International Tapetronics Corporation 770 Series User manual

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• J
TECHNlCAL MANUAL
7· 70 SERIES
REEL-TO-REEL
RECORDING AMPLIFIER
n Rn 10
2425 Sou Main Street B oommgton. llbn01 61701

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TECHNICAL MANUAL
(890-0025-000)
770 SERIES
REEL-TO-REEL
RECORDING AMPLIFIER
Th is Technical Manual is intended to be u se d as
a supplement to , and in conjunction with ITC
Technical Manual
890 - 0024 - 000 , for the 770
SeriesReel- to -Reel Reproducer.
1nreRnATIOnAL TAPETROn1cs CORPORATIOn
24 25 SOU TH MAIN STREET • BLOO MINGTON, IL LIN OIS 617 01
© Cop y right 1981 lnt e rnatlonal Tap etr onics Corp oration.
Madeunder
one or more of the following patents:
3.800, 3233, 801, 0433.801.3293,833. 925 3.865,719
otherpatentspending

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0381OM
PREFACE
THEITC INSTRUCTION MANUAL
International Tapetronics Corporation Manuals are
written with the intent
of assisting the reader-user toward
a better understanding
of ITC equipment. Most instruc-
tion manuals are seldom read except
at the time of crisis
when equipment malfunction is suspected. When this
happens. the manual is usuaJly missing,
or at best, diffi-
cult to locate. PLEASE FIND A CONVENIENT SPOT
TO KEEP THIS MANUAL.
We at ITC have tried lo produce a useable manual.
But, being human. we are subject lo the frailties of be-
havior, Therefore, should you discover any errors
or
omissions. or should you wish to contribute any recom-
mendations, please send us
your comments. We will be
mostappreciative.

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TABLE OF CONTENTS
PREFACE .......... .. ... .. .. . ....... . ... .. ........ - ................... i
TABLE OF CONTENTS ... . . .. .. . .... .. ....................... , ...... iii
ILLUSTRATIONS. . .................. . .... . , .,. ,, .. , ..... , .. , ...... , .. v
SECTION I. INTRODUCTION
A. General ........... . . . . . .. •• .............. , ................ • ... l ·l
B. Reco r der Electronics . . . . . . • . . . . . . . . . . • . .. . . . . . . . . . . . . . . . . . . . . . . . .. 1-1
C. HeadAssembly ...... • ............. • .... ,.,, •• . • . , ., ....... 1-1
D. Specifications . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . • . .l •l
E. Warranty. . . . .• . . • .•• •. .• ••... .• ... •• ... • .................•.. 1-2
SECTION II . INSTALLATION
A. Unpacking and Handling ................................. . .......... 2-1
8 . Installation in Rack or Console ............. • ... • .... , ...... •• .. .•• .. 2-1
C. Connecting Audio Lines . .......... . ..........• . ...... . .... • ... , ..... 2-1
D. Remote Control Connections . . • , •. • ... • , • .. . , • , . . . •. . . . • . . . .• . . .. ,2· l
E. Preliminary Tests ............................. . .................... 2-2
SECTION Ill. UNIT OPERATION INSTRUCTIONS
A. Controls and Indicators . . . . . . . . . . . . . . . . . . . . . . _ ... • ..... •• ... , .•. .... 3-1
1. Record Set Switch
2 .
Channel Select and P.R.S . (Play- RecordSynchr onization)
3. MeterSelect
Switches
4. LED Indicators
B. Recording
.......... ..• ,
..... , ..... 3-2
SECTION JV . SETUP, ALIGNMENT, AND CALIBRATION
A. General .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..... • ....... 4-1
B. Playback Meter Calibration
....... .. .. , . . . . . . . . . . . • . . . • . . . . . . . . . . . . 4-1
C. Record
Head Alignment ... _. . . . . •. . . . . . . . . . . . • . . . • . ... • ......... 4-1
D. Bias Trap Adjustment .... . ..................... . ........... • ........ 4-2
E. Bias Adjustment .... . . . . . ..... . ... • ... • ........ . •. . ... . , .. , . , .... 4-2
F. Recording Amplifier Equalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . 4-3
G. Record Line MeterCalibration (Rec) . . . . .................. •. .... .. ... 4-3
H. Two Spe ed Re co rdingAmplifier Level Calibr ation ......... • ... •• ....• • . . . 4-4
I. P.R.S . Amplifier Bias Trap ........... , . . . . .. . ..... . - . . . . .... 4-4
J . Bias Meter Calibration . . . . . . . . . . . . . . • .. • . , . . . . . .... . .......... • .... 4-4
K P.R.S. Amplifier Meter Calibration
........• . ...•..... _.......... . .... 4-4
SECTION V. ROUTIN E MAIN TENANCE
A. General . . . . . . . . . . . . . . . . . . . . . . . . ... • .... ,• . . . ................. 5-1
8 . Maintenance Tools and Aids ...... . ...............•..........•• • ..... 5-2
C. Spare Part s ..... . .......... , ... • , . . . . . ..... • .. • ................... 5-2
SECTION VI . THEORY OF OPERATION AND DESIGN
A. General . . ............................................... , • . . . . 6·1
B. Recorder Control Logic ................... . ..... .. ........... • ... , .. 6-1
C. BlasOscillator ........... • ..... , • , ... • ... , ..... • .. • , , . .... , ......... 6-1
D. Meter Amplifiers ......... . .... . ..................................... 6-1
E. Program Recording Amplifier ., .. , . . . . . . . . . .... ,, , , . , • ... , ........... 6-2
F. Play-
Record Synchronizing (P. R.S .) Amplifier ... • ....• • .... •• ......... 6-2

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SECTION VU . ELECTRICAL DRAWINGS AND PARTS LIST
A. Record and MeterAmplifier Componen t Loading and Overlay .. .. .. ..... 7-1
8. Record and Meter Amplifier Parts List . . . . . . . . . . . . . .. . .... . . .. . . 7-2
C. Bias Oscillator
and RecorderControlCo mponent Loading and Overlay , ... 7-5
D. Blas Oscillator
and RecorderControlParts Ust ... . . . . . . . . . . . . 7-6
E.
L. E.D. Indicator Card Component Loading and Ov erlay . . . . • . ... . , , . 7•8
F. Mother
Board Component Loading and Overlay ... ... . ... . •... . . . ... 7-9
G. Mother
Board PartsList . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . • , 7- 10
H. R ecord Amplifier Schematic ... .. . .. ... .. ..... ,. , .... , . . .. . 7•11
iv

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Figure 2-1
Figure 2-2
Figure 2-3
Figure 2-4
Figure 3-1
Figure4 -1
Figure 4-2
Figure 4-3
thru 4-6
Figure 4-7
Flgure4-8
Figure 5-1
Figure 7-1
Figure 7-5
Figure 7-8
Figure 7-9
Figure7-
11
ILLUSTRATIONS
P age
Record Amplifier Input Connections . . . . . . . . . . . . . • .. . . 2-1
Remote
Control Connections . . . . . .. •. , • , • , , , . •.• . 2-2
CableInterconnect Diagram . . •. . . .. . . . . . . • . . . .. . . . . . . 2-2
RearPanel Connectors ........... .. , ...• , . . . . •• . . . . . 2-3
Front Panel Controls . . . . . . . . . . . . . . . . . . . . . . . . • . . . •. .3-1
MeterCalibration Adjustment Points . .. •. . . .• • •. , ., .. 4-1
Head AdjustmentPoints ........... . .. . ..... .••...•.. .. 4-2
Oscilloscope Phase Patterns ..... . .... .. .. .. . .•...•
Bias AdjustmentPoints . . . . . . . . . . . .. . . . . . .• . . . .
Equalization and LevelAdjustmentPoints
....... .•..•
MaintenanceSchedule. . ........... . ........ ..... .
Record andMeterAmplifier
Component Loading
. . 4-2
... 4-3
,. 4-3
.... 5-1
andOverlay
.... . .... ............ .. .. ... ......... 7-1
Blas Oscillatorand RecorderControl
Component Loading
andOverlay . .
................. . .......... . ........ 7-5
L.E.D . IndicatorCard Component Loadingand Overlay ... 7-8
Mother Board Component Loadingand Overlay . ,. . . . . . 7-9
Record AmplifierSchematic . . .. . . . .. . . . . .
... .••... 7-11
V

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SECTION I - INTRODUCTION
A. GENERAL
The 770 Se ries R ecorde r is designed for the broad -
caster. It
is idea ll y suited for use as a utility recorder
automation syst em. The 770 Seriesis:
• deslgned
to meet or exceed the N AB (National
Association of Br oadcaste r s) standards for reel- to •
reel tape recorders:
• available in a variety of con figurationsincluding,
. one or two track, mono or stereo capabilities
and
. tap e speeds of 3-3/4 to 7-1/2 and 7-1/ 2 to
15 IPS:
• designed with a heavy 1/ 2 inch (12.700 mm) thick
aluminum to ol plate deck for stability:
• designed with a unique , h ig h quality, professlonal
head assembly;
• utilizes individual
torque motors for supply and take
up reel handling,and a D.C. servo ca pstan mot or for
tape drive; and
• designed for simp li city and se rviceability ofelectronic
c
omponents .
The 770 Series Record Amplifier and Transp ort
ieatures:
• low maintenance. positive action differential disc
brakes:
• strong, cast stainless st eel turntables;
• long li fe co ntrol switch es and an ingenious swllch
s
upp ort:
• multispeed D
.C . servo caps t an motor ;
• im proved playback head .
All 770's ar e factory wired to accep t the ITC sub-
audible 25 Hz detector module assembly. which is avail-
able as an option. This plug-in module is designed to
provide a variety of opera ling mode s.
8. RECORDER ELECTRONICS
T he electronics of the 770 Series Recording Amp lifier
provides simplicity and se rviceability. Th e mother /
daug hter board and ribb on cable connectors elimi nat e
bulky wiring. All maintenance adjust m ents are eit h er
accessible at the fr on t panel or directly above t he printed
ci rcuit ca rds.
Front
pane l meter switching allows the o perator to
monitor the playback ou tputs . the recorder inputs, Pl ay -
Re co rd Synchronizi ng , and program re co rding bias. T he
meter m onito ring mode m ay be au tomatically switch ed to
pr
ogram play when In th e play mode ev en though the
r ecorde r inpu t monitor switch ma y be selected.
An input fr om the meter am plifier is brought ou t to the
front panel of the recorder . H eadphones may be plugged
in al th is point for moni to ri ng purp oses. An additional
o
utpu t is brought out to th e rear panel or the re co rder
which may be used for the same purp ose.
0381DM
T he stereo model is equipped wi th the Play-Record
Synch ronizing feature. P.R.S. allows the recor ding of
information
on one track in sync hronizati on with material
previously recorded on the o th er track.
The
recorder electronics may be mounted directly
below the reprodu ce transp ort or in a remote locati on up
to 42 inches (1066 . 80 mm) away . A roll- around console
is available as a sp ec ial option .
C. HEAD ASSEMBLV
T he ITC 770 Se ri es recorder is equip ped With a
unique, high quality professional head assembly The
head is mounted in a bracket designed to allow total
azimuth, height and zenith adjust ments . Three plug -In
heads are used in conjunction with independenUy
mounted tape guides. Th e head assembly Is eq uipped
with a solenoid actuated tape lifter. EJectr!cal co nnec-
tions to the h ead assembly. l ocated on the transport
deck , are ma de thro ugh special in t erconnec t cables.
D. SPECIFICATIONS
Power :
(includes reprodu ce deck and recorde r electronics)
10 5- 12 5 volt s. AC, 60 Hz , 165watts max.
Recorder Sourc e Impedance :
600o hms
Re c order Jnput Impedanc e:
5000 oh ms balanced (15 K ohm bridging str;:1p -
pable)
Input Lev el:
- 22 dBm (.061 volts) m1n1mum to record 1) 1 '' O''
refer ence level (1 85 nWb / m flux level) + 8 dBm
(1.96volts) maximum
Distortion (Record to Play):
Using 4 00 Hz ton e r eco rd ed at NAB standard
referen ce level (•) with r eproduce amplifier ad-
justed for O dBM output , and meas uri ng on a
distortion. analyzer with a
700 H z. to 20 kHz band -
width
15 JP S 1. 2%
7.5 IPS 1.5%
3.
75 lPS 2. 0%
NOTE! All distortion r eadings are t ape -limited.
Amplifi er Headroom:
Maximum amplifier he ad r oom above reference
level (1 85 n Wb / m) using frequencies of l kHz and
10 kHz.
Tap e Speed
15 !PS
7.5 JP S
3. 75 I PS
1 kHz
+23dB
+2 3d B
+23dB
IO kHz
+ 23d8
+ 19dB
+ 12 dB
1- 1

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1-2
Crosstalk:
Better than 50 dB at 1 kHz
Fre qu e nc yResponse:
3-3/ 4 ips (+ 2d8-3.5d8) 25 to 35 Hz; ±2d8 35 to
8, 000 Hz .
7-1/ 2 ips (+ 2d8 - 3d8) 25 to 35 Hz ; ± 2d8 35 to
15.000 Hz.
15 ips (+2dB -3.SdB) 25 to 35 Hz ; ±2d8 35 to
18 ,000 Hz.
Equalization :
NAB withadjustments for highfrequencycontrol
Hea dphone Output :
8 ohms or greater
Meter Amplifier Monit or:
600 ohms (available at rearchassis)
Remote Control :
Record se t switch and recordindicator lamp
External Connectors:
Latching and phono types Mating plugs and
sockets furnished.
H ea d and Track Configuration:
F1JII Tr ack monophonic
Half Track monophonic
Hal f Tra ck stereophonic (2 channel)
Qua rter Track stereophonic(2 channel)
Metering:
T aut -band moveme nt with "A" scale. Meter switch
selection for metering the following:
Normal line recording level, P.R.S. bias and pro •
gram play, (Meter sensitivity may be
ca librat ed for
0 to + 18 dBm o utput level.)
Erase De pth :
Below Noise Level
Ambi e nt Op e rat i on Te mperature :
55° C - 131 °F maximum
Mounting :
Rack mo unt ing. (Console cabinet op tional.)
Dimen sions:
19 inch es wide (482, 60 mm)
9 inches deep (228.60 mm)
3-1/2 inches high (88 . 90 mm)
Weight :
15 pounds (6, 805 kg) unpacked
(•) Measureme
nt s made using 3M type 206 or
equivalent tape
E. WARRANTY
Seller warrants to purchaser that the equipment sold Is
free of defects of workmanship or material and conforms
to the specifications refe
rr ed to set out herein. This
war r anty extending only to the original useris For a period
of two years from date of shipmentand no claim sha ll be
maintained hereunderunless written notice is received by
Seller within thirty days after discovery of thefacts giving
rise to the claim. Thesole
or exclusive liability of Seller for
breach
of warranty shall be to refund th e purchase pri ce
of the item sold, or at its option, to replace or repair the
item
or part concerned FOB its fac tory, or such other
place
as it may designate. Seller's liability shall arise only
if pu rchaser causes the defective part or item to be
delivered
to Seller f or inspection upon Seller'srequest at
pu rchaser's expense. Items manufactured by persons
other than Seller shall bear the warranty given by such
otherpersons and
no other warranty. This warranty shall
not be effective if the alleged defect is due to maltreat-
ment, exposure. excessive moisture. or any other
use of
equipment other than the use for which the manu-
facturer prescribed.
0381DM

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SECTION II -INSTALLATION
A. UNPACKING AND HANDLING
Carefully remove the 770 Series Recording Amplifier
from
the shippingcarton and inspect1he unit for damage .
All packing material must be retained if a claim for
shipping
damages is to be flied. and therefore, should be
kept on hand until installation has been c ompleted in case
concealed damage is discovered_ If shipping damage Is
found, contact ITC for assistance in claims. It is sug -
gested
that packing material be retained for any future
use .
B. INSTALLATION IN RACKOR CONSOLE
All 770 Serles Re cording Amplifier modules are
supplied in a 19" (482. 60 mm) rack mounting configura-
tion. If
an excessive amount of heat Is present in the rack
in which
the machine is to be mounted, be certain to
supply adequate ventilation for proper operation of this
unit. Ideally,
the recording amplifier module should be
mounted directly under the 770 SerlesPlayback Deck, so
that heat rising from the torque motors and other heat
producing components will not contribute any heat lo the
recording electronics.
All consoles for I TC reel to reel recorders and re -
producers
are shipped separately and , therefore, will
require mountingfollowing shipments.
After removing
the console from the packing material,
install the four casters
in the bottom of the console legs.
Set the console upright and rotate the transport deck
table
to its vertical position by pressing the release button
located
on the front upper right hand side of the console
cabinet. This
will allow the table to rotate and lock in
various planes. With the aid of another person , carefully
slide the transport mechanism into
the mounting area .
NOTE:
When handling the transport, be careful not. to
damage Items such as motors and brakes_
After
the transportis properly located, carefully rotate the
table back to its horizontal position. Secure the assembly
wi th the enclosed rack mounting screws and washers.
Included with
the co nsole is a 1-3/ 4' ' (44.45 mm) filler
panel . This panel must be mounted toward the top end of
the transport deck assembly in order to fill the vacant
space .
The recorder chassis is mounted by sliding it into
position from
the front of the console and then securing ii
with the enclosed hardware.
C. CONNECTING AUDIO LINES
A 6-pln socket is provided with each 770 Series
Recording Amplifier for
the audio input connections.
R
efer to Figure 2-1 for the connection of this socket
Observe the proper phase relationship on two channel
units.
0381OM
A 600 ohm unbalanced output of the meter
amplifier(s) is provided on the rear of the recording
amplifier chassis.
J703 and J704 are standard phono
type connector sockets.
It is recommended that two conductor shielded cables
be used for recorder inputconnections. Single conductor
shielded cable may be used for the meter amplifier output
connections.
C HANN EL +
I
C HANN EL +
2
- ----- -
" '
FIGURE2 -1
P l
RE C. ORO £~ t NP tJ T
CQNf'IE
C. T IO NS
ln order to provide proper monitoting and control
facilities. several interconnect cables
are used to connect
the recording amplifier chassis and the reproducer deck .
Th e first cablecontains two 6-pin plugs. one at each end.
One end connects to J 102 locat ed on the reproducer
deck.
the other end plugs into connector J4 located on
the rear panel of the recording amplifier chassis. The
playback audio output connections must now be con-
nected
to output connector J3 which is also located on
the back of the reco rdingamplifier.
The second interconnect cable has 15 -pin plugs
located
at each end . One end plugs into connector JlOl ,
which Is located on the reproducer deck, the other end
plugs Into connector J2, which Is located on the
recording amplifier.
In addition
to the two previously desc ribed inter-
connect cables, there are two head cables (4 cables in
stereo units) which must be connected between the
appropriate head connectors on the recording amplifier
and the reproducer deck. T hese cables are individually
identified
and must be connected lo their matching
sockets and plugs. If not connected properly, bias wUI
need to be recalibrated.
D.REMOTE CONTROLCONNECTIONS
Remote control functions are provided through
connector JlOl for START. STOP , FAST REWIND,
FASTFORWARD,
and associated lampcircuits (24 volt,
40 ma .). All functions are direct, pin for pin connections.
The control functions, record se t. and record lamp are
shown in Figure 2-2. Ifdesired. the RECORD SET switch
may be wired from pin 17 to pin 1 rather than pin 17 to
2·1

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•
pin 11 as shown on the remote schematic. When wired in
this manner , RECORD SET is active both prior to and
during the START • RUN mode of operat ion. The
remote switch must be a momentary contact, normally
open single pole type . Rem ote indication of the
RECORD SET function is obtained by connecting the
RECORD SET LAMP between pin 16 and pin 1. The
circuit is designed to operate a 24V. 40 ma . incan-
descent bulb.
2-2
RECOROER
JI
11
RECORO SE, RECORO SE:i
PRtsn Strol\E SlART PRESET AND SET DURING S1AfH
F IGURE2-2
E. PRELIMI NARY TESTS
Check all motors and rotating parts before operating -
the 770 Series machine . They sho uld rotate freely. Be
ce rtain the P. C. cards, relays, and ribb on cable con-
nectors
are properly seated. Beforeplugging in the power
cord insure th at the line frequency and voltage are
correct. 117 volts ± 10% , 60 Hz.
The ready indicator LED should illuminate if the tape
has been properly loaded onto the deck . After loading
the tape press either or both channel select switches.
(Only one switch if the machine is mono .) When pressed.
the record set LED(s) indicator shou ld illuminate.
-11u.o,.o,. 10
~\.,IIYIACII. C0 111W Oi,.
..-.t(,-(QIIIJ1t(C'l10 '11
0381OM

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0 [u][u]
0381OM
PLAYBA CK
AUDIO
INTERCONNECT RECORDER
AUDIO
INTERCO NN ECT TO DECK INPUTS
OU TPUTS
CABLE
®
Jl
J4
CHANNEL Cl<A HH[I. ©
• I
@)@) @)@
t: flASE ttt:COflO E.IIASt "°£CORO
RECORD AND ER ASE
HEAD I NTERCONNECTS
FlGU R E2 -4
JI
coo
(?)
oc:10
aoo
□ oo
ooo
o □□
® □□ O
ooa
o □□
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oo □
□□□
J2
RE M OTE
CONTROL
CO N NECTIONS
PRS
OUTPUT
@@
CH I CH t
PLAY-RECORD-SYNC
OUTPUTS
0
I MET ER AMPI..I FIER OUTPUTS)
2·3

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SECTION Ill -OPERATING INSTRUCTIONS
A. C ON T ROLS AND INDICATOR S
Six switches are present on the stereo sys tem and five
onthe m
ono .
1. R ecor d Set Switch
T he record switch may be operated in two diffetent
configurations. The configuration depends upon
the strappableoption selected.
• If points A and B on the bias oscillator and
recorder control PC board are strapped together.
the record
se t switch will be active only during the
START-
RU N mode.
• If points C and D are strapped together. the
RECORD SET switch will be active in either the
READY mode
or during the ST ART • RUN mode
of operation.
The RECORD SET switch is active only when
the co
rr ect CH A NNEL SELECT swltch(es) is de-
pressed This provides a
"SAFE" condition where-
by pre-recorded material may
not be erased. On
a
two channel unit the individual CH ANNEL
SELECT switch es provide the Play-Record Syn
chronizing
as ano therbuilt-in feature.
2. Cha nnel Se le ct and P.R .S . (Pl ay-R ecor d-
Synchronlzatlon)
The P.R.S. feat ur e is standard on all two chan-
nel 770 reel to reel recording amplifiers. The P.R.S.
circuitry allows the recording
of information on one
track while monitoringmaterial previouslyrecorded
on t
he other track. The following conditions must
exist
for prope r operation of P.R.S.:
a) The METER SELECT switch must be in record
(REC) position;
b) Either Channel 1 or Channel 2 SELECT switch
rnust
be depressed; and ( If both CHANNEL
HE ADPHONE OUTP UT
(M ONITORS MCTE:R AM PLIFIER)
RECORD SE T
SW
ITCH
SELECT switches are depressed simultaneously
P.R.S.
is nonfunctional.)
c) The recorder must be set to the RECORD mode
and moving
ta pe,
If the operator is recording on Channel 1, the
Channel 2 met
er circuit will monitor program
material which
has been previously recorded on
Channel 2. The monitoring Is through the record-
ing head, and therefore is in perfect synchroniza-
tion
with thematerial being recorded on Channel 1.
The output of the P.R.S. amplifier may be moni-
tored through the front panel headphone output
and/
or the rear c hassis meter mode output con-
nector.
At all other times. the meter switching will
function norrnally,
3. Meter Sel ec t Swi t ch es
a) Play
With this switch depressed, the merer circuitry
will monitor t
he output of the reproduce amplifier
at all times.
b) Bias
With this switch depressed, program bias will
be
continuously monitored during the re cording mode.
There
will be no meter indication during the
play
mode .
c) Record (REC)
Thisswitch performs three baskfunctions
1) Monitors the input of the recorder if in the
RECORD SE T mode,
2) Monitors the P.R S. output as previously de-
scribed; and
3) Automatically switches to and monitors the re -
producer output
if not in the RECORD SET
mode .
CHANN EL
MET ER
CHANNEL 2
M
ETE R
INPUT L
EVEL
CH AN N ELi
INPUT LEVEL
CHANNEL 2 CHANN
EL SELEC T SW ITC HE S
0
0
0381OM
ANO IN DICATORS
RECORDER PROGR AM
INPUT LEVEL B IAS
PROGRAM
PLAYBACK
ME T ER SELECT SWI TCHES
FIGURE3 ·1
0
0
3-1

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4. LED Indicators
The red LED indicators will be illuminated only
when a
channel has been selected and t he RE-
CO RD SET switch depressed as previously de -
scribed.
8. RECORDING
To record a reel of tape:
1. L
oad and thread a reel of tape ;
2. Depress the app r opriate channel select switches;
3 . Press
the RECORD SET switch and obse r ve that
the record LED Uluminates, indicating the machine is in
the RECORD mode .
4. Press the START switch. The RECORDswitch can
be pressed after the ST ART switch. if so wired.
5. Adjust recording level
on t he VU meters so that
major
peaks do not exceed the O VU point, but should
remain
as close to the ZE RO indication as poss ibl e.
3- 2.
0381OM

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SECTION IV.
SETUP, ALIGNMENT, AND CALIBRATION
A. GENERAL
All ITC recording amplifiers and record/reproducers
are fully tested and adjusted
at the factory for optimum
performance and normally require no further adjust-
ments
prior to installation. However , due to normal
variations
in tape types and oxide formations, thefactory
adjustment
of theRecord Amplifier may be"tweaked" for
optimum pe rforman ce with thetape brand you are using
As with any tape rec
orde r, op timum performance is
achieved
only when the Record Ampl ifier is carefully
adjusted to a specific tape type and brand. Customers
using several types and brands
of tape should expect
varlations
in performance due to different oxides, and
should be aware that performance characteristi
cs of the
770 System can and may vary depending on the tape
used. Best consistent performance is achieved when a
single tape type
is used, and the Record Amplifier is
adjusted for thatparticular tape.
Adjustments
of the recording amplifier shou ld not be
undertaken unless a defined lack of performance exists
and the reproducer has been carefully tested and found
not
to be a contributing factor. The adjustments described
In this section
of th e Technical Manual should be fol-
lowed
in the sequence presented to achieve a fully and
accurately aligned recorder. Access to adjustments points
is
by removal of the front switch panel dress plate and top
stainless steel chassis plate.
Note that many adjustments
are dependent
upon and interact di rectly with each
other. Therefore. when one specific adjustment is
changed, it
may be necessary to perform through the
entire adjustmentprocedures
for therecorder.
Do not mak e any re c order a djustm ent until the
re producer has been totally and acc urat e ly c ali-
brat ed.
h
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8. PLAYBACK METER CALIBRATION
1. Depress the playmeterswitch S605 .
2. Connect a
600 ohm load(s) across pins 3 and 5
(Channel 1 for Mono) and pins 4 and 6 (Channel 2 for
stereo) of connector J3. Connect an accurate high Im-
pedance voltmeteracrosstheload on pins3 and 5.
3. Thread and play an NAB standard reference tape
or its equivaJent and observe that the voltmeter reads 0
dBm . If necessary. adjust the front panel level control on
the reproducerdeck to obtain this reading.
4. While playing the reference.tone, (700 Hz at 1 85
nW / m), adjust R 408 for a "O" VU reilding on the front
panel meter.
5.
Follow the same procedures outlined in Step 4 to
ca librate the Channel 2 VU meter. T he calibration
potentiometer
is R472. See Figure 4-1 for location of
these trimmers.
C. RECORD HEAD ALIGNMENT
Be certain that prior to making any record head
azimuth adjustments that the reproduce head
is
accurately aligned, as outlined in Section IV , B-1 of the
770 Reproducer Te chnical Manual.
1. Connect an audiosignal generator
to the Input plug
Pl , pins3 and 5. Set the frequency of th e oscillat or to 15
kHzand level to -
lOdbm .
2. Connect a high impedancevoltmeter to the load on
pins 3 and 5
of the reproducer output J3 and set the
range
to O dBm .
3. Thread a reel
of blank tape typical of that normally
used.
4.
Press the START and RECORD button.
r
~
-I I I I
FlGURE4 -l
0381OM
4-1

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5 Turn the Channel 1 re cord level control to provide
a mid-scalereading on the voltmeter.
6. Carefully adjust the record he ad azimuth for maxi-
mum reading on the voltmeter (reduce the record level as
necessary to keep the voltmeter on scale). Refer to F ig ur e
4-2 forlocation of the record head azimuth control
LOC K SCRE W
AZIMUTH
ADJUST
REAR HEIGHT
FRONT
HEIGHT
ERASE
HEAD
RECORD
HEAD REPR
ODUCE
HEAD
FlGUR E4-2
7. The followlng procedureshould be used on stereo
recorder/ reproducer
un its:
4-2
a) Connect the audio signal generator both
Channel 1 and
Cha nn el 2 input, adjust the oscilla-
tor frequency to
15 kHz, and amplifier level to
app rox imately - 10 VU . Be certain that t he Record
Amplifierinputsare beingfedin-phase.
b) Connect the "X '' or vertical input of an oscil-
loscope to
pi ns 3 and 5 of the reproducer output .
and connect the "
Y" or horizontal inputs of the
scope
to pins4 and 6. Ver ify thatbothscope inputs
are properly phased.
With tape loaded, press both
channel
se lect switches, the record se t switch, and
the start switch. Adjust the oscilloscope horizontal
gain to provide a deflection equal
to that of the
vertical.
c) While recording the 15 kHz tone, adjust the
record head azimuth screw until a pattern similar to
that sh
own in Figure 4 -3 is achieved. This pattern
represents
"O" or near "O" ph ase shift in the system.
d) Sweep the signal generator from 15
kH z to
1
,00 0 Hz and watch the phase shiftpattern on the
oscilloscope.
If th e pattern tu rns over (Figure 4-4 or
Figure 4-5) the record head azimuth screw mustbe
readjusted until no phase reversals occ
ur . An in -
phase scope pattern must be observed for all
frequencies between 15 kHz and
50 Hz. Adjust the
record head
azi muth until this conditi on exists.
NOTE : At very high au dio frequencies, a small
amount of scope pattern
"j itter·• is normal.
e) Once proper azimuth and phasing has been
obtained, c
ar efully tighten down the head locking
screw while watching the oscilloscope
to be certain
that alignment has
not changed,
f) Recheck alignment by starting and stopping
tape motion several times and also by sweeping the
generator the full audio range while in the record
mode.
0° PHASE SHIFT
,,
I, I
I,
L,
1,1
FIGURE4-3
FIGURE4 -4
90 ° or 2.70° PHASE SHI FT
1 80° PHASE SHIFf
FIGURE 4-5
D. BIA S TRAP ADJUSTMENT
1. Removethe topcover of the recording amplifier.
2. Connect a low capacity
pr obe and osdlloscope to
the ; un ction of resistors R450 and R451. See Figure 4 -6 .
3. Depress both channel se lect switches, the re co rd set
switch and thestartswitch.
4, Using a fiberscrewdriver, adjust bi
as coil L601 untll
a
minimum reading Is seen on the scope
5. Repeat the same procedure on ster eo uni ts except
monitor the signal
at the ju nction of resistor R514 and
RS
15 while adjustingbias trapcoil L602 ,
E. BIASADJUSTMENT
l. Connect a 600 ohm load to Pl . pins 3 and 5,
(Channel 1
or mono inp ut ) and pins 4 and 6 (Channel 2
on stereo units) 0£ the recorder.
2. Connect an audio signal gener
at or across the load
on pins 3 and 5.
Set the output to approximately • 10
dBm and the frequency to 1kH z.
3. Connect a high impedance voltmeter to the 600
o
hm load on pins 3 and 5 of the reproducer output J3 .
Set the range of the voltmeter
to O dBm .
4.
Th read a reel of tape, typical of that regularly used,
It is important that the type of tape used when setting bias
is the type that is to be regularly used, as various types of
magneticrecording tape havedifferingbias requirements. -
(Seecomments regarding tape type
in SECTION IV . A.)
5. Pr ess ST ART and RECORDbuttons.
0381OM

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CONNE CT
PROBE HERE
CH2 --, H-t- ---
CH l - -+-1-L. _
R450 RSl4
':8: g_
R45I R5l5
BIAS TRAP
D
R6'27 R628
CH.I Cli 2
BIAS BIAS
AOJ.
ADJ ,
FIGURE4 -7
6. Advance the Channel 1 level control to provide a
mid-
sca le reading on the voltmeter.
7. Adjust trimmer potentiometer R627 (see Figure 4-
6) £or a maximum reading on the voltmeter.
NOTE : A delay will be presented between the re-
cording and play process.
Make these adjust-
ments slowly.
8. On ste r eo units. u se the same procedure as out-
lined
above to adjust Channel 2 bias. using trimmer
potentiometer R628.
F. RECORDING AMPUFIER EQUALIZATION
L Thread a reel of blank tape of the type regularly
used in the machine . It should be noted that a single
tape type be used from day-to-day a.s hequency
response charac teristic s and bias re qu irements
vary· c onsiderably between th e various tape
formu lati ons.
2. Connect the audio signal generator across the load
on Pl pins 3 and 5. Set the frequency to 700 Hz and
level to approximately-10 dBm .
3.
Connect the high impedance voltmeter to the load
on pins 3 and 5 of the reproducer ou t puts J3 . Set the
Ta nge to O dBm.
4. Set the speed switch to the ''high'' position.
5. Press the record and start button.
6.
Advance the Channel 1 r ecord level control until a
10 dBm reading is observed on the voltmeter.
7.
Change the fr eq uency of the audio signal generator
to 15 kHz ( on 15 !PS and 7- 1/2 I PS machines only), and
observe t he output level on the vol tm eter .
8. While recording
the high frequency tone , adjust the
high speed equalization po l until the high frequency is
equal in level to the - 10 dB m reference tone establisbed
In st
ep 6. R efer to Figure 4-8 for location.
0381DM
9. Slowly sweep the signal generator from 15 kHz to
700 Hz while observing output level.
10. Set the speed switch lo the l ow speed position.
11. Record a
700 Hz tone and adjust the Channel 1
input l
evel control for a -10 dBm reading on the
voltmeter,
12 . Change the frequency of the signal generator to
15 kHz (7 ,5 kHz if this is a 3-3/ 4 IPS machine) and
adjust the low equalization contro l f or a - 10 dBm reading
on the voltmeter. See Figure 4-8,
G. RECORD LINE METER CALIBRATION (REC)
I Set the speed switch to the high s peed position.
2. C on nect the signal generator to the inputs of the
r
ecorder. and the voltmeter across the ou tput of the
repr od u ce r unit. Make certain that all 600 ohm loads are
in place .
3.
Record a 700 Hz tone and adjust the input level
controls for a O
dBm reading on the voltmeter.
LO W SPEE ti10'1 SPE.C'O
£0UALtZA1ION £0VAl..11ATION
A44 & ~•• 1
FIGU R E4-8
LOW SPUO
EOUAL!l~•I ON
R ~lO
4-3

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4. Depress the REC meter swit ch . S603
5. Adjust the record meter calibration control R403 for
a •
·o•· reading on the VU meter . See Figure4-1.
6.
On two channel units, repeat the above procedure ,
using R467
to calibrate the Channel 2 record line meter .
H. TWO SPEED RECORDING AMPLIFIER LEVEL
CALIBRATION
Make this calibration only after the steps in
Section G havebeen performed.
1. Set the signal generator input so that a ' 'O" VU
reading is obtained on the front panel VU meter at 700
Hz. (The REC meter select switch and the Record Set
switch must be depressed .)
2.
Put the speed select switch in the low speed
position.
3. Adjust R437 . balance for a OdBm reading on the
high impedance voltmeter connected across the output
terminals. Figure 4-1.
4 .
On stereo units, use lhe same procedure as
outlined above but use RSOl (or the Channel 2,
recording amplifier level calibrationcontrol. Figure 4-1
I. P.R.S. AMPLIFIER BIAS TRAP
I. Refer to Figure 4- 7 for the location of the com -
ponents used in the following adjustments.
2.
Connect an audio voltmeter to the meter amplifier
output ja ck J703 located on the rear panel of the record
chassis.
3.
Set the Channel 1 record select switch to t he off
position (out)
and set the Channel 2 record select switch
S602 to its on position (in).
4. Load a blank reel of tape onto the playback deck
transport.
5. Press the record and the startswitches.
6. While in the record mode wi th the tape in moti on ,
adjust bias t
rap L401 for a minimum reading on the
voltmeter.
7. R
epeat the same procedure for Channel 2.
Channel 1 record select switch should be in, Channel 2
record select switch
should be out. and the bias I.Tap for
Channel 2. L402 . should be adjusted.
J. BIAS METER CALIBRATION
1. Press the bias mete r select switch S604
2. Load a reel of tape and set the machine to record
and start. (Both channel select switches should be
depressed .)
3. Adjust potentiometer
R406 until a '' O' ' VU lndica•
llon
is read on Channel 1 mete r. See Figure 4-1.
4. Adjust potentiometer
R470 for a "O'' VU reading
on
the Channe l 2 meter ,
K. P.R.S. AMPLIFIER METER CALIBRATION
1. Record a 2-minute length of 700 1-lz tone on
Channel 1. Be certain that this ton e isrecorded at a
0 VU level.
2. Dep r ess the Channel 2 record select switch and be
certain that
the Channel l record select switch is out
(OFF).
3. Rewind the tape to the beginning of the 700 Hi
tone .
4
Set the machine for the record mode and pr ess the
start switch. While playing the
tape , adjust R4 05 for "O "
VU on the Channel 1 meter.
5. Repeat the above procedure for calibrating the
Channel 2 P.R.S. meter . The chann el select switch for
Channel 2 should be in th e o ff position and the channel
select switch for Ch
annel 1 would be in the on position
Use calibration potentiometer R4 69.

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..
SECTION V. -ROUTINE MAINTENANCE
A .GE NERAL
International Tap etronics Corporation has desi gned
the 770 Series Reel-to-R ee l for high reliability, and
maximum leng th of service before routine scheduled
service.
The DC Servo capstan motor utilizes both a perma-
nently lubricated ball bearing and an oillte bearing. Under
contin uous use the oilite bearing should be periodically
oiled.
and will be detaUed later,
The solenoid plunger Is TEFLON coated, and operates
within a brass tube. This combination eliminates the need
for any lubrication and wear is negligible.
Brake discs and pads are a high strength metal alloy,
and will endure 250,000 operations or more before
maintenance is required.
Torque motor bearings are permanently sealed and
shou ld never require maintenan ce.
Daily inspection of the heads is recommended , and
more frequent Inspection is desireable if the unit is in
heavy or continuous use . Head cleaning should be
perfo rmed on a frequent and regular basis to In su re
optimum performance . Use a clean co tt on swab dipped
In lsopropyl alcohol for this procedur e. All metal
compon e nts in the tape path - capstan, t ape guides, idler
arm, and guide posts-should also be fr e qu ently cleaned.
The 770 pressure roller should also be kept dean in order
to maintain the best tape pulling characteristics. During
the cleaning, Insure that all traces of oxide and lubricant
are removed from mechanical co mp onents in the tape
path . All ow all cleaning fluid to dry before re-threadi ng
tape onto th e mach ine. to reduce the possibility of
damage toth e tape .
CAUTION: Do not allow cleaning fluid to enter
the bearings ln the pre ss ure roller and the guide
posts . Cleaning fluids may deteriorate the
lubricant In th ese bearings and cause prema-
turefailure.
Front panel overlays and dress plate may be brushed
periodically wi th a soft came l 's hair or synthet ic bristle
MAINTENANCE SCHEDULE
This maintenance schedule is intended as a guide for
maintaining your unit in op timum condition, and is for
units In routine daily use . The schedule may be varied
depending on your particular machine duty cycle. Th e
I ntent is to develop a schedule to allow maxi mum use
with mi nimum maintenance time. In most cases, this
main t enance schedule will enable you to pinp oint
potential tr oub le area s b efo re they become problems that
may potentially remove the machine fr om se rvice.
CLEAN HEADS,
PRESSURE ROLLER, TAPE GUIDES, TAPE GUIDE POST S ,
AND IDLER ARM
CLEAN FRONT PANELOVERLAY, HEAD
COVE R, AND ESCUTCHEON
DEGAUSS ALL HEADS AND TAPE GUIDES
CHECK HEAD AZI MUTH , ZENI TH . HEIGHT
CHECK FREQUENCY RESPON SE -EQUALIZATION
CHECK BRAKE SLIP TORQUE
CHECK TORQU E MOTOR TORQUE
CHECK CA PST AN MOTOR SPEED (H I GH AND LOW SPEED)
CHECK PRESSURE ROLLER PRESSURE
LUBRICATE
CAPSTA N MOTOR
CHECK RECORDER BIAS AND EQUALIZATI ON
CHECK RECORDER METER CALIBRATION
CHECK 25 Hz TONE DETECTOR SENSITlVITY•
CHECK INPUT, OUTPUT LEVEL CA LIBRATION
'I F APPLICABLE
0381OM
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• • •
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• •
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5-1

www.SteamPoweredRadio.Com
paint brush to remove dust and oxide buildups. Should
thorough cleaning be required, use a soft rag and a mild
household
cleaner such as " 409 "® or "FANTASTI K" lli>
Be sure to use cleanerssparingly, and wipe dry with a soft
cloth
to eliminate residue and smudges .
The Servo Capstan mot or requires periodic oiling.
Please refer to
the 770 Series Reproducer Technical
Manual for specifics regarding
capstan motor lubrication
procedures.
B. MAINTENANCE TOOLS AND AIDS
NEEDLE-NOSED PLI ERS
STANDARD SLOT SCREWDRIVER. 6" SHAFT. 1/ 4''
BLADE
1/ 8" H EX WRENCH
3/ 64" H EX WRENCH
MINIATURE SLOT SCREWDRIVER. 3" SHAFT, 1/ 8"
BLADE
MINIATURE PHILLIPS SCREWDRIVER, 3" SHAFT ,
# OB IT
SPRING SCALE, 2 POUND
10-1/ 2" NAB HUB EMPTYTAPE REEL
3 FT LACING CORD. OR HEAVY TW I NE
ITC TAPEHEIGHT GAUGE, PARTNO. 830 - 0022-021
ITC BR AKE GA PGAUGE. PART NO. 830-0036-001
TAPEHEADDEGAUSSER
NAB ALIGNMENT TAPE·
FREQUENCYCOUNTER
V.O.M., V.T.V.M.. ORF.E.T.V.O.M.
OSCILLOSCOPE
INSULATED OR NON-METALLIC SLOT SCREW•
DR IVER, 6" SHAFT, 1/ 4" BLADE
AUDIOOSCILLATOR
FLUTTER TAPE•
·ONE TAPE NEEDED FOR EACH SPEED OF
OPERATION
5.2
C.SPARE PARTS
Your new 770 Series Record Amplifier unit was ship•
ped with a Maintenance Parts Price List enclosed in the
front of this Technical Manual. We sincerely hope you
never have to replace parts on your unit. But being a
mechanical device, we recognize that components wear
out after a time and mu st be replaced. Should parts
replacement
become necessary, ITC will supply those
parts to you, and at no charge if within the warranty
period.
(See Warranty, in the front of the Technical
Manual.)
If you desire a quantity of spa re parts in case of break•
downs, please review the Maintenance Parts Price List
Thislist does not contain every partin the 770, but Is a list
of the mos t frequen tl y requested parts, and are readily
availablefrom inventory.
If you have questions regarding
spares, or items
not listed, call ITC Tec hnical Service for
assistance.
0381OM

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SECTIONVI -THEORY OF OPERATION AND
DESIGN PRINCIPLE
A. GENERAL
The I TC 770 Series Reel to Reel Rec ording Amplifier
electronics
are contained on two plug-in printed circuit
c
ards and one mother board assembly. Th e plug-in PC
cards contain the pr ogram recording amplifiers, the bias
oscillators,
the met er amplifiers, and con trol electronics.
On so me models ii also con tains a play record sync
amplifier, The recorder derives its p ower and related
con tr ol information from the associated r eproduce r unit
through the inter connec t cabl es .
B. RECORDER CONTROL LOGIC
The major portion of the r eco r de r 's co ntrol logic is
located
on th e bias oscillator and con trol PC board.
Please refer to the 770 Series Recording Amplifier
sc
hematic Figure 7-11 for location of the following
compo n ent references.
Tr ansistor Q607 serves both as a "ready" switch and as
a "safe" switch. Forward bias to Q607 ls supplied through
R630
and /o r R 634 through the channel select switches
S601 and S602 to " ready '' ground, if both c hannel
switches are depressed and the machine Is in a true ready
condition . Th e "ready " ground c ontro l is obtained
through pin 15 of J702, through the inte r connec t cableof
the playback portion of t
he 770 Se ries. This point is at
ground po tential only when the machine is in a " ready ''
condition and tape is lo aded prope rl y. If this "ready "
conditi
on does not exist, no forward bias curre nt is
possible for transistor
Q607 and therefore. the record set
ci rcuitry. Q609 and Q608 , cannot be activated.
If the. "ready'' conditi on exists. Q608 and Q609 are
t urned on by depressing the record s et switch S606 . This
action c
au ses a ground potential at the collector of Q6 08
wh ich In turn forward biases Q609. and latc he s the two
transistor
on .
A
24 volt DC potential will now exist at the collector of
transistor
Q609 which supplies c urr ent to the fr ont panel
LED indicators CR604 and C R606 . This 24 volts also
sets up a potentialforward bias
cu rrent loop for transistor
Q
61 l. Q611 functions as an AND gate which. ifa record
set and a run condition exist. causes transistor Q610 to
turn on and in turn supp ly voltage to the bias oscillator
circuitry.
T
he ch annel select switches S601 and S602 may be
ope rat ed independen t ly and still cause the previously
described circuit functions
to exist. During this condition
one LED inst ead of both LED indicators will be illumi-
nated
and one p owe r oscilla tor section as opposed to
bo th power oscillator se ctions will be active.
The secon dari es of T602 and T60 3 provide recording
and er ase bias cu rr ents to the appropriate heads .
0381PD
Potentiometers R 627 and R62 8 are used to adjust r e•
co rding head bias current.
C, BIASOSCILLATOR
The bias and erase oscillator ci r cuit ry in t he 770 Series
Re co rding Amplifier Is co mp osed of a master oscillat or
wi th two slave power oscillators. Th e master oscillator Is
turn ed on whenever either channel se lect switch is
activated.
The recording mode is en ter ed by way ofdiode
matrix CR
601 and CR 602 . The power oscillators are
independentlyactivated depend ing on the channel se lect
switch selection.
Transistors
Q601 and Q602 a re connected as a push-
pull oscillat
or circuit, with powe r su pplied to the cen t er
tap of th e primary winding of the transformer T60 1 Bias
frequency is approximately
120 kHz. The turn• on time of
the oscillator is controlled by resistor R 60 7 and capacit or
C 604 . T he seconda ry of T 601 is coupled to the t wo slave
power oscillators, which are essentially the same ci rcuitry
as the master oscillator with the exception that the feed-
bac k loops are connec t ed to the secondary of T601 so
th at both os cillat or s op erate al th e same frequency.
0. METER AMPUFIERS
The meter amplifier circuitry consists of IC U403. Sec -
ti on A and B. This is a low impedance output amplifier
which
is u sed to drive three sepa rate sources: (1) the
headphone monitor output J40 1, (2) the full wave bridge
rectifier
and meter . and (3) the rear c ha ssis mode monitor
outputs
J703 and J704 .
The switching of
the meter amplifier ci rcuitry required
for the
va rious monitoring modes is controlled through
the
use of an analog switch U402 . and its associated con -
trol logic.
U402 consists of four inputs which ma y
independently
be switched to a common output bus .
P.R.S ., normal r
ecord, bias. and playback are fed into
th
ese four individual inputs on pins 2, 6, 9. and 13.
I
nputs are switched at the ap pr opri ate times to the output
terminal pin 11. Output signals are then fed to the Input
of
the meter amplifier U403A . To "switch" any of the
four monitoring points to t he output terminal of the
analog switch, a low or ground po tential Is required at the
appropriate con trol pin. To prevent an input from being
switched through to t
he ou tput, its appropriate con trol
point must be at approximately 15 volts DC poten ti al.
Transistors Q401 . Q402, and Q403 pe rf orm the
appropriate switching function at the r equired time_
Switching voltages to cont rol these transistors are
obtained thr oug h the contacts of the pushbutton switches
6-1