11,
Service Administrative Support
S-3200
2943 2944
CORRECTION
FOR
SIGNAL
EDE
JI
TER
C
NT.
These
changes
should only
be
used
on
systems
that
have
had
the
2943/2944
Clock
Generator standardization
mod
installed.
There
are
040
kits
available to
install
the
standardization
mod.
The
kit
P/Ns
are
040-1110-00
for 7
Phase
systems
and
the
040-1111-00
for
14
Phase
systems.
With
the
2943/2944
standardized
any
standardized clock
is
a
direct
replacement without
having
a
major
reskew
or calibration of system.
Without
standardization replacing
any
part or
all
of the clock
my
require a
major
reskew
or calibration of
systems.
w2
Issue
13-19
TDCl/2
SPURIOUS
OUTPUT
REF:
TDCl/2
Instruction
Manual
070-2754-00
SAR
#05211
A recent inquiry
from
the Field
questioned the presence of a spurious
signal at about
31
MHz
when
the
TDC2
was
tuned to
Channel
69
or
70.
This
spur
was
about
-30
down
from
the
fundamental
which
gave
a
total
of
about
-80dBm.
In
either
case,
it
was
judged to
be
worse
than other units
(TDC2's)
under
similar conditions, but
was
not
out of specs.
One
of the
problems
encountered in
making
this
measurement
centered
around
the
067-0886-01
Test Modulator.
The
signal
coming
out of
RF
OUT
is
spec'd
at
-25dBm.
However,
due
to the
lack of
any
filtering
on
this
output,
harmonics generated
by
the
RF
Mixer
stage will
be
present.
In
the case of
Channel
69, the
second
Harmonic
would
be
at
2 X Visual
Carrier+
I.F.,
or 2
X (801.25 +
37)
or 1676.5
MHz.
October,
1883
la8&1e
31
If
one
assumes
no
harmonic
attenuation
out of
RF
OUT,
this
frequency (1676.5
MHz)
would
be
at
-25dbm
when
it
was
applied to the
TDC2,
and
would
mix
with the
first
L.O.
in the
TDC2.
Due
to the input
Bandpass
Filter's
image
rejection of
40dB,
the
first
Mixer
would
produce
a signal of
about
-65dBm
at
about 434.5
MHz.
Mixing
this
frequency with the
second
L.O.
(403.75
MHz)
will
produce
a signal at
30.75MHz,
giving
us
the presence of a
spur.
The
amplitude of
this
spur
is
dependent
upon
the
first
IF
Image
Rejection Ratio,
which
is spec'd
at
40dB
or greater for the
TDC2,
and
the
level of
harmonics
coming
out of the
Test Modulator,
which
are
not
spec'd.
-10-
Some
places to
look
for cures to
this
"problem"
are:
---Pay close attention to balancing
the
RF
mixer
in the Test
Modulator.
---Check cable dress in the
TDC2.
---Use care
when
adjusting the
Pin
Attenuator in the
TDC,
along
with the
Mixer,
Bandpass
Filter,
IF
Amp
other associated areas.
---Don't
use
the Test
Modulator
to
look
at
Image
Rejection.
Follow
the procedures in the
TDCl/2
manual.
w2
Issue
13-21
TV
LINEARITY
GRATICULES
REF:
650HR
Manual
070-2646-01
670A
Manual
070-2201-01
690SR
Manual
070-3821-00
When
adjusting the convergence of a
color monitor to
meet
specifications,
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