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. In addi-
tion to determining the delay characteristics of the line, the
output waveform reveals any distortion that may be in-
troduced from an impedance mismatch.
T O H O R I Z O N T A L A M P L I F I E R .
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
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 .
V I D E O
A M P L I F I E R
S E T B O T H P R O B E S F O R
1 0 : 1
A T T E N U A T I O N
D E L A Y L I N E
' N O T E : S E T T I N G O F V E R T I C A L
A T T E N U A T O R S S H O U L D B E T H E
S A M E , B U T M A Y V A R 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. 10. Checking " Y " delay line in color television receivers
Stereo Amplifier Servicing:
Another convenient use for a dual-trace oscilloscope is in
troubleshooting stereo amplifiers. If identical amplifiers are
used and the output of one is weak, distorted or otherwise
abnormal, the dual-trace oscilloscope can be efficiently used
to localize the defect. With an identical signal applied to the
inputs of both amplifiers, a side-by-side comparison of both
units can be made by progressively sampling identical signal
points in both amplifiers. When the defective or malfunc-
tioning stage has been located, it can be immediately
observed and analyzed.
Improving the Ratio of Desired to Undesired
Signals:
In some applications, the desired signal may be riding
on a large undesired signal component such as 60Hz. It is
possible to minimize or for practical purpose eliminate the
undesired component. Fig. 11 shows the oscilloscope set-
tings for such an application. The waveform display of
CH1 indicates the desired signal and the dotted line in-
dicates the average amplitude variation corresponding to the
undesired 6 0 Hz component. The CH2 display indicates a
waveform of equal amplitude and identical phase to the
average of the CH1 wavejorm. With the MODE switch set
to S U B , and by adjusting the CH2 vertical attenuator con-
trol, the 60 Hz component of the CH 1 signal can be cancell-
ed by the CH2 input and the desired waveform can be
observed.
A D J U S T F O R O N E
C O M P L E T E C Y C L E
A T 6 0 H z
Fig.
11.
Improving desired-to-undesired signal ratio
13
T O V I D E O
O U T P U T
A M P L I F I E R
S T A R T W I T H
D U A L
C H A N G E T O
S U B
