RCAVICTOR 721TS Mounting instructions

^rcaVictor
TELEVISION RECEIVER
MODEL 721TS
Chassis No. KCS 26-1 (60 cycles) ,KCS 26-2 (50 cycles)
Mfr. No. 274
Service Data
Model 72ITS
Walnut or Mahogany
—1947 No. T4
RADIO CORPORATION OF AMERICA
RCA VICTOR DIVISION
CAMDEN, N.)., U.S.A.
GENERAL DESCRIPTION
Model 721TS is atwenty-one tube, direct-viewing, table-model
Television Receiver having a10" picture tube (kinescope). The
receiver is complete in one unit and is operated by the use of
seven front-panel controls. Features of the receiver include:
Full thirteen channel coverage; f-m sound system: improved
picture brilliance: two stages of video amplification; A-F-C
horizontal hold, stabilized vertical hold; improved sync ampli-
fier and separator; and reduced-hazard high-voltage supply.
ELECTRICAL AND MECHANICAL SPECIFICATIONS
r
PICTURE

72 ITS ELECTRICAL AND MECHANICAL SPECIFICATIONS (Continued)
PICTURE INTERMEDIATE FREQUENCIES
Picture Carrier Frequency 25.75 Mc
Accompanying Sound Traps 21.25 Mc
SOUND INTERMEDIATE FREQUENCIES
Sound Carrier Frequency 21.25 Mc
Sound Discriminator Band Width (between peaks) 350 Kc
VIDEO RESPONSE To 3Mc
FOCUS Magnetic
SWEEP DEFLECTION Magnetic
SCANNING Interlaced, 525 line
HORIZONTAL SCANNING FREQUENCY 15,750 cps
VERTICAL SCANNING FREQUENCY 60 cps
FRAME FREQUENCY (Picture Repetition Rate) 30 cps
OPERATING CONTROLS (front panel)
Station Selector )t^ i^^ .it^ i_
LDual Control Knobs
Fine Tuning J
Sound Volume and On-Off S'witch Single Control Knob
.Dual Control Knobs
..Dual Control Knobs
Horizontal (Picture Horizontal Hold) -i
Vertical (Picture Vertical Hold) J
'
Picture (Contrast)
Brightness (Brilliance)
NON-OPERATING CONTROLS (not including r-f and i-f ad-
justments)
Horizontal Centering rear chassis adjustment
Vertical Centering rear chassis adjustment
Width rear chassis screwdriver adjustment
Height rear chassis adjustment
Horizontal Linearity top chassis screwdriver adjustment
Vertical Linearity rear chassis adjustment
Horizontal Drive rear chassis screwdriver adjustment
Horizontal Frequency (Fine) rear chassis screwdriver
adjustment
Horizontal Oscillator Frequency (coarse) bottom chassis
screwdriver adjustment
Horizontal Locking Range. ...rear chassis screwdriver adjustment
Focus rear chassis adjustment
Focus Coil top chassis wing screw^ adjustment
Ion Trup Magnet top chassis thumb screw adjustment
Deflection Coil top chassis wing nut adjustment
J
HIGH VOLTAGE WARNING
OPERATION OF THIS RECEIVER OUTSIDE THE CABINET OR WITH THE
COVERS REMOVED INVOLVES ASHOCK HAZARD FROM THE RECEIVER
POWER SUPPLIES. WORK ON THE RECEIVER SHOULD NOT BE ATTEMPTED
BY ANYONE WHO IS NOT THOROUGHLY FAMILIAR WITH THE PRECAU-
TIONS NECESSARY WHEN WORKING ON HIGH-VOLTAGE EQUIPMENT. DO
NOT OPERATE THE RECEIVER WITH THE HIGH-VOLTAGE COMPARTMENT
SHIELD REMOVED.
KINESCOPE HANDLING PRECAUTIONS
DO NOT OPEN THE KINESCOPE SHIPPING CARTON, INSTALL, REMOVE, OR
HANDLE THE KINESCOPE IN ANY MANNER UNLESS SHATTERPROOF
GOGGLES AND HEAVY GLOVES ARE WORN. PEOPLE NOT SO EQUIPPED
SHOULD BE KEPT AWAY WHILE HANDLING KINESCOPES. KEEP THE
KINESCOPE AWAY FROM THE BODY WHILE HANDLING.
The kinescope bulb encloses ahigh vacuum and, due lo its large surface area, is subjected
to considerable air pressure. For these reasons, kinescopes must be handled with more care
than ordinary receiving tubes.
The large end ol the kinescope bulb—particularly the rim of the viewing surface—must not be
struck, scratched, or subjected to more than moderate pressure at any time. In installation, if
the tube sticks or fails to slip smoothly through the deflecting yoke, investigate and remove
the cause of the trouble. Do not force the tube. Refer to the Receiver Installation section for
detailed instructions on kinescope installation. All RCA kinescopes are shipped in special car-
tons and should be left in the cartons until ready for installation in the receiver. Keep the
carton for possible future use. J

RECEIVER OPERATING INSTRUCTIONS 72 ITS
The following adjustments are necessary when turning the
receiver on ior the first time:
1. Turn the receiver "ON" and advance the SOUND
volume control to approximately mid-position.
2. Set the STATION SELECTOR to the desired channel.
3. Turn the PICTURE
control fully counter-
clockwise.
4. Turn the BRIGHT-
NESS control fully coun-
terclockwise, then clock-
wise until afaint glow
just appears on the
screen.
5. Turn the PICTURE
control approximately
three-fourths clockwise.
6. Adjust the FINE
TUNING control for best
sound fidelity and the
SOUND control for suit-
able volume.
7. Adjust the VERTI-
CAL hold control until
the pattern stops vertical
movement.
PICTURE
BRIGHTNESS
8. Adjust the HORIZONTAL hold control until the picture
appears on the screen.
9. Adjust the PICTURE control for suitable picture contrast.
10. After the receiver has been on for some time, it may be
necessary to readjust the FINE TUNING control slightly for
improved sound fidelity.
.^^=^
\==J^
ON-OFF SOUND' IFINE TUNING
STATION SELECTOR
IN SOME RECEIVERS "BRIGHTNESS" IS THE OUTER KNOB AND 'PICTURE' THE INNER
Fig/iie I—Receiver Operating Controls
CIRCUIT DESCRIPTION
11. In switching from
one station to another,
it may be necessary to
repeat steps number 6
and 9.
12. When the set is
turned on again after an
idle period, it should not
be necessary to repeat
the adjustments if the
positions of the controls
have not been changed.
If any adjustment is
necessary, step number
6is generally sufficient.
13. If the positions of
the controls have been
changed, it may be nec-
essary to repeat steps
number 1through 9.
c
The general design features of the 721TS television receiver
are conventional. However, the a-f-c horizontal hold circuit is
new and will be described briefly.
Fundamentally the horizontal oscillator is afree running block-
ing oscillator and discharge circuit. The incoming sync is
superimposed on the horizontal oscillator waveform and ap-
plied to the control tube grid. If the two voltages are not in
the proper freguency and phase relations, the control tube ap-
plies abias to the oscillator to bring it into sync.
Aportion of the bias from the blocking oscillator is applied
to the grid of the control tube and is sufficient to keep the
control tube cut off except when the sync pulse is high
on the slope of the grid waveform as shown in Figure 2-A.
If the oscillator changes phase so that the pulse slides down
the slope, the plate conduction time decreases as shown in
Figure 2-B. If the pulse slides up the slope, then the plate
conduction time increases as shown in Figure 2-C. When the
control tube conducts capacitors C16I and CI67 in its
cathode circuit charge to ad-c potential proportional to the
plate conduction time. This potential is applied as abias
to the oscillator grid thus shifting the oscillator frequency
and pulling it into phase with the sync pulses.
The effect of the various controls associated with the circuit
are as follows. LI2I is tuned with aslug to effect coarse
adjustments in oscillator frequency. C136C is provided to
effect fine adjustments in frequency. RI56 the horizontal
hold control is provided on the front panel to permit a5%
variation of frequency by varying the control tube plate volt-
age. CI 36Ais avariable portion of acapacity voltage
divider and is provided to set the amplitude of the waveform
on the grid of the control lube so that conduction occurs only
on the positive peaks of the waveform. The horizontal drive
control C136B is part of acapacity voltage divider and is pro-
vided to vary the amount of sawtooth voltage on the VI 09
grid and hence is acontrol for picture linearity.
Several components of the oscillator and control circuits
have special coefficients or characteristics and in case of
failure, should be replaced only by exact replacement. RI73
is aspecial resistor capable of stability of 1% or better.
R191 is ahigh negative coefficient resistor to compensate for
warm up drift. It is mounted within about Vi inch of the
power transformer and chassis for good heat transfer. The
dress of this component should not be disturbed.
Strains or excessive heat should not be applied to the leads or
bodies of the resistors associated with the horizontal oscillator
and control circuits. Such conditions may cause excessive
changes of resistance with age. See "Critical Lead Dress" on
page 18.
VIOBA GRID CUTOFF
NORMAL CONTROL SYNC TOO LATE SYNC TOO EARLY
SHADED AREA IS PORTION OF W/AVEFORM EFFECTIVE IN PRODUCING
OSCILLATOR CONTROL VOLTAGE,
Figure 2—Horizontal Control Waveforms

721TS INSTALLATION INSTRUCTIONS
The Model 72 ITS television receiver is shipped complete in
one carton except for the 10BP4 kinescope. The kinescope is
shipped in aspecial carton and should not be unpacked until
ready ior installation.
UNPACKING—To unpack the receiver, tear open the carton
flaps, pick the receiver up from under the bottom of the cab-
inet and lift it out of the shipping carton.
Take the metal grill off the back of the cabinet. Remove the
front panel from the cabinet as indicated in Figure 3.
TO REMOVE CABINET FRONT
TAKE OUT SCREWS UNDER CABINET
LOOSEN WING NUTS INSIDE CABINET
TURN PLATES AND REMOVE FRONT
Figure 3
—
Cabinet, Front View
The operating control knobs are packed in apaper bag which
is tied to the focus coil mounting bracket inside the cabinet.
Remove the bag.
Remove the protective cardboard shield from the 5U4G recti-
fier. Make sure all tubes are in place and are firmly seated
in their sockets.
Loosen the two kinescope cushion adjustment wing screws and
slide the cushion toward the rear of the chassis. Loosen the
deflection yoke adjustment, slide the yoke toward the rear
of the chassis and tighten. See Figure 4for the location of
the cushion and yoke adjustments.
/FLAGS
Ml
FRONT MACNET GAP
ON THIS SIDE AND EVEN
WITH REAR MAGNET GA»
Figure 4—Yoke and Focus Coil Adjustments
From the front of the cabinet, look through the deflection yoke
and check the alignment of the focus coil with the yoke. If
the focus coil is not in line, loosen the three focus coil adjust-
ment wingnuts and raise, lower, or rotate the coil until align-
ment is obtained. Tighten the wingnuts with the coil in this
position.
Loosen the two lower kinescope face centering slides, and set
them at approximately mid position. See Figure 3for loca-
tion of the slides and their adjustment screws. Loosen the
ion trap magnet adjustment thumb screws.
KINESCOPE HANDLING PRECAUTION—Do not open the kine-
scope shipping carton, install, remove, or handle the kinescope
in any manner, unless shatterproof goggles and heavy gloves
are worn. People not so equipped should be kept away while
handling the kinescope. Keep the kinescope away from the
body while handling. The shipping carton should be kept for
use in case of future moves.
INSTALLATION OF KINESCOPE—The kinescope second anode
contact is arecessed metal well in the side of the bulb. The
tube must be installed so that this contact is approximately on
lop. The final orientation of the tube will be determined by
the position of the ion trap flags. Looking at the kinescope
gun structure, it will be observed that the second cylinder from
the base inside the glass neck is provided with two small
metal flags, as shown in Figure 5. The kinescope must be
installed so that when looking down on the chassis, the two
flags will be seen as shown in Figure 4.
T
FLAGS "S'3^
Figure 5—Ion Trap Flags
Insert the neck of the kinescope through the deflection and
focus coils as shown in Figure 6until the base of the tube
protrudes approximately two inches beyond the focus coil.
If the tube sticks, or fails to slip into place smoothly, investi-
gate and remove the cause of the trouble. Do not force the
tube.
Figure 6—Kinescope Insertion
Early production receivers employed an EM type of ion trap
magnet like that in the model 630TS receiver. Late production
receivers employed aPM type magnet as shown in Figure 4.
If an EM type of magnet is applied, slip the assembly over
the neck of the kinescope with the coils down and the large
coil towards the base of the tube. Tighten the magnet ad-
justment thumbscrews sufficiently to hold it in position but still
free enough to permit adjustment.
If the PM type is employed, slip the assembly over the neck
of the kinescope with the large magnet towards the base of
the tube and with the arrow on the assembly up as shown in
Figure 4. The front magnet is movable on the assembly. The
correct position of the front magnet is with the gap on the left
side (from the rear of the cabinet) and even with the gap of
the rear magnet.
Connect the kinescope socket to the tube base. Insert the
kinescope until the face of the tube protrudes approximately
one-eighth of an inch outside the front of the cabinet. Adjust
the four centering slides until the face of the kinescope is in
the center of the cabinet opening. Tighten the four slides
securely. Wipe the kinescope screen surface and front panel
safety glass clean of all dust and finger marks with asoft cloth
moistened with the Drackett Co.'s "Windex" or similar cleaning
agent. Install the cabinet front panel by reversal of the remov-
ing process as shown in Figure 3. Install the control knobs
on the proper control shafts.
3-

INSTALLATION INSTRUCTIONS (Continued) 721TS
C
c
c
Slip the kinescope as lar forward as possible. Slide the
kinescope cushion firmly up against the flare of the tube and
tighten the adjustment wing screws. Slide the deflection
yoke as far forward as possible. Connect the high voltage
lead to the kinescope second anode socket.
The antenna and power connections should now be made.
Turn the power switch to the "on" position, the brightness
control fully clockwise, and picture control counter-clockwise.
ION TRAP MAGNET ADJUSTMENT—The ion trap rear magnet
poles should be placed over the ion trap flags as shown in
Figure 4. Starting from this position adjust the magnet by
moving it lorward or backward at the same time rotating
it slightly around the neck of the kinescope for the brightest
raster on the screen. Reduce the brightness control setting
until the raster is slightly above average brilliance. Adjust
the focus control (R129 on the chassis rear apron) until the
line structure of the raster is clearly visible. Readjust the ion
trap magnet for maximum raster brilliance. The final touches
on this adjustment should be made with the brightness control
at the maximum position with which good line focus can be
maintained.
FOCUS COIL ADJUSTMENTS—Turn the centering controls R152
and R166 to mid position. See Figure 7for location of these
rear apron controls.
If acorner of the raster is shadowed, it indicates that the
electron beam is striking the neck of the tube. Loosen the
focus coil adjustment wing nuts and rotate the coil about its
vertical and horizontal axes until the entire raster is visible,
approximately centered and with no shadowed corners. Tighten
the focus coil adjustment wing nuts with the coil in this
position.
HOR.
LINEARITY a.
RI48 VERT.
LINEARITY FOCUS q;^
WIDTH a
CONTROL
Ct36A
HOR. LOCKING^
(OX (CIX HOR. DRIVE «
*il>/VERT. ^CjpHOR. CI36C e
CENTERING CENTERING HOR.FREa.''
Figure 7—Rear Chassis Adjustments
DEFLECTION YOKE ADJUSTMENT—If the lines of the raster
are not horizontal or squared with the picture mask, rotate
the deflection yoke until this condition is obtained. Tighten
the yoke adjustment wing screw.
PICTURE ADJUSTMENTS—It will now be necessary to obtain a
test pattern picture in order to make further adjustments. See
steps 2through 9. of the receiver operating instructions on
page 3.
CHECK OF HORIZONTAL OSCILLATOR ALIGNMENT—Turn
the horizontal hold control to the extreme counter-clockwise
position. The picture should remain in horizontal sync. Mo-
mentarily remove the signal by switching off channel and
then back. Normally the picture will be out of sync. Turn
the control clockwise slowly. The number of diagonal bars
will be gradually reduced and when only 3'/2 to iVi bars
sloping downward to the left are obtained, the picture will pull
into sync upon slight additional clockwise rotation of the con-
trol. Pull in should occur when the control is approximately
90 degrees from the extreme counterclockwise position. The
picture should remain in sync for approximately 90 degrees
of additional clockwise rotation of the control. At the extreme
clockwise position, the picture should be out of sync and
should show from 3'/2 to 4'/2 bars sloping downward to the
right.
If the receiver passes the above checks and the picture is
normal and stable, the horizontal oscillator is properly aligned.
Skip "Alignment of Horizontal Oscillator" and proceed with
"Focus" adjustment.
ALIGNMENT OF HORIZONTAL OSCILLATOR—If in the above
check the receiver failed to hold sync with the hold control
at the extreme counterclockwise position or failed to hold
sync at least 60 degrees of clockwise rotation of the control
from the pull in point, it will be necessary to make the fol-
lowing adjustments.
Horizontal Frequency Adiustment—Turn the horizontal hold
control to the extreme clockwise position. Tune in atelevision
station and adjust the rear apron horizontal frequency trim-
mer C136C until the picture is out of sync and shows 3Vi to
41/2 bars sloping downward to the right. If the trimmer has
insufficient range, set the trimmer to mid-position (1 turn out
from max. capacity) and adjust the L121 horizontal frequency
adjustment until this condition is obtained. See figure 22 for
the location of L121.
Horizontal Locking Range Adjustment—Set the horizontal
hold control to the full counter-clockwise position. Momentarily
remove the signal by switching off channel and, then back.
Slowly turn the horizontal hold control clockwise and note
the least number of diagonal bars obtained just before the
picture pulls into sync.
If more than 4'/2 bars are present just before the picture pulls
into sync, adjust the horizontal locking range trimmer C136A
slightly clockwise. If less than 3'/2 bars are present, adjust
C136A slightly counterclockwise. Turn the horizontal hold
control counterclockwise, momentarily remove the signal and
recheck the number of bars present at the pull in point. Re-
peat this procedure until 3V2 to 4'.^ bars are present.
Repeat the adjustments under "Horizontal Frequency Adjust-
ment" and "Horizontal Locking Range Adjustment" until the
conditions specified under each are fulfilled. When the hori-
zontal hold operates as outlined under "Check of Horizontal
Oscillator Alignment" the oscillator is properly adjusted.
HEIGHT AND VERTICAL LINEARITY ADJUSTMENTS—Adjust
the height control (R141 on chassis rear apron) until the picture
fills the mask vertically (6% inches). Adjust vertical linearity
(R148 on rear apron), until the test pattern is symmetrical from
top to bottom. Adjustment of either control will require aread-
justment of the other. Adjust vertical centering to align the
picture with the mask.
WIDTH. DRIVE AND HORIZONTAL LINEARITY ADJUSTMENTS
—Turn the width control LI 12 to the maximum clockwise posi-
tion. Vary the horizontal drive trimmer C136B to yield the
best compromise between brightness and linearity. Adjust
the horizontal linearity control LI 13 for best linearity of the
right half of the picture. Readjust the width control until the
picture just fills the mask. Adjust horizontal centering to
align the picture with the mask.
FOCUS—Adjust the focus control R129 for maximum definition
of the vertical wedge of the test pattern.
Check to see that all cushion, yoke, focus coil and ion trap
magnet thumb screws are light. Replace the cabinet back
grille. Make sure that the back is on tight, otherwise it may
rattle at high volume.
CHECK OF R-F OSCILLATOR ADJUSTMENTS—With a crystal
calibrated test oscillator or heterodyne frequency meter, check
to see if the receiver r-f oscillator is adjusted to the proper
frequency on all channels. If adjustments are required, these
should be made by the method outlined in the alignment pro-
cedure on page 10. The adjustments for channels 1through 5
and 7through 12 are available from the front of the cabinet
by removing the station selector escutcheon as shown in Figure
8. Adjustments for channels 6and 13 are under the chassis.
Tune in all available Television Stations, Observe the picture
for detail, for proper interlacing and for the presence of
interference or reflections. If these are encountered, see the
section on antennas on page 6.

72 ITS INSTALLATION INSTRUCTIONS (Continued)
Figure 8—R-F Oscillator Adjustments
VIDEO PEAKING LINK—Avideo peaking link is provided to
permit changing the video response. This link is connected at
the factory with the peaking in. However, if transients are
produced on high contrast pictures the peaking should be
taken out by removing the link on the terminal board under
the chassis near the VI04 socket. See Figures 49 and 51 for
the connection and location of the link.
ANTENNA TRAP—In some sets, aseries resonant trap across
the r-f amplifier grid circuit is provided to eliminate interference
from FM stations on the image of channel 2, from interference
on channel 6from astation on channel 10 or interference on
channel 5from astation on channel 7. In production, this
trap is adjusted to reject the channel 6-10' interference. How-
ever, in the field, it may be necessary to retouch the adjust-
ments or to readjust the trap for channel 5-7 or FM image
interference.
To adjust the trap in the field, tune in the station on which
the interference is observed. Tune both cores of the trap for
minimum interference in the picture. See Figure 21 for the
location of the trap. Keep both cores approximately the same
by visual inspection. Then, turn one core V2 turn from the
original position and repeak the second for maximum rejec-
tion. Repeat this process until the best rejection is obtained.
In severe cases of such interference, it may be necessary to
reorient the antenna to eliminate this difficulty.
RECEIVER LOCATION—The owner should be advised of
the importance of placing the receiver in the proper location
in the room.
The location shjDuld be chosen
—
—Away from bright windows and so that no bright light
will fall directly on the screen. {Some illumination in the
room is desirable, however.)
—To give easy access for operation and comfortable viewing.
—To permit convenient connection to the antenna.
—Convenient to an electrical outlet.
—To allow adequate ventilation.
VENTILATION CAUTION—The receiver is provided with
adequate ventilation holes in the bottom and back of the
cabinet. Care should be taken not to allow these holes to
be covered or ventilation to be impeded in any way.
ANTENNAS—The finest television receiver built may be said
to be only as good as the antenna design and installation. It
is therefore important to use acorrectly designed antenna,
and to use care in its installation.
RCA Television Antennas, stock No. 225 and No. 226, are de-
signed for reception on all thirteen television channels. These
antennas use the 300-ohm RCA "Bright Picture" television
transmission line. Installation personnel are cautioned not to
make any changes in the antenna or to substitute other types
of transmission line as such changes may result in unsatisfac-
tory picture reproduction.
The stock #226 antenna is bi-directional on channels one
through six (44 to 88 Mc). When used on these channels, the
maximum signal is obtained when the antenna rods are broad-
side toward the transmitting antenna.
The stock #225 antenna with reflector is unidirectional on
channels one through six. When used on these channels, the
maximum signal is obtained when the antenna rods are broad-
side toward the transmitting antenna, with the antenna ele-
ment between the reflector and the transmitting antenna.
When operated on channels seven through thirteen, (174 to
216 Mc), both types of antennas have side lobes. On these
channels, the maximum signal will be obtained when the
antenna is rotated approximately 35 degrees in either direc-
tion from its broadside position toward the transmitting an-
tenna.
In general, the stock #225 antenna should be used if re-
flections are encountered, if the signal strength is weak, or if
the receiving location is noisy. If these conditions are not en-
countered, the stock #226 antenna will probably be satisfac-
tory.
In some cases, the antenna should not be installed permanently
until the quality of the picture reception has been observed on
atelevision receiver. Atemporary transmission line can be
run between receiver and the antenna, allowing sufficient
slack to permit moving the antenna. Then, with atelephone
system connecting an observer at the receiver and an assistant
at the antenna, the antenna can be positioned to give the
most satisfactory results on the received signal. Ashift of
direction or afew feet in antenna position may effect atre-
mendous difference in picture reception.
REFLECTIONS—Multiple images sometimes known as echoes
or ghosts, are caused by the signal arriving at the antenna
by two or more routes. The second or subsequent image oc-
curs when asignal arrives at the antenna after being re-
flected off abuilding, ahill or other object. In severe cases
of reflections, even the sound may be distorted. In less severe
cases, reflections may occur that are not noticeable as re-
flections but that will instead cause aloss of definition in the
picture.
Depending upon the circumstances, it may be possible to elim-
inate the reflections by rotating the antenna or by moving it
to anew location. In extreme cases, it may be impossible to
eliminate the reflection.
Under certain extremely unusual conditions, it may be possible
to rotate or position the antenna so that it receives the cleanest
picture over areflected path. If such is the case, the antenna
should be so positioned. However, such aposition may give
variable results as the nature of reflecting surfaces may vary
with weather conditions. Wet surfaces have been known to
have different reflecting characteristics than dry surfaces.
INTERFERENCE—Auto ignition, street cars, electrical ma-
chinery and diathermy apparatus may cause interference
which spoils the picture. Whenever possible, the antenna
location should be removed as far as possible from highways,
hospitals, doctors' offices, and similar sources of interference.
In mounting the antenna, care must be taken to keep the
antenna rods at least Vi wave length (at least 6feet) away
from other antennas, metal roofs, gutters, or other metal objects.
Short-wave radio transmitting and receiving equipment may
cause interference in the picture in the form of moving ripples.
In some instances it may be possible to eliminate the inter-
ference by the use of atrap in the antenna transmission line.
However, if the Interfering signal is on the same frequency as
the television station, atrap will provide no improvement.
WEAK PICTURE—When the installation is near the limit of the
area served by the transmitting station, the picture may be
speckled, having a"snow" effect, and may not hold steady on
the screen. This condition is due to lack of signal strength
from the transmitter.
3

SERVICE SUGGESTIONS 72 ITS
C
C
Some of the possible troubles that may be encountered,
with their effects and causes, are listed below:
NO RASTER ON KINESCOPE—The effect of no raster can
be caused by the following:
(1) Incorrect adjustment of ion trap magnet.
(2) No high voltage. Check V109 (6BG6-G) and VI 10
(8016) tubes and circuits. If the horizontal-deflection circuits
are operating, as evidenced by the correct waveform measured
on terminal 4of horizontal output transformer T105, the trouble
can be isolated to the high-voltage rectifier (VllO) circuit.
Either the high-voltage winding (points 2to 3on T105) is open;
the 8016 tube is defective; its filament circuit is open; or the
high-voltage filter capacitor C142 is shorted.
(3) Damper tube (VI 11, 5V4-G) inoperative. Plate voltage
supply for 6BG6-G horizontal output tube is obtained through
the damper tube. Check tube, and heater winding on T106.
If tube is O.K., check LI 13 (horizontal linearity coil) for con-
tinuity, and capacitors C139 and C140 for short circuit.
(4) Defective kinescope. Heater open; cathode "return"
circuit open.
(5) No plate voltage. Shorted electrolytic capacitor; open
speaker field coil. All -j-B measurements are accessible for
measurement by removing cover from bleeder box.
(6) Horizontal osc. and control tube (V108, 6SN7-GT) in-
operative. Check for sawtooth on grid of horizontal output
tube (V109. 6BG6-G). If not present, check waveforms, volt-
ages, and components in V108 circuits.
HORIZONTAL DEFLECTION ONLY—If horizontal deflection
only is obtained, evidenced by a"straight line" across the
face of the kinescope, it can be caused by the following:
(1) Vertical oscillator and output tube (V107, 8SN7-GT)
inoperative. Check waveforms and voltages on grid and plate.
(2) Vertical output transformer (T103) open.
(3) Yoke vertical coils open.
POOR VERTICAL LINEARITY—If adjustment of the vertical
height and linearity controls will not correct this condition,
any of the following may be the cause:
(1) Vertical output transformer (T103) defective.
(2) Capacitors C128-C or C127-B defective.
(3) V107 (6SN7-GT) defective. Check waveforms and volt-
ages.
(4) Excess leakage or incorrect value in capacitor C130.
(5) Low plate and bias voltages. Check rectifier tube and
capacitors in -|-B supply circuits.
(6) Capacitor CI 29 defective.
POOR HORIZONTAL LINEARITY If adjustment of controls
does not correct this condition, check the following:
(1) Check or replace horizontal output tube (V109, 6BG6-G).
(2) Check or replace damper tube (VI 11, 5V4-G).
(3) Check waveform on grid of V109.
(4) Check linearity coil L113 for short circuit.
(5) Check capacitors C139 and C140 for defects.
TRAPEZOIDAL OR NON-SYMMETRICAL RASTER This condi
lion can be caused by:
Defective yoke.
WRINKLES ON LEFT SIDE OF RASTER -This condition can be
caused by;
Defective yoke due to RlOl, H151. or C141 (internal in yoke
assembly) being wrong value or open. These components are
mounted in rear of yoke assembly.
SMALL RASTER This condition can be caused by:
(1) Low +B or line voltage.
(2) Insufficient output from horizontal output tube Vi09
(6BG6-G). Replace tube.
RASTER—NO IMAGE, BUT ACCOMPANYING SOUND—This
condition can be caused by:
(1) No signal on kinescope grid. Check picture if amplifier
tubes VlOl (6AG5), V102 (6AG5). V103 (6AG5), second de-
tector V104 (6AL5), and' video amplifier V105 (12AU7).
(2) Bad contact to kinescope grid. (Lead to socket broken.)
SIGNAL APPEARS ON KINESCOPE GRID BUT IMPOSSIBLE TO
SYNCHRONIZE THE PICTURE VERTICALLY AND HORI-
ZONTALLY—Acondition of this nature can be caused by:
(1) Defective sync amplifier and separator (V106, 6SN7-GT).
(2) If tube is O.K., check voltages, waveforms and associated
circuits.
SIGNAL ON KINESCOPE GRID AND HORIZONTAL SYNC
ONLY —If this condition is encountered, check:
Vertical integrating network capacitors C164, C123, C124,
C125, and resistors R13B, R137, R138.
PICTURE STABLE BUT WITH POOR RESOLUTION—If the pic-
ture resolution is not up to standard, it may be caused by any
of the following:
(1) Defective picture detector (V104, 6AL5) or video amplifier
(V105, 12AU7).
(2) Open video peaking coil. Check all peaking coils
(L104, L105, L106, L107) for continuity. Note that L105 and
LI 06 have shunting resistors.
(3) Leakage in V105 grid capacitor CI 15.
If above components are not found to be defective, check the
following:
(1) Check all potentials in video circuits.
(2) Check kinescope grid circuit for poor or dirty contact.
(3) Check adjustment of focus control (R129). It should be
effective on either side of proper focus.
(4) Check and realign, if necessary, the picture if and r-f
circuits.
PICTURE SMEAR—
(1) Normally, smear can be attributed to phase shift at the
low-frequency end of the video characteristic. This can be
caused by improper values of Rand Cin the video circuits.
Check for grid current on video amplifier tube V105.
(2) This trouble can originate in either the transmitter or
the receiver. Check reception from another station.
PICTURE JITTER—
(1) 1! regular sections at the left of the picture are displaced,
replace the horizontal output tube (V109, 6BG6-G).
(2) Vertical instability may be due to loose connections or
"noise" received with the signal.
(3) Horizontal instability may be due to unstable transmitted
sync, or to "noise."

721TS ALIGNMENT PROCEDURE
TEST EQUIPMENT—To service this receiver properly, it is
recommended that the following test equipment be available:
R-F Sweep Generator meeting the following requirements:
(a) Frequency ranges:
18 to 30 mc, 1mc sweep width
40 to 90 mc, 10 mc sweep width
170 to 225 mc, 10 mc sweep width
(b) Output adjustable with at least .1 volt maximum.
(c) Output constant on all ranges.
(d) "Flat" output in all attenuator positions.
Cathode-ray Oscilloscope, preferably one with awide band
vertical deflection and an input calibrating source.
Signal Generator to provide the following frequencies:
(Output on these ranges should be adjustable and at least .1
volt maximum.)
(a) Intennediate frequencies:
21.25 mc sound Mand sound traps
22.8 mc converter transformer
23.9 mc first picture i-f coil
24.5 mc third picture i-f coil
26.0 mc second picture i-f primary
27.25 mc second picture i-f secondary
(b) Radio frequencies:
Picture Sound
Channel Carrier Carrier
Number Freq. Mc Freq. Mc
145.25 49.75
255.25 59.75
361.25 65.75
467.25 71.75
577.25 81.75
683.25 87.75
7175.25 179.75
8181.25 185.75
9187.25 191.75
10 ,193.25 197.75
11 199.25 203.75
12 205.25 209.75
13 211.25 215.75
Heterodyne Frequency Meter with crystal calibrator if the
signal generator is not crystal controlled.
Electronic Voltmeter of "Junior VoltOhmyst type" and ahigh
voltage probe for use with this meter to permit measurements
up to 10 kr.
SERVICE PRECAUTIONS—Cutouts in the bottom of the cabinet
make it possible to do some of the servicing of the receiver
without removing the chassis. If the receiver is serviced in
the cabinet, asoft pad should be placed under the cabinet
when it is inverted, in order to avoid scratching the surface.
In manufacture, the cabinet receives aClass 1rub finish and
every effort should be made to preserve that finish.
If necessary to remove the chassis from cabinet, the kinescope
must first be removed. See Figures 3, 4and 6. If possible,
the chassis should then be serviced without the kinescope.
However, if it is necessary to view the raster during servicing,
the kinescope should be inserted only after the chassis is
turned on end. The kinescope should never be allowed to
support its weight by resting in the deflecting yoke. Abracket
should be used to support the tube at its viewing screen.
By turning the chassis on end with the power transformer
"up," all adjustments will be made conveniently available.
Since this is the only safe position in which the chassis will
rest and still leave adjustments accessible, the trimmer location
drawings are oriented similarly for ease of use.
CAUTION: Do not permit the kinescope second-anode lead
to become "shorted" to the chassis. To do so will cause a
considerable overload on the high-voltage filter resistor HI 87.
ADJUSTMENTS REQUIRED Normally, only the r-f oscillator
line will require the attention of the service technician. All
other circuits are either broad or very stable and hence will
seldom require readjustment.
Due to the high frequencies at which the receiver operates,
the r-f oscillator-line adjustment is critical and may be affected
by atube change. The line can be adjusted to the proper fre-
quency on channel 13 with practically any 6J6 tube in the
socket. However, it may not then be possible to adjust the
line to frequency on all of channels 7, 8, 9, 10, 11, and 12.
For an oscillator tube to be satisfactory, it should be possible
to adjust the line to proper frequency with the fine-tuning
control in the middle of its range. It may therefore be neces-
sary to select atube for the oscillator socket. In replacing, if
the old tube can be matched for frequency by trying several
new ones, this practice is recommended. At best, however,
it will probably be necessary to realign the oscillator line
completely after changing the tube.
Tubes which cannot be used as an oscillator may work satis-
factorily as an r-f amplifier or aconverter.
The detailed alignment procedure which follows is intended
primarily as adiscussion of the method used, precautions to
be taken, and the reasons for these precautions. Then, for
more convenient reference during alignment, atabulation of
the method is given. All the information necessary for align-
ment is given in the tables; however, alignment by the tables
should not be attempted before reading the detailed instruc-
tions.
3

ALIGNMENT PROCEDURE (Continued) 721TS
ORDER OF ALIGNMENT—When acomplete receiver alignment
is necessary, it can be most conveniently periormed in the
following order:
Sound discriminator
Sound i-f transformers
Picture i-f traps
Picture i-f coils
R-F and converter lines
R-F oscillator line
Retouch picture i-f transformers
Sensitivity check
SOUND DISCRIMINATOR ALIGNMENT—
Set the signal generator for approximately .1 volt output at
21.25 mc. and connect it to the second sound i-f grid.
Detune T108 secondary (bottom).
Set the "VoltOhmyst" on the 10 volt scale. r
Connect the meter in series with aone megohm resistor to the
junction of diode resistors R181 and R182.
Adjust the primary of T108 (top) for maximum output on the
meter.
Connect the "VoltOhmyst" to pin 1of V118 and set on the
3volt scale.
Adjust T108 secondary (bottom). It will be found that it is pos-
sible to produce apositive or negative voltage on the meter de-
pendent upon this adjustment. Obviously to pass from aposi-
tive to anegative voltage, the voltage must go through zero.
T108 (bottom) should be adjusted so that the meter indicates
zero output as the voltage swings from positive to negative.
This point will be called discriminator zero output.
Connect the sweep oscillator to the grid of the second sound
i-f amplifier.
Adjust the sweep band width to approximately 1mc. with
the center frequency at approximately 21.25 and with an
output of approximately .1 volt.
Connect the oscilloscope to pin 1of V116.
The pattern obtained should be similar to that shown in
Figvure 13A. If it Unot, adjust T108 (top) until the wave iorm
is symmetricaL
The peak to peak bandwidth of the discriminator should be
opproximotely 350 ke. and should be linear from 21.175 mc.
to 21.325 mc.
SOUND IF ALIGNMENT—
Connect the sweep and signal generator to the top end of the
trap winding of T3 (on top of the chassis).
Connect the oscilloscope to the second sound if grid return
(terminal AT107) in series with a33,000 ohm isolating resistor.
Connect a5600 ohm resistor from terminal A, T107 to ground.
Insert a21.25 mc. marker signal from the signal generator
into the first sound if grid.
Adjust T107 (top and bottom) for maximum gain and sym-
metry about the 21.25 mc. marker. The pattern obtained should
be similar to that shown in Figure 13B. The band width at
80% response from the first sound i-i grid to the second i-f grid
should be approximately 250 kc.
The output level from the sweep should be set to produce
approximately .3 volt peak-to-peak at the second sound i-f grid
return when the final touches on the above adjustment are
made. It is necessary that the sweep output voltage should
not exceed the specified values otherwise the response curve
will be broadened, permitting slight misadjustment to pass
unnoticed and possibly causing distortion on weak signals.
PICTURE IF TRAP ADJUSTMENT—
Connect the "VoltOhmyst" to the junction of R106 and R107
and adjust the picture control for -3 volts on the meter.
Set the channel switch to channel 13.
Connect the "VoltOhmyst" across the picture second detector
load resistor RI18 and set it on the 3volt scale.
Connect the output of the signal generator to the junction of
C14 and R8. This connection is available on aterminal lug
through ahole in the side apron of the chassis, beside the r-f
unit.
Set the generator to 21.25 mc. and check it against acrystal
calibrator to insure that the generator is exactly on frequency.
Adjust T3 (top) and TlOl for minimum indication on the "Volt-
Ohmyst."
Set the generator to 27.25 mc and adjust T104 secondary (bot-
tom) for minimum indication on the "VoltOhmyst" {this adjust-
ment is omitted on some chassis).
PICTURE I-F COIL ADJUSTMENTS—
Set the signal generator to each of the following frequencies
and peak the specified adjustment for maximum indication on
the "VoltOhmyst."
22.8 mc—T3 (bottom)
23.9 mc.—LlOl (top of chassis)
26.0 mc.—^T104 primary (top of chassis)
24.5 mc.—L103 (top of chassis)
Picture I-F Oscillation—If the receiver is badly misaligned and
two or more of the i-f coils are tuned to the same frequency,
the receiver may fall into i-f oscillation. I-F oscnllation shows
up as avoltage in excess of 3volts at the picture detector
load resistor. This voltage is unaffected by r-f signal input
and sometimes is independent of picture control setting.
If such acondition is encountered, it is sometimes possible to
stop oscillation by adjusting the coils approximately to fre-
quency by setting the adjustment stud extensions of T3.
LlOl, T104 and LI03 to be approximately equal to those of
another receiver known to be in proper -alignment. If this
does not have the desired effect, it may now be possible
to stop oscillation by increasing the grid bias. If so, it should
then be possible to align the coils by the usual method.
Once aligned in this manner, the i-f should be stable with
reduced bias.
If the os<dllation cannot be stopped in the above matmer,
shunt the grids of the first two i-f amplifiers to ground with
1000 mmf. capacitors.
Connect the signal generator to the third i-f grid and adjust
L103 to frequency.
Remove the shunting capacitor from the second i-f grid, connect
the signal generator to this grid and align T104.
Remove the shunting capacitor from the first i-f grid, connect
the signal generator and align LlOl.
Coimect the signal generator to the junction of C14 and R6
(in the r-i tuning luit) and align T3 to frequency.
Bthis does not stop the osdllation, the difficulty is not due
to i-f misaligiunent as the i-f section is very stable when prop-
erly aligned. Check all i-f by-pass condensers, coil loading
resistors, tubes, socket voltages, ete.

721TS ALIGNMENT PROCEDURE (Continued)
H-F AND CONVERTER LINE ADJUSTMENT—
Connect the r-f sweep oscillator to the receiver antenna ter-
minals. If the sweep oscillator has a50 ohm single-ended
output, it will be necessary to obtain balanced output by
connecting as shown in Figure 9.
DIZO A.
—(/VA/"
—
BO OUM
UNBALANCED
SWEEP OUTPUT
CABLE
MSa2T
RECEIVER
ANTENNA
TERMINALS
<S)
db
figure 9—Unbalanced Sweep Cable Termination
Connect the oscilloscope to the junction of C14 and R6 (in the
r-f tuning unit) through a10,000 ohm resistor.
By-pass the first picture if grid to ground through a1000 mmfd.
capacitor. Keep the leads to this by-pass as short as possible.
If this is not done, lead resonance may fall in the r-f range
and cause an incorrect picture of the r-f response.
Connect the "VoltOhmyst" to the junction of R170 and R171
and adjust the picture control for -1 volt on the meter.
Connect the signal generator loosely to the receiver antenna
terminals.
Since channel 7has the narrowest response of any of the
high frequency channels, it should be adjusted first.
Set the receiver channel switch to channel 7(see Figure 18
for switch shaft flat location versus channel).
Set the sweep oscillator to cover channel 7.
Insert markers of channel 7picture carrier and sound carrier
175.25 mc. and 179.75 mc.
Adjust L25, L26, L51 and L52 (see Figure 16) for an approxi-
mately flat topped response curve located symmetrically be-
tween the markers. Normally this curve appears somewhat
overcoupled or double humped with a10 or 15% peak to val-
ley excursion and the markers occur at approximately 90% re-
sponse. See Figure 17, channel 7. In making these adjust-
ments, the stud extension of all cores should be kept approxi-
mately equal.
Check the response of channels 8through 13 by switching
the receiver channel switch, sweep oscillator and marker
oscillator to each of these channels and observe the response
obtained. See Figure 17 for typical response curves. It should
be found that all these channels have the proper shaped re-
sponse with the markers above 70% response. If the markers
do not fall within this requirement on one or more high fre-
quency channels, since there are no individual channel ad-
justments, it will be necessary to readjust L25, L26, LSI and
L52, and possibly ^compromise some channel slightly in order
to get the markers up on other channels. Normally however,
no difficulty of this type should be experienced since the
higher frequency channels become comparatively broad and
the markers easily fall within the required range.
Channel 6is next aligned in the same manner.
Set the receiver to channel 6.
Set the sweep oscillator to cover channel 6.
Set the marker oscillator to channel 6picture and sound car-
rier frequencies.
Adjust Lll, LI2, L37 and L38, for an approximately flat-topped
response curve located symmetrically between the markers.
Check channels 5down through channel 1by switching the
receiver, sweep oscillator and marker oscillator to each chan-
nel and observing the response obtained. In all cases, the
markers should be above the 70% response point. If this is
not the case, Lll, L12, L37 and L38 should be retouched. On
final adjustment, all channels must be within the 70% spec-
ification.
Coupling between r-f and converter lines is augmented by
alink between L12 and L37. This link is adjusted in the
factory and should not require adjustment in the field. On
channel 6with the link in the minimum coupling position, the
response is slightly overcoupled with approximately a10%
excursion from peak-to-valley. With the coupling at maximum,
the response is somewhat broader and the peak-to-valley ex-
cursion is approximately 40%. The amount of coupling per-
missible is limited by the peak-to-valley excursion which should
not be greater than 30 °o on any channel.
Remove the 1000 mmf capacitor from the first picture i-f grid.
R-F OSCILLATOR LINE ADJUSTMENT—
The r-f oscillator line may be aligned by adjusting it to beat
with acrystal calibrated heterodyne frequency meter, or by
feeding asignal into the receiver at the r-f sound carrier fre-
quency and adjusting the oscillator for zero output from the
sound discriminator. In this latter case the sound discriminator
must first have been aligned to exact frequency. Either method
of adjustment will produce the same results. The method used
will depend upon the type of test equipment available.
Regardless of which method of oscillator alignment is used,
the frequency standard must be crystal controlled or calibrated.
If the receiver oscillator is to be adjusted by the heterodyne
frequency meter method, the frequencies listed under "R-F
Osc. Freq." in the table must be available.
If the receiver oscillator is adjusted by feeding in the r-f
sound carrier signal, the frequencies listed under "R-F Sound
Carrier" must be available.
Receiver R-F Sound
Channel R-F Osc. Carrier
Number Freq. Mc. Freq. Mc.
171 49.75
281 59.75
387 65.75
493 71.75
5103 81.75
6109 87.75
7201 179.75
8207 185.75
9213 191.75
10 219 197.75
II 225 203.75
12 231 209.75
13 237 215.75
If the heterodyne frequency meter method is used, couple the
meter probe loosely to the receiver oscillator.
If the r-f sound carrier method is used, connect the "Volt-
Ohmyst" to pin 1of V116.
3
10

ALIGNMENT PROCEDURE (Continued) 72 ITS
c
c
Connect the signal generator to the receiver antenna terminals.
The order of alignment remains the same regardless of which
method is used.
Since lower frequencies are obtained by adding steps of
inductance, it is necessary to align channel 13 first and con-
tinue in reverse numerical order.
Set the receiver channel switch to channel 13.
Adjust the frequency standard to the correct frequency (237
mc. for heterodyne frequency meter or 215.75 mc. for the signal
generator).
Set the fine tuning control to the middle of its range while mak-
ing the adjustment.
Adjust L77 and L78 for an audible beat on the heterodyne
frequency meter or zero voltage from sound discriminator. The
core stud extensions should be maintained equal by visual
inspection.
Switch the receiver to channel 12.
Set the frequency standard to the proper frequency as listed
in the alignment table.
Adjust L76 for indications as above.
Adjust the oscillator to frequency on all channels by switch-
ing the receiver and the frequency standard to each channel
and adjusting the appropriate oscillator trimmer for the speci-
fied indication. It should be possible to adjust the oscillator
to the correct frequency on all channels with the fine tuning
control in the middle third of its range.
After the oscillator has been set on all channels, start back at
channel 13 and recheck to make sure that all adjustments are
correct.
RETOUCHING OF PICTURE I-F ADJUSTMENTS—
The picture i-f response curve varies somewhat with change
of bias and for this reason it should be aligned with approxi-
mately the same signal input as it will receive in operation.
If the receiver is located at the edge of the service area, it
should be aligned with approximately —1 volt i-f grid bias.
However, for normal conditions, (signals of 1000 microvolts
or greater), it is recommended that the picture i-f be aligned
with agrid bias of —3 volts. Set the picture control for —3 volts
at the junction of R106 and R107.
Connect the r-f sweep generator to the receiver antenna ter-
minals.
Connect the signal generator to the antenna terminals and
feed in the 25.75 mc. if picture carrier marker and a23 mc.
marker.
Connect the oscilloscope across the picture detector load re-
sistor, R118.
Set the channel switch to channel (between 1and 6) found
to have the best response during the r-f and converter line ad-
justment.
Set the sweep output to produce approximately .3 volt peak-to-
peak across the picture detector load resistor.
Observe and analyze the response curve obtained. The re-
sponse will not be ideal and the i-f adjustments must be
retouched in order to obtain the desired curve. In making
these adjustments, care should be taken that no two trans-
formers are tuned to the same frequency as i-f oscillation may
result.
On final adjustment the picture carrier marker must be at
approximately 45% response. The curve must be approxi-
mately flat topped and with the 23 mc. marker at approxi-
mately 90% response.
The most important consideration in making the i-f adjust-
ments is to get the picture carrier at the 45% response point.
If the picture carrier operates too low on the response curve,
loss of low frequency video response, of picture brilliance, of
blanking, and of sync may occur. If the picture carrier oper-
ates too high on the response curve, the picture definition is
impaired by loss of high frequency video response.
SENSITIVITY CHECK—Acomparative sensitivity check can be
made by operating the receiver on aweak signal from a
television station and comparing the picture and sound ob-
tained to that obtained on other receivers under the same
conditions.
This weak signal can be obtained by connecting the shop
antenna to the receiver through an attenuator pad of the type
shown in Figure 10. The number of stages in the pad de-
pends upon the signal strength available at the antenna. A
sufficient number of stages should be inserted so that asome-
what less than normal contrast picture is obtained when the
picture control is at the maximum clockwise position.
1ZO
-vww- .^vvvvv-
I20 ^
RECEIVER
I
ANTENNA
I
TERMINALS
-vww- -WWAr- -JWSA/V-
Vigure 10—Attenuator Pad
Only carbon type resistors should be used to construct the
attenuator pad. Since many of the low value moulded re-
sistors generally available are of wire wound construction,
it is advisable to break and examine one of each type of re-
sistor used in order to determine its construction.
RESPONSE CURVES—The response curves shown on pages
12, 14 and 15 and referred to throughout the alignment pro-
cedure were taken from aproduction set. Although these
curves are typical, some variations can be expected. Chan-
nel 2r-f response (not shown) is similar to that of channel 3.
The response curves are shown in the classical manner of
presentation, that is with "response up" and low frequency to
the left. The manner in which they will be seen in agiven
test set-up will depend upon the characteristics of the oscillo-
scope and the sweep generator. The curves may be seen in-
verted and /or switched from left to right depending on the de-
flection polarity of the oscilloscope and the phasing of the
sweep generator.
ALIGNMENT TABLE—Both methods of oscillator alignment are
presented in the alignment table. The service technician may
thereby choose the method to suit his test equipment. If it
is found that the dual listing is confusing, the unwanted listing
can be easily erased.
11

721TS ALIGNMENT TABLE
THE DETAILED ALIGNMENT PROCEDURE BEGINNING ON PAGE 8SHOULD BE READ BEFORE ALIGNMENT BY USE OF THE TABLES IS ATTEMPTED.
DISCRIMINATOR AND SOUND IF ALIGNMENT
STEP
No.

ALIGNMENT TABLE (Continued) 72 ITS
THE DETAILED ALIGNMENT PROCEDURE BEGINNING ON PAGE 8SHOULD BE READ BEFORE ALIGNMENT BY USE OF THE TABLES IS ATTEMPTED.
PICTURE IF AND TRAP ADJUSTMENT
STEP
No.

721TS ALIGNMENT TABLE (Continued)
THE DETAILED ALIGNMENT PROCEDURE BEGINNING ON PAGE 8SHOULD BE READ BEFORE ALIGNMENT BY USE OF THE TABLES IS ATTEMPTED.
R-F AND CONVERTER LINE ALIGNMENT
STEP
No.

c
ALIGNMENT TABLE (Continued)
R-F OSCILLATOR ALIGNMENT
72 ITS
STEP
No.

721TS CHASSIS VIEWS
T106
POWER
TRANSFORMER
I
Figure 21 —Chassis Top View (Showing Location of Major Components)
3
NOTE: IN SOME RECEIVERS. LI02 IS USED IN PLACE OF TI04
Figure 22—Chassis Bottom View (Showing Location of Major Components)
16

c
WAVEFORM PHOTOGRAPHS 72 1TS
Peak to peak voltages shown are nominal when 1volt peak to peak video signal is applied to Isl video amplifier (V105).
Video Signal Input to 1st Video ma >
Amplifier (At Pin 2of V105)
Figure 25—Vertical
(1.0 Volts, Pto P) Figure 24—Horizontal
(1.0 Volts, Pto P)
S=
'
.'P- 'i
'
Figure 25—Vertical
(5.0 Volts, Pto P)
Output of 1st Video Amplifier
(Pin 1of V105)
Figure 26—Horizontal
(5.0 Volts, Pto P)
cFigure 21—Vertical
(32 Volts, Pto P)
Input to Kinescope Grid
(]unction of L106 and Green head
to Kinescope Socket)
Figure 28—Horizontal
(32 Volts, Pto P)
i^^WMIK Input to Grid Sync Amplifier
(Pin 1of V106) ffl ffl I
Figure 29—Vertical
(8 Volts, Pto P) Figure 30—Horizontal
(8 Volts, Pto P)
Figure 31 —Vertical
(90 Volts, Pto P)
Input to Sync Separator
(Pin 2of VI 06)
Figure 32—Horizontal
(90 Volts, Pto P)
c
Figure 33—Vertical
(10 Volts, Pto P)
Output of Sync Separator
(Pin 6of V106)
17
Figure 34—Horizontal
(10 Volts, Pto P)

72 ITS WAVEFORM PHOTOGRAPHS (Continued)
Figure 35—Vertical (25 Volts,
PtoP)
Output of Integrating Network
(Junction of R138 and C125)
Figure 36—Grid of
Oscillator Tube
(175 Volts, Pto P)
(Pin 1of VI07)
Vertical Figure 37—Input to Vertical
Output Tube
(65 Volts, Pto P)
(Junction of CI 29 and CI 30)
Figure 38—Plate of Vertical
Output Tube
(750 Volts, Pto P)
(Pin 5of V107)
Figure 39—Voltage Across Ver-
tical Deflection Coils (L108,
L109) (90 Volts, Pto P) (At
Green Lead of T103 to Ground)
Figure 40—Horizontal Oscilla-
tor Waveforms and Sync Pulse
(20 Volts, Pto P)
(Junction of C122 and C133)
^Y
Figure 41 —Horizontal Oscilla-
tor Control (45 Volts, Pto P)
(Junction R158 and R164)
Figure 42—Grid of Horizontal
Oscillator (400 Volts, Pto P)
(Pin 4of VI 08)
Figure 43—Horizontal Oscil-
lator Output (60 Volts, Pto P)
(Junction of C135 and C163)
Figure 44—Grid of Horizontal
Output
(40 Volts, Pto P)
(Pin 5of V109)
Figure 45—Plate of Horizontal
Output (Approx. 5000 Volts,
Pto P) (Measured Through a
Capacity Divider Connected
from Plate to Ground)
Figure 46—Voltage Across
Horizontal Deflection Coils
(Approx. 1100 Volts, Pto P)
(Pin 4or 6of Vlll to
Ground)
Figure 47—Test Pattern Show-
ing Out of Sync Condition
When Horizontal Hold Control
Is in aCounterclockwise Posi-
tion—Just Before Pulling Into
Sync
Figure 48—Test Pattern Show-
ing Out Of Sync Condition
When Horizontal Hold Control
Is at the Maximum Clockwise
Position.
CRITICAL LEAD DRESS
1. Do not permit any strains to be
placed on the leads of R126, R157,
R158, R164, R165, R173, R188 and
R191. Do not permit these re-
sistors to be exposed to the heat
of asoldering iron any more
than is absolutely necessary.
2. Dress the temperature compen-
sating resistor R191 approxi-
mately one-quarter inch from
the power transformer and the
chassis.
3. Dress all video coupling capaci-
tors and peaking coils up and
aivay from the chassis.
4. Contact between the r-f oscilla-
tor frequency adjustment screws
and the oscillator coils or chan-
nel switch eyelets must be
avoided.
18
i^Db.

CHASSIS WIRINQ DIAGRAM
--11 niT^
SE7J 'S' J
"IMOTE ;t'
:^hzJ
(^ oLi-:^
Early production sets employed bright-
ness and picture control #71784 in which
the brightness is the outer knob end pic-
ture, the center knob. Late production,
shown in the above wiring diagram employs
control #73193 in which picture is the
outer knob and brightness the center.
The front panel control decals are af-
fected by the control changes. Decal
#72805 is for control #7 1784. Decal
#73194 is for control #73193.
The operating instruction book is also af-
fected by the control change. Instruction
Book #49050-1 is for sets employing con-
trol #71784.
Supplementary sheet #49050-15 h
been issued to convert -1books for l
with sets employing control #73193. Su
sequent printings of late production i
struct ion books will be designated
iJ49050-2.
19 Figure 49—Chassis Wiring Diagram

CHASSIS WmiNQ DIAGRAM 72
«E»-;i(eS--.»N.-_^
^^~Jb1I9 to ion trap UlMiNEJ?-"^^ *«vJl f
—f'o^l-
The front panel control decats are af-
fected by the control changes. Decal
#72805 is for control #7 1784. Decol
#73194 is for control #73193.
The operating instruction book is oiso af-
fected by the control change. Instruction
Book #49050-1 is for sets employing con-
trol #71784.
Supplementary sheet #49050- 1Shas
been issued to convert -1 books for use
with sets employing control #73193. Sub-
sequent printings of late production in-
struction books will be designated as
£r49050-2.
In early production receivers, an EM
type of ion trap mognet was employed and
was connected as shown by the dotted
lines.
R196 was omitted in receivers employ-
ing on EM type magnet.
R197 was employed only in receivers
with the 247-ohm focus coil.
19 Figure 49—Chassis Wiring Diagram