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shown in Fig. 15B. The distance between cor-
responding points on the horizontal axis for the two
w a v e f o r m s
then
represents the
between the two waveforms. In this case, the zero
crossover points of the two waveforms are com-
pared. It is shown that a difference of 1 div exists.
This is then interpreted as a phase shift of 4 5 ° .
Television Servicing:
Many of the video servicing procedures can be per-
formed using single-trace operation.
outlined later in the applications section covering
single-trace operation.
viewing the V I T S (vertical interval test signal), can
be accomplished much more effectively using a
dual-trace oscilloscope. A s outlined in the single-
trace applications section and as shown in Fig. 19
and 26, the information on the Field 1 and Field 2
vertical blanking interval pulse is different. This is
shown in detail in Fig. 19. Also, because the os-
cilloscope sweep is synchronized to the vertical
blanking interval waveform, the Field 1 and Field 2
waveforms are superimposed onto each other.
With dual-trace operation, the signal information
on each blanking pulse can be viewed separately
without overlapping.
Fig. 18 indicates the os-
F I E L D I
F I E L D 2
F I E L D
I & 2
16
phase
shift
These are
One of these procedures,
L I N E No.17
V E R T I C A L B L A N K I N G I N T E R V A L ( N O : 1 ~ N O . 2 1 )
No.279
V E R T I C A L B L A N K I N G I N T E R V A L ( N O . 2 6 3 ~ N O . 2 8 2 )
( M U L T I - B U R S T )
No. 17
No.279
Fig. 16 V I T S signal. Fields 1 and 2
cilloscope control setting for viewing the alternate
V I T S .
Most network television signals contain built-in
test signals (VITS) that can be very valuable tools in
troubleshooting
and servicing video
The V I T S can localize trouble to the antenna, tuner,
IF or video sections and shows when realignment
may be required. The V I T S signal is being used in
some television receivers for automatic color cor-
rection.
The V I T S signal is transmitted during the vertical
blanking interval. On the television set, they can be
seen as a bright white line above the top of the pic-
ture, when the vertical linearity or height is ad-
justed to view the vertical blanking interval. (On T V
sets with internal retrace blanking circuits, the
blanking circuit must be disabled to see these
signals.)
The transmitted V I T S is precision sequences of
specific frequencies, amplitudes and waveshapes
a s shown in Fig. 16. The television networks use
the precision signals for adjustment and checking
of network transmission equipment, but the techni-
cian can use them to evaluate television set perfor-
mance. The first frame of V I T S at the " B " section
(line 18) in Fig. 16 begins with a white reference
No. 18
H O R I Z . S Y N C .
P U L S E
No.280
No. 18
No.280
equipment.
( M U L T I - B U R S T )
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