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attenuate the audio i-f.
completes the amplifier stages and feeds the video
detector (V 4 ).
The audio level is maintained just below the
point of interference with the video i-f.
the audio i-f is not completely rejected, as the audio
signal is recovered (at the output ot the video de
tector) by heterodyning with the video i-f.
4.5 me. beat between the video and audio inter
mediate frequencies is obtained from the shunt-
tuned circuit consisting of L2 and C79 and is fed
to the first audio i-f amplifier (V 7 ).
b.
VID E O DETECTO R AN D A .G .C .: The video
detector (V 4 A ) rectifies the negative portion of
the video i-f.
The resultant signal is coupled
through peaking coil LI to the grid of the first
video amplifier (V 5 ).
gain control and develops a delayed negative A.G.C.
voltage which is used to bias the first two video
i-f stages and the r-f amplifier.
c.
VID E O A M P L IF IE R : The video amplifier con
sists of two stages (V5 and V 6 A ).
stage is series-peaked and is coupled to the grid
of the kinescope (V 25) and the sync separator
and d. c. restorer ( V I 5A ).
V5 is varied by the C O N TRA ST control (R19)
which varies the bias of V5, to control the signal
input to V6A.
d.
D. C. RESTO RE R AN D SYNC C L IP P E R :
The output of the video detector contains both a.c.
and d.c. components of the video signal, as well
as the blanking and sync pulses.
amplifiers will not pass the d.c. component of the
video signal, the background level of the picture
will vary.
The d.c. restorer (V I5 A ) develops a
bias voltage across R24 which varies with the
average video signal level.
fed to the grid of the kinescope, thus maintaining
the proper brightness level.
output of V I 5A, developed across R28, is coupled
through C22 to the first sync amplifier (V 15B ).
4.
DEFLECTION SECTION— The sync and sweep
stages produce and control the deflection of the elec
tron beam in the kinescope.
cuits incorporate a horizontal phase detector (sync
discriminator) to maintain automatic sync with the
horizontal pulses of the video signal.
a.
SYNC A M P L IF IE R AN D IN V E R T E R :
sync pulse output of V I 5A is amplified by two
triode stages (V15B and V6B) and fed to the
horizontal phase inverter (V I1 A ).
ing network of the vertical deflection circuit is
coupled to the output of V I 1 A, which provides
push-pull output for the horizontal sync discrimi
nator (V 1 2 ).
b.
H O R IZ O N T A L SW E E P :
flection circuits contain an automatic frequency
stabilizing arrangement which improves stability
and ease of operation. The phase inverter ( V I 1 A )
feeds the horizontal sync pulses to the horizontal
phase detector (V 12).
receives voltages fed back from the horizontal out
put (V 17) through C58.
the horizontal sync pulses and the horizontal os
cillator signal will cause the input voltage applied
An overcoupled i-f (T 4 )
However,
The
V5B acts as the automatic
The second
The output signal of
Since the video
This bias voltage is
The video sync pulse
The horizontal sweep cir
The
^he integrat
The horizontal de
At the same time, V12
Any phase shift between
Scanned by mbear2k - Jan 20121/17
to one diode section of V12 to differ from that of
the other and result in a d.c. bias voltage on the
grid of the horizontal control tuoe ( V I l b ) .
bias voltage will be proportional to the phase dis
placement between the incoming sync pulses and
the horizontal oscillator voltage and of a polarity
determined by the lead or lag of the oscillator fre
quency.
The plate resistance of V IIB is part of
the bias network of the grid circuit of the horizon
tal oscillator ( V lJ ). The output of the phase de
tector (V 12) will thus synchronize the oscillator
to the horizontal pulses of the video signal.
The horizontal blocking oscillator ( V I 3) operates
at a. frequency determined by C57, R75, R76, and
the plate resistance of V IIB . The horizontal sync
pulses cause V13 to lock in at the sync irequency
when the H O R IZO N T A L HOLD control (R 75)
is properly adjusted.
of V13 is developed across R79 and is ted to the
horizontal output tube ( V I 7).
to the horizontal output tube is adjusted by the
H O R IZ O N T A L D RIV E control, R80.
V19 supplies the required driving power for the
horizontal deflection coils (L 9 ).
V17 is coupled to the horizontal deflection coils
through output transformer T9. A portion of the
output transformer secondary is shunted by the
H O R IZO N T A L SIZE control L6.
the inductance of L6, the horizontal sweep current
may be controlled.
The horizontal damper tube ( V I 9) acts to damp
out oscillations which occur over part of the hori
zontal scanning cycle. The H O R IZO N T A L LIN
E A R IT Y control (L 7 )
trace.
V19 is a type 6W4 to eliminate the need
for a separate damper filament winding,
c.
V E R T IC A L SW E E P: Vertical oscillator V14 is
free-runn.ng and operates at a frequency determ
ined by C71, R95, and the V E R T IC A L HOLD
control (R 94), in the absence of a vertical sync
pulse.
The integrated sixty-cycle sync pulse de
rived from the video signal reaches the grid of
V14 just before it would normally trip. This sync
pulse is great enough to drive the tube to conduc
tion and cause it to lock-in at the sync frequency.
The sync pulse thus maintains control of the verti
cal oscillator sweep frequency when R94 is cor
rectly adjusted.
The output of V14 is fed to the vertical outptu
stage (V 16) through C72.
controlled
by the V E R T IC A L
(R 96).
R100 varies the operating point of V16
by varying the bias, acting as the V E R T IC A L
L IN E A R IT Y control. The sweep voltage of V16
is coupled to the vertical deflection coils (L 8 ) by
means of the vertical output transformer ( T i l ) .
5.
POWER SUPPLIES — Two power supplies are
used to supply the required voltages.
supply uses a transformer and full-wave rectifier* The
high voltage supply for the kinescope is of the fly-back
lype and is energized by the horizontal output tube,
a.
HIGH V O L TA G E S U P P L Y : The high voltage
power supply makes use of the energy supplied to
th$ horizontal output transformer by V I 7. When
the plate current of V I 7 is cut off at the instant
Emerson Radio
This
The sweep voltage output
The signal level
ihe output of
By varying
helps provide a linear
The output of V14 is
SIZE
control
The low voltage
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