeup Torque Switch S503 not opening.
for adjustment.

Bad Tape worn,

8..

Recorder

See Section VIII-7

ragged, or of poor quality.

subjected

to excessive

external

vibration.

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

SE PIES 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 Vill-lO.
Safety Switch Condenser C50l shorted.
-

d.
D.

III.

Instability

of Tape on Capstan.

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

Capstan Solenoid 1501

Constant Tension Brake Spring 49 disconnected or broken.

Constant Tension Arm 44 binding in Bushing 5.

Bad Tape stretched

Idler Pressure

Adjustment.

See Section VIII-l.

not seating.

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:

Recorder

depressed.

See Section VIII-l.

IN FAST FORWARD OR REWIND MODE.

stops when Fast Forward

or Rewind

Buttons are

Check the following:

Fast Forward

Rewind Button S505.

Fast Forward

Rewind Relay K507.

Rewind Tilt Solenoid 1503.
VIII-8.

Button S504.

Relay 1506.

For adjustment,

see Section

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

________
B.

Recorder

sluggish

in Fast Forward

the following:

or Rewind.

Check

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.

S’e

3cc

4. Turntable Motor 6 for insufficient lub’-ication.
Section V-TV.
5. Slippage between Turntable Motor Tire 7
Drums 34 or 35.
a. Tilt Solenoid 1503 and K504.
*
Section VIII-8.

and Brace

For Ec’ustrflent ee

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 IRREGULARITIES
A. Braking too severe causing breaking or deforrnatior
*

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

Brake Solenoid Stop 67 deformed.

tape.

17 r oint G

See 5’

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

e. Se

Section VIII_ZF, for cleaning procedure
C.

Braking rotationally uneven.
1.

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

3LRIES 400, SZCTION VlI, Page 6

11/1/52

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

Constant Tension Brake Adjustment.

Turntable and Brake Drum Height.

Rewind Holdback Brake Adjustment.

Reel Idler Adjustment.

Takeup Torque Switch Adjustment.

Forward

Play Takeup Torque Adjustment.

10.

of Braking

and Rewind Tilt Solenoids

Adjustment

Safety Switch Adjustment.

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

System.

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 2-1/2 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 °ivot.

I ne 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 Ant 62 in the onerating pa
siUo. ae
the "fechanical Assembly in a position so that the
Brake .i’-toes -anbe observed and start the recorder.
2.

Loosen ftc --c sc -ews that secure the Brake Solenoid 1502 to
ftc jolenoid --ounting Bracket. See Figure 18, Point C. Slide
L-e Sclenod tn the required direction to establish a cle arance of
i/o4 to i 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 will increase
slightly, but this will not affect the performance 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
11/1/52

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 surface 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 re;eased, The Constant Tension Arm
44 should have a very short travel
approximately i/s inch at
the end of the arm.
-

SERLES 400, SECTION VIII, Page 4
11/1/52

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 18,
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

the Brake Drum thoroughly as explained in Section VIII-2F as it will
become contaminated by handling.
5.

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 z-s/s 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

11/1/52

VIII,
-

Page 5

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 bali Bea- ---g is in place. Si e the
Peel Idler Spacer 84 on the shaft. HoL3-rg the Reel Idler Ely
heel 78 by the Sauare Hub, ottom it against the Spacer and
fall Bearing. Then tighten the set scre
.
-’

*5%
C433

395V

tRAm staG

C430

-ISV

IOO

J4o75
TOP PLATE POWER

400V

ERASE
TRIMMER

C.I.

1402
*445

M1CROPARACS

AMPEY

ELECTRONICS
MODEL - 400A
ELECTRIC

PED*000 CITY,

.1406P

lAA

IIIJ$j

2-rOt
30 2 50 011W>. PACROPHONE
SEE INSTALL AT0’I
3.*LL VOLTAGES MEAMEO WITH 20,000 OHMS PER VOLT ICIER WITH
Ill V AC UNC VOLTAIC ALL !EAOING EXCEPT V409 OSCILATOP
VOLTAGES TAKEN WITH P401 OE-EHERGIZ2S.

t2V

METER SOUTPUT
SWITCH

TES:
I-ALL

Ij23

IIkItI-I>’>’
Io.SITItiOl
P11
‘1

==fl

V409

Frt1___

Lf01x18 IIII

N
S
0

IA
‘4.0.-Sw

*43?

*315V

1jJL.4soV!I0*

1--i’
P

C 427
25
159

SHORTING
ON TIC T S

I ItO

*440
MEG.

I-

ISV
‘Xv

P435
*435
SAO47R
PLAYGAK
LEVEL

cORPORATION

CALIPNIA

T*ANSSC*MEIP
MUST

IMPEOAIICE

SE ASIUSTED

500 ‘0400
335

OHMS
OHMS

CONNECT
CONNECT

200*250
1231.150
SO

01111$
OHMS
OHMS

CONNECT
CONNECT
CONNEd

TO
TO
TO

CONNECTIONSOUTPUT

IMPEDAP:E

I I I,
I
S*

JOIN
JOIN

3 10 4

123,
64,
114.

JOIN
R
JOlt.

3 TO 4
I T0524706
I Toss 4105

_____________
_______________
__________
___________
___________

TPANSFEP
6401 SWITCH

IFUT
MIC
1401
ISO.

SAL

INPUT

V 401
25.17

*40

P412
IMEG

V402
125.17

.75,,

UNBAL BR

.14015

NOTE

SEE
TlOI

_
__-

+1209j
P400
lOOK
1%

*407
330*

-If-C 411
OS
400,

SWItCH

£401
25
400

P404.
1200

25
25+

*405

C407
0001

P411
47K

- =-

EOUALIIEPS
P413
lOOK

1C404

.y5.
+

lOOK
H KCL30Lf

‘11415
‘39K
±5%

*414
lOOK

25’

471+

V406.
171j7
ILELECTI

c
£416
I
700w

6454
*428
MEG
1%

----

C4SBJ,,
.015

239
0416 4

C4IL

IMEG
PLAyBACK 455+
LEVEL
I

T-I t

P416
2200,..

P430
2200
1’

PLAYBACK HEAO

44 Ol
+407
2 5J7

N455
6*0K

200V

C41 j12OK.
25
25i
"

C 421
4
4509

400+

+406
SC 5/6.1 5

0qI’Y

._.4I’I’

4340+

J4IIS

LINE
TERMINATION
SWITCH 3404

PHONES

-$t

l403

__ii_.-.i

ItTOP
AMPLIFIEP

LINE 0.111

P441
I MEG

P455
*?Oa
.5%

5436
2700’

I’
C425
I
400V

40I

P426
15K
OW
C445

43309

C437
L_02
600+

£413
Sn
150+

11461
22K

1015*

P445
OK
29

C424
-0025

470+

64.ANCE

L401
20M6

4220+

003

*435

P437
Mb

C410
0 I

C4OPT

P433

N431
.IMEG
61%

6419
2200

400+

1509

P420
470
+13+

*417

C409
25
25+

-T-41

330+
1%

N427P0HDlSOICI1G
lOOM

N 410
2200’4:

+405
003/ YPISO

:t120,

641$
47011

+59

‘Ti,0,

72.11
7W

00l?1p

*25V
5011

400+

‘471

-- - -

C40
4

________

C412

y4Q4
6C5/6J5

+709

4O3
00

+403
12347

±5%

_____
__

C427
25
25+

PL Al S AC II
EQUALIZER

P442
2200CL

M 401

-__P4n
360021.
55+
AC

+ 1%

26+
OC

Xxv
‘I

±4
20001
I

HHf

C429 I
20 ..i.M4S7
2K

CL0:

23iJ5!J

C ON TAC T SI

IA
SL0L0

,±crI ...tff

U00
A C P066* INPUI
44095

: rrj I
tfl

F’

100 A

SSN7
V*:
I

-n
p

25V

u===

.14085
IPOWEI SUPPLYI

1403

-25+

£450
0004
E5%

004
I 446

450+

I’ ALL CAPACITIES APE IN MICPOFAPADS
2-FOP

50 6 50 OHMS

MICPOP.IONE SEE INSTALLATIONS

S-ALL VOLTAGES MEAS4JPED WITH 20.000 OHMS PEP VOLT 4ETJP WITH
1179 AC LINE VOLTASE. ALL READING EXCEPT 9409 OSC.LATOP
VOLTMES TAKEN WITN 1401 OIENEPGIZEO

AMPEX

ELECTRONIt S
MODEL 402-403
ELECTRIC CORPORATION

REDWOOD CITY

CALIFORNIA

C 436
0002
500+

II
ERASE
TNIMMER

£433
-NOTES

.1 4056
PECORO HEAD
P449

004

*453

BIAS
CON TPOL

.14075
TOP PLATE POWEPI

*450
SOOA

BIALI5PATl0N

47111

-t---3959

-I

METEP S OUTPUT
S WITCH

A’
-

J 4066
ERASE HEAL

CASS
001

T402 TRANSFOPMEP IMPEOANCE CONNECTIONS
*443 MUST SE ADJUSTED FOR OUTPUT IMPEDANCE
500 TO 600 OHMS CONNECT TO I S 6. JOIN 3 TO 4
333 OHMS CONNECT TO I S S. JOIN 3 TO 4
200 TO 250 OHMS CONNECT TO 285. JOIN 3 TO 4
125 TO ISO OHMS CONNECT TO 1S4, JOIN I TO 364
50 OHMS COPNECT TO 264. JOIN 27036 4T05

T05

TURRET
SEE
PIN

CAE

KET

PICTORIAL VIEW F
NUMBERS ORIENTATION

0
C
J 604 P

C
F.
Ii

C
0

REINS!

SLOT
NOTE

PA
0
‘P
F.

TUARET

SCOUT

POWER

SUPPLY

-I.
C

U
N

C
‘I

SERIES 400 SINGLE CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REOW000

1
ALL VOLTAGES MEASURED WITH
20.000 OHMS PER VOLT METER WITH
lIly
AC POWER INPUT JGOIP IS
C0I**CTEO TO THE Ek1CT*IICS WITH
TIlE RECORD RELAY DE-ENEPGIZED

- -

POWER CABLE

ISEE PICTORIAl. VIEW FOR
PIN NUMBERS 0RIENTAT3

C
J

SOIP

REYWAY

11+?

TURRET

SLOT

SOCIKET

SUPPLY
SERIES 400
AMPEX ELECTRIC CORPORATION
POWER

REDWOOD CITY.CALIFORNIA

NOTE: ALL VOLTAGES MEASURES WITH
20.000 OHMS PER VOLT METER WITH
lIlY AC POWER INPUT JGOIP IS
COMIECTED TO THE ELECTRONICS WITH
THE RECORD RELAY 05-ENERGIZED

FIG 6A

INPUT FOR HIGH IMPEDANCE MICROPHONE
SEE INSTALLITION
401
$

LOW

CAPACITY

CACLE

TO GRIO
V4OI

S MEG

PLATE
+404

*409

D
GROUND

BUSS

FIG 68

INPUT TRJNSFORMER CONNECTION FOR
30 & 50 OHMS MICROPHONES
SEE INSTALLATION

-‘1

-J

SERIE 400
AMPEX ELECTRIC CORPORAT!ON
REDWOOD CT% CALIFOVNIA

FIG

__________
______________

_________________________
______

_____

FIG 76
REMOTE CONTROL CIRCUIT
PLUG IN

FIG lA
REMOTE CONTROL CIRCUITS

I
REMOTE CONTROL
TERMINALSTRWI
TI-SOt
REMOVESTRAP
BETWEENTEMSAM.
I
7S6AI10C0143*CT
I
ASSNOWM
C-701 IIWO-SOOV

REMOTE CONTROL
TERMINAL STRIP
TS- 502

REST
FORYRO SUTTON
5-701

STOP BUTTON
1-703

NOT MED INSERT
*SYPtUSNO.S4
OR STRAP 7 TO S

3
I

I
I I

I
I

REMOVE STRAP BETWEEJI
ITEIWIINAI37I$ANDCOISIECT
ITOREMOTEICI4ASSISCONHECTOR J7OIS AS 3110814

I
I

REMOTE CONTROL
JOKES 04*5145 C08ECTOR
J-7OIS

111111111!

flMnCONOLI
RECORD BUTTON
5-705

2
I

START BUTTON
5-704
IQTE CONTRa
JOltS CABLE CONNECTOR
- J702P

CONIECT REMOTE CONTROL CIROAT AS SHOWN IN
FIG SA TO TERMINAL I TOS OF 2-702 P11
0 PIN MALE JONES CONNECTOR

TAPE MOTION LIQif
A-tOt

FIG 7C

FIG 70

60*/’ AP*UFIER CONNECTIONS

601I/’4 AMPLiFIER CONNECTIONS
SEE NOTE

SOIPAJUF%E%
TERMINAL STRIP

1111

LII

REMOVE STRAP
*1BETWEENTEM

*SAE404AND4KIEC

I
I

I AS SHOWN

*
I

I
I

WHEN BOI.P AMP

I J

WIlTS

REMOVE STRAP
BETWEEN TEIWSMU

I364C06tdT
TO 601/1 045555

AS SHOWN

40.1’ Alt JOKES
QIASSIS OOKIECTUM
4-7O3S

44T

I I I I

I
I

flaIR

DUMMY PLIISNO
S4?ORST*AP ITO
NOTUSEDINSLRT[
2

BLACK

81OWH

I
I

II?? R
CALL
FUSIISHED WITH 60.1’ Alt

-I--- f
If

JOKES C0414ECTOR
ON NO. 77 POWER

LCAt
-

PLUG IN
60,11 *aani
TERAON*LSTRIP
15501

60.1’AMP JONES
CASt! CONNECTOR

RED

nfl

WHITE

CAt NO- IIfl POWER
CAStE FURNISHED
WITH SO’IAIL$ER

JONES COllECTOR
044 NO. II?? PORER
CAStE
I
NOTE:

THE 6011’ AMPLIFIER IS A SUPPLY OF
ISV 00./’ FOR OPERATING THE DRIVE
MOTOR WHEN THE POWER LINE
FRECUENCY STASILITT IS INADECJATE.

REMOTE CONTROL & 6OJ’
AMPLIFIER CONNECTIONS

SERIES 400

AMPEX ELECTRIC CORPORATION
REDWOOD CITY, CALIFORNIA

FIG. 7
3-27-SE

50-3476

tE:

-H

ITT
p
FHt -rr

-r- -I--r-r-r-rrrrn-r
1

S-T

I,,,,.,:,,I.,,Trn-rT-I-rI-I-tT-ttrTttIK

p144

F-

I----

-4-

------I--’-----‘

Eli

- --

iv::
-

1i11t

- - -

j:f

ItL1I-i 1c!

a
a
-4

tj4±t
,T
4FH

iv-

C
0

1-1-f m
:

t-i-

U] I ‘[
I frtfltf

---

14II
-1I
-s

H
a---,
-

4Th 4ti
-r 4-44- I4
-LiFt-i

Vr4

ti;

4flflwIfl

‘I-I

:i4li:l.

N
--F

F-

r
-

-r
114

-I.

C
CO

I--

-t
--

L
-

--4-

[1-1

:1]

I
200

67891

thliv
3

2000

FREQUENCY IN CYCLES PER SECOND

20000

2
20000

14-

Ui±L
-

I
-

H4E--l-

4
--

III

!
-

SRI

S
20

67991

III

5
100

1FF

67897

2
1000

FREQUENCY IN CYCLES PER SECOND

67897

2
10000

*0000

P401

P402

11401

NE4OI

TOP PLATE FUSE
-

S405

5402

7-5
0

RECORD
110

PLAY

LEVELS
ncr LEVEL

,BIAS

CHASSIS FUSE

AMPIEX
ELECTRIC

RECORD
C

CHASSIS POWER
EQUALIZATION

-a

RECORD GAIN

PHONES

RECORD
BIAS

LINE

OUT

C
0

2405$

P449

INPUT

TERMINATION

I-

J4O33

INPUT

LINE OUT

ADJ.

5406

METER & OUTPUT SWITCH

SPEED SWITCH

CORPORATION

J4b4P

5404

44015

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

$403

TRANSFER SWITCH
SAL
BRIDGE

MIC
I ,UNSAL.
BI4IDCE

P409

LU
-I

wO
-

wQ.a

F-uO
C

ERASE

435

u-i
Cn_J

‘

2oo

LI
-

zzfl
o
ir

cflUo

I-0ui2
oO

WuJ
-Jv,O
4/

FACTORY

FIG

IIT

C428

C429

J408S

J4075
1402
tAO
C41 2
C414

1403
1401
V408
V409

V 404
R437

C4U
C406

C435
J406P
C425
1407
J4OSP
V405
V406
J402P
5401
J4O1S

ELECTRONIC ASSEMBLY

BOTTOM

VIEW

SERIES 400 SINGLE CASE PORTABLE
AMPEX ELECTRIC CORPORATION
REDWOOD CITYCALIFORNIA

FIG 12

5406

P401

F402

cç

$403

[401

$404

/
Ie

.
-

4
At

A_p
--

41 -

‘4

jcY

R 409

5402

ELECTRONIC
-I’

C
0

5401

FRONT

ASSEMBLY
PANEL

SERIES 400

AMPEX ELECTRIC CORPORATION
REDWOOD CITYCALIFORNIA

R437

J4035

1402

AC1

R432

---I--

C406

V403

V4O1

V406

L / L Z// L L405
J404P

J4085

J407S

ELECTRONIC ASSEMBLY
TOP & REAR VIEWS
SERIES 400
ELECTRIC
CORPORATION
AMPEX
REDWOOD CITYCALIPORNIA

FIG 14

PLAYBACK
INPUT

RECORD
INPUT

J40S1T401

K401

R
V

R449
T403

V409
V406

CL!] 2
C435

R4O9

ELECTRONIC ASSEMBLY
BOTTOM VIEW
-II

a
UI

SERIES 400
ELECTRIC
CORPORATION
AMPEX
REDWOOD CITY,CALIFORNIA

TAPE SUPPLY TURNTABLE

J
51

TAKEUP TURNTABLE

TAPE GUIDE

CAPSTAN IDLER ARM
TAKEUP TENSION ARM

44
46
89

45 TAPE GUIOE
TAPE GUIDE HOOK

CAPSTAN TAPE GUIDE
90 SPACER
91 SHIM
p

CAPSTAN DUST CAP

MECHANICAL ASSEMBLY

S504
$505

FAST FORWARD

S507

START

5506

STOP

REWIND

ESCUTCHEON

REEL IDLER PULLEY
69

SPEED SWITCH

CAPSTAN IDLER

$502

TOP

VIEW

SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

REEL IDLER ASSEMBLY

33
32

RETAINING RING
BEARING

TURNTABLE

0
22

REWIND

TAPE

WASHER

BRAKE

LINING

5501 SAFETY SWITCH
BRAKE PIVOT SPRING
£2
BRAKE BOD

TAKEUP

TORQUE

CONSTANT TENSION

BRAKE ADJUSTING CLAMP
39

TAKEUP BRAKE

40
BRAKE LINING
99
BRAKE SPRING LINK
BRAKE SPRING
41
BRAKE ROD RETAINING RI-

100

BRAKE SPRING

HOLOBACK BRAKE

SUBASSEMBLY

SUPPLY BRAKE
BRAKE LTNING
37
BRAKE PIVOT SPRING
36

HOUSING

BALL BEARING

BRAKE

LINING

BRAKE

SPRING

SWITCH

BRAKE

PRESSURE SPRING
64

RETURN SPRING

RETURN

SPRI NO

CAPSTAN
CLEVIS

SOLENOID

COTTER PIN
PELT WASHER
TAK EUP

62
63

COLLAR

BUSHING

TENSION ARM

STOP
ARM

ANCHOR

54
65

COUNTER BALANCE SPRING
SHOWN CONNECTED FOR

MECHANICAL ASSEMBLY-BOTTOM VIEW
BRAKE DRUMS REMOVED

SERIES 400
AMPEX ELECTRIC CORPORATION

-4

REDWOOD CITYICALIFORNIA

‘1

BOLT

CONDENSER

RACK MOUNT OPERATION

EYE

WASHER
BRACKET

K504

FAN

FORWARD TILT SOLENOID

MOTOR ARM & PIVOT

RETURN SPRING

FELT WASHER

SPADE BOLT
MOTOR POSITIONING
SPRING

SOLENOID BRACKET
REWIND TILT SOLENOID

K503
24

CAPSTAN DRIVE MOTOR

COTTER PIN

CLEVIS PIN

TAPE SUPPLY BRAKE DRUM

TAPE SUPPLY BRAKE

TAKE-UP BRAKE DRUM

TS502

REMOTE TERMINAL STRIP

C509

TAPE SUPPLY BRAKE SPRING

C510

42
67

-u
C
S

K502 BRAKE SOLENOID

BRAKE ROD

BRAKE SOLENOID STOP

TOP PLATE

REAR VIEW

SERIES 400
AMPEX ELECTRIC CORPORATION
REDWOOD CITYICALIFORNIA

C51 I

TS5O1

60 CYCLE AMP TERM STRIP

KSO6
101
lB

WASHER

FRONT PIVOT

1111

PAST

PORWARD RELAY

REWIND RELAY

C505
K507

TURNTABLE MOTOR

RELAY BRACKET
MOTOR

MOUNTING

MOTOR
TOP PLATE

BRACKET

CASTING
PULEEY

FACING PLATE

TAPE SUPPLY

TURNTABlE

PAD

REEL CENTERING ADAPTER

MECHANICAL ASSEMBLY-SIDE VIEW
BRAKE DRUMS REMOVED
SERIES 400
AMPEX ELECTRIC CORPORATION
C
‘C

REDWOOD CITY,CALEFOINIA

TURNTABLE

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

ASSEMbLY
V MECHANICAL

!Tcr-c
-

HOLDD0’ SCREWS

ELEVATING ROD

MECHANICAL ASSEMbLY
LEVELING ADJUSTMENT

V’
-

tr:

ELECTRONIC ASSEMBLY
HOLOO0W$ SCREWS

CONSOLE CABINET
MODELS 402 &403
CORPORATtON
AMPEX ELECTRIC
CAL%FORN
REDWOO0 CITY,

FIG 21

7
MECHANICAL

ASSEMBLY CASE

SERIES 400
TWO CASE PORTABLE
AMPEX

ELECTRIC CORPORATION
REDWOOD CITY,CALIFORNIA

FIG

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