Text preview for : rca_chassis_xl-100_color_tv_ctc97_ctc108_info-1.pdf part of RCA CTC 97-108, XL 100 TV set. From Popular Electronic 1980.



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Popular Electronics
JUNE 1980




THE new 1980-81 XL -100 color-TV
chassis introduced only recently by
RCA's Consumer Products Division em-
phasizes new technology, reduced parts
count, and lower power consumption.
New technology includes SAW (surface
acoustic wave) filters and more sophisti-
cated ICs, including one that processes
most luminance and chroma functions.
A few discrete transistors are used in
these chassis, mainly in the power sup-
ply, sweep circuits, and final picture -
tube drivers. The entire circuit assembly
fits on a single "planar" printed -circuit
board that measures 121 sq in.
Three chassis are included in this to-
tally new line of moderately priced. color
receivers-13" CTC 107, 17" and 19"
CTC 108, and 25" CTC 109. The only
notable difference among the three is a
few extra turns on the flyback trans




Popular Electronics Tests
NewRCA XIiOO
Col rTVCIrnsss
former of the CTC 109 console series to
obtain additionally high voltage for the
larger picture tube. Therefore, the fol-
lowing description (for the CTC 108
CTC108 chassis) generally includes the salient
features of all receivers in the new line.
The 19" Table Model FER450, with
a suggested retail price in the area of
$400, is the one that this preview report
is based on. It will likely be in retail
stores at this time or shortly thereafter.
It features a 10 -button channel -selector
keypad, with LED digital readout for
any vhf or uhf channel.
Use of integrated circuits In -the
CTC 108 chassis results in a ttal of General Description. The chassis
combines video i -f and final amplifiers,
_76 fewer parts than in the older CTC 97 chassis.
automatic gain control (age), automatic
frequency control (arc), and synchro-
nous video detection circuits into a sin-
gle IC. A second IC houses the complete
JUNE 1980 45
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Weller _ Xcelite




Boker
1SS
Crescent Lufkin
Lufkin
Nicholson
Weller, Wiss
Cre .111,,,e
Xcelite
Take a quick look round this ad and
you'll agree that "All together" is no
exaggeration. Whether you're making
or mending,cutting or joining, measuring
or stripping,there's a Cooper tool that's
just right for the job. Don't take chances
Boke-r on tools.Specify Cooper and get 'em
right the first time!




from Co.oper The 'Ibolmaker.
41 The Cooper Group
COOPER BOKER'CRESCENT'LUFKIN'NICHOLSON'WELLER'WISS'XCELITE'
INDUSTRIES
PO. Box 728, Apex, North Carolina 27502. Tel: (919) 362-7511.Telex: 579497.
CIRCLE NO. 170N FREE INFORMATION CARD
XL -100 chassis
audio system, while a third large-scale 71), called the midband cable channels. Following the SAW filter and its dis-
integration (LSI) chip performs all Sound and picture keyboard changes are crete preamplifier are the i -f, aft, age, &
chroma and luminance processing. Fur- instantaneous. video detector circuits, contained in one
thermore it has SAW filters, which are When a signal reaches the pho- multifunction IC (Fig. 2). This IC, the
being used more frequently in TV re- toetched input electrodes of a SAW fil- RCA TA7607, requires only a few ex-
ceivers because of considerably simpli- ter (SF 301 in the RCA chassis), a sur- ternal components: a tunable aft cross-
fied input circuits and the better selec- face wave is generated. This deforms the over between pins 7 and 10, and a simi-
tivity they make possible due to sharper internal lithium-niobate material and lar LC circuit between pins 8 and 9 for
passband skirts. Here are highlights on creates "waves" similar to those made the synchronous detector. Other than
circuit operation in this new chassis. when a stone is dropped into a still pond. the 47.25 -MHz sound trap preceding
The tuning system is a carryover from When these waves encounter the output, the SAW filter, there are only six tuned
last year and features a 10 -button fre- a reverse piezoelectric effect restores the circuits following the tuner that require
quency -synthesized manual -scan tuning electrical signal. Length and spacing of adjustment.
arrangement with combined uhf/vhf electrodes in the SAW device determine Three amplifiers, all age controlled,
tuners and SELECT/LOCK switch for frequency characteristics. and another amplifier that supplies
complete channel access in any area. The SAW filter used in the new XL - push-pull aft outputs for the tuners
The keyboard connects to a frequency - 100 otters excellent response between make up the i -f section. With its cross-
synthesizer (U/), operational -amplifier the 41.25 -MHz sound carriers and the over LC tuning, the aft detector pro-
(U2), and LED display driver (U3). 47.25 -MHz lower adjacent -channel duces a do voltage for tuner oscillator
There is also a prescaler for U/ and an sound carrier trap. (See Fig. I.) Color corrections within some 30 to 50 kHz.
MST005 tuner module that connects to begins at 41.25 MHz, color suppressed Any undue noise through the video
a CABLE/NORMAL switch on the rear of subcarrier at 42.17 MHz, and video car- amplifier is normally shunted to ground
the receiver for I I CATV channels A-2 rier at 45.75 MHz. This single device by the noise inverter, which traditionally
through I(uhf displayed channels as 31, actually determines the overall i -f pass - removes sync and age momentarily until
35, 39, 43, 47, 51, 55, 59, 63, 67, and band response. annoying microsecond-duration im-




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Photo shows that all receiver components, except for a few discrete parts, are mounted on a single pc board.
JUNE 1980 47
XL -100 chassis
CHASSIS MODEL CTC 108
LABORATORY DATA

V
.. Parameter Measurement

Tuner sensitivity (min. signal (Ch. 3) -70 dBm
\4-IF
for noise-free picture): UHF (Ch. 40) -65 dBm
Voltage regulation (line: Low voltage: 118.5 to 120.7 V
varied from 105 to 130 V): High voltage: 24.5 to 26.5 kV
Horizontal overscan: 15% (adjustable)
^ `_,-r
A%
Video detection:
Video bandpass at CRT:
4 MHz
3.5 MHz
11.7 / S!N at CRT:

. /
Convergence (measured
with crosshatch generator):
Power consumption (with
45 dB
Greater than 90%

75 watts
incoming signal):
f ! I.


I 1
41.25 I 44.00 45.75 47.25
39.75 42.17
Fig.1. Scope trace shows how pulses have passed. A dc adjustment sets this IC are current limiting and thermal
response of SAW filter determines the bias so r -f age doesn't operate until
bandpass for all of TV chasis.
shutdown, low quiescent current, excel-
the i-fs are almost at saturation. lent 50 -dB AM rejection, -3 -dB sensi-
Sound i -f and audio -output IC U201 tivity of 200 V, differential peak detec-
Fig. 2. Entire i-f, aft, agc, and is an RCA CA3134 that can deliver up tion, and electronic control of volume.
video detector functions are to 3 watts through a capacitor into a 32 - Gain is controlled by feedback and do
contained on a single monolithic IC. ohm speaker (Fig. 3). Some features of bias applied to the internal amplifiers.
(Text continued on page 50.)

Vcc AFT
18 +1 OUTPUTS


1
I




AFT
'CROSSOVER



BIAS AFT
CIRCUIT DETECTOR




I 'V DEO
TANK



LIMITER




VIDEO
DETECTOR VIDEO
AMP




RF
AGC



NOISE
INVERTER



L_ 1

RF AGC
AGC FILTER




48
POPULAR ELECTRONICS


AmericanRadioHistory.Com
V*30V r ---- - - 1
-O
OPTIONAL
UNATTENUATED
AUDIO OUTPUT
-1_
100 pF 1 1 4700 pF
36K
002
'T' 1
(IF NOT USED,
GROUND TERM. 8)

pF_




OPTIONAL I
(BY-PASS .1
REGULATED UN ATTEN UATED THERMAL & -




POWER AUDIO CURRENT
DEPENDENT _1
UPON POWER
SUPPLY SENSING SUPPLY RIPPLE/
SHUT DOWN
SOUND TAKE - OFF _1-
TRANSFORMER


IF AUDIO t 100pF
AM PL PAIR
DETECTOR AMPL.
i LIM.

2,7 52

32 S2

SUBSTRATE
0.047 pF 0.01 pF




22 K 0.01 pF
Fig. 3. All sound i -f and audio VOLUME CONTROL - DE - EMPHASIS
6.8 pF
output functions are performed 4700 pF
by one IC to drive the speaker.




SANDCASTLE
INPUT
Fig. 4. Complex luminance/chroma IC 10.9V

greatly simplifies component count.



POWER SANDCASTLE OVERLOAD
BUFFERS DECODER FLESH ENABLE
SUPPLIES




KEYED ACC AND AFPC
11 _EL
BURST
AMP SAMPLE/HOLD
-90 -180'
HUE CARRIER
VCO
ONT ROL LIMITER
CH ROMA
INPUT
KILLER
AMP
FLESH
PHASE BUFFER
DETECTOR


CH ROMA --I. KEYED
AMP
OVERLCAD
DETECTOR
U MODULATOR




SAT
CONTROL
L CHROMA
'

AMP
BUFFER
CH ROMA
LIMITER




LUM
INPUT LUM
J IG -YI
BUFFER
DEMOD
AMP
IR YI
LUM/ iR
r-
CHROMA
MATRIX
(B Y)
FIX KEYED
CONTROL COMPARATOR



TO RED,
BLUE, AND
I

I
BEAM GREEN OUTPUTS
LIMITER BLANKING
PULSE

BEAM
CURRENT
REFERENCE L J

49
JUNE 1980


AmericanRadioHistory.Com
XL -100 chassis

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.fi
The recovered audio can be delivered
unattenuated (pin 8) or electronically
attenuated (pin 9).
+ .
from a bridge rectifier connected direct-
ly to both sides of the ac line, which
places this chassis about 30 volts above
Audio signals at pin 9 of U201 are ground. A single 600-F capacitor sup-
coupled through a .047-F capacitor, de- plies ripple filtering for the fairly com-
emphasized by another capacitor, and plex B+ regulator. In stabilizing the
fed to the internal audio amplifier via raw 150 -volt output, regulator action re-
pin 7. Audio output from pin 2 is routed duces it to 33 volts for the supply's regu-
to outboard Darlington power output lator -error, control -amplifier, and oscil-
stages that are current -limited or/and lator circuits (this is a switching power
shut down by separate shunt transistors. supply). The oscillator feeds the primary
A complex 28 -pin LSI device (shown of the coupling and driving transformer.
in block -diagram form in Fig. 4) pro- An SCR in the secondary of the trans-
cesses all luminance and chroma, after former delivers current and regulated
delay -line and burst keyer inputs, to pro- B+ to the primary winding of the fly-
vide signals for the final red, green, and back, the collector of the horizontal out-
blue amplifier stages before the cathode put transistor, and line and load regulat-
ray tube. The chroma portion is last ing auxiliary flyback operating voltages.
year's CA3151 device, which appears in Regulated B+ is compared with the
both the CTC 99 and CTC 101 chassis. In top photo, upper trace is multiburst 33 -volt reference zener potential at its
Burst and chroma, peaked and band- at CRT showing usable 3.5 -MHz emitter by the regulator -error amplifier.
pass -limited to the usual 1 MHz, are information; lower trace shows 4 MHz at High B+ makes the SCR deliver less
routed to the first chroma amplifie., video detector. In lower photo, top current and reduces B+ output; subnor-
which delivers signals to both chroma trace is typical staircase with some mal B+ causes the reverse action.
and burst pulse-keyer amplifiers. Here, transients at CRT's green cathode.
color killer, automatic color control Lower trace shows excellent reproduction Comments. Although the actual cir-
(acc), and automatic phase control de- of color bars at video detector. cuitry is quite elaborate, this is a very
tectors (afpc) receive color burst that is input and integrated flyback feedback. compact and sparsely populated chassis.
detected and applied to sample -and -hold However, since the horizontal oscillator All components are soldered into place
circuits. Burst amplitude is also sampled has improved noise immunity, pull -in on the single pc board, however, which
by the acc amplifier, which establishes range is greater than heretofore possi- makes service in the home extremely
gain correction for the first chroma am- ble, and there is no agc gating pulse difficult, if not impossible. On the other
plifier. In the absence of color, the killer drain. Hence, there is little necessity for hand, as reliability should prove very
amplifier biases the second chroma am- operator manipulation, and the de bias high, servicing might not be much of a
plifiers off. An external potentiometer for horizontal frequency is controlled by problem.
offers manual phase shifting for these a factory -set potentiometer. High- and low -voltage regulation are
and the hue control stages, whose sig- Afc diodes and a do level, preset at exceptional, assuring better -than -aver-
nals then proceed to the flesh phase de- the factory, control the switching rate of age performance under fluctuating pow-
tector, carrier limiter, and buffer. the horizontal oscillator. This consists of er conditions. (See Laboratory Data Ta-
Flesh -tone phase correction through two transistors in parallel with collectors ble.) Automatic gain control (agc),
the buffer is also aided by the flesh connected together and emitters sharing though not ultra -effective, should serve
detector. Chroma from the second Amp a common resistor. The first half of this well in most areas. Overall video band-
is buffered and limited. Both signals circuit rate -modulates the second, which pass is very good indeed and, coupled
then enter a modulator, where output in- is inverted and switched by a separate with very good tuner sensitivity and even
creases or decreases according to the pair of feedback transistors, locking the better CRT signal-to-noise ratio, en-
signal phase. The result is chroma sig- horizontal switch portion to its nominal sures crisp picture quality. While there
nals constantly amplitude -modulated by I5,734 -Hz color repetition rate. The is some horizontal overscan in the pic-
flesh -tone -corrected information from usual transistor driver, its current trans- ture (common in color receivers), a
the flesh phase detector. Flesh -tone cor- former, single -stage horizontal output, width control can be adjusted to mini-
rection cannot be defeated. and damper diode efficiently do the mize it. Like other low -power chassis,
The luminance portion is considera- rest. this one is not isolated from the power
bly less involved than chroma, but there Half-wave rectifiers in series with fly- line, so an isolation transformer should
are interesting circuits here too. Delayed back secondary taps furnish various be used if, for any reason, servicing is
and 3.58-MHz-chroma-trapped video is operating voltages for the remainder of required.
amplified and gain -controlled by both the receiver, as is usual. Stacked diodes This receiver obviously has a number
Pix-ganged brightness and chroma con- among the upper flyback windings de- of points to recommend it. It is sensitive
trol, as well as the brightness -beam cur- liver do anode voltage to the cathode ray enough (assuming a good antenna is
rent limiter connected between high tube. A three -transistor and diode X- used) to pull in signals in most areas. If
voltage resupply and the flyback trans- ray/overcurrent shutdown circuit sam- you live in an area served by cable TV,
former. Feedback from the blue output ples regulated B+ and high voltage. If the midband channels (in addition to A-
amplifier and beam current are sampled either is excessive or too much current is 1 and A-2 for those odd areas) would be
in the keyed comparator, and automatic drawn, it biases the horizontal driver a distinct asset. Clearly, this new chassis
limiting occurs in the luma amplifier. into continuous conduction, shutting offers high performance in its moderate
The horizontal circuits use discrete down the high voltage, flyback -diode price class. Anyone in the market for a
transistors, and even include the peren- generated do voltages, and the receiver. color -TV receiver in these inflation -rid-
nial pair of automatic phase control Operating power in addition to that den times would do well to consider it.
diodes with 15,734-Hz broadcast sync sourced from the flyback originates -Stan Prentiss
50 POPULAR ELECTRONICS