Text preview for : Zenith Chromacolor J TV chassis 1977.pdf part of Zenith Chromacolor J Zenith Chromacolor J from Electronic and Technician Dealer.
Back to : Zenith Chromacolor J TV c | Home
Zenith Color TV for 1978
We continue with our review of changes,
improvements and innovations in color television
for 1978. This month-the `updating' of
the Zenith "J" line. By Don W. Mason
Fig. 1-Modules used in vertical circuitry in the Zenith J line of color TV. Top four modules are
DC -coupled, and bottom three are AC -coupled modules.
As with most other TV set manu- modules are completely inter-
facturers this year, Zenith is "up- changeable, but the AC -coupled
dating its color television line for modules are not, and must be used
1978-refining the circuitry and as intended with specific chassis
adding new customer features- and deflection angle receivers.
rather than introducing new chas- Actually, the AC -coupled mod-
sis and new models. (Zenith has ules can be interchanged for ser-
introduced a new videocassette vicing purposes, but should not be
recorder and a new black -and - left in the receiver for normal op-
white TV chassis, however, as ad- eration as a poor linearity condi-
ditions to their 1978 product line.) tion will exist.
The improvements in circuitry A schematic of AC -coupled ver-
are concentrated on the "J" line of tical module 9-120-01A is pro-
Zenith color chassis. Circuits in- vided in Fig. 2. Whenever servic-
volved are: vertical, horizontal, ing for vertical problems involving
high voltage multiplier, low level this module, the emitter resistors,
luminance, video output, IF and RX213 and RX214, of the output
the tuner. amplifiers should be checked for
an open condition. And, if resistor
The Vertical Modules RX728 has opened, do not replace
The seven different modules the module before checking for a
(Fig. 1) used in the vertical circuit short or other fault in the output
of the Zenith "J" line of receivers transistor, deflection yoke, or the
are of two basic types-AC- wiring. If resistor RX728 failed
coupled and DC -coupled. AC - because of a short, and the short is
coupled modules are used in the not removed or repaired, the re-
100 and 110 degree deflection re- placement module will also fail.
ceivers, and DC -coupled modules
are used in the 90 -degree deflec- The Horizontal Sweep System
tion receivers. The DC -coupled Several improvements have
28 / ELECTRONIC TECHNICIAN/DEALER, OCTOBER 1977
R212 C216
134V
390K. C240
SY. .47 -
24V 11 20Y.
0.1
TO L204
AT 9-87C U2 U6 M11
*SYNC .704
FRON 221-45
5S270 ffR716 R715
9-120-01R
I/2N Y330K {56041 VERT . OSC . 8
CR704 R709 0706 (RI//
N v9.
270 .c7o1 DRIVER DRIVER L207 BLK
ER705
23.5V 1,2K 259
0701 R702
25.94 4-nnw--
R706 OSC tt8731 47K
1 OK S 660
R717
0.6V 350E 41.4V
® C704 Z CR702 SIZE
RX720, I
R711 ,47 ZCR703 22 0T
1R7.5K
1 1610 K 0709 OUTPUPU T
CR701
M
0702 cR7o6 'RX213 RX214
-C705 23.2V OSC --
- .015 SWITCH 40.741_1.5
R707
4MAr1 .03V
1417 40.19
tR704 R727
C702 OV 512011 470.2M
3'9K
R712
:::511: 4...I- 22K C715
tR703
.047
C7071 C703
I r-- 2241 li
R732 0202
.047 R7oe .0022 CÓÓ22 YEL
690 OUTPUT
£ 1504 R734.150K 1/2W
RT HOLD
L---_-J U4 NI
ALL RESISTORS ARE 1/4 WATT. FILM. *52 TOLERANCE
UNLESS OTHERWISE SPECIFIED.
U22 U14
TO 7204-7
C219
500. 7Sv
R215
Ir TO U4
Fig. 2-Schematic of vertical module 9-120-01A. 2.71 9-89-064
DEFLECTION YOKE b PLUG ASSEMBLY SIDE PINCUSHION REACTOR
r BLU TX205
_DEFLECTION YOKE r
HORIZONTAL
BW l
*C231
15
504
8233
I
.244
L --4
I
I II
1.314
RED
rLX2I5 R232
I
12.311. 6.20 1K CR214
YEL 1.ItEAR-
114
ITY
VERTICAL I ,
E201 L222
WIDTH
r-
C232
100
R230 1009
L lK
I
-,
CX230
1.33 I
TOP/BOTTOM PINCUSHION
to
I1
` 4O 0
1s/Y p p
RED
YEL
J204
ILEAC END VIEM1
12 OO ©,
WHT/YEL
©000 good]
P204
(LEVO END VIEN1 10 O O d
Fig. 3-Partial schematic showing location
of width coil in the 19JC55Z chassis.
been made in the horizontal sweep Tier H line chassis, preventing the As Fig. 3 shows, the coil is in
system of Zenith's "J" line of color viewer from seeing the entire pic- series with the deflection yoke, be-
chassis. The main improvement is ture. tween linearity coil LX215 and "S"
the addition of an adjustable width The new coil is composed of two capacitor, CX230. The yoke circuit
coil. The partial schematic of the layers of No. 26 gauge wire wound stores energy which is propor-
19JC55Z chassis in Fig. 3 shows on a paper form with an adjustable tional to the, added inductance
the location of the new width coil. ferrite core, and a ferrite cup core provided by the new width coil.
The new coil was added to the J fitted over the outside of the wind- This storing of energy reduces the
line chassis because of an 'over - ings. This construction offers a energy available to the horizontal
scan', or variation in horizontal high range of inductance from 10 yoke winding for the deflection of
width which occurred in the ear - to 150 microhenries. the electron beam, and therefore,
OCTOBER 1977, ELECTRONIC TECHNICIAN/DEALER / 29
reduces the horizontal width. trolling raster overscan but be- the screen. A shorted coil would
Because the yoke circuit is part cause it also has an influence on cause excessive width, but it
of the fundamental resonant cir- brightness and high voltage. To might or might not be objection-
cuit, the resonant frequency de- adjust, the core of the coil is turned able unless lettering in the image
creases as the total inductance in- clockwise until both vertical edges is off the screen at the sides of the
creases, and in turn, the width of of the raster are tangent to the es- raster. An open width coil would
the horizontal pulse is increased. cutcheon. Then the core is turned cause symptoms in the receiver
As a result, the retrace time in- three complete turns counter- similar to an open deflection yoke
creases. clockwise. At this point, the raster winding, reduced high voltage,
The change of inductance in the should have an overscan of about and wide retrace time. The symp-
fundamental resonant circuit, 6.5%to8.5%. toms would occur because an open
caused by variation of the width Centering of the raster is ac- width coil would, in turn, cause
coil inductance, can be expected to complished by adjusting the width the 390 ohm parallel resistor,
reduce high voltage by approxi- coil until the short scan side is R257, to open because of excessive
mately 700 volts, or depending on tangent to the escutcheon, and current. Also, if R257 becomes
the tuning of the sweep trans- then turning the core counter- open, ringing will be exhibited on
former, can increase it by as much clockwise three more complete the left side of the screen.
as 500 volts. turns.
Correct adjustment of the width Troubleshooting the width coil Horizontal Driver Circuitry
coil is important not only for con- is somewhat a matter of observing The circuitry for the horizontal
driver has been improved in the J
line of chassis with several new
components added (Fig. 4). A new
driver transistor (121-1014) which
has a higher voltage and power
rating is used along with a new
800 ohm B+ dropping resistor
which will not change value under
stress. The driver transformer
(95-3275) is new in the J line, also.
It is said to have better current
handling capabilities. In fact, the
Zenith service literature suggests
that should the transistor or trans-
former in the horizontal driver cir-
cuit of previous models fail, the
new 121-1014 transistor and the
95-3275 transformer should be
used as replacements.
Fig. 4-Simplified schematic of "J" line horizontal driver circuitry with new type components The ferrite bead used in the
(marked with arrows). horizontal driver circuit to remove
Fig. 5-Low level
luminance module
.12v
«s -..?. P
I
A241 TO GRN LERO
9-88-06A. CR905
M1 < IS ""OF TX204
U901E 1.29018 .124
10EC14 11 U90111
- N 210 ass
i
ISOK
.O.e« 100«
110 E907
U901MS.W
"24: /34 V
2W
4 v. t. 1 e
1.1X
0209 U901C
147. O04
1F
.11 M0141C905 RASTER
11 12.70 T .001
410E0
RELAY
LINE l L902
=a1901 290 Ue 01J
IM (---0 BLANK SHARP-
NESS
4217
IS
nu 1201-12
1.2« T 1.20. 5X i O2
121`9
T > N11
i« .25101
11201-13
92. 1W
I
, 124 124 2/P
P201-13
92051 9
:< /201_IS
U901C
S 1J201-11
^ 270
C0S
1201-7 1
9-88-06A
-1.014 LEVEL P201-7
LUMINANCE
!LACK
LEVEL
1219
tit
5«
P20
.MOOMT IC LICMT SONSOS
WITCH 495EIELT (SOME MOCEL11
10 C219.1215 1
222. 9-120-0:1
30 / ELECTRONIC TECHNICIAN/DEALER, OCTOBER 1977
or reduce the high energy RF new delay line which will tend to 190-01, to change the conven-
spikes, or `snivets' has been im- equalize any video preshoot to tional `haystack' bandpass re-
proved in the J line. It is said to overshoot, and thus, will improve sponse to a `flat -top' IF bandpass
assure more consistent snivet re- the video response. Also, as part of response. This change is said to
jection. the improved peaking changes, improve the IF synchronous detec-
Also new in the J line is the the capacitor (C220) in series with tor transient response and reduce
horizontal output transistor, the arm of the sharpness control the apparent strong signal back-
121-1029, and the transistor sock- has been changed to 39 pfd for im- ground noise in the picture.
et. In the J line, the socket consists proved reduction of background As shown in Fig. 6, the conven-
of a single piece, thermoset plastic noise. And the Brightness control tional IF bandpass response on a
transistor carrier, held in place by has been renamed "Black level" linear voltage scale appears as a
mounting screws instead of rivets. control in the J line to more accu- `haystack'. This shape provides a
Two tinnerman clips are provided rately describe its function. This certain amount of video peaking in
for collector connections. The `black level control' has also been the region of 1.5MHz to 2.0MHz
emitter and base connections, detented for optimum setting in from the picture carrier. In a diode
however, are soldered. most instances. `envelope' detector system, this
peaking is necessary because of
Low Level Luminance Module The IF Module the apparent de -peaking in that
The 100 degree, EFL CRT Chas- An alignment modification has frequency region caused by distor-
sis, 19JC55Z, features a newly de- been made in the IF module, 150- continued on page 44
signed module for the low level
luminance circuit. The new mod-
ule, designated 9-88-06A replaces Fig. 6-IF response curves.
the 9-88-03. The new module in-
corporates circuit modifications
which are said to improve picture
quality in the J line. COLOR PICTURE COLOR PICTURE
In Fig. 5, the schematic of mod- CARRIER CARRIER CARRIER CARRIER
ule 9-88-06A, you'll see a 3.58 42.17 MHZ 45.75MHZ 42,17 MHZ
6DB
45.75MHZ
MHz trap, L901, used in associa- 6DB
tion with a 43 pfd capacitor, C906.
This combination can decrease -11.11,75MHZ 14 - I.75MHZ -
noise immunity, but according to HAYSTACK RESPONSE FLAT -TOP RESPONSE
Zenith, also enhances picture
quality.
The new module also features a
25V 'H' LINE
I0iFNi/ CH.6
l 10111.11
CH IS
V
01,
/ CH.7
_
CH.2
CH.2 CH.6 CH.7 CH.I3
V.X.F. CHANNEL V.H.F. CHANNEL
Fig. 8-Hyperabrupt tuning curve. Fig. 9-Abrupt tuning curve.
fol
C /2/-779 C /2I-/O/B
C O UHF SECTION C O UHF SECTION
RF AMP RF AMP
!
C VHF RF C
AMP FEEDTHRO
I
CAPACITOR A TRAPEZOID
A CAPACITOR
4 SOLDERED
LEADS CONVERTER CONVERTER
6_f,L.OPEN COIL- SHIELD
IF JACK
ro1 IF JACK
PREVIOUS UN TUNER NEW UN TUNER
Fig. 7-Photo of Zenith 14 pushbutton varactor
tuning assembly. Fig. 10-Drawings of previous U/V Tuner (left), and the new 1978 U/V Tuner (right).
OCTOBER 1977, ELECTRONIC TECHNICIAN/DEALER / 31
able coupling level related to the in- SLIDEPROOF WORK PAD 156
sertion depth of its sampling connector
into the line section. Available with A new, slide -proof plastic material
types of UHF, BNC, or N connector. for use on service benches and other
B
Priced in the $35 range. work areas has been developed by
Kager International. Called Slide -
stop, the new material prevents tools
WIRE MARKER TAPE 155 and components from sliding or rolling
NEW EKO 1200 off the bench, yet it is said to be com-
A new line of pre-printed, pressure -
30 MHz FREQUENCY sensitive cloth markers for wire iden- pletely non -sticky. It comes in rolls
tification has been introduced by Pan-
COUNTER duit Corporation. Called Insta -Code,
the new markers are mounted on
3 Operating Modes: Freq.,Period, Count smooth -coated cards for easy removal
MOS/LSI IC design gives excep-
tionally high reliability and labora-
tory performance. Guaranteed to
30 MHz minimum, 45 MHz typical
(250 MHz with EICO FE -250 Pre -
scaler, $39.95) with 1 Hz resolu-
tion. Sensitivity is a low 15 mV
RMS. Period mode: Measures inter-
vals up to 9.99999 seconds. Count
mode: adds up event pulses up to and can be cut to any size desired. It is
a count of 999999. Features: Six available in green, red, blue, yellow
0.5" LED displays; Timebase Switch and white and is said to be non-toxic.
(KHz/MHz); input attenuator; over- Slidestop is also reported to reduce
flow indicator; 120 VAC or 12 VDC noise.
mobile operation.
Assembled $169.95
ZENITH
FREE '78 MO CATALOG and application to the wire. Available
Check reader serice card or send 75¢ in all popular legends, the markers are
continued from page 31
for first class mail. See your local EICO
Dealer or call (212) 272-1134, 9:00 11/2 inches long and will wrap around tion in the detection system.
a.m.-5:00 p.m. EST. Major credit cards all wires up to % inches outside diame- As pointed out in the Zenith
accepted.
ter. Material is vinyl impregnated Training Manual for the J -line,
EICO-283 Malta St., 1-7
Brooklyn, N.Y. 11207
EICO cloth suitable for use in temperature "The IF bandpass response which
ranges from -40°F to 250°F. provides optimum peaking, video
...for more details circle 112 on Reader Service Card transient response, and the least
amount of video background noise
(which also occurs in the 1.5MHz
-QUICK CHARGE IRON - to 2.0MHz range) is the "flat -top"
If bandpass response (Fig. 6). This
QUICK CHANGE TIPS response decreases the peaking in
the 1.5MHz to 2.0MHz video range
~Quick Charge Cordless by depression of the `nose' of the
Soldering Iron recharges in bandpass."
3-4',/1 hours. Uses any of J Line Tuning Systems
Wahl's 16 snap -in tips. The U/V Integral Tuning sys-
Low voltage, battery powered, tems that were first introduced by
ground free isolated tip design.
=7571 -BEVELED TIP ::2
tIs
7573 -TINNING TIP ::5
=7556
TUNER
EXTENSION TIP
Zenith in their H line of color re-
ceivers will be continued in the
majority of J line receivers. How-
ever, not all receivers, for example
the 13 inch size, can accommodate
rtI
::7569 - "V" TIP
::7579 - BEVELED TIP =3 ::5
ll
the new U/V integral type. These
will continue to use the two sepa-
tilrs.
=7592 - BEVELED TIP =5 7572 --BLUNT TIP =5
rate VHF and UHF tuner systems.
:7593 --BEVELED TIP =6 '7577 - CHISEL TIP ,5 The U/V Integral configuration
of tuning systems features simpli-
rll
=7566 -MICRO SOLDERING MP =7545 - FINE TIP :'2 fied interconnections between
1 IIIrate UHF and VHF tuners, reduced
=7535 -REGULAR TIP F5 =7596 - KNIFE TIP size, lower manufacturing cost,
-`-_-rte
7546 -HEAVY DUTY TIP =5 =7574 -CONCAVE CENTERING TIP =5
and improvements in serviceabil-
ity and reliability.
The integral system uses two
=7541 - CIRCUIT BREAKER TIP
basically different varactor di-
odes-the hyperabrupt junction
WAHL CLIPPER CORPORATION varactor diode and the abrupt
ORIGINATORS OF PRACTICAL CORDLESS SOLDERING.
Sterling, Illinois 61081 (815) 625-6525 junction.
"Manufacturing Excellence Since 1919" The hyperabrupt junction diode,
...for more details circle 133 on Reader Service Card
44 / ELECTRONIC TECHNICIAN/DEALER, OCTOBER 1977
used previously in Zenith's G line, And a larger tuning voltage varia-
is now used in the J -line's Push tion is required by the high VHF
Button Manual Varactor Tuning band, channels 7 through 13.
System and in the 14 -position Several changes have been
Space Command system (as pic- made in the U/V Integral Tuners
tured in Fig. 7). used in the J -line. For comparison,
These hyperabrupt diodes pro- Fig. 10 shows the previous U/V
duce a large capacitance change tuner and the new 1978 U/V tuner
per voltage change. In Fig. 8 the side by side. NEW EICO 480
tuning curve illustrates how this Notice, first of all, that an open
relates to the frequency change of IF output converter coil/trans- D SWEEP
circuits to which these diodes are former has been replaced by a 10 MHz SCOPE
added. Channels 2 through 6 are shielded coil that mounts directly
tuned with an average voltage to the circuit board, thus wires 100% Solid State Includes 10:1 Probe
range of +1 to +9 volts. Channels that previously were easily broken
More Professional scope perfor-
7 through 13 are tuned by voltage are now protected by the shield. mance for your money! DC to 10
ranging between +10 and +24 Another change eliminates the MHz bandwidth, AC and DC coup-
volts. feedthru capacitor in the FET RF ling, 11 position calibrated atten-
uator, 10 mV/cm sensitivity, push-
The abrupt junction type of var- Amplifier circuit that acted as the button operation. Outstanding
actor diode is used in the J -line's source bypass. Originally, the features: Built-in TV Sync Separa-
source lead was connected to the tor; Digitally controlled trigger cir-
18 Position Rotary Channel Selec- cuits; reference baseline display;
tor assembly. The chart in Fig. 9 heat sink clamp, which in turn, calibrated 21 step sweep speed;
illustrates the frequency versus was connected to the feedthru ca- Fully regulated power supply; Cus-
voltage curves produced by the pacitor. Sometimes, when the RF tom Bezel for standard camera
mounting. Assembled $425.00
abrupt junction diode. transistor was changed, the feed-
thru capacitor was accidentally
The curves demonstrate the fact FREE '78 EICO CATALOG
broken. In the new version, the
that these abrupt junction diodes Check reader service card or send 75¢
are less sensitive to voltage feedthru capacitor has been re- for first class mail. See your local EICO
Dealer or call (212) 272-1134, 9:00
change. Almost the total tuning placed by a circuit board -mounted a.m.-5:00 p.m. EST. Major credit cards
accepted.
voltage range from +1 to +24 trapezoidal capacitor. Now, when EICO-283 Malta St.,
volts is required to tune the VHF the transistor is changed, the ca- Brooklyn, N.Y. 11207 /E/COL®
low band channels 2 through 6. pacitor is not touched.
...for more details circle 113 on Reader Service Card
Your new RCA QT Parts Inventory Program
with annual drop -ship updating.
Here it is! Your new RCA QT (Quick Turnover)
Parts Program that assures you an up-to-date
inventory of the most used RCA exact replace-
ment TV parts.
Simply contact your RCA Distributor and
register as a QT Dealer. You will receive your
package of 150 of the most -needed, fastest -
moving parts.
Automatically, once a year, OT parts will be
evaluated, and the program will be updated to
include only the 150 fastest -moving parts. You
return the parts that are dropped from the
fastest -movers list to your RCA Distributor,
and get full credit. At the same time, the new
parts added to the QT list will be shipped
directly to you from RCA. A quick, automated
inventory control system designed for your
convenience.
And, to keep your parts organized for fast
servicing, ask your RCA Distributor about the
QT Parts Rack. It's sturdy, but light enough to
hang on a wall. Saves you time and space.
Call your RCA OT Parts Distributor for all the
details, or write to RCA Distributor and Special
Products Division, Deptford, N.J. 08096.
RC/1 QT Parts
...for more details circle 128 on Reader Service Card
OCTOBER 1977, ELECTRONIC TECHNICIAN/DEALER / 45