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AN-879
MONOMAX -APPLICATION OF
THE MC13001 MONOCHROME
TELEVISION INTEGRATED CIRCUIT
Prepared by
Ben Scott
Technical Consultants:
C.I. Tsui. Hong Kong
Peter Bissmire, Geneva
Lowell Kongable, Phoenix
Mike McGinn. Tempe
This application note presents a complete 12" black and
white line-operated television receiver, including artwork for
the printed circuit board. It is intended to provide a good start-
ing point for the first-time user. Some of the most common
pitfalls are overcome, and the significance of component
selections and locations are discussed. The design has only 4
factory adjustments: H. Hold, Height, AGC Delay, and V.
linearity, and there are no alignments.
Note that while this discusses MC13001 (525 line. positive
tuner AGC) there are also parts for 625 line and negative
tuner AGC, in all combinations.
INTRODUCTION pation. Special attention was given to ESD (electro-
Monomax has been on the market since mid-1981. It static discharge) immunity on all pins. An extremely
was originally developed in a joint effort between stable horizontal oscillator was devised.
Zenith and Motorola for the purpose of creating a high Additional features which resulted from this design
performance B&W receiver. It was intended for all effort included: a completely integrated IF and detector
types of monochrome receivers, including the demand- with no detector tuning or external filtering components,
ing portable and mobile applications, which require an on-chip de contrast control which permits remote lo-
immunity to noise, "airplane flutter" and multipath cation of the control without shielded cable, and fully
signal conditions. Features suggested by these require- black level clamped video with blanking and beam cur-
ments included: noise filtering and cancelling, dual- rent limiting. The combination of system functions in the
loop horizontal PLL, countdown vertical, and a flexible Monomax chip· permitted some elegant solutions which
AGC system. would not have been practical or economically feasible
It was also required that the resulting receivers be in more conventional designs .·
low in component and manufacturing cost. To meet It is not the purpose of this AN to describe the overall
this objective, effort was made to minimize external Monomax chip in any greater detail than is required
components (especially precision components) and for understanding receiver design decisions. The reader
adjustments. is urged to obtain a copy of the MC13001 data sheet
Above all, the receiver was to be reliable, so the chip available from Motorola Literature Distribution or
was designed to operate at low voltage and low dissi- Linear Applications. It contains some of the basic
MONOMAX is a trademark of Motorola Inc.
207
Sound
Output
IF
Stage
Video
Output
RF AGC
AGC System
1200 V 1.5 A
Honz Hor1z Honz
Def
Sync Processor Output
Vert Vert Vert
Coils
Sync Processor Output
FIG,URE 1 - Simplified Block Diagram
11[31J
+
+
Flyback
+ Pulse
to Pin 15
FIGURE 2 - Monomax Functional Block Diagram
208
application information which will not be repeated in output. The audio output section is usually a Class B
tl:)is note. Also recommended is a paper entitled type, operated directly from 12 Vdc. An IC combining
"Monomax - An Approach to the One-Chip TV" by the sound IF, detector, and audio output is ideal in this
Geraid Lunn and Mike McGinn of Motorola. This can architecture. TDAl 190 is an example which fits well
be obtained from the proceedings of the IEEE Chicago with Monomax.
Spring Conference on Consumer Electronics, June, Figure 4 shows the basic power supply structure for
1981, or from Linear Applications, Motorola. the ac line operated type of design. This is the most
Monomax is not difficult to apply. A functional TV economical and the most common approach for B& W
set is.virtually assured on the first try. But as anyone television in most of the world, and it is the subject of
closely associated with television design can attest, much of this AN. Special thought was given to this
there are, in every new design, a number of small but type of set in the design of the MC13001 itself. Note
objection al problems which stubbornly resist solution. that the horizontal oscillator and driver are supplied
The receiver described here does not. represent. the "la~t. through high value resistor. direr.Uy from the re<:"tified
word", but it is pretty close to production quality, and power line de (120 V). Only 4.0 mA are needed into
it includes solutions to some of the most common Pin 18 to power the horizontal oscillator system. The
beginner's problems. In the following text, an attempt balance of the horizontal circuit is also line operated
will be made to explain component value choices and so it is fully operable from the line supply. The hori-
locations in terms of problems solved or behavior zontal section then produces the 12-14 Vdc for the rest
avoided, so that the future experimenter will be alerted. of Monomax (50 mA), and for the tuners, the sound IF,
the vertical output, etc., about 150 mA in all. This
THE BASIC DECISIONS/POWER SUPPLY
method avoids the problem of developing 12 Vdc
One of the first considerations in a new TV design is directly from the line; i.e., the waste of power in a
whether the set is to be ac/dc (12 Vdc operable) or ac linear approach, the extra components for a switch-
line only. Monomax fits well into either, and has been mode de-de converter, or the cost of a line tran·sformer.
used in production designs of both types. As in the previous example, the TDA1190 can be used
Figure 3 shows the architecture of an ac/ de type for the entire sound system, but many designers prefer
with all systems operated from 12 Vde. In this case, to use a Class A, line operated, discrete output stage,
the horizontal output st.age is of the "boost" type, to and one of the standard sound IF /detector !Cs, such as
minimize horizontal deflection current and make the MC1358, CA3065 or TBA120. This removes the 12 V
yoke easier to manufacture. The flyback transformer supply ripple caused by loud low-frequency audio pas-
contains auxiliary windings which provide supply sages, but costs a small audio output transformer. This
voltages for the video output, picture tube grids, and is the approach presented in the complete receiver in
vertical deflection. Sometimes the boost voltage of 20 this AN, but it could be easily changed to the single-
to 30 Vde is used as a power supply for the vertical chip sound system.
To Audio
Boost
Output Stage
.--~-.''""+--::i~
(Vert. Output ... \; - - - HV
Supply) I ;i _
-=- ;::) I:;; Video
Ill ~ 2: lilt +~ Supply
ioort"~
Input
+ Jf1=z PYoke
_L
17
H. Output
H. Driver
+
MC13001
I I. 0.01
MONO MAX
+ Io.01 Lone r7>-r 2
V
Adapt~-
I
-=- AC/DC
FIGURE 3 - Basic AC/DC Architecture
209
l\,r-- T 120Vdc
To Video Output
120Vac~
I
MC13001
MONOMAX
FIGURE 4 - Line Operated Architecture
It is important to use good bypass techniques on all This means keeping color and sound subcarriers low
power supplies, not only for low frequencies, but also enough to avoid 920 kHz beat generation in the detec-
for RF. It is critical in prevention of faint but objec· tor, and yet not attenuating the sound so deeply that
tional vertical lines in the picture, caused by hori· good sound quieting is irretrievably lost. A well·
zontal deflection system waveforms getting into the proven characteristic for achieving this goal is as
supplies. Good high-frequency bypasses on Pins 18 shown in Figure 5, taken from tuner-mixer input to
and 19, with respect to Pin 16, are essential. detector. Of this, some selectivity comes from the
mixer-tuned circuits, but most of it is provided by the
THE IF
SAW filter.
The four stage IF in the MC13001has80 µ V sensitiv- Table I shows some available types, data normalized
ity, sufficient for excellent overall performance when to 0 dB picture carrier. The major difference is the
used with an ordinary tuner and a conventional L/C depth of 41.25 MHz. In this regard, the Toshiba
input bandpass network. It is recommended that the Fl032U, Kyocera, and the muRata parts are best for
input always be used differentially to reduce the pos· B& W design. The mixer-tuned circuits will supply the
sibility of feedback problems'. The differential input
capacitance decreases from its normal 5.0 pF, to about
2.0 pF, in the top 10 dB of gain-range of the IF. This ·10
can be used to narrow the input L/C filter, at very
weak signals, to reduce overall detected noise, and - - - --
0
improve picture lock. 42 17
If a SAW (surface acoustic wave) filter is used, as in Color
this AN, the above bandpass "walking" technique can- -10 ~
not be used. Furthermore, if a SAW filter is used, an ~
41.25
additiunal fixed gain-preamplifier is needed to over- -20 ~ --- - - -
Sound
come the 20 to 25 dB loss thus imposed. Nevertheless,
this approach has become increasingly popular with 301!
the introduction of low cost SAW filters, because it
eliminates a crucial and time consuming production -40 39.75
alignment. Adj. Pix
There is a steadily increasing supply of SAW filters
-50
in the marketplace, so soine criteria for choosing the
Fi'1q.-MH1
best one for the design are in order. Bear in mind that --.2 43
all of the video selectivity is concentrated in the tuner
40
" ·· 45 46 47 48
and theJF input filter in this design. In a B&W receiver,
it is important to obtain a good compromise of picture
and sound quality with a single selectivity channel. FIGURE 5 - IF Bendpa11 Characteristic
210
TABLE 1 - Some Available SAW Filters
Toshiba Kyocera muRata
Relative Response FJ032B F1032U F1032V F1052 KAF45MR-MA SAF45MC 027
39.75 Adjacent Picture -40 -48 -45 -40 -37 -37
41.25 Sound -12 -16 -6.5 -25 -18 -19
42.17 Color +1.0 0 0 0 0 0
Peak +4.0 +4.0 +4.0 4.0 4.0 4.0
45.75 Picture 0 0 0 0 0 0
47.25 Adjacent Sound -45 -48 -47 -40 -42 -38
Insertion Loss -18 -19 -18 -21 -2:3 -20
··~·'······
additional slight amount of narrowing required. The Remember that AGC loops have a large amount of
F1032V part is too wide, and F1052 is too narrow. gain, and fast AGC loops, with good airplane flutter
These are intended for color receiver architectures of performance, are especially vulnerable to deflection
different types. The SAW manufacturers loading currents. Only a few millivolts on the AGC lines from
recommendations should be adhered to closely to stray fields or ground loops can cause a significant
prevent ghosts (before and after the picture) caused "bar" in the picture. Keep the tuner AGC lead away
by capacitive feed-through and/or "triple transit" from yoke leads. The small bypass capacitor on Pin 11
reflections. further reduces this problem, and should be placed as
At the input of the MC13001, it is important to use close to the MC13001 as possible.
good bypass capacitors on Pins 2, 4 and 6 with respect Monomax was designed so that in the strong signal
to Pin 1 of the MC13001. The best value was found to be region," above the delay", the IF gain is held constant
a straight lead, low-inductance 0.02 µF disc ceramic while AGC acts upon the RF stage in the tuner. This
for reducing the infamous channel 6 beat. Pickup in means that a small amount of IF AGC range may not
this area is also a possible source of vertical scan bars be accessible in the normal implementation. Optimum
in the picture caused by horizontal sweep currents. It setting of the delay pot keeps the RF section at maxi·
is desirable to keep the SAW filter close to Pins 1, 2, 4 mum gain for RF signal levels of from <10 µV to
and 6. See the PC board layout Figure 14, Also, the IF 1.0 m Vrms· using 40 dB of the IF AGC range. The tuner
preamplifier must be kept compact and well grounded is not likely to be able to provide more than 40-46 dB of
to prevent feedback and oscillation with the tuner. additional AGC, which Will accommodate signal levels
AGC up to approximately 200 mVrms· This is adequate for
the Monopole antenna applications, but certainly
The AGC system was implemented here essentially doesn't offer a lot to spare. Above this level, the AGC
as described in the Data Sheet, including the AGC system loses control, the receiver overloads and even·
speed-up capacitor between Pins 9 and 10. This keeps tu ally falls out of sync. One way to improve this, and
the AGC airplane fl utter response time fast, even when pick up the remaining 6.0 dB or so of IF AGC capabil-
the signal is strong enough to move the AGC into the ity, is to put a resistor from Pin 11 to Pin 10. The value
tuner control region. The RF AGC delay setting is one of the resistor will be about 33 k for delay resistor values
of onfy 4 factory adjustments. Ideally it should be shown, but will have to be tailored to the particular tuner
made with a calibrated signal level, but acceptable used. This can also be accomplished by a resistor from
results can be obtained with a strong off-the-air signal Pin 9 to Pin 10. This, in fact, is the only solution in parts
and a switch type attenuator. A discussion of this providing negative tuner AGC.
adjustment is contained in Appendix I.
Delay
Setting
---------,,....~----~
1.0 200 1.0 400
SIGNAL STRENGTH lmV) SIGNAL STRENGTH lmVl
FIGURE 7 - Modified AGC CuMltl
FIGURE 8 - Mono~x AGC Behavior (Raaiatorfrom Pin 11 to Pin 10)
211
THE SYNC SEPARATORS H. Sync
Composite ~ync is stripped from noise-cancelled
video in a peak detecting sync separator, as shown in
Figure 2. The time constants for setting the slice. level
of the detector are connected at Pin 7. As always, there
is the compromis11o between optimum noise immunity
and tilting of the slice level during vertical interval.
For best horizontal separation, a shorf time constant 0.471+
is required. There is also an AGC anti-lockup system 8.2 k
which responds to the voltage at Pin 7. It also requires
a sho.rt time constant. A second, longer time constant
can be diode connected to the same pin, to prevent too
(Al ORIGINAL CIRCUIT
much charge-up during the vertical interval.
Composite sync is subsequently integrated internally
and fed to another amplifier whose emitter is brought
out at Pin 23. Satisfactory vertical sync can be
obtained (internally) by simply connecting Pin 23 to
a divider. Weak signal performance can be improved by
using an RC network on Pin 23 to make the separation
self compensating, as in the horizontal separator. Also
AGC from Pin 9 can be fed to Pin 23 to improve airplane
flutter v~rtical hold.
FLYBACKINPUT
(Bl NEW CIRCUIT
, The only flyback pulse input to the MC13001 is at
Pin 15. It takes care of keying the AGC, blanking the FIGURE B - Horizontal Phase Detector
video output stage, and phase locking the horizontal
system. The Pin 15 input is a base-emitter junction, The second horizontal phase detector compares the
with a reverse polarity diode for protection. The input flyback output phase with that of the oscillator, and
requirement is for a negative-going pulse of 0.6 mA, develops a proportional de voltage, which is filtered at
but it is best to choose a pulse voltage and series resis- Pin 14. This de voltage then sets the slice level on the
tor to give about -2.0 mA peak. This will make the oscillator ramp to produce the output timing desired.
effective width be the pulse width near its base. See Figure 9(a). Picture phasing can be adjusted
slightly by a high value resistor on Pin 14 to +8.0 V or
HORIZONTAL OSCILLATOR/ AFC ground. A 220 k to +8.0 V will move the picture about
Monomax contains a really unique group offeatures 2.0 µs to the left. A 220 k to ground will move it 2.0 µs
in this area: dual-loop; variable-loop-gain (bandwidth) to the right.
on the first (sync) PLL; externally adjustable phasing Another application of Pin 14 provides a method of
in the second PLL; simple fly back pulse input, requir- changing the duty cycle of the horizontal output wave-
ing no ramp generation. These are described in detail form from Pin 17. Normally, the desired waveform
in the data sheet, and will not be repeated here. would be 50%. This has been assured in the MC13001
Shown in Figure 8(a) .are the first PLL components by operating the slicer at 31.5 kHz. This permits output
as presented in earlier publications, and in 8(b) a new phasing correction without changing duty cycle, as
var,iation which has been implemented in this receiver. shown in Figure 9(a). In some receivers, when large
This very simple change retains the dual time constant amounts of de power are drawn from the fly back, the
on the phase detector. The improvement is the 13 k/22 k "on" time of the horizontal output inay have to be more
divider which sets a 5.0 V point for the return of the than 50% of the cycle. This can be accommodated by
longer time constant filter. Since 5.0 Vis the reference feeding back some driver collector signal to the second
level in the oscillator, it is also the operating voltage at phase detector filter, as shown in Figure 10. This
Pin 12, and at Pin 13 when in-lock. The benefit, ilien, is imposes alternate slice levels and hence, the desired
that the 0.47 µ.F doesn't have to charge up, so there's change of duty cycle. Some tentative values for a set
very little frequency pulling during power-up or power- configured like the one in this AN are given in Figure
down. This reduces audible chirps and momentary stresses 10. This was not actually used in the final design,
due to long cycles on the horizontal output device. Also because it wasn't needed. It is supplied here as a ref-
ilie picture locks-in quickly, which is highly desirable erence for future designs having more power drain
with fast warm-up picture tubes. from the horizontal output. Bear in mind that the
Note that the proper setting of the horizontal hold driver collector voltage would be much lower in the
control occurs when no average current flows through 12 Vde receiver architecture mentioned earlier, requir-
the 390 k resistor, either to, or from, the oscillator. A ing much different values to implement this idea. A
simple alignment procedure is to set the average Pin 12 practical limit of control by this technique is about
to Pin 13 voltage to zero by adjusting the hold control, a 60/40 duty cycle. The 0.001 capacitors on Pin 17 and
when locked to a standard broadcast signal, using a the driver base are to "soften" waveform edges, to
high impedance voltmeter. reduce their radiation into signal circuits.
212
osc. many customers like to have one, but also because it
permits using a smaller coupling capacitor for the
../\ ../\
../\/Ramp
yoke. The smaller coupling capacitor saves money and
Z:\ Z!\~\ )Pin14
reduces picture bounce, but introduces some curvature
/'f I \7'1 I V'ji \
I I I I I I which must be compensated. Feedback to Pin 21 pro-
I I I I I I
I I I I I I vides overall output stage linearization and prevention
Pin 17 of deflection current change with temperature. It is
J Output also a handy place to feedback a variable parabolic
waveshape for linearity control, as shown in Figure 11.
.-----
J
(A) NORMAL APPLICATION. PHASING Uncompensated
SHOWN AT TWO CONDITIONS Yoke Curren«
I
'
-- --- ............
~~- ....
' -p;n 14
I
I
I
I
I
1 1 1 Correction
' I Signal at
__Jl___ ___ .JPin17 linearity
1 Control
! max lbk 1 1
(Bl DRIVER COLLECTOR FEEDBACK TO PIN 14 · 1 1 Compensated
I Yoke Current
I
FIGURE 9 - Second Phase Detector Slicer
FIGURE 11 - Vertical Unearity Control
MONOMAX
17 14
.I0.01
THE SOUND SECTION
The buffered video detector output at Pin 28 is a
0.0011 wideband signal used for sound take-off. A ceramic
47 k .,,.
.,,. .,,. sound take-off filter and detector "tank" were chosen
to eliminate alignment steps. The MC1358 is a popu-
lar, multi-sourced, FM IF, detector and de volume
control. It can be used with conventional L-C circuits
FIGURE 10 - Driver Feedback For Extended or the ceramic devices shown here. The L-C application
Horizontal Output "On" Time costs less in piece parts, but has a higher manufactur-
ing cost in assembly-and alignment.
Keep in mind that a limiting IF produces a wide
spectrum of 4.5 MHz harmonics. The sound IF grounds
THE VERTICAL SYSTEM should be kept together and returned to Pin 1 by a
Aside from all of the sophistication of the count- single path as shown in the copper layout of Figure 14.
down vertical system within the Monomax chip, what Also it is a good idea to keep the input of the sound IF
remains to be accomplished outside of the device is IC close to Pin 28 to reduce radiJtion of video IF har-
fairly conventional. At Pin 20, there is an external monics, generated in the video detector, from getting
capacitor, charged from a high voltage, to produce a back to the tuner or IF input.
good linear ramp. It is discharged within the chip, In the receiver described here, an ac volume control
usually by vertical sync, but sometimes by the count- has been used. A potentiometer is placed between the
down circuit when sync is momentarily absent. It is MC1358 detector output, Pin 8, and the post ampli-
important for the capacitor to be a good stable low ESR fier input, Pin 14. The de volume control, Pin 6, is
type and to be located close to Pin 20 and grounded as grounded for maximum volun;ie. If the volume control
closely as possible to Pin no avoid pickup of horizontal is to be mounted some distance away, and deflection
sweep which could hurt interlace. pickup is likely, then the de volume control could be the
The approximately 1.5 Vp-p waveform on Pin 20 is better choice. This can be done by ac coupling Pin 8 to
inverted and buffered to Pin 22 to drive the external Pin 10, and placing a variable 50 k pot from Pin 6 to
output circuit. In the receiver design in this AN, a fairly ground. The disadvantage is that the control contour
conventional vertical output stage has been used. An is less predictable in the de control configuration. It is,
optional linearity control has been added, because no.netheless, a production proven method.
213
THE VIDEO OUTPUT tortion of high-frequency detail, due to excessive load-
ing of the video driver. This can be reduced by adding
Pin 24 provides up to 1.4 V, black-to-white video
a resistor between Pin 24 and the trap, and by return-
drive, black level clamped, with a widened and ampli-
ing the bottom of the trap to the video output stage
fied blanking pulse added. This is sufficient to drive a
emitter. The compromise chosen is shown in the full
single stage common-emitter video output transistor.
schematic. Again, it is good to keep these parts close
A de voltage ofO to 5.cl'V applied to Pin 26, varies the
to Pin24 to reduce radiation of video detector products
black·to-white amplitude at Pin 24 from 1.4 V to 0.1 V
back to the tuner and IF front end.
without changing the absolute black level of the output
voltage. Beam current limiting can also_ be used to The video output circuit can take many forms.
control maximum brightness. This is accomplished by Monomax was designed to accommodate full de cou-
circuit shown in Figure 12. As beam current increases, pling, as described earlier. However, many TV design-
the H.V. winding current flowing in the 39 k resistor, ers, and users, don't like full de coupling, because it
pulls the Pin 27 voltage down. When Pin 27 falls sometimes seems to go too black, creating the suspicion
below about 1.0 V, the contrast begins to be reduced. that some information is hidden. Also, a directly
This circuit was not used in the complete receiver in coupled video output to picture tube cathode usually
this AN, for reasons which will be explained shortly. requires a negative voltage for at least one of the grids
The black level clamp capacitor on Pin 25 is usually for proper set-up at high contrast settings. Finally,
shown connected to ground. It can alsp be connected to fully de coupled designs are harder to protect from
+8.0 V to cause the screen to be blanked for about 1 power-off flash or spot burn.
second after turn-on. This permits the scan systems to For these reasons the receiver described in this AN
stabilize before the picture becomes visible. Note: If was a partially de coupled type. This puts the bright-
the brightness control design window is set too high, ness control in the cathode circuit, removes the need
the raster may still be visible during start-up. for the brightness limiting configuration, and makes
There are several approaches to sound trapping in spot/flash prevention easier. (The diode and electro-
the video output stage: series tuned L-C from the lytic in G 1 are for this latter purpose).
video output base to ground; parallel tuned L-C in the
video output emitter; or a ceramic shunt element in the In the video output stage emitter, some de set-up
video output base circuit. All of these can be detri- from the+ 12 V supply has been used to adjust the out-
mental_ to picture quality, if not carefully done. The put de level, to minimize overall dissipation. Also some
ceramic element is in keeping with the "no alignment" additional vertical blanking has been fed through a
philosophy successfully implemented thus far, so there diode, from the top of the vertical yoke. This blanking
was a strong motivation to use it. However, shunt will be accomplished in the IC internally in later
loading Pin 24, if too severe, causes considerable dis- Monomax devices.
Video
Output
FIGURE 12 - Beam Currant Umiting
214
APPENDIX I - AGC DELAY ADJUSTMENT means a horizontal (saddle) winding of about 3.4 mH
and a vertical (toroid) winding of approximately 3.0 n,
Ideally, a known antenna signal level of 1.0 mV
(300 n balanced) or 500 µ V (75 n unbalanced) is sup- 10 mH. Numerous substitutions are available, but
plied to the tuner input. This signal level corresponds the above values must be adhered to for this set
architecture.
to the threshold of "snow" in the picture, for most
receivers. With this signal level, the AGC delay pot is Horizontal Output Transistor - The board was
turned until the RF AGC voltage just begins to rise, designed for a T0-3 type, such as a BU205, BU204, or
and then is backed off slightly. The picture should be MJ12003. A plastic T0-220 type MJE12007 will do the
snow-free. If the RF AGC is permitted to rise, the job with some mechanical revision. The important
picture will start to show some snow, which therefore parameters are V(BR)CEX = 1300 V and Ic = 2.0 A. A
represents less than optimum overall performance. If small amount of heat sinking, such as a U channel
the setting is backed-off too much, the delay may be with 2 flags of 1 square inch each is recommended. A
too large and mix.er overload may occur at stronger mica or Thermalloy isolator is suggested to reduce
signals. shock hazard to the experimenter. If an ac/dc design is
The correctness of this setting should be checked contemplated, as referred to back in Figure 3, a lower
at weaker and stronger signals. At weaker signals, say voltage, higher current part like BU806 will be required
6.0 dB down, it should not be possible to improve the for the horizontal output, along with a different yoke and
picture noise by resetting the RF Delay. At stronger flyback.
signal, say 40 ·dB stronger, there should be neither
snow or overload evident in the picture, although the Vertical Output Transistors - It is possible to
distance between these two conditions, as a function of "get by" with a T0-92 complementary pair, such as
delay setting, may be very narrow. The AGC system MPS6560 and MPS6562, or the new, tall T0-92,
should automatically avoid these troubles. It may be MPSWOl and MPSW51. However, the author's opinion
necessary to make a slight compromise to avoid over- is that these operate too hot, with dissip~tion ap·
load, which may produce a slight amount of snow in proaching I watt, each, worst case. Recommended
the 1.0 m V picture. alternatives include D40E I and 041 El in the T0-202, or
The above compromises can be achieved successfully TIP29 and TIP30 in T0-220. No heat sink is required.
without calibrated signals, with just a switchable The devices need only V(BR)CEO = 30 V and good
attenuator and a strong signal. Starting at strong hFE at 1.0 A.
signal, note the available AGC Delay setting range Video Output Transistor - For the load value
between picture overload and snow.Using the switched shown in this design, a case 152 uniwatt, such as
attenuator, reduce the signal strength and make sure MPSUlO, is best. The 300 V V(BR)CEO is not needed,
that neither problem appears. If necessary tweak the but the device must be "small geometry"; i.e., high fr
Delay, but don't move outside the original range. and low Ccb to preserve picture resolution. A tall T0-92
Eventually the picture will get snowy, but the control or even an MPSA43, T0-92, can be used if the collector
will only be able to make it snowier. Setting it to the load is increased to 6.8 k, but some picture quality will
optimum (just barely) should still be within th'e noted be lost. ·
range.
Audio Output Section - The transformer should
be approximately 30:1 turns ratio, capable of handling
APPENDIX II - COMPONENT & 1 watt into 8.0 n. The output transistor should be set
CONSTRUCTION DETAILS up at about IQ= 12-14 mA, and should be capable of
1.5 W continuous dissipation. A T0·220 type MJE2360T,
In order to make the enclosed PC board pattern easy
mounted on at least.3 square inches of aluminum is
to use, the following components are recommended:
suggested.
Remember that these are pertinent to this design
architecture and this specific design. Many variations H. Driver Stage - In the prototype receiver, the
are possible with a little redesign work. available driver transformer had only about 12:1 turns
Flyback - Gold Star Type 154-028A with self- ratio. This necessitated a large wattage dropping
contained H.V. rectifier. Certainly, su.bstitution is resistor to provide the rather low-voltage, high-current
possible, but very careful attention to pin-outs and taps primary waveforms. It would be better to obtain a
is required. The primary is, of course, a 120 Vdc type, transformer of 30:1 or so, to permit a more efficient
which corresponds to about 800 Vp-p positive pulse at driver stage. The 4.3 k/2.0 W resistor could then be
reduced considerably. In either case a T0-92 driver,
Pin 2. Pin 3 is a negative going pulse of 35 V p-p and
type MPSA42, is a good choice.
Pin 7 is a negative-going pulse of about 120 Vp-p· The
H.V. terminal, which is internal in the above model, SUMMARY:
would be a positive going pulse of about 12 kVp-p· Figures 13 and 14 provide the copper pattern for the
Very little flexibility can be permitted on these values.
PC board and the component locations. Note that
Be careful to watch pin-outs and horizontal polarity.
signal input circuits are compact and grounded near
Yoke -Gold Star Type 153-020A for 90° 12" - Pin 1. Subsequently these and·all other circuits are
20 mm neck picture tube. It requires approximately connected to the central ground at Pin 16, without being
1.0 Ap-p in both horizontal and vertical windings to interconnected beforehand. The full receiver schematic
give proper overscan in the 90° tube at 10-11 kV. This is given in Figure 15.
215
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