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
.

Introduction
CIRCUIT
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 50 S2 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 10 mV 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
InputCoupling
Attenuator
Delay Lines
Section 3---7A19
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 52 resistors reduces
the inductance associated with
the resistors so that the
combination will remain
50 92
for
all frequencies within the
limits
of
this plug-in
.
Connected in a similar mannerand 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
100 2 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 .95 k2 and the input to the Attenuator is 50 2, the
PRE-CHG position will act as a X100 attenuator .
The effective overall deflection factor of the 7A19 is
determined by the setting of the VOLTS/DIV switch, S135
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 .
Unless Variable Delay Option 4 is requested, all 7A19's
are equipped with a
Fixed
Delay Line
consisting
of a
precision length of 50 S2 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 Q76 . The current through R74 is set by the current
generator Q73 and Gain control R73 . As the thermal
resistor R74 changes with temperature so will the voltage at
the collector of Q73 ; 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 Q56 is set by R66 . In the
20 mV position the gain of 056 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 Q50 . 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 POLAR ITY
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 .

Introduction
General
Cleaning
Lubrication
General
TROUBLESHOOTING
M
PREVENTIVE MAINTENANCE
NT
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, 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 .
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 .
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 .
The following is provided to augment information
contained in other sections of this manual when trouble-
shooting the 7A19 . The schematic diagrams,
circuit descrip-
N N
Section 4--7A19
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 7A 19 .
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 .

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 1 k 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 .
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 ohmmeteron 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 .

General
CORRECTIVE MAINTENANCE
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 .
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 .
NO TE
2 . Instrument Serial Number .
3 . A description of the part (if electrical, include circuit
number) .
4 .
TEKTRONIX
Part Number .
Soldering Techniques
IN
ARNING
_
Disconnect the instrument from the power source
before soldering .
Maintenance-7A19
Circuit Boards . 1`he 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
WARNING . . . ,
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 shownon 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 unplugthe
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 .
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 :
Fig . 4-1 . Inductor ("T"
coil) replacement .
4-4
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 .
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 .
Saveand re-usethe package in which your instrumentwas
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 instrumentwith polyethylene sheeting
to
protect the finish of the instrument .
3 .
Cushion
the instrumenton all sides by tightly packing
dunnage or urethane
foambetween carton and instru-
ment, allowing three inches on all sides .
4 . Seal carton with shipping tape or industrial stapler .
SHIPPING CARTON TEST STRENGTH
REV .
A, AUG . 1976
Gross Weight (lb) Carton
Test
Strength
(lb)
0-10 200
10-30 275
30-120 375
120-140 500
140-160 600

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 \/ CHECK
steps . Performing the steps
marked with a \/ 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 .
General
TEST EQUIPMENT
REQUIRED
Section 5---7A19
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 .

2 . Time Base Plug-
In Unit
3 . Vertical Plug-In
Unit
4 .
Standard Amplitude
Calibrator
5 . Constant
Amplitude
Signal
Generator
6 . TimeDomain
Ref
lectometer
7 .
Differental Sampling
System
ACCESSORIES
8 . Cable
9 . GR Cable
5- 2
TEKTRONIX
7B-Series
time base unit . 0 .5
ns
sweep rate required
for
complete procedure
.
EKTRONIX
7A-Series
vertical plug-in
unit .
Dual trace
with 500 pV
per division
sensitivity
'Requires TM
500 - Series Power Module
required .
Amplitude
accuracy
within 0
.2_5%
;
range,
60 mV

to

2 V

into
50 S2 ;

frequency,
1 kHz .
Reference
frequency,
less than
10 MHz ;
amplitude
accuracy,
within
1% of reference
frequency ; frequency
range,

to

500 MHz ;
amplitude range,
80 mV

to

8 V

into
50 S2 .
System
rise time,
350 ps

±35 ps ;

pulse
amplitude,

200 mV .
Sensitivity, to
100 mp .
System rise
time, at
least

350 ps ;

pulse
amplitude,

200 mV ;
Input,
differential ;
sensitivity, 50 mV/div .
Impedance,
50 ohms ;
length,
42 inches ;
connectors,
BNC .
Impedance,
50 ohms
t5% ;
length, 10 inches ;
connectors, GR .
Used throughout
procedure to provide
sweep .
Used for Common
Mode Check/Adjust
(step 3) and I nput
Resistance Adjust .
------------ - -
Used for GAIN
Check/Adjust only
(step 6) .
Used for Frequency
Response Check (step
9) .
Used for Reflection
Coefficient
Check only
(step 10) .
Used
for Rise Time and
Aberration Check /
Adjust
only (step 8) .
Used
throughout
procedures
for signal
connections
.
Used
for signal
connections
during
reflection coefficient
and HF aberrations .
Examples of Applicable
Test Equipment
a . TEKTRONIX 7904 oscilloscope
.
a
.
TEKTRONIX 7B92A Time Base unit .
a .
TEKTRONIX

7A22 Dual Trace
Vertical Amplifier .
a .
Tektronix PG 506 Calibration Gen-
erator .)

., . . ."
.
,
a . SG 504 Leveled Sine Wave
Gener-
ator,
l--
.
.
b . Wavetek 1002
Sweep/Signal Gener-
ator .
c . General Radio 1362
UHF oscillator
with 1263-C
Amplitude Regulating
supply .
a . TEKTRONIX 7512 TDR/SAMPLER
plug-in unit with S-1 sampling
head and
S-52 Pulse Generator head
. (This system
is to be used with the
Calibration
Oscilloscope .)
a . Use the Time Domain
Reflectometer
system with the addition of
a 7S11
vertical sampling plug-in
and a S-1
sampling head .
a . TEKTRONIX Part No .
012-0057-01 .
a . TEKTRONIX
Part No . 017-0513-00 .
REV . A, MAR . 1978
Calibration-7A19
Test Equipment
Description
Minimum Specifications 1
Usage
1 . Calibration
T E K T R O N
I X Used throughout the
Oscilloscope
7000-Series 500
MHz procedures to provide
bandwidth required
for display .
complete
procedure .

20 . Signal ' Pick-off
with GR adapters
General
---------- --
Impedance, 50 ohms ;
connectors, GR .
Impedance, 50 - ohms ;
accuracy, ±2% ;

con-
nectors, GR .
Rigid plug-in extender
for 7000-Series plug-
ins .
- - --------------- ----
Flexible plug-in ex-
tender for 7000-Series
plug-ins,
Signal pick-off connects
to the rear connector of
7000-Series vertical
amplifiers
for gaining
access to signal and
trigger lines .
CALIBRATION PROCEDURE
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
'Test Equipment (cont)
Minimum Specifications

Usage
Y
Impedance, 50 ohms
±5%
;
length, 20 inches ;
connectors, GR .
BNC male to

_ . .^,-_ . . .
Control titles which are printed
on
the
front panel of
the 7A 19 are capitalized in this procedure
(e .g .,
Used during reflection
coefficient check for
signal connection .
Used
- throughout

pro-
cedures .
Used Y~ for
_, .

common
mode check/adjust .
Used for common
mode check/adjust .
~Used .~ for u reflection co-
efficient and risetime
and
aberrations .
Used for reflection co-
efficient check .
Used for risetime and
a berrations check/
adjust
.
Used

' for

common
mode check/adjust, HF
aberration check and
adjust .
Examples of Applicable
Test Equipment
Calibration---7A19
. TEKTRONIX Part No . 017-0515-00 .
a . TEKTRONIX Part No . 017-0063-00 .
. TEKTRONIX Part - No .
103-0030-00
.
w
. TEKTRONIX Part No . 017-0078-00 .
a . _ TEKTRONIX Part No . 067-0616-00 . '
i . TEKTRONIX
Part No . - 067-0655-00 . ^
POSITION) . Internal adjustments and associated
equipment controls are initially capitalized only (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
5- 4
NOTE
Preliminary Control Settings
Trigger
Balance
4 . Connect the oscilloscope to a suitable power source .
Turn the oscilloscope
on and allow - 20 m
. . .
_inute
.s ___ --
warmup b efar_e_proc
eedinq .
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 .
Set the calibration oscilloscope and 7A19 as follows :
Fig . 5-1 . Location of Adjustments
17A19 shown) .
7A19
POSITION

Center trace
POLARITY
+UP
VOLTS/DIV

10 mV
Input Coupling

GND
Index to Calibration Procedure
1243-02
1 . Trigger Balance Check/Adjust
2 . Balance Check/Adjust
3 .
Common
Mode
Check/Adjust
4 . Input CurrentAdjust
5 . Temperature
Compensation Adjust
REV . A, MAR . 1978
-,/6 . GAIN
Check/Adjust
Calibration
Oscilloscope
Intensity
Midrange ,,/7 . Input
Resistance Adjust, Input Current Check
Focus
Adjust for a well-
defined display
8 .
Aberration Check/Adjust
Control I Ilum As desired
Grat Illum As desired
\/9 . Frequency Response Check
Vertical Mode Left
Trigger Source Left Vert
N/10 . Reflection Coefficient Check