3M Series 410 User manual

31M Brand
Professional , Audio Recorder
Series 410
INSTRUCTION MANUAL
MINNESOTA MINING AND MANUFACTURING COMPANY
300 SOUTH LEWIS ROAD. CAMARI LLO, CALI FORNI A 93010
M64 PAR 3-72
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INTRODUCTION
This Instruction Manual has been prepared for the convenience
and use of owners of the 3M Brand Professional Audio Recorder . The
manual is supplied with each recorder shipped from the factory, and
should be consuHed before installation and operation of the recorder
is attempted .
Eight head and speed configurations of th is model are presented
in the text of this manual. They are: 1/2 inch, 4 track, 7 1/2 and
15 ips, 60 Hz; 1/2 inch, 4 track, 15 and 30 ips, 60 Hz; 1/4 inch, 2
track , 7 1/2 and 15 ips, 60 Hz; 1/4 inch, 2 track, 15 and 30 ips,
60 Hz; and the above four at 50 Hz . A 1/4 inch full track is available
upon special order.
The text will note the differences, where applicable, in the above
configurations including the 1/4 inch full track. Differences are mainly
found in the heads, and in the capstan drive motors listed in the parts
list section. Operation and maintenance of aLL models are identicaL.
M64 PAR 2-71
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FOR SALES INFORMATION
WESTERN U. S.
Mincom Division
3M Company
300 South Lewis Road
Camarillo, California 93010
[phone]
NORTHEAST
76 Bryant Road
Blackwood , New Jersey 08012
[phone]
FOR PARTS AND SERVICE
WESTERN U. S.
Mincom Division
3M Company
300 Sou th Lewis Road
Camarillo, California
93010
[phone]
-..,- -- ~- ' --
. - ----
EASTERN U. S.
Mincom Division
3M Company
4701 Lydel\ Avenue
Cheverly
Industrial Center
Cheverly , Maryland 20781
[phone]
EASTERN U. S.
Mincom Division
3M Company
4701 Lydell Avenue
Cheverly
Industrial Center
Cheverly, Maryland 20781
(30 I) 77 3-5050

LIST OF EFFECTIVE PAGES
This page indicates the effective pages for a specific issue of this publication. The latest issue of this
publication may not be the correct version for
your equipment. When ordering a publication, please
specify the issue originally received with the equipment.
To order a publication, give the catalog number
of this publication, and the complete manual number
shown
at the bottom of this page.
Issue, date and manual number are:
Issue I Feb.
71
Issue 2 Mar. 72
TOTAL NUMBER
OF PAGES IN THIS PUBLICATION IS 196 CONSISTING OF THE FOLLOWING:
Page Issue Page Issue
No. No. No. No.
Title 2
103A/I04A.
2
A.
2 105/1 06 2
i through v/vi 1 107 through
II 2 I
I through 102 I
113/114 through 117/lIB
2
103/1
04
2 119 through
204 . 1
This manual
is Catalog No. 83-5990-1174.
M64 PAR 3-72 A
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TABLE OF CONTENTS
GENERA L DESCRIPTION
Functional Description
lsoloop Tape Transport
Physical Description .
Equipment Description
Specifications . . . .
INSTALLA TION
Receipt Inspection
General . . . . .
Location Considerations.
Console Model Installation.
Rack (or Custom) Mounting
Electrical Connections
Power and Control Cable
Head Cables. . .
Signal Connectors
Pilot Tone. . . .
Remote Control .
Edit Foot Control
Power Cord. . .
Inte rface Information
Signal Input .
Signal Output
Remote Meter
Pilot and Loudspeaker
Phones .....
Auxiliary Ground
OPERATING CONTROLS AND DETAILS
Tape Transport Controls
PLA Y Button
FORW ARD Button .
STOP Button
REWIND Button
RECORD Button
POWER Switch
A-B OUTPUT Transfer Switch
RUNOUT Switch .
SPEED Switch. .
BALANCE Switch
M64 PAR 2-71
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4
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TABLE OF CONTENTS (Continued)
OPERA TING CONTROLS AND DETAILS (Cont. )
Tape Transport, Tape Handling Components
Reversing Idler.
Head Assembly. .
Tape Lifters
Head Shield Door .
Capstan. . . . .
Capstan Idler (Incoming)
Capstan Idler (Outgoing)
Tape - Threaded Sensor
Reel Holders .....
Electronics Assemblies ..
RECORD LEVEL Control
REPRO. LEVEL Control
REC. SELECT Switch
METER Switch. . . . .
OUTPUT SELECT Switches
REC. Indicator.
PHONES Jack . . . . . .
GENERAL OPERA TING PROCEDURES
Preliminary
Threading
Monitoring
Recording
Playback
Overdubbing
Erasure ..
ALIGNMENT AND ADJUSTMENT
Tape Transport. . . .
Capstan Belt Adjustment
Flutter . . . . . . . .
Record Alignment
15 IPS Tape Speed Alignment . .•
7 1/2 IPS Tape Speed Alignment
Dynamic Range Adjustment (NAB)
Miscellaneous Adjustments and Circuit Arrangements
Heads ...
Tape Guides
Reel Hubs
M64 PAR 2-71
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48
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ii

TABLE OF CONTENTS (Continued)
MAINTENANCE
General Precautions
Troubleshooting. . .
Field Service
. . . .
Factory Repair Service
PRINCIPLES OF OPERATION
Introduction. . . . .
Tape Drive Components . . . . .
Tape Transport Circuit Descriptions
Power Circuits .....
Threaded Tape Condition.
From Standstill to Play
From Play to Stop .. . .
From Stop to Rewind. . .
From Rewind to Stop (Tape Moving i.n Rewind Direction)
From Rewind to Stop (Tape Moving · in Forward Direction)
From Stop to Forward . . . . . . . . . . . . . . . . . .
From Forward to Stop (Tape Moving in Forward Direction),
From Forward to Stop (Tape Moving in Rewind Direction)
From Forward to Rewind
From Rewind to Forward.
From Rewind to Play
From Forward to Play
Tape Runout . . . . .
Record Mode Operation
Speed Change Switch.
Reel Size Switch . . .
Torque Control Relay
Monitor Switching
Runout Switch . . . .
Fail-Safe Brakes
Signal Electronic s Functions
NAB Electronic s . .
NAB Recording . . . . .
NAB Reproducing . . . .
Detailed Circuit Descriptions
. '
NAB Record Amplifier (4)
Bias and Erase Amplifier (1)
Preamplifier (7/9) ... .
Line Amplifier (6) . . .. .
Power Supply Assembly (5)
NAB Erase Coupler (3N) ..
M64 PAR 2-71
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TABLE OF CONT, ENTS (Continued)
Page
SCHEMATICS
PARTS LISTS
Introduction . . . . . . . . 12 J
Ordering Replacement Parts
121
LIST OF ILLUSTRATIONS
Figure No.
Page
1 3M Brand Professional Audio Recorder. . . . . . . . 2
2
Isoloop Tape Drive ..... . ........... 3
3
3M Brand Professional Audio Tape Recorder Systems 5
4
Tape Transport .." . .... . 6
5
Electronics Assembly (One Channel) . . . 7
6
Outline Dimensions, Console Models . . . 13
7 Outline Dimensions for Rack Mounting and Custom Installations. ]4
8 Typical Rack Mounting Layout . . . . 15
9 Transporter Case Outline Dimensions 16
10
Cable Connections . . . . . . 17
11 Signal Input Connector Wiring
20
12
Signal Output Connector Wiring
21
13 Pilot Connector Wiring
22
14
Tape Drive Components
28
15 Electronic Controls
31
16
Tape Threading
36
17
Tape Transport Adjustments, Top View
38
18
Tape Transport Adjustments, Bottom View
39
19
Capstan Motor Mounting Bracket . . . . . 41
20
Example of Simple Stroboscope Lamp
42
21
Electronics Assembly Adjustment Locations
51
r'
22
Record and Playback Head Azimuth Adjustments
53
23
Reel Hub Adjustment . . . . ..
62
24
Tape Recorder, Block Diagram
74
25
Tape Transport Schematic ...
99/100
26
Tape Transport Circuit Board Layout
101/102
27
Tape Transport Wiring Diagram . .
103/104
28
Electronics Block Diagram .. ..
105/106
29
Remote Control Assembly Schematic
107/108
30
Bias and Erase Amplifier Schematic
109/110
31
NAB Erase Coupler Schematic . . .
111/112
iv
M64 PAR 2-71
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LIST OF ILLUSTRATIONS (Continued)
Figure No.
Page
32 NAB Record Amplifier Schematic ... . ..
113/114
34 Electronics Assembly Power Supply Schematic
115/116
34
Line Driver Amplifier Schematic . . . . .
117/118
35
NAB Preamplifier with Overdub Schematic
119/120
36
Tape Editing Switch Assembly
37
Tape Deck Assembly ........ .
38
Remove Control Assembly ....... .
39
Audio Signal Electronics Housing Assembly
LIST OF TABLES
Table No. Page
3M Brand Professional Audio Recorder Components . . . . .. 8
2
Standard Dynatrack and NAB Head and Signal Cable Connections 19
3
Capstan Speed Error (for 48 element strobe wheel) 42
4 Spring Scale Reading to Motor Torque Conversion Table 44
5
Takeup Motor Torques. . . . . . . 44
6
Supply Motor Torques . . . . . . . 45
7
Components Contributing to Flutter 48
8
Troubleshooting . . . . . . . . . . 64
9
Line Operating Level Calibrating Resistors 94
10
Parts List Index. . . . . . . . . . . . . . 122
M64 PAR 2-71 v/vi
:

GENERAL DESCRIPTION
The 3M Brand Professional Audio Recorder is manufactured by the
Mincom Division of the 3M Company in Camarillo, California. It fulfills a
requirement in the professional rec ording industry for the ultimate quality in
tape rec ording. The continued improvements in records, tape s, and playback
equipment revealed deficiencies in original master recordings. The 3M Brand
Profe s sional Audio Recorde r overcomes the se problems and provide s improved
master music tapes - - improvement readily discernible by ear.
The 3M Brand Professional Audio Recorder provides a significant
improvement over present professional audio recorders in three basic areas.
Probably the most important of these is the improved dynamic range . The
second area of improvement is a new tape drive system that reduces flutter to
half that present in other tape transports in the audio field. Third, the entire
system affords an operating ease unmatched by any other tape recorder. Other
improvements not readily apparent, are an increase in the long-term reliability
due to the exclusive use of silicon transistors in the electronics assemblies
plus the simplified tape -drive sy stem.
The 3M Brand Professional Audio Recorder achieves its outstanding
performance from a patented technique of an Isoloop tape drive system ; plus
experience gained from over a decade of design and manufacture of Mincom,
state-of-the-art, aerospace tape recorder /reproducer systems.
FUNCTIONAL DESCRIPTION
Functionally , the 3M Brand Professional Audio Recorder operates on
the same basic principles as any other tape recorder. These principles are
covered in many text books and will not be presented in this manual. As stated,
the feature that gives this recorder its outstanding performance is the Isoloop
tape drive.
ISOLOOP TAPE TRANSPORT
The tape transport mechanism of the 3M Brand Professional Audio
Recorder is derived from designs used in instrumentation recorders, where
standards of timing accuracy, and wow and flutter are even more demanding
than they are in audio recording. The heart of the patented Isoloop tape drive
is the differential capstan, which maintains a constant tape tension within the
drive and positive contact of the tape against the heads (figure 2). In addition,
the unsupported tape path is extremely short in comparison to standard design
tape recorders. This short path reduces longitudinal oscillation to a new low
and eliminates the need for a series of tape guides to maintain a proper tape
path.
M64 PAR 2-71

2
_ J
=
Figure 1. 3M Brand Professional Audio Recorder
M64 PAR 2 -71

The tape tension required to mlnImize flutter and hold the tape against
the heads is generated within the closed loop by the differential drive capstan.
The tape drive surface of the capstan is divided into regions of two different
diameters. The incoming idler roller is contoured so as to press the tape firmly
into the matching "grooves" (of the smaller diameter) of the capstan. The out-
going idler roller is shaped so as to press the tape firmly against the "ridges"
(of the larger diameter) of the capstan. This differential of capstan diameters
constantly tries to extract more tape than is being fed into the loop and creates
the necessary tension by means of the slight elasticity of the tape itself. This
tape tension is always kept safely within its elastic limits.
The Isoloop tape drive, short tape path, and flywheel driven capstan all
aid in reducing the flutter of the tape transport to approximately half that found
in other professional tape drive systems.
INCOMING CAPSTAN IDLER
OUTGOING CAPSTAN IDLER
1186
Figure 2. Isoloop Tape Drive
M64 PAR 2-71
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3

4
PHYSICAL ' DESCRIPTION
The recorder is supplied in eight configurations. It is available in a
standard console, or unmounted for installation in a 19-inch equipment rack
(figure 3). Complete installation instructions are given under Installation.
Physically, each recorder consists of a tape transport and electronics as re-
quired. This may be either 2 or 4 channels of NAB electronics. A single
channel is available on special order for use with a 1 /4-inch full track recorder .
EQUIPMENT DESCRIPTI , ON
Each tape recorder will have a tape transport (figure 4), and one elec-
tronics assembly (figure 5) for each record and play channel, see table 1. Also,
a recorder may have any of the accessories listed in table 1.
The basic tape transport is the same in all recorders, the on l y difference
is in the tape width, magnetic heads, and capstan speed. The tape guide sand
magnetic heads are installed depending upon the number and type of channels . The
transport is available with either of two capstan sizes - 1/4-inch or 1 /2-inch tape.
The electronics assembly contains the electronics required for a single
channel of NAB record and playback. Each electronics assembly contains a plug-
in power supply, controls and indicators, and five plug-in circuit boards. There
is an input and an output transformer located behind the control panel. All elec-
trical connections for each channel are made on the rea r panel of the electronic s
assembly. A VU meter for each electronic assembly is located on the meter
display panel.
The electronics assembly plug-in circuit boards are numbered I, 3, 4,
6, and 7/9 on the board handle indicating the slot that the board goes in. Slot 2
is always empty and the power supply is slot 5. An optional plug-in circuit board
7/9 can be installed in slot 9 if permanent overdubbing is desired without having
to remove circuit board 7/9 from slot 7.
The tape transport operates at either of two electrically selectable tape
speeds. The speeds are 7 -1/2 and 15 ips or 15 and 30 ips. The electronics
equalization is automaticaliy switched to the selected tape speed.
The tape transport contains the tape motion controls and tape handling
controls; plus, it performs functions common to all of the electronic assemblies.
It provides tape speed equalization control, the source of bias and erase fre-
quency, the A-B transfer function, and control of the record function. The
POWER button on the transport controls the power to the entire system. The
electronics assembly contains all of the remaining controls, such as the record
and reproduce level controls, and the meter control.
._,
M64 PAR 2-71
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UNMOUNTED
Consists of tape transport and electronics.
Transport is complete with required magnetic
r
heads and ready for horizontal or vertical
mounting. Electronics are individual modular
panels and provide standard NAB.
CONSOLE
Transport and electronic s
mounted within a console
cabinet.
Figure 3. 3M Brand Professional Audio Tape Recorder Systems
M64 PAR 2-71
-- ;-..-;- ------_.
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REEL "-...
/
/TAKEUP
REEL
UTGOING
TAPE GUIDES
AND TAPE SENSOR
INCOMING
TAPE GUIDES
DIFFERENTIAL
MANUAL TAPE DRIVE CAPSTAN
LIFTER OVERRIDE
AUTOMATICALLY
POWER
SHIELD
ON-OFF
A-B
SIGNAL OUTPUT
SELECTOR
~~[Q]~~!hJ
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PROFESSIONAL
RECORDER
SPEED SELECTOR SWITCH • _"I ~
~Ik@frlkihj
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I~~--+-------------~~---;r-----OPERATED HEAD
RUNOUT SELECTOR SWITCH ~ .. i ..
REEL BALANCING S\MITCHES ~ _. •
(UNDER SLIDE COVER)
1174

OUTPUT TRANSFORMER
" 76
Figure 5. Electronics Assembly (One Channel)
M64 PAR 2-71
7

8
Table 1. 3M Brand Profe ssional Audio Recorder Components
COMPONENT DESCRIPTION
TAPE TRANSPORT CHASSIS ASSEMBLY
TAPE TRANSPORT ASSEMBLY
64013A085
SEeed ~i:es)
Tracks
Ta:ee
7 1/2,
15 4 1
/2 inch
15,
30
4 1
/2 inch
64013A080
7 1/2,
15 2 1/4 inch
15,
30 2 1/4 inch
COVER PLATE
23000A005-1
24 inch (10 1/2 inch reel)
This assembly is used for
either 60 Hz or 50 Hz input
power.
This as sembly is used for
either 60 Hz or 50 Hz input
p ower .
ELECTRONICS ASSEMBLY
ELECTRONICS ASSEMBLY
64059AO 10
BIAS & ERASE AMPLIFIER CIRCUIT BOARD
23059A020
NAB ERASE COUPLER CIRCUIT BOARD
23059B030
NAB RECORD AMPLIFIER CIRCUIT BOARD
23059B040
POWER SUPPLY ASSEMBLY
6403lAOOO -1 (4 track)
6403lAOOO -2 (2 track)
LINE DRIVER AMPLIFIER CIRCUIT BOARD
23059A060
NAB PREAMPLIFIER VI ITH OVERDUB
23059B090-1 (7.5 - 15 ips)
23059B090-2 (15 - 30 ips)
Consists of the basic elec-
tronics chassis assembly
less all of the plug-in units .
Part of the rec ord circuit -
installed in slot 1.
Part of the NAB record cir-
I cuit - installed in slot 3.
Part of the record circuit -
installed in slot 4.
Power supply - installed in
slot 5.
Part of the reproduce circuit
- installed in slot 6.
Part of the reproduce circuit
with overdub feature - nor-
mally used in slot 7. Installed
in slot 9 for overdub operation.
M64 PAR 2-71
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Table 1. 3M Brand Professional Audio Recorder Components (Cont'd)
COMPONENT
DESCRIPTION
METER HOUSING PANEL
Housing Panel VU meters are mounted on this
22028A040 -2
panel. Two (2) meters for 2
track; four (4) meters for 4 track .
Special order 1/4 inch. full track
panel utilizes 1 meter.
VU Meter
Monitors record. playback. as
23059B052
erase signal levels. and the mag- I
nitude of high frequency bias
current.
CABLES
TRANSPORT - TO-ELECTRONICS
POWER AND CONTROL CABLES
23028A050 (2 and 4 track)
HEAD CABLES
23000AO 1 0-2 (2 tracks)
23000AOIO-4 (4 tracks)
3-foot cable. 15 -pin connectors.
This cable is about 66 inches long,
and connects between the head plate
on the transport and ehca channel
of electronics. There is a play (P).
record (R). and erase (E) head
ca ble for each track.
ACCESSORIES
REMOTE CONTROL (with 5-foot cable)
This unit provides remote control
23017AOOO
of the RECORD, PLAY. STOP,
REWIND, FORWARD. and A-B
OUTPUT transfer functions.
REMOTE CONTROL EXTENSION CABLE A 25-foot extension cable for the
23017AOI0 remote controls.
EDIT FOOT SW ITCH Permits hand-free spill/standby /
23000A950 wind for rapid tape editing.
EXTENDER BOARD Extender board for circuit boards
23059AIIO in the electronics assembly.
t -.
M64 PAR 2-71 9

SPECIFICATIONS.
Specifications for the 3M Brand Professional Tape Recorder are presented
at the end of this section. These specifications are based upon operation in
accordance with the procedures and conditions presented in this manual. Deviation
from these procedures, use of other than recommended magnetic tapes, or modi-
fication of the equipment may result in degradation of the equipment performance.
These specifications are subject to change without notice.
.,
M64 PAR 2-71
10

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PROFESSIONAL
RECORDING SYSTEMS
Model PAR 410 M·64
Console Mounted
1/2 Inch 4 Track
Recorder/Reproducer
SPECIFICATIONS
NAB ELECTRONICS
NUMBER OF CHANNELS: 4
SIGNAL·TO-NOISE
RATIO :
Standby Biased Tape
Normal
65dB
62 dB
70
mil track width 20 Hz . 20 kHz bandwidth, with
reference to 3% maximum third harmonic distortion level
at 700 Hz, using tape specified below.
TAPE TYPE:
Spec ifications based on employment of
"Scotch" Brand recordi ng tape 201 , 202, 203,206, or 207.
Adjustable bias
and equalization permits accommodation
of wide range
of tape characteristics.
EQUALIZATION : Machines are normally equalized to
NAB 15 and 7 1/2 ips speeds . Equalizers automatically
switched when tape
speed is changed. Other forms of
equalization may be provided on order.
FREQUENCY RESPONSE:
7.5
ips reproduce :1:2 dB 30 Hz . 12 kHz
7.5 ips record/reproduce response
±2 dB 30 Hz . 12 kHz
15 ips reproduce
±2 dB 30 Hz· 16 kHz
15 ips record/reproduce
±2 dB 30 Hz . 15 kHz
PHASING: On all channels signal input to output polaritx
is maintained. 1 mil wavelength phase error less than 90
between any two tracks.
CHANNEL SEPARATION : Channel to channel crosstalk
separation
is greater than 50 dB at 500 cycles (zero VUI.
ELECTRONICS INPUT: 20,000 ohm fully floating or un·
balanced line. ·10
dBm to +8 dBm signal on 600 ohm bus.
ELECTRONICS OUTPUT: +4 dBm reference level
into 600
ohms. Distortion less than 1% at +28 dBm . 600 ohm termi·
nation switch provided.
PHASE CORRECTION: Playback
amplifier includes phase
rotation circuit to optimize square wave and transient
response
for each speed .
BIAS AND ERASE OSCILLATOR . Master oscillator on
tape transport supplies 120
kHz low impedance bus feeding
individual bias and
erase power amplifiers for each channel.
DEGREE
OF ERASURE: A 1,000 cycle signal at 3% dis·
tortion level is reduced 72 dB or more by the era .. head.
POWER
INPUT : 110 to 13S volts ac . 60 cycles. Internally
regulated power supplies make transformer tap changes
unnecessary over this range. Optional
SO cycles power.
MECHANICAL
SIZE AND WEIGHT :
Height:
53·3/4 inches.
Width: 27 inches.
Depth:
22 · 112 inches.
Weight:
Approximately 250 pounds.
SPEEID: 7·
1/2 and lS ips standard.15 and 30 ips available.
REEL SIZES: NAB hUb .Adaptable to CCIR or small plastic
reel hubs. Standard reel
10·1/2" diameter. Alternatively,
l1-1/r diameter reels can be furnished for CCI Rapplications.
FLUTTER:
Speed (iPS)
Flutter Band 1Hz) Maximum Flutter (rms)
30 0.5 to 200 O.
OS%
0.5 to Sooo 0. 08%
15
O.S to 200 0. 06%
0.5. to Sooo 0.08%
7·1/2 O.S to 200 0.1%
O.S to Sooo O.lS%
NOTE: All mMsuremenu of fluner made by record i ng e tone on
mec:hine under test, rewinding end me.uring flutter on repley.
Flutter meesurement is ITlIIllimum cumulative un_ighted.
TIMING ACCURACY: :1:0 . 1% .
START TIME: Less than 1.0 seconds to reach sync speed .
STOP
TIME: 1.0 second from play or record mode.
REWIND TIME: 1.7 minutes for 2,400 feet.
TRANSPORT CONTROLS: Operating controls located on
lower
edge of transport.
Left Corner: POWER ON/OFF
(backlighted pushbutton)
SPEED
HIGH/LOW
(slide switch)
OUTPUT A (pushbutton) . Commands
signal electronics
to present incoming
lines
to output jacks of recurder.
OUTPUT B (pushbunon) . Commands
signal electronics
to present the recorded
signals at the
output jacks.
Right Corner: Backlighted pushbuttons
for
PLAY
FORWARD
RECORD" REWIND
STOP
'Play and record button must be pressed simultaneously to
initiate the record mode;
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