TFT 724A User manual

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STEREO
MONITOR
MODEL
72
4A
fflEffL
TIMEAND FREQ,
LJENCY
TECHNOLOGY, INC.

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STEREO MON !TOR
MODEL 724A
Time & Frequency Technology Inc.
3000 Olcott Street
Santa Cla. ra, CA 95051
1
( 408) 246-6365
Serial No
Rev Lev •el B
----

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SECTION
1
SECTION
2
SEC
TION
3
TABLE
OF
CO
NTENT
S
GENERAL
INFORMATION
1.1
Genera
l Descr
iption
...•.....
.
..•..••..
.
1.2
Spec
ifications
•.........
•...•.
•.
..
...
. .
1.
3 Accessory
Equipment
.•.
...
.
...
. .
...
...
..
1.4 Warranty
.....
....•.....
•
..
.
...
.•
.
.....•
1.5 Cl
aim
for
Damage
in Shipment
...
•....
. ••
IN
ST
ALLATION
Page
1-1
1-1
1-3
1-3
1-3
2
.1
2.2
2.3
2
.4
Unpacking
and
Inspection
.....•.
...
.
....
2
-1
Po
wer
Requ
i
rem
en
ts.
•. . •. . ••. .
..
•. . . ••. . . 2-1
lnstal
l
at
ion Procedures
..
.
...
..
...
.....
2
-1
Model
7
04C
Remote
Pane
l Meter
OPERATION
3.1
3.2
3.2.1
3.2.2
3.3
3.4
3.4.1
3.4.2
3. 4. 3
3.5
3.6
3.6.1
3.6.2
3.6.3
3.6.4
3.6.5
3.6.6
3.6.7
3.
6.8
3.
6.9
3.6.10
3.6
.
11
3
.7
Connection
....
.
•.•.•
.
...
••
..•..•••
2-1
General
......
.
.....
..
....
.
......
......
.
Co
ntrol,
Co
nnections
and
Indica
tor
...
•.
F
ront
Pane
l
.••
••••..
•.
•.
•••
•....
..•
..••
Rear Panel
•..
.
•..
.
...
..
.
..
.•.•.••
....•.
Turn
On
and
Wann
Up
••
.•...
••
••.••.•.••
.
Ca
libration
Procedures
..
••
•.....
••...•.
Meter C
alibration
Usi
ng
Model
763
•.••
..
Meter Calibration with a
Composi
te
Input.
..
. .
....
..
....
.
......
..
..
...
.
P
ha
se
Ca
li
bra
tion
•• . ••• . .
.•.
.•
..•
•. . . •.
Use
of
th
e
Model
72
4A
for
Monitoring
••.
Use
of
the
Model
72
4A
for
Measurement
•.
Main-Channel
(L+R)
Mo
dulation.•• . .
•.
•
..
Stereo S
ub
channel
(L-R)
Modula
ti
on
•
.•
••
Pilot
Ca
rrier
Modulation
..
..••
•.
....•••
38
kHz
S
ub
c
arrier
Suppression
••••.•..••
S
tereo
Channel
Se
paration (Left
C
hann
el
Modulated
).
•.
...•.....•.•
•
Stereo
Channel
Se
paration (Right
Channel
Modulated) •• .
....•
.
•...•
..
Main
Chan
nel to S
ub
cha
nnel
Cross
talk
..
•
S
ub
channel
to
Main
Channel C
rosstalk
•••
FM
No
i
se
...
....
...
•
•.••..•
....
. .
..
..
...
Dis
tortion
.•
••
..
•..
. •
•..
•....•.
....•..
•
Pi
l ot Frequency
.......
•.
••
..•...
.•
..
. •.
Use
of
the
Model
70
4C
Remote
Meter
3-1
3-1
3-1
3-5
3-6
3-6
3-6
3-7
3-7
3-7
3-8
3-8
3-8
3-8
3-8
3
-9
3-9
3-9
3-10
3-10
3-1
1
3
-11
Panel........
....
.
...
.
....
.......
. 3
-11

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SECTION 4
SECTION 5
SECTION 6
TABLE OF CONTENTS {Continued)
Page
THEORY OF OPERATION
4.1
4.1.1
4. 1.2
4.2
4.2
.1
4.2.2
4.2.3
4.2.4
4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
4.3.7
4.3.8
4.3.9
4.4
General Block
Diagram Discussion .. 4-1
Modulation Monitoring Circu its .... 4-1
Measureme nt Circuits .•............ 4-2
Meter Amplifier &Attenuator
Boa rd (A-3) . ..... . .. .•...•... 4-2
Attenuator...... . ................. 4-3
Modulation/Test Meter Amplifier
... 4-3
Left-Channel
Meter Amplifier ..• ... 4-3
Audio Amplifiers...... .. .......... 4-3
Demodulator &
Filter Boa rd {A-2) .. 4-4
Buffer Amplifiers &F
un ction
Sw itche s. . ..... ... . ... . ...... 4-4
19-kHz Filter ...... . ....... . .... .. 4-4
38 -kHz Filter .....•. . . ..... .•....• 4-5
L+R Channe l Filter {FU) .......... 4-5
L-R Cha nn el Filter {FL2) .. . . . .. ••. 4-5
38-kHz Phase-Locked Loop ..... . ..•. 4-5
Stereo Demodulator
•. ......•. . ...•• 4-6
Left-Channel Filter (Fl3) and
Right Channel {FL4) •...•....• 4-6
Phase
Calibrat ion .. •..•.•..••..... 4-6
Power Supply Board {Al) ... . .... ... 4-7
MAINTENANCE
5.1 General ...• . ............. ...•.....
5.2 Periodic Maintenance ... . •..... . •..
5.3 Perfonnance Checks ......•••.•.• . . .
5.3.1 Ca libration Accuracy Check •••.....
5.3.2 Amplitude Response Check ....... . . .
5.3.3 Stereo Pilot Indicator. .......... .
5.3.4 Output Check ... .. •. ... . .. ... .• . ...
5.3.5 Stereo Separation C heck .•..•••....
5.3.6 Crossta lk and Distort ion Check . .. .
SCHEMATIC DIAGRAMS
6.1
6.2
6.3
6.4
6.5
Block Diagram .. . . •.•....• •. ..... . .
Wiring D ia gram - Main Chassis
Front & Rear
.....•.••.•....••
Audio Meter Amplifier (A3) ........
Demodulator/Filter Board {A2) •. ...
Power Supply (Al) ..... . ...... . ... .
5-1
5-1
5-1
5-1
5-2
5-3
5-3
5-4
5-5

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SECTION 1
GENERAL INFORMATION
General Description.
The Model 724A Stereo Mo nitor is intended for use with
the
TFT Model 763 FM Frequency and Modulation Mon itor to meet all FM
stereo monitoring requirements and to provide proof-of-perfonnance
measurements.
Two separate meters allow monitoring of right and left
channels simultaneously. The meters can also be used to measure
separation between
right and le ft channels, crosstalk between main and
sub channels, 38 kHz carrier suppression, 19 kHz injection level, and FM
signa l-t o-n oise ratio. The various meter functions are selected by
front-panel pushbutton switches. Power for the Model 724A is supplied
by the Mo del 763 .
The Model 724A Stereo Moni tor, when used with the Model
763 FM Frequency and Mod ulat ion Monitor, meets the requirements of
Section 73 .332, Sub-sections d and e, of the FCC regula ti ons relating to
FM stereo monitors.
1.2
Spec ification s.
Co mposite input
Level ........ .... .....•. . .. . 500 mV RMS
lmpedanc e. . . . . . . . . . . . . . . . . . . 600 ohms unba 1 anc ed
Pilot Measurements
Level accuracy ..... . .......• ... . . +O. 5% from 6% to 12 %
-modulation
The 19 kHz pilot frequency is returned to the digital
counter in the Model 764 . Accu racy and resolution are ~0.1 Hz.
Mod ulati on Meters
Frequency response measurements:
Left channel,
right channel,
and L+R channel .. .... ... ...• ~4 %, 50 Hz to 15 kHz
L-R channel. .... .•. ....... .. ~4 %, 23 kHz to 53 kHz
1-1

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Ou tp ut s
Separation measurements:
Left to right and right to
l eft .......•... . ......•••.... . .. . . . 45 dB m in. , 50
Hz to 15 kHz
Crosstalk measurements :
(L
+R) to ( L-R) . .. .. •. . . . . •. . . . .. . • 60 dB min.
(L-R)
to (L+R) . ... . ..... . •.•••.•.. 60 dB min.
SCA to (L-R) . . ••.•. ....•. ••• .. .•.. 66 dB min.
SCA to (l+R) •...•.•..•..••....•..• 66 dB min .
Left and right channel monitoring:
Impedance
....••.••.•.......••..... 600 ohms unbalanced
Level
•..•••• . .•..••.•..•..•.• . .... 1 V RMS at 100'.t
modulation, 400
Hz
Frequency response
(without de-emphasis)
•..•.......•. +4 '.t , 50 Hz to
Ts kHz
Distortion . .• ... . ..•.•.•••..••••.• 0.5% max.
No ise level ( wi th
de-emphasis) .... ...............••. 60 dB min. below
100 '.t
Remote meter ........................... Outp ut s for Model
704C remote meter
panel
(bot h meters).
Pilot frequency (19 kHz):
Leve l .... . ....•.... • .... • ••.. ••. .• 100 mV RMS
Composite Output
Impedance
•..••.•••••••.• . . ...... .. 10k ohms
Level ...... .... . ...... ...•• •• ••.. . 1 V RMS (1001)
Power Requirements
Requires 25.2
VAC, center tapped from Model 763 .
Physical
and Environmental Specifications
Operating temperature •.... . ............ o0 to so° C
1-2
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1
Di men si on s. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
11
Wx 7
11
Hx
16
11
D
Weight ... .... .. . ...... ........ . ....... . 15 pounds
Cabinet ... . ....... . ... . ......... • ...... Rack mounting
1. 3 Accessory Equipment.
The TFT Model 704C Remote Readout Pa nel duplicates the
readings
of the two Model 724A front-panel meters.
1.4
Warranty.
TIME & FREQUENCY TECHNOLOGY, INC., warrants each of the
instruments
of its manufacture to be produced to meet the specifications
delivered to the BUYER; and to be free from defects in material and
workmanship and will repair or replace, at its expense, for a period of
one year from the date of de livery of equipment, any parts which are
defective
from faulty material or poor workmanship.
In stru ments found to be defective during the warranty
period shall
be returned to the factory with transportation charges
prepaid
by BUYER. It is with respect to any nonconforming equipment and
parts there of and shall be in lieu of any other remedy available by
applicable law. Al l returns to the factory must be authorized by the
SELLER, prior to such returns. Upon examination by the factory, if the
instrument
is found to be defe cti ve , the unit will be repaired and
returned to the BUYER, with tran spo rtation charges prepaid by SEL L ER.
Transportation charges for instruments found to be
defective within the first thirty (30) days of the warranty period will
be paid both ways by the SE LLER.
Transportation charges for warranty returns, wherein
failure is found not to be the fault of the SELLER, shall be paid both
ways by the BUYER. -
NO OTHER WARRANTY IS EXPRESSED OR IMPLIED. TFT IS N OT
LIABLE FOR CONSEQUENTIAL DAMAGES .
1.5
Claim for Damage in Shipment.
Your instrument should be inspected and tested as soo n as
it is received. The instrument is insur ed for safe delivery. If the
instrument is
damaged in any way or fails to operate properl y, file a
claim with the
carrier, or if insured separately, with the insurance
company .
WE SINCERELY PLEDGE OUR IMMEDIATE AND FULLEST COOPERATION TO ALL USERS
OF OUR PRECISION ELECTRONICS INSTRUMENTS.
1-3

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PLEASE ADVISE US IF WE CAN ASSIST YOU IN ANY MANNER
Time &Frequency Techno logy, Inc.
3000 Olcott Street
Santa Clara,
CA 95051
408-246 - 6365
1-4
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2.1
S
ECTION
2
INSTA
LL
ATION
Unpacking
and
Inspection.
Upon
receiving the instrument,
in
spect the packing
box
and
instrument
for
signs
of
possible shipping
damage.
Operate the
instrument in accordance with the procedures
of
Section 3
of
this
manual.
If
the instrument
is
damaged
or
fails
to operate properly,
file
a
cla
im
with
th
e
transportation
company,
or
with the insurance
company
if
insured
separatley
.
2.2
Model
Power
Reguirmen
ts.
Power
for the
Model
724A
(25.2
VAC)
is
s
up
plied
by
the
763
FM
Modulation Monitor. Refer to Paragraph 2.3
below
for
connections.
2.3
2.4
Installation
Procedures.
a.
Mount
the
Model
724A
in
the equipment rack.
b. Connect the furnished three-wire
power
cable
between
JlO
on
the
Model
724A
and
J2
on
the
Model
763.
A
ground cable
between
the
two
instruments
is
also
required.
Re
f
er
to Figure
2-1
for
connection.
c.
Connect the furnished coaxial cable
between
COMPOSITE
INPUT
connector
J7
on
the
rear
panel of
the
Mode
l
724A
a
nd
JS
(TO
STEREO
MO
NI
TOR)
outp
ut
on
the
Model
763.
d.
If
the studio
stereo
generator
is
to
be
monitored,
connect
it
s
compos
it
e ou
tput
to
COMPOSITE
INPUT
connector J7
on
Mode
l
724A
.
e. Connect another furnished coaxial cable
from
STEREO
PILOT
(19
kHz)
connector J3
on
the
Mode
l
724A
to
PILOT
CARR
co
nn
ector
on
the
rear
panel
of
the
Model
764.
NOTE
For information
on
installing
and
making
connections
to
the
Model
763, r
efer
to
the
Model
763
instruction
man
ual .
Model
704C
Remote
Panel Meter Connection.
Con
n
ect
the
50
foot,
three
wire cabl e furnished with the
Model
704C
to terminals
A,
B,
and
C
of
JlO
on
the
Model
724A
rear
panel .
Wraparound
labels
identify
the cable wires.
2-1

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