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Calibration — Type
3A74
g. Connect the probe from the test oscilloscope to pin 11
of the oscilloscope
Y-axis
interconnecting
socket.
(As
mentioned in step 14, pin 12 of the X-axis socket can
also be used as thé test point.)
. Check
the waveform
display on the test oscilloscope
for an amplitude of 12 volts or more (see Fig. 6-8a}.
Decrease
the
vertical
deflection
factor
of
the
test
oscilloscope for increased sensitivity to make
the dis-
play exactly four major divisions in amplitude on the
test oscilloscope crt.
(Do not move the Output Ampli-
tude contro] on the generator.)
Using
an appropriate
sweep
rate on the test oscillo-
scope
(2 usec/div.
and
set
5X
Magnifier
to
"on")
measure
the
risetime
between
the
10%
and
80%
amplitude levels on the rising portion of the waveform
(see Fig. 6-8b).
The risetime should be 0.7 microseconds
or faster.
18.
Adjust
High-Frequency
Compensation
. Set the square-wave generator for an output frequency
of about
100 kc.
Set
the
oscilloscope
Time/Div.
switch
to 1 usec
and
the Trigger Slope switch to —.
Adjust the oscilloscope Triggering Level control to ob-
tain a stable display.
Adjust the generator Output Amplitude control so the
waveform display is four major divisions in amplitude.
Readjust
the
Triggering
Level
control,
if necessary.
. Adjust L464 and L474 in equal increments to obtain an
optimum
square corner {see Fig. 6-10a) on the wave-
form,
without
appreciable
overshoot
and
ringing.
(Overshoot
and
ringing
should
not exceed
Y
minor
division.)
Fig. 6-10b shows one form of waveform dis-
tortion when
L464 and
L474 are improperly adjusted.
NOTE
.
igh-
f
Chan-
The
80%
instead
of the 90%
amplitude
level is
19.
Check
High-Frequency
Response
of
Chan
used
in
this
risetime
measurement
to exclude
the
nels
2,
3
and
4
rounded-top
portion of the rise.
Fig. 6-8b wave-
a. Disconnect the signal from channel
1 and apply it to
form
is actually four major divisions in amplitude
channel 2.
if viewed
at a slower
sweep
rate so that several
cycles of the waveform
are displayed
as in steps
16i and 16).
+
Optimum
Square
17. Check
Composite
Int. Trigger Output
Y___
Comer
ar
KE
a. Push the Type 3A74 TRIGGER switch in.
G
=
|
b. Set
the
square-wave
generator
for
an
output
fre-
4
+
|
quency of about 10 ke.
HE
EEL
HHH
.02
+
c. Adjust the generator Output Amplitude control to ob-
Volts /Div.
|
+
|
tain
a vertical
deflection
of 4 major
divisions
on
the
+
oscilloscope used with the Type 3A74.
+
d. With
the
test
oscilloscope
probe
connected
to
the
|
£
X
same
test point as described
in step
16g
and
using
+
the
calibrated
vertical
deflection
factor
on
the
test
(a)
7 Sweep Rate: 1 uSec/Div
oscilloscope,
check
the
amplitude
of the
waveform.
The
amplitude
should
be 9.5 volts or more
(see Fig.
6-9).
+
.
Overpeaked
e. Disconnect the probe.
YN
)
-
ij
Y
+
+
.02
|
+
¢
Volts/Div.
|
+
:
AAD NARAA DRBAN RIERA RARESCAREERARRARRRREK
CRRTKREAT
9.5 Volts Lili
laetererteeleele telat
+
cr more,
(TTT
HHH HHH
+
Sweep
Rate:
50 uSec/Div.
(b)
+
Sweep
Rate:
1 uSec/Div.
T
|
|
{
1
Fig.
6-9.
Measuring
the
amplitude
of
the
composite
internal
trigger
as displayed
on
the test oscilloscope
crt.
Vertical
deflection
factor:
5
volts/div.
Fig.
6-10.
Adjusting
the
high-frequency
compensation
of
the
Type
3A74.
(a)
L464
and
L474
properly
adjusted.
(b)
Overpeaking
caused
by
an
incorrect adjustment
of L464
and
L474.
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