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ELECTRONIC TECHNICIAN/DEALER NOVEMBER 1973 insulated screwdriver into the hole of
the center knob in the COLOR LEVEL
TEKLAB REPORT control and readjust for desired
color intensity. For TINT, insert the
screwdriver into the hole of the TINT
control knob and adjust for desired
Zenith's Titan 300V facial skin tones.
The TV set's back cover is easily
removed by removing five standard
Vertical Color -TV Chassis 1I-in. screws-the antenna termi-
I -in.
nals stay intact with the cabinet.
Even at first glance, we were
by Joseph Zauhar amazed at the chassis-a vertical
wall of easy -to -remove modules.
The 19EC45 chassis employed is
A new Power -Sentry system employs a one of the three new all solid-state
chassis used in the "E" line color -
magnetic rather than an electronic system of voltage TV receivers. This chassis is used in
the new 19V and 2 3V models em-
regulation for protecting all chassis circuitry ploying the new type (29.6kv)
Chromacolor II picture tube.
The vertical Titan 300V is one
About nine and a half million Chromatic color adjustment (fac- of the most powerful chassis ever
Americans are expected to buy a tory pre-set) for personal prefer- produced by Zenith for either its
color -TV set this year and table ence, it can easily be done from the big- or small -screen color -TV sets.
model color -TV sets arc still high front of the TV set while viewing It is an expansion of the company's
on the list in demand. the picture-which we feel is a good modular solid-state circuitry that
The consumer buying a TV set feature. Should you desire to change began in 1969 with the use of dura-
today will benefit not only from ad- the picture color -tones received, set modules in the company's TV sets.
vancements in technology and inno- the chromatic color switch to ON The Dura-modules are special
vative set designing, but also from an (the color switch will glow), and carrier panels that mount and inter-
increased emphasis on consumer use an insulated screwdriver to connect solid-state devices in a de-
benefits by manufacturers. One -but- make the following adjustments: sired circuit configuration. The
ton tuning, brighter picture tubes, First pry off panel cover emblem modules vary in size from single
voltage regulation for increased for access to the panel -holding ones that are 31/2 in. by 23/4 in. to
component life and extended war- screw, then remove this screw and the largest that measures 43/4 in. by
ranties are just a few examples. the panel. To readjust the BRIGHT- 31/2 in.
After reviewing the new sets for NESS and CONTRAST level, insert an This chassis has five integrated
1974, we received for lab purposes a insulated screwdriver into the hole circuits, one more than last year.
Zenith table color -TV set, Model in thecenter of the customer The newcomer includes the audio
E4025W, employing a 19 -in. (mea- BRIGHTNESS and CONTRAST knob. amplifier and sound -output stage.
sured diagonally) screen. It em- To adjust the color level, insert an Each integrated circuit does the
ploys a Power -Sentry system of
magnetic voltage regulation, Chro-
matic tuning, Automatic Tint Guard
and an advanced Chromacolor pic-
ture tube.
Viewing the TV set from the
front, most of the customer tuning
controls are found to be located on
the front control panel with the ex-
ception of the PICTURE PEAKING
and HORIZONTAL HOLD controls,
which arc located on the rear cabi-
net panel. The Chromatic tuning
system has a push-button switch lo-
catcd at the top of the control panel.
Pressing the button selects Auto-
matic Tint Guard and factory pre-
set adjustments of BRIGHTNESS,
CONTRAST, COLOR LEVEL and TINT. Zenith's Model E4025W Chromacolor II color -TV set enploys a 19 -in. (measured diagonally)
If you should want to change the screen.
NOVEMBER 1973, ELECTRONIC TECHNICIAN/DEALER 25
work of many larger components.
One of the IC's (the chroma am-
plifier/color demodulator) for ex-
ample contains the equivalent of 43
transistors, 53 resistors, 14 diodes
and 3 capacitors. (See this month's
Tekfax Schematic No. 1496.
In addition to the chroma am-
plifier/color demodulator, the in-
tegrated circuits include color sub-
carrier regenerator, signal proces-
sor/fringe-lock circuit, audio am-
plifier and sound output and the
sound IF, limiter, detector and pre -
driver circuit.
The vertical chassis consists of a
Most of the customer tuning r3rt-ols are lo- After removing one screw aid plying off the vertical "wall" positioned on a nar-
cated on the front panel wits ti e:ception control panel cover, an insula-ed scrEwdrivEr
of the PICTURE PEAKING aid IORIZONTAL
row horizontal steel base. Eight
is inserted through the :elite- toles of the
HOLD. The AFC, CHROMATIC ?nd )N/ ]FF are customer controls to adjist the factcry pre- dura-modules are wall -mounted and
pushbutton type switches. set controls. secured by plastic turnbuckles. This
arrangement positions 74 percent of
the chassis circuitry on modules so
that these circuits directly face the
service technician when the cabinet
back cover is removed.
On the back of the chassis are the
plug-in connectors for the tuner
package plus the solid-state high -
voltage tripler and divider package
and the sweep transformer. The
power supply, including the protec-
tive Power -Sentry system, is located
on the horizontal base.
Removal of two screws and loos-
ening of the side support hinge al-
An. IR ,.,,y,, lows the vertical wall of the chassis
4-ITTP9.11. CiNildd to swing down for easy access to the
back -of -the -wall components by the
service technician. This also allows
The Titan 300V is one of the most powerful chassis produced by Zenith. Employing e ght Jura - access to the tuner package. The
modules, it is designed for a nomirai high voltage of 29.6kv. convergence circuitry is placed
IF on
kdiit_di di
a le alkb
ight "
.......11-1"a".1116.111Wir
.
After minving two screws and loosening the side -support hinge, the
Approximately 74 percent of th3 chassis circuitry are contained on vertical wall o' the chassis swings down for easy access to the back
the eigh-. dura-moduies, with five if :Egra:ed circuits. of the cha>sis.
26 I
ELECTRONIC TECHNICIAN/DEALER, NOVEMBER 1973
around the neck of the picture tube ing level. It operates internally within step it up to a design average of
for fast, convenient adjustment. the power transformer, which sup- 30kv, rectify it and provide the
plies all parts of the TV receiver, proper voltage regardless of applied
Power -Sentry System and thus all circuitry are protected. voltage changes. The high -voltage
The Power -Sentry system, em- The system helps to protect the re- transformer and tripler are mounted
ploying magnetic voltage regula- ceiver against transient surges or behind the vertical main chassis.
tion rather than an electronic system "voltage spikes" which are especial-
V.:deo IF Module
of regulation, replaces the conven- ly damaging to solid-state compo-
tional power transformer and com- nents. The Video IF amplifier stage of
plex electronic voltage regulation the 150-190 IF Subchassis module
High -Voltage System includes an added video amplifier
circuitry found in many other solid-
state color receivers. It converts un- An integrated solid-state high - transistor (the first Video Amplifier
regulated ac line voltages to a regu- voltage tripler and focus divider are for improved gain and better noise
lated ac voltage for use in the set, used in this chassis to take the out- factor performance). In the previous
maintaining it at the specified operat- put of the sweep transformer and IF module (150-180), an emitter -
The voltage regLlating type transformer employed in the Power -Sentry The convergence board is placed around the neck of the picture tube,
system appears a little higher and larger than the conventional -type allowing for a more compact chassis and simplifying convergence of
power transformer. the TV set.
The Video IF Module, 150-190, is shown with the shield removed. Also in-
Shown are the Jura -module connector pins and the plastic turnbuckles cluded is a Video IF transistor 2nd DETECTOR LEVEL control, previously
used to secure :he modules. located on the Video Processor board.
The Sound -IF Amplifier and Sound -Output
The Chroma Amplifier, Chroma Demodulator stages are two IC units on one dura-module The third Video Amplifier and the three (R
and the Sub -Carrier Regenerator have been (9-103) shown to the left and the luminance 6 & B) Video Output transistors are combined
combined into one module (9-86). dura-module (9.88) on the right in the picture. into one dura-module (9-89).
NOVEMBER 1973, ELECTRONIC TECHNICIAN/DEALER I 27
follower stage was known as the the horizontal circuit, except the coupling to the speaker voice coil,
first Video Amplifier. In this mod- horizontal output which is mounted thus eliminating the bulky sound
ule, the emitter follower is called above the board on the main part transformer.
the Video Follower. The Video Fol- of the chassis on an adequate heat- The Chromacolor II, 19VDZP22,
lower, the same as before, provides sink bracket. picture -tube employed in this chas-
better impedance matching and im- The vertical dura-module, 9-92, sis is the fourth generation of the
proved coupling to the video stages contains all of the vertical circuits company's Chromacolor family.
that follow. including the vertical -output transis- Until the first Chromacolor picture-
The DETECTOR LEVEL control, tors, mounted on special heat -sinks. tube was introduced by the manu-
previously located on the Video The vertical circuit contains a dif- facturer, a positive guard -band type
Processor board, has been incor- ferential amplifier, employing a pair was used to safeguard the color
porated into this IF module. The of 121-972 transistors. This new purity in their pictures. With the
150-190 IF module has all com- module has been designed for direct negative guard -band picture tube,
ponent symbols printed on the coupling to the deflection yoke, the electron beam is larger than the
board for easy parts identification. eliminating the bulky vertical out- phosphor dot. The beam illuminates
Chroma Module put transformer and the need for a the entire dot and some of the black -
VERTICAL LINEARITY control. The surround. Now, if the beam is
The Chroma Amplifier, Chroma vertical SIZE and CENTERING con- slightly misaligned, it still lights the
Demodulator and the Sub -Carrier trols are located on the board, not entire dot. The needed tolerance is
Regenerator have been combined the chassis. still provided; but the area between
into one dura-module, 9-86. The the dots is greater and black mate-
COLOR -ALIGN (set-up) switch, the Sound Module
rial is present in this area to reduce
TINT RANGE (hue) adjustment coil, The Sound -IF Amplifier and light reflection and improve con-
the ACC, APC, COLOR THRESHOLD Sound -Output stage are two IC trast, permitting use of a non -tinted
and CROSS -TALK controls are all lo- units located on one dura-module face plate and increased useful light
cated on this board, not on the (9-103). The integrated circuit output on the picture tube bright-
chassis. The basic circuit and align- unit, 221-48, is the 4.5MHz Sound ness. The negative guard -band con-
ment procedures, however, remain IF Amplifier and Quadrature De- cept was made possible through the
the same as in previous chassis. tector; the IC unit, 221-77, is the development of a new Iris mask.
Luminance Module Sound Preamplifier and Output. This mask, which fits over the in-
module is designed for direct side face of the tube and replaces
The Luminance dura-module the earlier standard shadow mask,
(9-88) includes the second Video has 450,000 apertures (in the 25 -in.
Amplifier, three blankers (horizon- diagonal size). These apertures in
tal,vertical and video) and the the original Chromacolor picture
brightness limiter transistors. The tubes were nine -thousandths of an
3.58MHz trap coil is located on this inch in diameter. The mask is first
board.
used much like a stencil during the
Video -Output Module application of the phosphor dots to
the inside face of the tube. The dots
Itte third Video Amplifier and of each color are applied and the
the three (R, G and B) Video -Out- mask is then acid etched so that the
put transistors are combined into center apertures are opened to 13.5
one dura-module, 9-89. The R, G The Horizontal dura-module (9-90) shown at
thousandths of an inch. In the pres-
the left, contains all of the transistors in :he
and B chroma gain taps are located ent generation of Chromacolor
horizontal circuit except for the output tran-
on this board and are adjustable sistor. The Video Processor module (9-87) is tubes, the center apertures are 14.5
from high (H), medium (M), to low shown in right of the picture. thousandths of an inch and with the
(L) by moving the red, green and new process they are nearly identi-
blue color -coded leads from the "H," cal in circularity.
"M," "L" (printed on the board) The mask is then mounted about
connection pins as required for 1/2 -in. behind the inside face of the
proper color alignment. tube. The beams coming from the
The Video Processor dura-mod- electron gun pass through the aper-
ule (9-87) contains the Sync and tures to reach the phosphor dots and
AGC circuits, the active element is the diameter of the beams striking
the Integrated Circuit unit, 221-45. the dots is larger than the dot itself.
The AGC delay control is located Additionally, a jet-black light -ab-
on this board. sorbing material surrounds each dot.
Horizontal and Vertical Module This black -surround reduces room
The Vertical dura-module (9-92) contains all
light reflections which cause color
The horizontal dura-module, wash -out and absorbs light splash
of the vertical circuitry, including the vertical
990, contains all the transistors in output transistor.
-
continued on page 43
28 I ELECTRONIC TECHNICIAN/DEALER, NOVEMBER 1973
USE UTMOST CARE... The correction of mistakes offers are properly made. You will not
continued from page 34 a wonderful opportunity to build only gain a reputation for excellent
time to guide not only yourself but lasting friendship for the business on work, but you will make more mon-
everyone on the staff in procedures the part of every customer. Do it ey by eliminating the cause of many
for the future. Doing so is the very always with that thought first in expensive recalls. In the process,
best way to reduce the number of mind. you will have to raise your flat rates,
times any steps will have to be takeli if you use flat rate schedules, but
in mistake correction in the future. TAKE THE TIME... remember that in the customer's
Give the customer no opportuni- continued from page 35 mind "the bitterness of poor quality
ty to demand that anything be done place a burned plate load resistor, remains long after the sweetness of
about the mistake when it is called probably destroyed by a shorted a low price is forgotten."
to your attention. Quickly seize the tube. You guessed it-the new re-
initiative from the first moment you sistor was tack solder bridged across TEKLAB REPORT .. -
are aware of what he is talking the original part with full leads. continued from page 28
about. Hold that initiative from Then, probably to avoid shorting from adjacent phosphor dots.
there on out and those demands the replacement to the cover, he left The development of the mask
from the customer will always be it, along with the screws, at one side along with the jet black -surround
less than if you neglect to do so. of the cabinet. Sure, he had a pic- that soaks up reflected ambient
Check back on each correction ture and ran in record time, but is room lighting made it no longer
that is made a day or so afterward this the kind of work you would necessary for the manufacturer to
in order to make sure that every- want on your equipment? Needless use the low -transmission glass in the
thing was all right the second time. to say, if and when you come across face of the picture tube.
Customers do not always call a sec- this kind of work, it behooves you
ond mistake to the shop owner's at- to take the time and clean it up be- Summary
tention, but just forget about the fore you call the job done. Even The vertical chassis will enable
whole thing and go elsewhere in the though you didn't do the work, the the service technician to quickly re-
future. If everything is not satis- last one in the set is usually the one move any of the eight dura-modules
factory with the correction that has blamed for it. with just a half turn of the plastic
been made, the odds are almost cer- Removing and not replacing turnbuckle. By removing two screws
tain that you have lost another cus- mounting and grounding screws in and loosening the side support
tomer. chassis, tuner assemblies and hinge, it allows the vertical wall of
Even when you have suspicions grounding straps. This can cause a the chassis to swing down for easy
that the customer may have basket full of problems all the way access -of -the -wall com-
good deal to do with the situation from arcing and a hot faced CRT ponents. If the chassis requires shop
-though he admits nothing-it is to blowing a string of IF transistors service, just unplug the tuner and
still best not to challenge him. The in a solid-state set. Take the time speaker leads, remove six screws
shop owner has little to gain if he and put them all back where they and the picture tube and all slide
succeeds with the challenge. The came from. out together as one single unit.
unpleasantness which is sure to Too much or too little solder The new "E" line chassis are de-
arise will be certain to produce a along with cold -solder joints, es- signed for a nominal high -voltage
lost customer regardless of how pecially on printed -circuit boards, and many picture tubes now in stock
many concessions have been given can cause thermal intermittent and supplied for use in earlier
to him. opens and shorts that can consume models are not rated high enough
Remember always that this is hours of wasted time later. Take for use with these higher voltage
probably not a pleasant situation for the time to do it right! chassis and may not be used.
the customer any more than it is for We were pleased with the opera-
yourself. Handle the whole thing ac- Conclusion tion of the Power -Sentry power sup-
cordingly. Call on every capability A proper repair should require ply and we were able to drop the
for consideration and good taste an expert to determine where the re- line voltage down to 68v before we
that you have available for handling pair was made. The defective com- noted margins on the screen of the
situations of this nature. ponents should be located with mod- TV set. The TV set produced a
Do a little something extra for the ern trouble -shooting techniques and good, bright, picture with plenty of
customer if it is possible to do so only the defective parts removed contrast and sharpness even under
without too great a cost while the and replaced with an exact replace- the bright lights of our laboratory.
correction itself is being made. Such ment part in the same manner as the
an action leaves him very much in original. Your author realizes that
debt to your business. many of these sloppy -work syn-
Give every customer a full record dromes are caused by hard-pressed
of exactly what has been done in technicians trying to put out more MOVING?
handling the correction. All of those work than can be properly done in Be sure to let us know your new address.
small details will make it something the time allowed. Hence the title of Please enclose a complete address label
of much greater importance to him this article. It is really more profit- from one of your recent issues.
than if he knows nothing about able-for you the technician and
them. you the boss-to insist that repairs
NOVEMBER 1973, ELECTRONIC TECHNICIAN/DEALER 43