VAC»
ov1V
c915
MANUFACTURERS
of
TV
receiv-
ers
unveiled
many innovations
in their 1975 models. For
example,
major moves
have
been made
toward
providing
brighter,
sharper color pic-
tures; tuning
is
getting closer to the
one -button
concept; power -supply
designs indicate
a
trend
toward com-
pensation
for
anticipated
voltage
fluc-
tuations
caused
by power
shortages;
and serviceability
has
been improved
with modular
designs
and other
niceties.
Here
are details
on what
each
major
color TV
manufacturer
is
offer-
ing in
their 1975
all-
solid -state chassis
lines.
Admiral.
The
latest in
Admiral's
line
of
color TV receivers
is the Touch
Tuning M25
chassis.
Its
main feature
is a tuning
system
programmed
with
toothed
cards.
Six printed-
circuit
cards are used to
program uhf chan-
nel
number readouts.
A
seventh is
for
programming
the
remote
control
channel
selector to
go to the
next
higher
active
channel,
bypassing
all
inactive
channels.
The
cards
are pre-
pared for individual
viewing
situations
with the
aid
of
longnose
pliers.
Once the
cards
are prepared,
they
are inserted
into
connectors
in the
tuner. This
permits the viewer
to
select
a channel from
the keyboard
or
the
remote
control transmitter.
The
chan-
nel
appears
on
the
screen, and
a sepa-
rate
readout
indicator
displays
the
channel number.
In
the
companion M30
chassis,
a
special
transformer
provides
voltage
regulation.
The
transformer
is wound
in
such
a
way
that its
secondary pro
-
NOVEMBER
1974
BY ART MARGOLIS
duces
fixed
-amplitude
square waves,
with the
transformer
operated
at
sat-
uration.
The
transformer
is
tuned
to
resonate
at the line frequency
with the
aid
of a
capacitor.
When
the input
voltage
is nominally
117
volts
ac, the
clipped
output volt-
age is
a
fixed
-amplitude
square wave.
Should the
line voltage
vary (within
±10 percent
of nominal),
any change
produces
an inverse
change
in the
clipping
action. The
peak -to
-peak
square
wave
applied to
the rectifiers
then remains
at about
the
same
am-
plitude.
While
the
Admiral
chassis
does
not
tilt (it is
horizontal),
it does
slide out for
easy
servicing.
General Electric. MB, MC,
QB,
and
YA
are
the designations
given by Gen-
eral
Electric
to its
1975
chassis. The
stress is
on
reliability, quality,
and per-
formance.
For
1975,
GE is introducing
the third
generation of its
Quadline
color picture tube.
In -line
gun ar-
rangements
are featured in
the
Porta
-Color 13-
and
15
-in. picture
tubes. The
tubes
have
short
necks
and
90°
deflection
angles. The
necks
are
up to 2
in.
shorter than
comparable
tubes
with triangular
gun
arrange-
ments,
which
eliminates the
bump
on
the rear
of the
cabinet. Also,
the in -line
arrangement
reduces
from
12
to 8 the
number
of convergence
adjustments
that
must
be made.
In
addition
to manual
and preset
color, tint,
and
brightness
controls,
there is
a Custom
Picture
Control.
Coupled
to
the contrast,
color,
and
brightness
circuits,
it adjusts
all three
parameters
simultaneously
to
main-
tain
a
balanced ratio.
A
One -Touch
Color
system
incorpo-
rates
tint lock,
avc, and the
preset
color tint
and brightness.
The
tint lock
widens
the
demodulation
angle
by
cross
-coupling
B -Y
and
G -Y
at
the
output
of
the
chroma
demodulator
IC.
The
seven models
in
the YA
series
have
chassis that
accommodate
about
90 percent
of all the
electrical
compo-
nents.
Off
-the
-module
components
are
overrated to increase
reliability.
More
than
95 percent
of component
failures
are claimed
to be repairable
by
module
replacement,
and all
IC's
plug in
for
easier servicing. To further
endear itself
to the
serviceman, GE
has
a lot
of
the
service information
pasted
on the inside
of the cabi net
and
printed
on
the
circuit
boards.
This
in-
cludes layouts,
catalog
part numbers,
detailed
adjustment
instructions,
and
even the
schematic.
In
the larger
chassis
(like the MC
series),
a high -voltage
quadrupler
that
develops
30
kV is used
instead
of the
usual tripler.
Regulation
of the 30
kV is
achieved
with
a
three
-winding
satura-
ble reactor
circuit.
Heath
Company.
The
latest kit mar-
vel from Heath
is its Model
GR
-2000
digital
color TV
receiver.
The
tuner
uses
a
varactor
diode
that
eliminates
41
Comments to this Manuals