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can be examined more closely either by increasing
the sweep time or by pulling the
control to obtain 5 times magnification.
Delay Line T e s t :
The dual-trace feature of the oscilloscope also can
be used to determine the delay times of transmis-
sion type delay lines as well as ultrasonic type
delay lines.
The output of delay lines can be
observed on CH2 while being synchronized with
the input pulse of C H 1 . A repetitive type pulse will
make it possible to synchronize the displays. The
interval between repetitive pulses should be large
compared to the delay time to be investigated. In
addition, to determining delay time, the pulse dis-
tortion inherent in the delay line can be determined
by examination of the delay pulse observed on CH2
waveform display.
P U L S E
G E N E R A T O R
5 0 0 0 P P S
sec.
tjj.
P U L S E
W I D T H
U S E 1/10
V I D E O
FOR B O T H C H A N N E L S
A M P L I F I E R
• N O T E : S E T T I N G O F V E R T I C A L "
tATTENUATORS
T H E S A M E , B U T M A Y
W I D E L Y , D E P E N D I N G O N C I R C U I T
T Y P E .
Fig. 13 Checking " Y " delay line in color television receivers
14
POSITION
C H
-1
( I N P U T
P U L S E )
C H
2
( O U T P U T P U L S E )
U L T R A S O N I C D E L A Y
L I N E (5M sec)
I N P U T
Fig. 12 Delay line measurements
C H 1 ( I N P U T )
C H 2 ( O U T P U T )
T O H O R I Z O N T A L
P R O B E
A M P L I F I E R
S H O U L D B E
V A R Y
Fig. 12 demonstrates the typical oscilloscope set-
tings a s well as the basic test circuit. Typical input
and output waveforms are shown on the os-
cilloscope display. A common application of delay
line checks is found in color T V receivers. Fig. 13
s h o w s the oscilloscope settings and typical circuit
connections to check the " Y " delay line employed
in the video amplifier section. The input waveform
and output waveform are compared for delay time,
using the horizontal sync pulse of the composite
video signal for reference. The indicated delay is
approximately
one microsecond.
determining the delay characteristics of the line,
the output waveform reverals any distortion that
may be introduced from an impedance mismatch or
a greatly attenuated output resulting from an open
line.
O U T P U T
1jLtS D E L A Y
N O T E : N O E L E C T R I C A L C O N N E C T I O N :
P L A C E C L I P O N I N S U L A T I O N O F P L A T E
C A P L E A D O R I N C L O S E P R O X I M I T Y O F
H O R I Z O N T A L A M P L I F I E R T U B E .
In addition to
E X T T R G
ON S I D E
P A N E L
T O V I D E O O U T P U T
A M P L I F I E R
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