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APPENDIX A:
System Description
The
purpose
of
this
Appendix
is
to
provide
the
installing
engineer
with
an
overview of system design, to answer questions and deal with uncertainties about
various unconventional aspects of the design, and to provide the service technician
with a moderately detailed overview of the system.
Each card is numbered. Reference will be made in each section to the number of
the card on which the described circuitry is located.
The
paragraphs
in
Appendix
B (CIRCUIT
DESCRIPTION)
that
correspond
with
topics
in
this
Appendix
have
identical
numbers
and
titles
in
order
to
expedite
access to further information on a topic of interest.
REFER TO THE BLOCK DIAGRAM ( p. J-25)
Comparison With OPTIMOD-TV Model 8180A: If you are familiar with the 8180A,
this
section
may
help
you
become
familiar
with
the
8182A
more
quickly.
The following changes were made:
--
The Loudness Controller was added in the # 2 card slot.
--
Two Hilbert- Transform
Clippers were
added in slots # 0 and # 1,
substituting
for the clippers on Cards # 8 and # 9.
The
compressor
control
card (# 5)
was
modified
to
accept
control
current
from
the Loudness Controller
card,
and
to
provide
a choice
of
LINear
or
EXPonential compressor release shape. The circuit was also modified so that
both Master and Bass bands gate to " 0" on the G/R meter regardless of the
setting of the BASS COUPLING control.
The Preemphasis/HF
Limiter Card (# 6) was
modified to enable easy routing
of
the
signal
through
the
Hilbert- Transform
Clipper
cards.
In
addition,
its
LIMITER
PROOF/OPERATE
circuit
was
modified
to
defeat
the
distortion-
cancelled clippers on Cards # 8 and # 9 by forcing them
into PROOF
mode
whenever
the Hilbert- Transform
Clippers
are
in
use. ( The Hilbert- Transform
Clipper functionally replaces the clippers on Cards # 8 and # 9. However, when
the
appropriate
jumpers
are
moved
according
to
instructions
in
Emergency
Bypass Of Cards 10 And 11
in
Appendix F, the Hilbert- Transform
Clipper
cards
can be
removed for servicing,
yet
the OP1IMOD-T V system
can still
remain
in
service.
In
this
case,
the
simpler
distortion- cancelled
clipping
system on Cards # 8 and # 9 is re- activated.)
Cards # 8 and # 9 have
been
modified
with
jumpers
so
that
they
can
be
configured to serve as the crossover for the Hilbert- Transform Clippers ( their
normal
function), or so they can serve as distortion- cancelled clippers ( as in
the 8180A), permitting the Hilbert- Transform Clipper cards to be removed for
servicing if necessary.
--
Wiring
has
been
added
to
the
backplane
and
input
filter
card
to
permit
remote
control
of
the
Loudness
Controller
OPERATE/DEFEAT
function.
--
The
Nuise
Reduction
Port ( Accessory
Port # 1),
optional
in
the
8180A,
is
supplied
standard
in
the
8182A
and
provides
an
interface
to
the
Orban
8182A/SG
BTSC
Stereo
Generator.
The
wiring
has been
substantially
changed.
A-1
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