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ELECTRONIC TECHNICIAN/ DEALER NOVEMBER 1972
TEKLAB REPORT
RCA's Argosy Model ER475
Portable Color -TV Set
by Joseph Zauhar
The solid-state modular construction of this chassis
practically revolutionizes manufacturer's sery cing
In 1968 RCA introduced the with many updated features, which
CTC40 color -TV chassis which was included the high -voltage quadrupler
their first solid-state TV set, using and motorless remote VOLUME, TINT
only a high -voltage rectifier tube in and COLOR controls carried over
addition to the CRT. Next came the from the CTC47 chassis. The
CTC47 chassis which was released CTC49 chassis is a natural out-
in 1969. This TV -chassis retained growth of these predecessors.
most of the circuits used in the The Argosy Model ER475W,
CTC40 with several
significant employing the CTC59 chassis, sent
tuned to us for review is very similar in
VHF tuner and solid-state high -volt- concept and physical appearance to
age rectification, using a voltage the very familiar CTC49 chassis.
quadrupler. This 100 -percent solid-state chassis
The CTC44 chassis represented employs 12 plug-in boards that are
the third generation of their solid- compatible with those used in either
state color -TV receivers, including the CTC49 or the CTC46 chassis.
some of the basic circuit designs car- An ultra -rectangular, 110° deflec-
ried over from the CTC40 chassis tion picture tube (19BLP22) is
The Argosi, Model ER475, employing the CTC59 chassis, is continued as RCA's to,-0fthe-line, all
r
-
solid -state portable color -TV set.
mew
NOVEMBER 1972, ELECTRONIC TECHNICIAN/DEALER 39
used to provide a 19 -in (measured
diagonally) screen size.
When unpacking the TV set, we
were quite impressed with its cabi-
net. Not only is it made of nicely
styled high -impact plastic with
wood -grain acrylic finish, it is much
slimmer than earlier cabinets-hav-
ing been reduced 19 percent in depth
by using the new 110° deflection
picture tube rather than a 90° one.
A 7E2 antenna coneclor is located on the
back :over to allow direct connection to an Serviceability is also incorporated in
MA' systecr without additional adapters. the cabinet design, there being fewer
The 12 p u; -in modules contain a najority of screws on the back cover and no
the circu h employed in the CTC59 chassis screws on the bottom of the cover
and ors compatible with those usec in either under the cabinet. In most cases,
S-ARPNESS the CTC46 or CTC49 chassis.
AFT this has eliminated the need for tip-
-411= ON/OFF ping the set forward or removing the
SWITCH set from the stand for servicing.
The TV set has a 7551 coaxial ca-
ble input for direct -line MATV sys-
VOLUME tems. This cable can be connected
without a special adapter or addi-
ACCUMATIC tional service. Additional shielding
BUTTON is employed on the VHF tuner to
help prevent unwanted signal inter-
ference.
Many of the controls on the front
panel are only partially exposed,
giving the TV set a smooth unclut-
tered look. These include the ON/OFF
switch, SHARP/AFT, VOLUME, COL-
OR, BRIGHTNESS and TINT controls,
C ON TRA S- BRIGHTNESS
along with the ACM button. The
The ACM COLOR -LEVEL contrcl located at the rocker type ON/OFF switch is con-
The front control pa -el, showing the location top -rear of the tuner mum brackets is a
of the various contro s.
veniently located at the top edge of
screwdr e.r adjustment.
the cabinet within easy reach.
The AccuMatic switch (ACM),
when in the oN position, effectively
places the COLOR LEVEL and TINT
controls at predetermined settings.
It also produces a slight shift in the
color demodulator circuitry output
and color drive outputs.
The main chassis contains the
power transformer, power -supply
filters, audio -output transistor, two
vertical -output transistors, high -
voltage quadrupler and focus bleed-
er, plus the SCR's and diodes of the
horizontal deflection system. Al-
though transformer powered, one
side of ac line is connected to the
chassis.
The PW200 board mounted on
the main chassis contains the three
SCREEN controls, plus the CONTRAST,
NOISE, KINE BIAS, VERTICAL HOLD
and HEIGHT controls, and the three-
position SERVICE switch.
The PW300 board serves as the
Rear v ew of RCA's CTC59 :ilor-TV chassis which is quite s mils to the CTC49 parent board for all but the MAB,
40 I ELECTRONIC TECHNICIAtI/DEALER, NOVEMBER 1972
MAH and MAG modules. In addi-
tion to containing edge connector
sockets for these modules, this
board also contains the audio -driver
and brightness limiter transistors
(Q301 and Q302) and the three
KINE DRIVE controls. Module MIK contains two transistcrs and two
The PW400 board contains the IC's, and ilciudes all the IF amplifiers and the
MAH and MAG modules, plus most keyed-AGC cicuit.
of the components for the horizon-
tal -deflection and high -voltage sys-
tems, including the high -voltage reg-
ulator and the side -pincushion am-
plifier and control potentiometer.
Most wire connections to the
main chassis are made with sockets,
making chassis removal easier if re-
quired for servicing.
Much of the circuitry employed The plug-in modules with edge connectors are
held securely in place by two spring clips,
in the CTC59 chassis is quite simi- simplifying removal.
Partial schematic showing the new "Sync
lar to that in the CTC46 and CTC49 Blanking C.rcaitry" lin bold lines) added to the
chassis, and our review will cover MAG001 mjdule. Courtesy of RCA.
some of these circuit modifications.
The circuits for this chassis can be
followed in Tekfax Schematic No.
1408, March 1972.
Signal Processing Circuit
The signal processing circuitry re-
mains the same as in the CTC46
chassis with some minor component
value differences on the main circuit
board (PW300), and the same cir-
cuit configuration and adjustment
procedure is used. However, the
ACM COLOR-LEVEL control is ad-
justed with a screwdriver and is
The ceram c MAD modules are interchangeable, A hermetically sealed solid-state quadrupler re-
mounted at the top -rear of the tuner requiring Lilly readjustments of the KINE-DRIVE duces the required pulse from about 23kv to
mount bracket. control fo- tracking. 6kv.
Vertical Circuit
A change was made in the verti-
cal module, MAG001, which ap-
pears in all currently produced mod-
ular chassis; however, the new UHF
TUNE.
MODULE
SOUMO OE TEC ma
YAM
MODULE
SJDIO
SuDIO 014144
r ...
4011,,
1ST VIDEO AMP
2 MO VIDEO AMP
MAGOO1B module is compatible as [
AUDIO 1111 SOU. OWE, Vv. St It 111011
51.1
a replacement for all MAGOO1A SIGML SOUP°
boards before the change was effect-
ed. Shown in the partial schematic
is the new "Sync Blanking Circuit- NMI 0.:4141
ry" which has been added to the
MAG001 module. The added com- MAC
MUMMA
00/01/1S I IMIOIDIASS MAO SO I
MAE
SmMOINS
.,F*0/Cf ox .111.
ponents are shown in bold lines. FCC MOD10. TOMS
I
FVC
CONVERSIMA
The operation of this circuit can ASZE":1111. I
56
be more clearly understood if we VERT/DAL
MODULE
KK CU *00
C.01 V tiK.0
DE1LIC/I01
TOKE
follow the basic operation of the mmogoi
r
AIM( AL
VenC M.. Ord
SSIIOl
,..,
vertical switching transistor, 01. ,.
-'-...
mowPam,
PM CVS.41014
The yoke circuitry feedback pulses 2av IMAMS
.04A
27:12714
SCRlel SC02
MOMS ISIEFFVE
1011, DOI TOM
are coupled to the transistor base to MORISOMSAL
vORI EOM E
FIE
Os
MEFOOMS
sustain the free -running operation
of the vertical oscillator. Sync pulses
at the vertical rate are applied A functional block diagram of the CTC59 color -TV chassis. Courtesy of RCA.
NOVEMBER 1972, ELECTRONIC TECHNICIAN/DEALER ! 41
through board contact No. 12 to the ry involve minor component value some resemblance to the ones found
base of transistor 01, synchronizing changes on the main circuit board in earlier chassis. The matrixing of
the oscillator operation to the prop- (PW400), but these changes do not luminance and chrominance video
er frequency. change the circuit operation or con- outside the picture tube has not
The sensitivity of this vertical sys- figuration. been done in an RCA color -TV
tem to low-level sync pulses makes The CTC59 and the CTC49 chas- chassis since the CTC2 color -TV
its output acceptable despite noise sis employ the same deflection yoke; chassis was discontinued. The most
pulses, such as those found in im- while the high -voltage power sup- important advantage of this system
properly maintained CCTV systems ply differs from the conventional is that the load offered by the three
where the vertical sync pulses ac- types, which rectify a positive pulse picture tube cathodes may now be
tually become clipped off or badly from the flyback transformer with a divided equally among three mod-
suppressed. In problems like this, half -wave rectifier. Instead, the erately rated drivers instead of one
the only signal present in the sync CTC59 chassis uses a solid-state relatively high -power device, thus
system of the receiver is an abnor- quadrupler to produce high voltage, eliminating the three kine-control-
mal blanking pulse. thus reducing the required ampli- grid drivers.
Noise produced by cross -modula- tude from about 23kv to 6kv. The The three identical MAD mod-
tion, thermal noise, ripple, or other quadrupler is hermetically sealed, ules are used to drive the three pic-
sources, can appear on this blank- repairable, and located on the lower ture tube cathodes. The luminance
ing pulse and trigger the vertical right of the main chassis. signals are driven in parallel, but
switch a second time, shortly after each is driven by its respective col-
the beginning of the vertical scan, Videc System or -difference signal and the output
producing the appearance of verti- Most of the video system has signals are true color -video signals:
cal jitter. The new MAGOO1B ver- red, blue and green. Each module
tical module helps prevent the noise also contains a bias regulator stage
from prematurely triggering the ver- which stabilizes the dc operating
tical switch. point of the output amplifier by re-
The sync blanker circuit is used turning the output voltage to the
to permit only the leading edge of same point during each horizontal
the vertical -sync pulse to be effec- blanking interval. This system is the
tive in triggering the vertical switch same as the one used in the CTC49
oN. A yoke circuit pulse is coupled chassis.
to the base of the sync blanker tran-
sistor, this feedback pulse driving Summary
the sync blanker into saturation and We feel that the picture and color
thus effectively shorting the remain- quality produced by the set is very
ing portion of the sync pulse to good and that the AccuMatic color
ground. Only a short duration spike, The CTC59 chassis now employs metal -cased, monitor (ACM) button is excellent
vertical -output transistors.
representing the leading edge of the for customers having trouble ad-
sync pulse, is employed in synchro- justing a color -TV set, while others
nizing the vertical oscillator to the may still adjust the set manually for
correct scanning frequency. personal preference of the color de-
sired.
Vertical -Output Transistors From the serviceability stand-
This chassis also employs metal - point, this chassis is designed to per-
cased transistors in its vertical -out- mit easy access to all modules, mak-
put stage to provide greater reli- ing the substitution method of
ability. The circuit configuration re- troubleshooting very feasible. The
mains unchanged, but to accommo- use of circuit modules should en-
date the new output transistors the able the service technician to correct
heat -sinks are changed from the the majority of problems in the
type used in other modular chassis home. Most of the circuitry used in
designs. The two vertical output this TV chassis is contained in but
transistors are located on the lower 11 modules, three of which are
right of the main chassis. identical so that only nine items
need be stocked in addition to the
High -Voltage System replacements for five plug-in tran-
The fixed -tuned flyback trans- sistors, two plug-in SCR's and two
former in the high -voltage system diodes of the horizontal -deflection
does not need a separate adjustment The co ivergence panel is placed around the
circuit. These should be carried on
for third harmonic tuning. Other neck of the picture tube to conserve cabinet service calls to reduce service time
differences in the deflection circuit- space and reduce wire lengths to the panel. in the home.
42 I ELECTRONIC TECHNICIAN/DEALER, NOVEMBER 1972