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.

Section 3—7A19
CIRCUIT DESCRIPTION
Introduction
This section of the manual contains a description of the
circuitry used in the 7A19 amplifier. The description begins
with a discussion of the instrument using the block diagram
shown in the Diagrams section. Then, each circuit is
described in detail using block diagrams to show the
interconnections between stages in each major circuit and
the relationship of the front panel controls to the individual
stages.
A complete schematic of the circuits are given in the
Diagrams section. Refer to this schematic throughout the
following circuit description for electrical values and
relationship.
BLOCK DIAGRAM
The following discussion is provided to aid in under-
standing the overall concept of the 7A19 before the
individual circuits are discussed in detail. Only the basic
interconnections between the blocks are shown on the
block diagram (see Diagrams section). Each block repre-
sents a major circuit in the instrument.
Signals to be displayed on the CRT are applied to the
INPUT connector. The signal passes through the Input
Coupling Switch, where the appropriate coupling is
selected, to the Attenuators. The VOLTS/DIV switch
selects the correct amount of attenuation.
Transit time for the 7A19 is standardized by the Fixed
Delay Line. An optional Variable Delay Line can be
ordered that allows the transit time of the plug-in to be
varied up to 1 ns.
Signals from the Delay Line are connected to the Signal
Line. The Signal Line represents a 5092 line that is
connected to Signal Amplifier, Trigger Amplifier, Limiter,
and is terminated in the Signal Line Terminater. Input
impedance is effectively adjusted, therefore, by the Input
Current control.
Overvoltage protection is provided by the Limiter
circuitry and the fuse located in the Input Coupler.
The Signal Amplifier and Trigger Amplifier circuits are
identical. They provide positioning and gain switching for
the 10mV and 20 mV ranges. GAIN calibration and
temperature compensation is provided by the Gain Current
Amplifier.
@
The Signal Amplifier and Trigger Amplifier is connected
to the Polarity circuit where the oscilloscope is provided
with +UP or inverted signal and trigger outputs. Outputs are
connected to the oscilloscope via the interface connectors.
DETAILED CIRCUIT DESCRIPTION
Input Coupling
Input signals connected to the INPUT connector can be
AC-coupled, DC-coupled, or internally disconnected. S5 is a
cam-type switch; a contact-closure chart showing the
operation is given on the schematic in the Diagrams section.
When the Input Coupling Switch is in the DC position, the
input signal is coupled directly to the Attenuator. The DC
GND position disconnects the input signal from the
Attenuators and connects it to ground through two 100 {2
resistors in parallel. Paralleling the 100 {2 resistors reduces
the inductance associated with the resistors so that the
combination will remain 50 Q for all frequencies within the
limits of this plug-in. Connected in a similar manner and for
the same reasons are the input fuses F6 and F7. In the AC
position, the input signal passes through capacitor C5. The
capacitor prevents the DC component of the signal from
passing to the Attenuator. AC GND position disconnects
the input signal from the Attenuators and connects it to
ground through C5 and the two 1002 resistors. This
represents the same load to the signal source. The PRE-
CHG position limits the instantaneous current caused by
connecting a large signal to the INPUT connector by
inserting a resistor in series with C5. Since this resistor is
4.95kQ and the input to the Attenuator is 50 Q, the
PRE-CHG position will act as a X100 attenuator.
Attenuator
The effective overall deflection factor of the 7A19 is
determined by the setting of the VOLTS/DIV switch, $135
and the Step Attenuator, A10. Gain switching for the
10 mV and 20 mV positions occur in the Signal and Trigger
Amplifiers. The signal in the 10 mV and 20 mV position is
passed through the Step Attenuator, unattenuated. Pre-
cision microwave attenuators, located in the Step Attenu-
ator, are switched in at all other VOLTS/DIV positions.
Delay Lines
Unless Variable Delay Option 4 is requested, all 7A19's
are equipped with a Fixed Delay Line consisting of a
precision length of 50 92 cable. The Fixed Delay Line is
inserted in series with the Signal Line so that the transit
times of all 7A19 plug-in’s can be closely regulated. The
optional Variable Delay Line, when requested, replaces the
Fixed Delay Line.

Circuit Description—7A19
Signal Line Terminator
The Signal Line Terminator consists of a current sensing
operational amplifier connected to the Signal Line. This
operational amplifier senses changes in currents at the
Signal Line and compensates by adding or subtracting
currents. The Input Current control sets the quiescent
current at the Signal Line. This is the major controlling
factor for input impedance. Changes of input current due
to positioning or polarity switching are also compensated
by this circuit. R121 and C121 compensate for the addition
of this circuit to the Signal Line.
Limiter
CR124, CR125 provide overload protection. An over-
load
condition at the signal INPUT connector will cause
one or both diodes to forward bias. If this condition
continues, the current flowing through the diodes will soon
cause the fuses F6, F7 to burn out. Diodes CR124,CR125
are connected to the Signal Line through an impedance
matching “T’’ network, L124, L125, and C123.
Signal Amplifier and Trigger Amplifier
The Signal Amplifier and Trigger Amplifier circuitry are
identical. The description for the Signal Amplifier applies
equally to the Trigger Amplifier.
The Signal Amplifier consists mainly of a TEKTRONIX-
made hybrid integrated circuit (U40) and its related
circuitry. A representation of U40 is shown in the
schematic diagrams section. The Signal Line is connected to
the Signal Amplifier input through a ‘“T’’ network con-
sisting of C20, L21, and L22. The “’T” coils, L21 and L22
are adjusted for minimum aberrations at high frequencies.
The paraphase input of U40 converts the single ended input
to a differential signal. Frequency compensation, signal
balancing, gain, and temperature compensation are all
accomplished in the emitters of the paraphase amplifier.
Frequency compensation is achieved through the use of the
series of resistors, capacitors, and an inductor connected to
pins 5 and 11. R38 signal balance control balances our the
resultant currents in the amplifier.
Gain Current Source
Temp Comp control, R76, sets the voltage at the emitter
of O76. The current through R74 is set by the current
generator O73 and Gain control R73. As the thermal
resistor R74 changes with temperature so will the voltage at
the collector of O73; therefore, compensating for temper-
ature changes within the plug-in.
Positioning is achieved by varying the DC level at the
input of the paraphase amplifier (pin 4, U40). Q56A and
Q56B is a DC amplifier having an inverting input and
non-inverting input. Gain of this amplifier is selected by the
VOLTS/DIV switch. With the VOLTS/DIV switch in the
10 mV position, the gain of O56 is set by R66. In the
20 mV position the gain of O56 is doubled. The POSITION
control (R68) applies a DC signal to either the inverting or
non-inverting input. This is selected so that a clockwise
rotation of the POSITION control will always produce an
upward deflection of the displayed trace. The output of the
position amplifier is applied to the Signal and Trigger
Amplifier through an inverting buffer O50. This signal is
also applied to the Signal Line Terminator which com-
pensates for the current changes that occur as a result of
the positioning circuitry.
Polarity Circuit
The output from the Signal and Trigger Amplifiers is
connected through the Polarity switch to the interface
connector. The Polarity switch, in the INVERT position,
not only inverts the Signal and Trigger outputs but it
inverts the polarity signal so that a clockwise rotation of
the POLARITY control always produces an upward deflec-
tion. See the description for the Position Circuit for details.
Connectors
All connections made to the mainframe by the 7A19 are
shown on the schematic located in the Diagrams section of
this manual. Also shown are the power supply decoupling
components.
Readout
The 7A19 incorporates standard vertical readout en-
coding circuitry. Refer to any 7000-Series Oscilloscope
with readout for more information.

Section 4—7A19
MAINTENANCE
Introduction
This
section of the manual contains maintenance infor-
mation for use in preventive maintenance, corrective
maintenance, and troubleshooting of the 7A19.
Further maintenance information relating to general
maintenance can be found in the instruction manuals for
the 7000-Series oscilloscopes.
PREVENTIVE MAINTENANCE
General
Preventive maintenance, consisting of cleaning, visual
inspection, etc., performed on a regular basis, will improve
the reliability of this instrument. Periodic checks of the
semiconductor devices used in the unit are not recom-
mended as a_ preventive maintenance measure. See
semiconductor-checking information given under Trouble-
shooting.
Cleaning
Front Panel. Loose dust may be removed with a soft
cloth or a dry brush. Water and mild detergent may be
used; however, abrasive cleaners should not be used.
Interior. Cleaning the interior of the unit should precede
calibration, since the cleaning process could alter the
settings of the calibration adjustments. Use low-velocity
compressed air to blow off the accumulated dust. Hardened
dirt can be removed with a soft, dry brush, cotton-tipped
swab, or cloth dampened with a mild detergent and water
solution.
Lubrication
Use a cleaning-type lubricant on shaft bushings in
connecting plug contacts, and switch contacts. Lubricate
switch detents with a heavier grease. A lubrication kit
containing the necessary lubricating materials and instruc-
tions is available through any TEKTRONIX Field Office.
Order by TEKTRONIX Part No. 003-0342-01. Local
purchase is recommended whenever possible.
TROUBLESHOOTING
General
The following is provided to augment information
contained in other sections of this manual when trouble-
shooting the 7A19. The schematic diagrams, circuit descrip-
@
tion, and calibration sections should be used to full
advantage. The circuit description section gives detailed
information on circuit behavior and output requirements.
Troubleshooting Aids
Diagrams. Circuit diagrams are given on foldout pages in
Section 7. The circuit number and electrical value of each
component in this instrument are shown on the diagrams.
Important voltages and semiconductor lead configurations
are also shown.
Circuit Board. The circuit board used in the 7A19 is
outlined on the schematic diagrams, and a photograph of
the board is shown on the back of the schematic diagrams.
Each board-mounted electrical component is identified on
the photograph by its circuit number.
Component and Wiring Color Code. Colored stripes or
dots on resistors and capacitors signify electrical values,
tolerances, etc., according to the EIA standard color code.
Components not color coded usually have the value printed
on the body,
The insulated wires used for interconnection in the
7A19 are color coded to facilitate tracing a wire from one
point to another in the unit.
Troubleshooting Equipment
The following equipment is useful for troubleshooting
the 7A19.
1. Semiconductor Tester—Some means of testing the
transistors and diodes, used in this instrument is helpful. A
transistor-curve tracer such as the TEKTRONIX Type 576
will give the most complete information.
2. DC Voltmeter and Ohmmeter—A voltmeter for
checking voltages within the circuit and an ohmmeter for
checking resistors and diodes is required.
3. Test Oscilloscope—A test oscilloscope is required to
view waveforms at different points in the circuit. A
TEKTRONIX 7000-Series Oscilloscope equipped with a
readout system, 7D13 Digital Multimeter unit, 7B-Series
Time-Base unit, and a 7A-Series Amplifier unit with a 10X
probe will meet the needs of both items 2 and 3.
4-1

Maintenance—7A19
4. Plug-in Extender—A fixture that permits operation of
the unit outside of the plug-in compartment for better
accessibility during troubleshooting. Order TEKTRONIX
Part No. 067-0616-00.
Troubleshooting Procedure
This troubleshooting procedure is arranged in an order
which checks the simple trouble possibilities before pro-
ceeding with extensive troubleshooting.
1. Check Control Settings. An incorrect setting of the
7A19 controls can indicate a trouble that does not exist. If
there is any question about the correct function or
operation of a control or front-panel connector, see
Section 2.
2. Check Associated Equipment. Before proceeding
with troubleshooting of the 7A19 check that the equip-
ment used with this instrument is operating correctly. If
possible, substitute an amplifier unit known to be operating
correctly into the indicator unit and see if the problem
persists. Check that the input signals are properly con-
nected and that the interconnecting cables are not
defective.
3. Visual Check. Visually check the portion of the
instrument in which the trouble is suspected. Many troubles
can be located by visual indications, such as unsoldered
connections, broken wires, damaged circuit boards, dam-
aged components, etc.
4. Check Instrument Performance. Check the calibration
of the unit, or the affected circuit by performing Perfor-
mance Checks of Section 5. The apparent trouble may only
be a result of mis-adjustment and may be corrected by
calibration.
5. Check Voltages. Often the defective component or
stage can be located by checking for the correct voltage in
the circuit. Typical voltages are given on the diagrams;
however, these are not absolute and may vary slightly
between instruments. To obtain operating conditions
similar to those used to take these readings, see the
instructions in the Diagrams section.
6. Check Individual Components. The following
methods are provided for checking the individual com-
ponents in the 7A19. Components which are soldered in
place are best checked by disconnecting one end to isolate
the measurement from the effects of surrounding circuitry.
4-2
A. TRANSISTORS AND INTEGRATED CIRCUITS.
The best check of transistor operation is actual perfor-
mance under operating conditions. If a semiconductor is
suspected of being defective, it can best be checked by
substituting a component known to be good; however, be
sure that circuit conditions are not such that a replacement
might also be damaged. If substitute transistors are not
available, use a dynamic tester (such as TEKTRONIX Type
576). Static-type testers may be used, but since they do not
check operation under simulated operating conditions,
some defects may go unnoticed. The schematic shows base
pin and socket arrangements of semiconductor devices. Be
sure the power is off before attempating to remove or
replace any semiconductor component.
Integrated circuits can be checked with a voltmeter, test
oscilloscope, or by direct substitution. A good under-
standing of the circuit description is essential to trouble-
shooting circuits using integrated circuits. Use care when
checking voltages and waveforms around the integrated
circuits so that adjacent leads are not shorted together.
B. DIODES. A diode can be checked for an open or for
a short circuit by measuring the resistance between termi-
nals with an ohmmeter set to the R X 1k scale. The diode
resistance should be very high in one direction and very low
when the meter leads are reversed. Do not check tunnel
diodes or back diodes with an ohmmeter.
CAUTION
Do not use an ohmmeter scale that has a high internal
current. High currents may damage the diodes.
C. RESISTORS. Check resistors with an ohmmeter.
Resistor tolerance is given in the Electrical Parts List.
Resistors normally do not need to be replaced unless the
measured value varies widely from the specified value.
D. CAPACITORS. A leaky or shorted capacitor can be
detected by checking resistance with an ohmmeter on the
highest scale. Use an ohmmeter which will not exceed the
voltage rating of the capacitor. The resistance reading
should be high after initial charge of the capacitor. An open
capacitor can best be detected with a capacitance meter, or
by checking whether the capacitor passes AC signals.
7. Repair and Readout the Circuit. Special techniques
required to replace components in this unit are given under
Component Replacement. Be sure to check the perfor-
mance of any circuit that has been repaired or that has had
any electrical components replaced. Recalibration of the
affected circuit may be necessary.
—
—

CORRECTIVE MAINTENANCE
General
Corrective maintenance consists of component replace-
ment and instrument repair. Special techniques required to
replace components in this instrument are given here.
Obtaining Replacement Parts
Standard Parts. All electrical and mechanical part re-
placements for the 7A19 can be obtained through your
local TEKTRONIX Field Office or representative. However,
many of the electronic components can be obtained locally
in less time than is required to order them from Tektronix,
Inc. Before purchasing or ordering replacement parts, check
the parts list for value, tolerance, rating and description.
NOTE
When selecting replacement parts, it is important to
remember that the physical size and shape of a
component may affect the performance of the
instrument, particularly at high frequencies. All re-
placement parts should be direct replacements unless
it is known that a different component will not
adversely affect instrument performance.
Special Parts. In addition to the standard electronic
components, some special parts are used in the 7A19. These
parts are manufactured or selected by Tektronix, Inc., in
accordance with our specifications. These special parts are
indicated in the parts list by an asterisk preceding the part
number. Most of the mechanical parts used in this
instrument have been manufactured by Tektronix, Inc.
Order all special parts directly from your local
TEKTRONIX Field Office or representative.
Ordering Parts. When ordering replacement parts from
Tektronix, Inc., include the following information:
1. Instrument Type.
2. Instrument Serial Number.
3. A description of the part (if electrical, include circuit
number).
4. TEKTRONIX Part Number.
Soldering Techniques
Disconnect the instrument from the power source
before soldering.
Maintenance—7A19
Circuit Boards. The components mounted on the circuit
boards in the 7A19 can be replaced using normal circuit
board soldering techniques. Keep the following points in
mind when soldering on the circuit board:
1. Use a pencil-type soldering iron with a wattage rating
from 15 to 50 watts.
2. Apply heat from the soldering iron to the junction
between the component and the circuit board.
3. Heat-shunt the lead to the component by means of a
pair of long-nose pliers.
4. Avoid excessive heating of the junction with the
circuit board, as this could separate the circuit board wiring
from the base material.
5. Use electronic grade 60-40 tin lead solder.
6. Clip off any excess lead length extending beyond the
circuit board. Clean off any residual flux with a flux-
removing solvent.
Metal Terminals. When soldering metal terminals
(potentiometers, etc.) use 60-40 tin lead solder and a 15 to
50 watt soldering iron. Observe the following precautions
when soldering metal terminals:
1. Apply only enough heat to make the solder flow
freely.
2. Apply only enough solder to form a solid connection.
Excess solder may impair the function of the part.
3. If a wire extends beyond the solder joint, clip off the
excess.
4. Clean the flux from the solder joint with a flux-
removing solvent.
Component Replacement
Disconnect the equipment from the power source
before replacing components.
4-3

Maintenance—7A19
Semiconductor Replacement. Transistors and integrated
circuits (IC’s) should not be replaced unless actually
defective if removed from their sockets during routine
maintenance, return them to their original sockets. Unnec-
essary replacement of semiconductors may affect the
calibration of this instrument. When semiconductors are
replaced, check the performance of the part of the
instrument which may be affected.
Replacement semiconductors should be of the original
type or a direct replacement. Lead configuration of the
semiconductors used in this instrument are shown on the
schematic diagrams. If the replacement semiconductor is
not .of the original type, check the manufacturer’s basing
diagram for proper basing.
TEKTRONIX Integrated Circuits. If it should become
necessary to replace the TEKTRONIX integrated circuits
U40 and U100 use the following procedures:
1. Remove the common heat sink (No. 64 in Fig. 1
EXPLODED of the Mechanical Parts List section).
2. Unsolder the two ground straps from either side of
the integrated circuit case and unplug the integrated circuit.
3. To install, align the tab of the integrated circuit with
the dot, marked on the circuit board. Then, making sure
pins are aligned with their sockets, gently push into the
socket.
NOTE
The leads of the integrated circuit are cut at the
factory to prevent the integrated circuit from resting
directly on the circuit board. Defeating this purpose
may allow the pin sockets to short against the
integrated circuit case. Solder the ground leads to the
case and replace the heat sink.
Inductor Replacement (L21, L22, L81, L82, L124,
L125). Inductors are replaced as a pair along with their
associated capacitor (e.g., L21, L22, and C20). The
inductors are formed by the leads of the capacitor, see Fig.
4-1. To replace a pair of inductors, proceed as follows:
=3/8"
ZL AN LLL
1243-01
Fig. 4-1. Inductor (“T”’ coil) replacement.
4-4
1, Remove the inductors and associated capacitor by
using a low wattage soldering iron and a vacuum type
desoldering device.
2. Insert the replacement capacitor on the circuit board
and bend the leads to form a loop approximately 3/8 inch
high.
3. Solder the capacitor and inductors to the circuit
board,
Replacement of any of the inductors will affect the high
frequency characteristics of the 7A19 and re-calibration
will be necessary.
REPACKAGING FOR SHIPMENT
If the Tektronix instrument is to be shipped to a Tektronix
Service Center for service or repair, attach a tag showing:
owner (with address) and the name of an individual at your
firm that can be contacted, complete instrument serial
number and a description of the service required.
Save and re-use the package in which your instrument was
shipped. If the original packaging is unfit for use or not
available, repackage the instrument as follows:
1. Obtain a carton of corrugated cardboard having inside
dimensions of no less than six inches more than the
instrument dimensions; this will allow for cushioning.
Refer to the following table for carton test strength
requirements.
2. Surround the instrument with polyethylene sheeting to
protect the finish of the instrument.
3. Cushion the instrument on all sides by tightly packing
dunnage or urethane foam between carton and instru-
ment, allowing three inches on all sides.
4. Seal carton with shipping tape or industrial stapler.
SHIPPING CARTON TEST STRENGTH
Gross Weight (Ib) Carton Test Strength (Ib)
0-10 200
10-30 275
30-120 375
120-140 500
140-160 600
REV. A, AUG. 1976
oat

Section 5—7A19
CALIBRATION
Introduction
To assure instrument accuracy, check the calibration of
the 7A19 every 1000 hours of operation or every six
months if used infrequently. Before complete calibration,
thoroughly clean and inspect this instrument as outlined in
the Maintenance section.
TEKTRONIX Field Service
Tektronix, Inc., provides complete instrument repair and
recalibration service at local Field Service Centers and the
Factory Service Center. Contact your local field office or
representative for further information.
Performance Check
The performance of this instrument can be checked by
performing only the J CHECK steps. Performing the steps
marked with a J indicates that the instrument is checked
against the tolerances listed as a Performance Requirement
(see Specification section).
Limits and tolerances given in other check steps are
calibration guides and should not be interpreted as instru-
ment specifications. Operator front-panel adjustments are
adjusted as part of the Performance Check procedure.
Calibration
To verify proper calibration of the 7A19 and to prevent
unnecessary re-calibration of the entire instrument, perform
the Adjust- portion of a step only if the tolerance given in
the Check- part of the step is not met.
For best overall instrument performance when _per-
forming a complete calibration procedure, make each
adjustment to the exact setting even if the Check- is within
allowable tolerance.
TEST EQUIPMENT REQUIRED
General
The following test equipment and accessories, or its
equivalent, is required for complete calibration of the
7A19. Specifications given for the test equipment are the
minimum necessary for accurate calibration. Therefore, the
specifications of any test equipment used must meet or
exceed the listed specifications. All test equipment is
assumed to be correctly calibrated and operating within the
listed specifications. Detailed operating instructions for the
test equipment are not given in this procedure. Refer to the
instruction manual for the test equipment if more infor-
mation is needed.
Special Calibration Fixtures
Special TEKTRONIX calibration fixtures are used in this
procedure only where they facilitate instrument calibration.
These special calibration fixtures are available from
Tektronix, Inc. Order by part number through your local
TEKTRONIX Field Office or representative.
Calibration Equipment Alternatives
All of the listed test equipment is required to completely
check and adjust this instrument. The Calibration pro-
cedure is based on the first item of equipment given as an
example of applicable equipment. When other equipment is
substituted, control settings or calibration setup may need
to be altered slightly to meet the requirements of the
substitute equipment. If the exact item of test equipment
given as an example in the Test Equipment list is not
available, first check the Specifications column carefully to
see if any other equipment is available which might suffice.
Then check the Usage column to see what this item of test
equipment is used for. If used for a check or adjustment
which is of little or no importance to your measurement
requirements, the item and corresponding step(s) can be
deleted.

Calibration—7A19
Test Equipment
Description
Minimum Specifications
Usage
Examples of Applicable
Test Equipment
1. Calibration
Oscilloscope
TEKTRONIX
7000-Series 500 MHz
bandwidth required for
complete procedure.
Used throughout the
procedures to provide
display.
a. TEKTRONIX 7904 oscilloscope.
2. Time Base Plug-
In Unit
TEKTRONIX 7B-Series
time base unit. 0.5 ns
sweep rate required for
complete procedure.
Used throughout
procedure to provide
sweep.
a. TEKTRONIX 7B92A Time Base unit.
3. Vertical Plug-In
Unit
TEKTRONIX 7A-Series
vertical plug-in unit.
Dual trace with 500 pV
per division sensitivity
required.
Used for Common
Mode Check/Adjust
(step 3) and Input
Resistance Adjust.
a. TEKTRONIX
Vertical Amplifier.
7A22 Dual Trace
4. Standard Amplitude Amplitude accuracy |Used for GAIN a. Tektronix PG 506 Calibration Gen-
Calibrator within 0.25%; range, |Check/Adjust only erator.’
50 mV to 2 V into (step 6).
50 Q frequency,
1 kHz.
5. Constant Amplitude Reference frequency, Used for Frequency a. SG 504 Leveled Sine Wave Gener-
Signal
Generator
less
than
10
MHz;
Response
Check
(step
ator.!
amplitude accuracy, 9).
within 1% of reference b. Wavetek 1002 Sweep/Signal Gener-
frequency; frequency ator.
range, to 500MHz;
amplitude range, c. General Radio 1362 UHF oscillator
80mV to 8V_ into with 1263-C Amplitude Regulating
502. supply.
6. Time Domain System rise time, Used for Reflection a. TEXTRONIX 7812 TDR/SAMPLER
Reflectometer 350 ps +35 ps; pulse Coefficient Check only plug-in unit with S-1 sampling head and
amplitude, 200 mV. (step 10). S-52 Pulse Generator head. (This system
Sensitivity, to 100 mp.
is to be used with the Calibration
Oscilloscope.)
7. Differental Sampling
System rise time, at Used for Rise Time and
a. Use the Time Domain Reflectometer
System least 350ps; pulse |Aberration Check/ system with the addition of a 7S11
amplitude, 200 mV; |Adjust only (step 8). vertical sampling plug-in and a S-1
Input, differential; sampling head.
sensitivity, 50 mV/div.
ACCESSORIES
8. Cable Impedance, 50 ohms; Used throughout a. TEKTRONIX Part No. 012-0057-01.
length, 42 inches; procedures for signal
connectors, BNC, connections.
9. GR Cable Impedance, 50 ohms Used for signal a. TEKTRONIX Part No. 017-0513-00.
+5%; length, 10 inches; connections during
connectors, GR. reflection coefficient
and HF aberrations.
‘Requires TM 500
5-2
- Series Power Module
REV B OCT 1979
——
¥

- Ss
Test Equipment (cont)
Calibration—7A19
Description Minimum Specifications Usage Examples of Applicable
Test Equipment
10.
GR
Cable
Impedance,
50
ohms
Used
during
reflection
.
TEKTRONIX
Part
No.
017-0515-00.
+5%; length, 20 inches; coefficient check for
connectors, GR. signal connection.
11. Adapter BNC male to GR. Used throughout pro- a. TEKTRONIX Part No. 017-0064-00.
cedures.
12. Adapter BNC female to GR. Used throughout pro- a. TEKTRONIX Part No. 017-0063-00.
cedures.
13. Adapter BNC “'T”. Used for common . TEKTRONIX Part No. 103-0030-00.
mode check/adjust.
14. Adapter BNC female to BNC |Used for common . TEKTRONIX Part No. 103-0028-00.
female. mode check/adjust.
15. Adapter SMA (3-mm) male to Used for reflection co- |a. TEKTRONIX Part No. 015-1007-00.
GR. efficient and risetime
and aberrations.
16. 50 Q Power Impedance, 50 ohms; Used for reflection co- . TEKTRONIX Part No. 017-0082-00.
Divider connectors, GR. efficient check.
17.
10X
Attenuator
Impedance,
50
ohms;
Used
for
frequency
re-
.
TEKTRONIX
Part
No.
017-0078-00.
accuracy, 2%; con- sponse check.
nectors, GR.
18. Plug-in Extender Rigid plug-in extender |Used throughout pro- . TEKTRONIX Part No. 067-0589-00.
for 7000-Series plug- cedures.
ins.
19. Plug-in Extender Flexible plug-in ex- |Used for risetime and . TEKTRONIX Part No. 067-0616-00.
tender for 7000-Series aberrations check/
plug-ins. adjust.
20. Signal Pick-off Signal pick-off connects |Used for common |a. TEKTRONIX Part No. 067-0655-00.
with GR adapters to the rear connector of |mode check/adjust, HF
7000-Series vertical |aberration check and
amplifiers for gaining | adjust.
access to signal and.
trigger lines.
CALIBRATION PROCEDURE
POSITION).
Internal adjustments and associated
equipment controls are initially capitalized only (e.g.,
General
The following procedure is arranged so that the 7A19
can be calibrated with the least interaction of adjustments
and re-connection of equipment. The control settings and
test equipment setup throughout this procedure continue
from the preceding step(s) unless otherwise noted. Refer to
Fig. 5-1 for location of adjustments.
NOTE
Control titles which are printed on the front panel of
the 7A19 are capitalized in this procedure (e.g.,
oscilloscope Vertical Mode).
Preliminary Procedure for Calibration
1. Remove the side panels of the plug-in.
2. Insert 7A19 with plug-in extender in the calibration
oscilloscope left vertical compartment.
3. Insert the time-base unit in the calibration oscillo-
scope B Horizontal compartment.
5-3

Calibration—7A19
Fig. 5-1. Location of Adjustments (7A19 shown).
4. Connect the oscilloscope to a suitable power source.
5. Turn the oscilloscope on and allow 20 minutes
warmup before proceeding. ‘
NOTE
This instrument should be calibrated at an ambient
temperature of +20°C to +30°C for best overall
accuracy. The performance of the instrument can be
checked at any temperature within the 0°C to +50°C
range.
Preliminary Control Settings
Set the calibration oscilloscope and 7A19 as follows:
Calibration Oscilloscope
Intensity Midrange
Focus Adjust for a well-
defined display
Control IIlum As desired
Grat Illum As desired
Vertical Mode Left
Trigger Source Left Vert
5-4
7A19
POSITION Center trace
POLARITY +UP
VOLTS/DIV 10 mV
Input Coupling GND
Index to Calibration Procedure
1. Trigger Balance Check/Adjust
2. Balance Check/Adjust
3. Common Mode Check/Adjust
4. Input Current Adjust
5. Temperature Compensation Adjust
/6. GAIN Check/Adjust
/7. Input Resistance Adjust, Input Current Check
8. Aberration Check/Adjust
/9. Frequency Response Check
/10. Reflection Coefficient Check
REV. A, MAR. 1978
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