Tektronix 7A19 User manual

IN
Tektronix, Inc .
P.O
.
Box 500
Beaverton,
Oregon
97077

Serial Number
070-2129-00
U TI N MANUAL
First Printing
MAY 1976

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SECTION 1

SPECIFICATION
Introduction
Option 4
SECTION 2 OPERATING INSTRUCTIONS
Front Panel Controls and Connectors
Operating Instructions and Checkout
Applications
SECTION 3

CIRCUIT DESCRIPTION
Block Diagram
Detailed Circuit Description
SECTION 4

MAINTENANCE
Preventive Maintenance
Troubleshooting
Corrective Maintenance
SECTION5

CALIBRATION
Performance Check
Test
Equipment Required
Calibration Procedure
Index to Calibration Procedure
SECTION6

ELECTRICAL PARTS LIST
SECTION 7

DIAGRAMS
Circuit Board Illustrations
Semiconductor Electrode Configurations
SECTION 8

MECHANICAL PARTS LIST
Exploded View Drawing
CHANGE INFORMATION
CONTENT

7A19
Fig . 1-1 . 7A19 Amplifier plug-in (Left) and 7A19 with
Variable delay option (Right)
.
1243-12
REV .
A, AUG . 1976

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 .
Characteristic
Deflection Factor °
Calibrated Range
Gain Ratio Accuracy
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
Maximum Input Power
DC or AC coupled
Voltage (AC
coupled)
Input Impedance
Resistance (DC or
DC GND)
Reflection Coefficient
(Time Domain)
Maximum Input Current
REV . B, SEPT . 197 7
1 kHz or less
50 ohms ±1 ohm
Less than 0 .2 mA
TABLE 1-1
ELECTRICAL
Performance Requirement
Less than 0 .1 peak to peak
Option 4
10 mV/div to 1 V/div, 7 steps in a 1, 2, 5
sequence
Within 3% with GAIN adjusted at
10
mV/div when driven from 50 ohm source .
With 7400, 65 MHz
;
With 7500, 100
MHz ;
With 7700, 175 MHz ; With 7900,
500 MHz
2 watts average or 50 divisions peak
deflection .
100 volts (DC + peak AC) not to . exceed
2 watts average or 50 divisions peak .
Section
1-7A19
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 .
An optional
VARIABLE
DELAY may be ordered with
the 7A19
to
provide
a
signal delay
of up to ±500 ps .
Supplemental Information
Pre-Charge
circuit may be used as a
calibrated
100X attenuator
Front panel GAIN control allows calibra-
tion to mainframe .
CA U °77ON
Pre-charge circuit must be used
for
both
charging and discharging AC coupling
capacitor to potentials greater than 50
divisions
equivalent
voltage .
VSWR
is typically less than 1 .25 @ 500
MHz

Specifications-7A19
Display Noise
(Tangentially Measured)
Drift with ambient
temperature (line
voltage constant)
TABLE 1-2

TABLE 1-3
ENVIRONMENTAL
CHARACTERISTICS

PHYSICAL
Deflects trace approximately 0 .3 division
Size

Fits all 7000-Series plug-in compartments
Refer

to

the

specifications

for

the

associated

Weight

7A19 : .9 kilograms or 2 .1 lbs .
oscilloscope
.

7A19 (option 1) :

1 .3 kilograms or 2 .9 lbs .

General
Installation
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
.
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

10 mV/Div to

1 V/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 .
INSTRUCTION
Section 2-7A19
INVERT" : A positive-going signal at
the
INPUT connector deflects the
CRT display downward .
Input Coupling

Selects
signal input coupling mode .
Switch
Probes
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

Delays the signal up to
±500
(Option 4)

picoseconds by using a
calibrated
10 turn dial .
OPERATING INS'TRUC'TIONS
and CHECKOUT
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, 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
1 kHz, 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/D IV 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 .
General
APPLICATIONS
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

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 belowabout 1 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 1 V .
Operating Instructions--7A19
Fig
.
2-1
.
Measuring
the
peak to peak voltage of a waveform
.
vertical
VOLTS/DIV
probe
Volts
=
deflection X

setting

X attenuator
(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 .
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 :
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
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 .
Instantaneous Voltage = 3 .6 X

1 X 0
.5 V X

10
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
.