Tektronix 7A19 User manual

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TEKTROND©
INSTRUCTION MANUAL
)
Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon 97077 Serial Number
070-2129-00
First
Printing
MAY
1976

SECTION 1
SECTION 2
SECTION 3
SECTION 4
SECTION 5
SECTION 6
SECTION 7
SECTION 8
TABLE OF CONTENTS
SPECIFICATION
Introduction
Option 4
OPERATING INSTRUCTIONS
Front Panel Controls and Connectors
Operating Instructions and Checkout
Applications
CIRCUIT DESCRIPTION
Block Diagram
Detailed Circuit Description
MAINTENANCE
Preventive Maintenance
Troubleshooting
Corrective Maintenance
CALIBRATION
Performance Check
Test Equipment Required
Calibration Procedure
Index to Calibration Procedure
ELECTRICAL PARTS LIST
DIAGRAMS
Circuit Board Illustrations
Semiconductor Electrode Configurations
MECHANICAL PARTS LIST
Exploded View Drawing
CHANGE INFORMATION
Page
1-1
1-1
2-1
2-1
2-2
3-1
3-1
4-1
4-1
4-3
5-1
5-1
5.3
5-4
7A19

7A19
Fig.
1-1. 7A19 Amplifier plug-in (Left) and 7A19 with Variable delay option (Right).
REV. A, AUG. 1976

Section 1-7A19
SPECIFICATION
Introduction
The 7A19 Amplifier plug-in unit is a wide band amplifier
designed for use with TEKTRONIX 7000-Series oscillo-
scopes. Readout encoding circuitry is provided in the 7A19
to allow probe coding, deflection factor readout, and
IDENTIFY functions. The 7A19 can be operated in any
compartment of the 7000-Series oscilloscopes, but is pri-
marily intended for use in the vertical plug-in compartments.
The following electrical characteristics are valid over the
stated environmental range for instruments calibrated at an
ambient temperature of +20°C to +30°C, and after a five
minute warmup unless otherwise noted.
Option 4
An optional VARIABLE DELAY may be ordered with
TABLE 1-1
ELECTRICAL
the 7A19 to provide a signal delay of up to +500 ps.
Characteristic Performance Requirement
Supplemental Information
Deflection Factor
Calibrated Range
Gain Ratio Accuracy
10 mV/div to 1 V/div,7 steps ina1,2,5
sequence
Within 3% with GAIN adjusted at 10
mV/div when driven from 50 ohm source.
Pre-Charge circuit may be used as a
calibrated 100X attenuator
Front panel GAIN control allows calibra-
tion to mainframe.
Frequency Response (8 divi-
sion reference, mainframe
dependent)
Upper Bandwidth AC or
DC coupled 10 mV/div
to 1 V/div
Lower Bandwidth
AC Coupled
With 7400, 65 MHz; With 7500, 100
MHz; With 7700, 175 MHz; With 7900,
500 MHz
1 kHz or less
Maximum Input Power
DC or AC coupled
Voltage (AC coupled)
2 watts average or 50 divisions peak
deflection.
100 volts (DC + peak AC) not to exceed
2 watts average or 50 divisions peak.
CAUTION
Pre-charge circuit must be used for both
charging and discharging AC coupling
capacitor to potentials greater than 50
divisions equivalent voltage.
Input Impedance
Resistance (DC or
DC GND)
Reflection Coefficient
(Time Domain)
50 ohms +1 ohm
Less than 0.1 peak to peak
VSWR is typically less than 1.25 @ 500
MHz
Maximum Input Current
Less than 0.2 mA
REV. B, SEPT. 1977

Specifications—7A19
TABLE 1-1 (cont)
Characteristic Performance Requirement
Supplemental Information
IDENTIFY
Deflects trace approximately 0.3 division
Trace Positioning
At least +8 divisions
Display Noise
(Tangentially Measured)
Less than 0.1 division
DC Drift
Drift with ambient
temperature (line
voltage constant)
100 uV/C° or less
Variable Delay (Option 4)
Range Variable from —0.5 ns to +0.5 ns
Accuracy To 1 ns within +0.05 ns of dial setting
Input Polarity
Front panel switch selects +UP or
INVERT
TABLE 1-2
ENVIRONMENTAL CHARACTERISTICS
TABLE 1-3
PHYSICAL
Size
Fits all 7000-Series plug-in compartments
Refer to the specifications for the associated Weight
oscilloscope.
7A19: .9 kilograms or 2.1 Ibs.
7A19 (option 1): 1.3 kilograms or 2.9 Ibs.
1-2

—~
Section 2—7A19
OPERATING INSTRUCTIONS
General
To effectively use the 7A19, the operation and
capabilities of the instrument must be known. This section
describes front-panel control functions, general information
on signal input connections, and other subjects that pertain
to various measurement applications.
Installation
The 7A19 is calibrated and ready for use as received. It
can be installed in any compartment of TEKTRONIX
7000-Series Oscilloscopes, but is intended for principal use
in vertical plug-in compartments. To install, align the upper
and lower rails of the 7A19 with the oscilloscope tracks and
insert it. The front panel will be flush with the front of the
oscilloscope and the latch at the bottom left corner will be
in place against the front panel when the 7A19 is fully
inserted.
To remove the 7A19, pull on the latch (inscribed with
the unit identification ‘’“7A19”) and the 7A19 will unlatch.
Continue pulling to slide the 7A19 out of the oscilloscope.
FRONT PANEL
CONTROLS AND CONNECTORS
VOLTS/DIV Selects calibrated deflection factors
from 10mV/Div to 1V/Div; 7
steps in a 1-2-5 sequence.
POSITION Controls the position of the trace.
IDENTIFY Deflects the trace about
0.3 division for trace identification.
In instruments with readout, also
replaces readout with the word
“IDENTIFY”.
GAIN Adjustment Screwdriver adjustment permits
calibration of deflection factor.
POLARITY Provides a means of inverting the
display.
+UP: A positive-going signal at the
INPUT connector deflects the CRT
display upward.
@
INVERT: A positive-going signal at
the INPUT connector deflects the
CRT display downward.
Input Coupling
Switch
Selects signal input coupling mode.
AC: The AC component of the
signal is coupled to the amplifier
input while the DC component is
blocked.
AC GND: Grounds the amplifier
input while maintaining the same
AC load for the input signal.
PRE-CHG: Provides a charge path
for the AC coupling capacitor to
pre-charge the input circuit before
switching the Input coupling switch
to AC.
DC: Both AC and DC components
of the signal are coupled to the
amplifier input.
DC GND: Grounds the amplifier
input while maintaining the same
DC load for the input signal.
INPUT Connector Provides a means for connecting a
signal.
VARIABLE DELAY
(Option 4)
Delays the signal up to +500
picoseconds by using a calibrated
10 turn dial.
OPERATING INSTRUCTIONS and CHECKOUT
Probes
Probes recommended for use with the 7A19 are the
P6056 (10X) or P6057 (100X). Both probes are compatible
to 50 ohm systems, and will allow optimum frequency
response. These probes also contain trace IDENTIFY and
readout encoding functions.

Operating Instructions—7A19
If
the
P6201
Probe
is
used,
a
one
megohm
input
impedance
may
be
achieved.
Consult
your
local
TEK-
TRONIX
Field
Engineer
or
Representative
for
further
information.
Vertical
Gain
Check
and
Adjustment
To
check
the
gain
of
the
7A19,
set
the
VOLTS/DIV
switch
to
10
mV
and
connect
20
mV
into
50
{2,
1
kHz
signal
from
the
oscilloscope
Calibrator
to
the
INPUT
connector.
The
vertical
deflection
should
be
exactly
two
divisions.
If
not,
adjust
the
front
panel
GAIN
control
for
exactly
two
vertical
divisions.
Input Coupling
The
input
coupling
switch
allows
a
choice
of
input
coupling
methods.
The
type
of
display
desired
and
the
applied
signal will
determine
the
coupling
to
use.
The
DC
coupling
position
can
be
used
for
most
applications.
For
AC
signals
with
frequencies
below
about
1kHz,
and
square
waves
whose
low-frequency
components
are
important
to
the
display,
it
is
necessary
to
use
DC
coupling
to
obtain
a
satisfactory
presentation.
DC GND position disconnects the signal source from the
amplifier
and
connects
it
to
a
resistive
50
ohm
termination,
thus providing the same type of load to the signal source.
The input to the amplifier is also provided with a ground
reference.
In the AC coupling position, the DC component of the
signal is blocked by a capacitor in the input circuit. The AC
coupling position provides the best display of signals with a
DC component much larger than the AC component.
The PRE-CHG feature should be used when there is a
possibility of having a residual charge on the input
capacitor of the opposite polarity to the intended input,
and when the algebraic sum of the charges may be greater
than the maximum input limitations of the amplifier. To
use this feature, first set the coupling switch to PRE-CHG,
then connect the signal source to the INPUT and wait
about two seconds for the coupling capacitor to charge, set
the coupling switch to AC.
Another useful feature of the PRE-CHG position is that
it can be used as a calibrated 100X attenuator having an
input impedance of five kilohms in series with two
microfarads. This extends the Low Frequency response to
less than 20 Hz. Input power should be limited to 1/8 watt
in this mode.
2-2
The AC GND position disconnects the signal source from
the amplifier and connects it to a capacitive coupled 50
ohm termination, thus providing the same type of load to
the signal source. The input to the amplifier is also pro-
vided with a ground reference.
VOLTS/DIV Switch
The amount of deflection produced by a signal is
determined by the signal amplitude, the attenuation factor
of the probe, the setting of the VOLTS/DIV switch, and
the setting of the Input Coupling switch. Calibrated
deflection factors represented by the VOLTS/DIV switch
apply only when the probe attenuation is X1 and when the
Input Coupling switch is not in the PRE-CHG position (the
PRE-CHG position has an attenuation of 100X).
POLARITY Switch
The POLARITY switch provides a means of inverting the
displayed signal. With the POLARITY switch set to +UP, a
positive-going signal at the INPUT produces an upward
deflection of the CRT display. With the POLARITY switch
set to INVERT, a positive-going signal will produce a
downward deflection of the CRT display.
Trace Identification and Readout Functions
When the IDENTIFY button is pressed, the trace is
deflected upward about 0.3 division to identify the 7A19
trace. This feature is particularly useful when multiple
traces are displayed on the CRT. In mainframes with
readout, it also replaces the deflection factor readout with
the word “IDENTIFY”.
The 7A19 is equipped with probe encoding circuitry
that, when used with a coded probe, corrects the deflection
factor readout.
VARIABLE DELAY (Option 4)
The optional VARIABLE DELAY line provides a means
for delaying the signal applied to the INPUT for up to +500
ps.
APPLICATIONS
General
The following information describes the procedures and
techniques for making measurements with a 7A19 and the
associated TEKTRONIX oscilloscope and time-base. These
applications are not described in detail, since each
application must be adapted to the requirements of the
individual measurements. This instrument can also be used
for many applications which are not described in this
REV A OCT 1979

manual. Contact your local TEKTRONIX Field Office or
representative for assistance in making specific measure-
ments.
Peak-to-Peak Voltage Measurements (AC)
To make peak-to-peak voltage measurements, use the
following procedure:
1. Apply the signal to the INPUT connector.
2. Set the Coupling switch to AC.
NOTE
For low-frequency signals below about 71 kHz, use the
DC position to prevent attenuation of the signal.
3. Set the VOLTS/DIV switch to display about five
vertical divisions of the waveform.
4. Set the time-base Triggering controls for a stable
display. Set the time base to a sweep rate which displays
several cycles of the waveform.
5. Turn the 7A19 POSITION control so the lower
portion of the waveform coincides with one of the graticule
lines below the center horizontal line, and the top of the
waveform is within the viewing area. With the time base
Position control, move the display so one of the upper
peaks lies near the center vertical line (see Fig. 2-1).
6. Measure the divisions of vertical deflection peak to
peak.
NOTE
This technique can also be used to make
measurements between two points on the waveform,
rather than peak to peak.
7. Multiply the distance measured in step 6 by the
VOLTS/DIV switch setting. Include the attenuation factor
of the probe, if used.
EXAMPLE: Assume that the peak to peak vertical
deflection is 4.5 divisions using a 10X attenuator probe,
and the VOLTS/DIV switch is set to 1V.
@
Operating Instructions—7A19
Position to
center vertical
line
fa
Vertical
deflection
Fig. 2-1. Measuring the peak to peak voltage of a waveform.
vertical probe
Volts = deflection X oe ey X attenuator
woe setting
(divisions) factor
Substituting the given values:
Volts Peak to Peak = 4.5 X 1 X 10
The peak-to-peak voltage is 45 volts.
When using a coded probe and an oscilloscope equipped
with readout, simply multiply the distance measured in step
6 by the deflection factor displayed on the CRT.
Instantaneous Voltage Measurements (DC)
To measure the DC level at a given point on a waveform,
proceed as follows:
1. Connect the signal to the INPUT connector.
2. Set the VOLTS/DIV switch to display about five
divisions.
3. Set the Coupling switch to GND, and position the
trace to the bottom graticule line or other reference line. If
the voltage is negative with respect to ground, position the
2-3

Operating Instructions—7A19
trace to the top graticule line. Do not move the POSITION
control after this reference line has been established.
4. Set the Coupling switch to DC. The ground reference
line can be checked at any time by switching to the GND
position.
NOTE
To measure a voltage level with respect to another
voltage rather than ground, make the following
changes to Step 4. Set the Coupling switch to DC and
apply the reference voltage to the INPUT connector.
Then position the trace to the reference line and
disconnect the reference voltage.
5. Set the time-base Triggering controls for a stable
display. Set the Time Base sweep rate for an optimum
display of the waveform.
6. Measure the distance in divisions between the
reference line and the point on the waveform at which the
DC level is to be measured. For example, in Fig. 2-2 the
measurement is between the reference line and point A.
7. Establish the polarity of the waveform. With the
POLARITY switch in the NORM position, any point above
the reference line is positive.
8. Multiply the distance measured in step 6 by the
VOLTS/DIV switch setting. Include the attenuation factor
of the probe, if used.
EXAMPLE: Assume the vertical distance measured is
3.6 divisions (see Fig. 2-2) and the waveform is above the
reference line, using a 10X probe with a VOLTS/DIV
switch setting of 0.5 V.
Using the formula:
Instan- vertical VOLTS/ probe
taneous = distance X polarity X DIV X attenuation
voltage (divisions) setting factor
Substituting the given values:
Instantaneous Voltage = 3.6 X 1X O5V X 10
The instantaneous voltage is 18 volts.
Matching transit times using two 7A19’s, one
having VARIABLE DELAY (Option 4)
In some applications it is necessary to view the time
relationship of two signals, one with respect to the other.
2-4
Point A
Vertical
distance
eference line
Fig. 2-2. Measuring instantaneous voltage with respect to same
reference.
With high speed signals, the transit times of the probes and
amplifiers can distort the true time relationship of the two
signals. By using the VARIABLE DELAY (Option 4), the
transit times between two units can be matched to within
50 ps, thus giving a true time relationship of the signals
being viewed.
For matching transit times of two 7A19 with probes,
proceed as follows:
1. Install the 7A19 without the VARIABLE DELAY
option in the left vertical plug-in compartment.
2. Install the 7A19 with VARIABLE DELAY option in
the right vertical plug-in compartment.
3. Connect the probes to a common signal source of
greater than 100 kHz and adjust the time-base unit for the
fastest sweep available.
4. Set the Trigger Source switch to left Vert, and
Vertical Mode to Alternate.
5. Set both 7A19’s to the same deflection factor
settings.
6. Center both displays vertically.
7. Adjust VARIABLE DELAY so that the two displays
are superimposed. The transit times of both units are now
matched.