Tektronix 535A, Инструкция по эксплуатации

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Calibration Procedure — Type 535A
29. Set Lockout Level Adjust
Set the HORIZONTAL DISPLAY switch at A' DEL'D BY
B’ the B' STABILITY control fully clockwise, and the A'
TIME/CM switch at .1 MILLISEC. Slowly adjust the A'
STABILITY control until the sweep first appears. Connect
the test oscilloscope through a 10X probe to pin 3 of V133
using dc coupling. Adjust the test oscilloscope so that the
displayed waveform has a vertical amplitude of four divi­
sions. Adjust the Lockout Level Adj. control (see top view,
Fig. 6-3) until the square-wave portion of the displayed
waveform is 2.4 divisions in amplitude. During adjustments,
the A'
STABILITY control should be checked frequently to
be sure that it is set where the sweep just runs. At the
completion of the adjustment, the square wave portion
should be 2.4 centimeters in amplitude, the sawtooth portion
should be 1.6 centimeters in amplitude.
30. Set
Vertical Gain
Connect the EP53A Gain Set Adaptor between the oscillo­
scope and plug-in unit. Connect a jumper from the CAL.
OUT connector to the connector of the gain set adaptor.
Place the AMPLITUDE CALIBRATOR switch in the .2 VOLTS
position and adjust the oscilloscope for a stable display.
Set the Gain Adj. (see Figure 6-5) control for exactly 2 centi­
meters of vertical deflection.
31. Adjust Delay Line and High Frequency
Compensations
Delay Line adjustments are probably the most difficult
adjustments to make. This is due to interaction between the
large number of controls. The adjustments can be made
properly with a minimum of difficulty if the proper pro­
cedure is followed and if care is used in making the adjust­
ments. In general, it is not necessaary to completley re­
adjust the delay line. Rather it is a case of occasionally
touching up the line for best results. Before attempting to
adjust the line, briefly run through this procedure to estab­
lish the basic concepts in your mind. This will make the
actual adjustments considerably easier. Be sure that the
line requires adjustment before attempting to adjust it.
In general the procedure for adjusting the delay line and
high frequency controls involves application of a fast ris­
ing pulse or square wave to the vertical amplifier. The
delay line is then adjusted for minimum distortion of the
pulse wave displayed on the screen. In particular, the
delay line and amplifier high frequency controls are adjusted
for three characteristics of the displayed waveform; fastest
possible risetime without overshoot, minimum irregularities
on the top of the pulse, and minimum slope of the top of
the waveform.
Displaying the Test Signal
To determine the extent of misadjustment of the delay line
in your instrument, you will need to closely examine a dis­
played fast rising pulse or square wave. The waveform
used to make this examination should have a risetime of no
more than 7 millimicroseconds. A Tektronix Type 107
Square-Wave Generator or a Tektronix Type P Plug-In Unit
is recommended.
If a Type 107 Square-Wave Generator is used, the fre­
quency control should be set to obtain approximately 400 kc
squarewaves. The output of the generator should be con­
nected through a 52 ohm coaxial cable and termination
resistor to the input of either a Type K or a Type L Plug-In
Unit. The termination resistor should be connected at the
input to the plug-in unit.
When a Type P Plug-In Unit is used, it is only necessary
to insert the unit into the plug-in compartment of the oscil­
loscope. The pulse frequency of the P Unit is fixed.
If it is necessary to use a signal generator other than a
Type 107 or Type P, you must check the output waveform
from the generator for suitability. Obviously a waveform
which is distorted in any manner is not suitable for adjust
ing the delay line of an oscilloscope. A good check on the
suitability of your test equipment is to display the output
waveform on another Tektronix oscilloscope with a delay line
known to be correctly adjusted.
When the input signal has been connected, adjust the
oscilloscope triggering controls for a stable display using
Time Base A. Rotate the TIME/CM control to .1
µ
SEC and
adjust the oscilloscope and signal source for approximately
3 centimeters of vertical deflection.
With the oscilloscope display, it is possible to check the
delay line and amplifier adjustments for proper setting.
There are three general characteristics which you will have
to appraise, and to do this, you will need to use three dif­
ferent sweep rates. The first characteristic to look for is
the level of the display; the second is the amount of bump­
iness contained in the flat top of the displayed waveform;
and the third is the risetime of the displayed waveform.
Determining the Level of the Display
The level of the display refers to the top of the displayed
waveform. The waveform should show neither an upward
nor a downward slope anywhere along the top of the
waveform. Any slope of the waveform can be most easily
seen with a sweep speed of approximately 5
µ
seconds per
centimeter.
Checking the Bumpiness of the Display
The next characteristic to look for in the displayed wave­
form is the bumpiness in the top portion of the waveform
immediately following the rise. This is the portion of the
waveform affected by the delay line adjustments. To make
this observation, use a sweep speed of approximatly .2
µ
sec ­
onds per centimeter.
There are two general types of bumps to be found in a
poorly adjusted delay line. The first type is the irregularity
caused by the misadjustment of a group of capacitors. This
type is indicated by a fairly long duration bump. If the
bumps occur at random intervals along the delay line, they
are probably due to misadjustment of the delay line and can
usually be corrected by a few slight adjustments. However,
I A) (A)
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