Tektronix 7A29 User manual

Tektronix
COMMITTED TO EXCELLENCE
Tektronix. Inc.
P.O. Box 500
Beaverton. Oregon 97077
7A29
AMPLIFIER
WITH OPTIONS
INSTRUCTION MANUAL
070-2320 00 Firsi Printing APRIL 1979

Copyright i9'/9 Tektronix, inc. All rights reserved.
Contents of this purification may not be reproduced in any
form without tne written permission of Tektronix, Inc.
«/jL7fav*w Sr *wf jy Ip /* •/ 9
Products o! Tektronix me. and its subsidiaries -are
covered by U.S. anc foreign patents and/or pending
patents.
TEKTRONIX, TEK, SCOPE-MOBILE, and WsS are reg-
istered trademarks of Tektronix, Inc. TF.LEQU1PMENT is
aregistered trademark of Tektronix U.K. Limited.
Printed in U.S.A. Specification and price change
privileges are reserved.

7A29 Instruction
TABLE OF CONTENTS
PAGE
LIST OF ILLUSTRATIONS iii
LIST OF TABLES in
OPERATORS SAFETY SUMMARY iv
SERVICE SAFETY SUMMARY v
SECTION 1GENERAL INFORMATION
INTRODUCTION 1-1
INSTALLATION 1-1
INITIAL INSPECTION 1-1
OPERATING INFORMATION 1-1
OPERATING TEMPERATURE 1-2
PACKAGING FOR SHIPMENT 1-2
SPECIFICATIONS 1-2
STANDARD ACCESSORIES 1-6
RECOMMENDED ACCESSORIES 1-6
PROBES 1-6
SECTION 2OPERATING INSTRUCTIONS
CONTROLS AND CONNECTORS 2-1
CHECKOUT PROCEDURE 2-1
BEFORE YOU BEGIN 2-1
TEST EQUIPMENT REQUIRED 2-1
SETUP PROCEDURE 2-1
AMPLIFIER FUNCTIONS 2-3
DETAILED OPERATING INFORMATION 2-4
PROBES 2-4
VERTICAL GAIN CHECK AND
ADJUSTMENT 2-4
INPUT COUPLING 2-4
VOLTS/DIV SWITCH 2-5
POLARITY SWITCH 2-5
TRACE IDENTIFICATION AND
READOUT FUNCTIONS 2-5
VARIABLF DELAY (OPTION 4) 2-5
MATCHING DELAY TIMES USING TWO
7A29 UNITS. ONE HAVING VARIABLE
DELAY (OPTION 4) 2-5
THE REMAINING PORTION OF THIS TABLE OF
CONTENTS LISTS THE SERVICING INSTRUCTIONS.
THESE SERVICING INSTRUCTIONS ARE FOR USE
BY QUALIFIED PERSONNEL ONLY. TO AVOID
ELECTRICAL SHOCK, DO NOT PERFORM ANY
SERVICING OTHER THAN THAT CAl LEO OUT IN THE
OPERATING INSTRUCTIONS UNLESS QUALIFIED
TO DO SO.
PAGE
SECTION 3THEORY OF OPERATION
BLOCK DIAGRAM 3-1
DETAILED CIRCUIT OPERATION 3-1
INPUT SWITCHING AND READOUT 3-3
DELAY LINE 3-3
AC-OFF DC 3-3
INPUT ATTENUATORS 3-3
INPUT PROTECTION 3-3
POWER SUPPLIES 3-3
READOUT SWITCHING 3-3
INPUT AMPLIFIER 34
FAST OVERLOAD PROTECTION 3-4
FEEDBESIDE 3-4
INPUT AMPLIFIER 3-4
POSITION 3-5
TRIGGER AND OUTPUT AMPLIFIER 3-6
OUTPUT AMPLIFIER 3-6
TRIGGER AMPLIFIER 3-6
SECTION 4MAINTENANCE
PREVENTIVE MAINTENANCE 4-1
CLEANING 4-1
EXTERIOR 4-1
INTERIOR 4-1
VISUAL INSPECTION 4-1
PERIODIC ELECTRICAL ADJUSTMENT 4-2
SEMICONDUCTOR CHECKS 4-2
TROUBLESHOOTING 4-2
TROUBLESHOOTING AIDS 4-2
DIAGRAMS 4-2
CIRCUIT BOARD ILLUSTRATIONS 4-2
TROUBLESHOOTING CHART 4-2
TEST POINT AND ADJUSTMENT
LOCATIONS 4-2
COMPONENT COLOR CODING 4-2
SEMICONDUCTOR LEAD CONFIGURATIONS 4-5
WIRING COLOR CODE 4-5
INTER BOARD PIN CONNECTOR
IDENTIFICATION 4-5
MULTI-PIN CONNECTOR IDENTIFICATION 4-5
INTERFACE CONNECTOR PIN LOCATIONS 4-5
TROUBLESHOOTING EQUIPMENT 4-6
TROUBLESHOOTING TECHNIQUES 46
1CHECK CONTROL SETTINGS 4-6
2CHECK ASSOCIATED EQUIPMENT 4-6
3. VISUAL CHECK 4-6
4CHECK INSTRUMENT ADJUSTMENT 4-6
5ISOLATE TROUBLE TO ACIRCUIT 4-6
6CHECK VOLTAGES AND WAVEFORMS 4-7
7CHECK INDIVIDUAL COMPONENTS 4-7
8REPAIR AND ADJUST THE CIRCUIT 4-7
I

7A29 Instruction
TABLE OF CONTENTS (CONT.)
PAGE
CORRECTIVE MAINTENANCE 4-8
OBTAINING REPLACEMEN1 PARTS 48
SOLDERING TECHNIQUES 4-8
COMPONENT REMOVAL AND REPLACEMENT 4-9
OPTION 4VARIABLE DELAY LINE 4-9
CIRCUIT BOARDS 4-9
AC-OFF-DC SWITCH 410
INPUT ATTENUATORS 4-11
SEMICONDUCTORS 4-14
INTEGRATED CIRCUITS 414
INTERCONNECTING METHODS 4-15
COAXIAL END-LEAD CONNECTOR
(PELTOLA CONNECTOR) 4-16
END-LEAD PIN CONNECTOR (P220) 4-16
MULTIPLE END LEAD PIN CONNECTOR
(HARMONICA CONNECTOR) 4-16
INTERBOARD MULTI-PIN CONNECTOR
(COMB CONNECTOR. J70) 4-16
CIRCUIT BOARD PINS 4-16
FRONT PANEL RESET LIGHT 4-17
ADJUSTMENT AFTER REPAIR 4-17
SECTION 5CALIBRATION
USING THESE PROCEDURES 5-2
PERFORMANCE CHECK SUMMARY 5-2
ADJUSTMENT INTERVAL 5-5
TEKTRONIX FIELD SERVICE 5-5
TEST EQUIPMENT REQUIRED 5-5
SPECIAL FIXTURES 5-5
TEST EQUIPMENT ALTERNATIVES 5-5
PAGE
PART I- PERFORMANCE CHECK 58
INDEX TO PART I—PERFORMANCE CHECK 5-8
PERFORMANCE CHECK POWER-UP SEQUENCE ... 5 8
ALOW FREQUENCY 5-9
BHIGH FREQUENCY 5-14
CINPUT PROTECTION 5-18
PART II ADJUSTMENT AND PERFORMANCE
CHECK 521
INDEX TO PART II—ADJUSTMENT
AND PERFORMANCE CHECK 5-21
ADJUSTMENT AND PERFORMANCE CHECK
POWER-UP SEQUENCE 5-21
ALOW FREQUENCY 5-22
BHIGH FREQUENCY 5-29
C. INPUT PROTECTION 5-36
SECTION 6INSTRUMENT OPTIONS
SECTION 7REPLACEABLE ELECTRICAL PARTS
SECTION 8DIAGRAMS AND CIRCUIT BOARD
ILLUSTRATIONS
SECTION 9REPLACEABLE MECHANICAL PARTS
CHANGE INFORMATION
ii

7A29 Instruction
LIST OF ILLUSTRATIONS
FIGURE
NO. PAGE
7A29 Features vi
1-1 VARIABLE (Volts/Div) control effects on
bandwidth 1-4
1-2 Maximum rms input voltage 1-5
1-
37A29 dimensional drawing 1-7
2-
1Front-panel controls, connectors and
indicators 2-2
3-
1Basic block diagram of the 7A29 Amplifier 3-2
4-
1Color code for resistors 4-3
4-2 Semiconductor lead configurations 4-4
4-3 Inter board multi-pin connector assembly 4-5
4-4 Orientation of multi-connector holders 4-5
4-5 Location of pin numbers on interface
connector 4-6
4-6 HYPCON connector assembly 4-12
4-7 Coaxial end-lead connector assembly 4-15
FIGURE
NO. PAGE
4 8 Exploded view of circuit-board pin and
ferrule 4-16
4-9 Front-panel light socket assembly 4 17
The illustrations in section 8are located near their associated
diagrams on the foldout page.
8-1 Semiconductor Lead Configurations
8-2 Circuit Board Locations.
8-3 Al-Mam circuit board assembly
8-4 A3-Readout Switching circuit board assembly
8-5 Al-Mam circuit board assembly.
8-6 A2-High Frequency circuit board assembly
8-7 Al -Mam circuit board assembly
8-8 A2-High Frequency circuit board assembly
8-9 7A29 Troubleshooting Chart
8-10 Test Point &Adjustment Locations
LIST OF TABLES
TABLE
NO. PAGE
1-1 Electrical Characteristics 1-2
1-2 Environmental Characteristics 1-5
1-3 Physical Characteristics 1-6
4-
1Attenuator Fault Location 4-11
5-
1Calibration Procedure Electives 5-1
5-2 Performance Check Summary 5-2
5-3 Test Equipment 5-5
5-4 Vertical Deflection Accuracy 5-11
5-5 Control Settings for Low-Frequency
Step Response 5-12
5-6 1GHz Gain 5-15
5-7 Vertical Deflection Accuracy 5-26
5-8 Control Settings for Low-Frequency
Step Response 5-27
5-
9Vertical Amplifier Frequency Gain 5-33
6-
1Option Information Locator 6-1

7A29 Instruction
OPERATORS SAFETY INFORMATION
The following general safety information applies to all operators and service personnel Specific warnings and cautions
will be found throughout the manual where they apply and should be followed in each instance
WARNING statements identify conditions or practices which could result in personal injury or loss of life
CAUTION statements identify conditions or practices which could result in damage to the equipment or other property.
WARNING
GROUND THE INSTRUMENT
To reduce electrical-shock hazard, the mainframe Ioscilloscope)chassis must be properly grounded. Refer to
the mainframe manual for grounding information.
DO NOT REMOVE INSTRUMENT COVERS
To avoid electric-shock hazard, operating personnel must not remove the protective instrument covers.
Component replacement and internal adjustments must be made by qualified service personnel only.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERE
To avoid explosion, do not operate this instrument in an explosive atmosphere unless it has been certified for
such operation.
;CAUTION <
PREVENT INSTRUMENT DAMAGE
To prevent instrument damage, plug in units should not be installed or removed without first turning off the
mainframe power
IV

7A29 Instruction
SERVICE SAFETY INFORMATION
FOR QUALIFIED SERVICE PERSONNEL ONLY
The following are safety precautions which appear in the service information sections of this manual This Service Safety
Information is in addition to the Operators Safety Information given previously.
WARNING
DO NOT SERVICE ALONE
Do not attempt internal service or adjustment unless another person, capable of rendering first aid and
resuscitation, is present.
DISCONNECT INSTRUMENT POWER
To avoid electrical shock hazard, disconnect the instrument horn the power source before removing
protective panels, soldering, or replacing components
'CAUTION \
N^
AVOID EXCESSIVE MOISTURE
Circuit boards and components must be dry before applying power to prevent damage from electrical arcing.
Pins 2and 3of U246 and U266 are especially sensitive to moisture. Excessive moisture in this area of the
circuit board will cause the trace to wander irregularly and possibly leave the screen area
EXERCISE CARE WHEN SOLDERING
The Main Amplifier circuit board is amultilayer type with two identical conductive paths laminated between
the top and bottom board layers. All soldering on this board should be done with care to prevent breaking the
connections to the center conductors. Only experienced maintenance personnel should attempt repair of any
circuit board
USE PROPER CLEANING AGENTS
Avoid the use of chemical cleaning agents which might damage the plastics used in this instrument. Use a
nonresidue type of cleaner, preferably isopropyl alcohol, totally denatured ethyl alcohol, or afluorinated
solvent fie trifluorotrichloroethane). such as Freon TF cleaner or Spray-On U2002 Before using any other
type of cleaner, consult your Tektronix Service Center or representative.
DO NOT USE PIN SOCKETS FOR CONNECTION POINTS
The spring tension of the pm sockets ensures agood connection between the circuit board and the pin. This
spring tension can be destroyed by using the pin sockets as aconnecting point for spring loaded probe tips,
alligator clips, etc.
v

7A29 Instruction
7A29 7A29
OPTION 4INSTRUMENT STANDARD INSTRUMENT
2320 2
7A29 FEATURES
The 7A29 is awide-bandwidth Amplifier Plug-In Unit designed primarily for use in vertical compartments of the 7000-
Series Oscilloscopes The input is 50-ohm impedance with selectable DC or AC coupling and automatic overload
disconnect. Seven calibrated deflection factors. VARIABLE deflection factor and polarity INVERT selections are provided
Readout encoding provides for deflection factor readout including coded probes, uncalibrated indication, polarity INVERT
and IDENTIFY functions. AVariable Signal Delay of +0.5 ns is available with the Option 4instrument

Section 1—7A29
GENERAL INFORMATION
INTRODUCTION
The Instruction Manual is divided into the following main
sections:
Section 1—General Information contains instrument
description, electrical specifications, environmental
characteristics, standard and recommended
accessories, installation, and packaging for shipment
instructions
Section 2Operating Instructions contains
information relative to operating and checking the
instrument operation.
WARNING
THE REMAINING PORTIONS OF THIS
INSTRUCTION MANUAL CONTAIN SERVIC-
ING INSTRUCTIONS THESE SERVICING
INSTRUCTIONS ARE FOR USE BY QUALIFIED
SERVICE PERSONNEL ONLY. TO AVOID
ELECTRIC SHOCK OR OTHER PERSONAL
INJURY. DO NOT PERFORM ANY SERVICING
OTHER THAN THAT DESCRIBED IN THE
OPERATING INSTRUCTIONS UNLESS YOU
ARE QUALIFIED TO DO SO.
Section 3—Theory of Operation contains basic and
general circuit analysis that may be useful for
servicing or operating the instrument.
Section 4Maintenance describes routine and
corrective maintenance procedures with detailed
instructions for replacing assemblies, subassemblies,
and individual components
Section 5~Calibration contains procedures to check
the operational performance and electrical
characteristics of the instrument Procedures also
include methods for adjustment of the instrument to
meet specifications.
Section 6- Instrument Options contains adescription
of available options and locations of incorporated
information for those options.
Section 7Replaceable Electrical Parts contains
information necessary to order replaceable parts and
assemblies related to the electrical functions of the
instrument.
Section 8— Diagrams and Circuit Board Illustrations
includes detailed circuit schematics, locations of
assembled boards within the instrument, voltage and
waveform information, circuit board component
locators, and locations of adjustments to aid in
performing the Adjustment and Performance Check
portions of the Calibration procedure.
Section 9Replaceable Mechanical Parts includes
information necessary to order replaceable
mechanical parts and shows exploded drawings which
identify assemblies.
INSTALLATION
INITIAL INSPECTION
Dangerous voltages exist inside the
instrument To avoid electrical-shock hazards,
operating personnel must not remove
protective instrument covers. Component
replacement and internal adjustments must
be made by qualified service personnel only.
This instrument was inspected both mechanically and
electrically before shipment from the factory and it
should be free of mars or scratches and should meet or
exceed all electrical specifications To confirm this,
inspect the instrument for physical damage incurred in
transit. Test the electrical performance by following the
Operators Checkout Procedure in section 2and then
refer qualified service personnel to the Performance
Check Procedure in this Instruction Manual If there is
damage or deficiency, contact your local Tektronix Field
Office or representative.
OPERATING INFORMATION
'CAUTION '
lo prevent instrument damage, plug in units
should not be installed or removed without
first turning off the mainframe power
The 7A29 is calibrated and ready for use as received It
can be installed in any compartment of Tektronix 7000-
series oscilloscopes, but is intended principally for use in
vertical plug-in compartments. To install, align the upper
and lower rails of the 7A29 with the oscilloscope tracks
and insert. The 7A29 front panel will be flush with the
1-1

General Information—7A29
front of the oscilloscope and the latch at the bottom left
corner of the 7A29 will be in place against the front
panel when the 7A29 is fully installed
To remove the 7A29. pull on the release latch (inscribed
with the unit identification "7A29") and the 7A29 will
unlatch Continue pulling to slide the 7A29 out of the
oscilloscope.
OPERATING TEMPERATURE
The 7A29 can be operated where the ambient air
temperature is between 0° and *50° Cand can be stored
in ambient temperatures from -55° to *75° C. After
storage at temperatures outside the operating limits,
allow the chassis temperature to reach asafe operating
temperature before applying power
PACKAGING FOR SHIPMENT
If this instrument is to be shipped for long distances by
commercial transportation, we recommend that the
instrument be packaged in the original manner The
carton and packaging material in which your instrument
was shipped should be saved for this purpose
If this instrument is to be shipped to aTektronix Service
Center for service or repair, attach atag to the
instrument showing the following: Owner of the
instrument (with address), the name of the person at
your firm who can be contacted, complete instrument
type and serial number, and adescription of the service
required
If the original packaging is unfit for use or not available,
package the instrument as follows
1Obtain acorrugated cardboard carton with at least a
200-pound test strength and dimensions at least six
inches larger than the instrument's dimensions
2Surround the instrument with polyethylene sheeting,
or equivalent, to protect the instrument
3Allow a3inch cushion on all sides by tightly packing
dunnage or urethane foam between the carton and the
instrument
4Seal the carton with shipping tape or with an
industrial stapler.
5Mark the address of the Tektronix Service Center and
your return address in one or more prominent locations
on the exterior of the shipping carton.
SPECIFICATIONS
The electrical characteristics listed in Table 1-1 apply when the following conditions are met (1) Adjustment of the
instrument must have taken place at an ambient temperature between +20° Cand +30° C. (2) the instrument must be
allowed a30-minute warm-up period, and (3) all specifications are valid at an ambient temperature of 0° to +50° C.
unless otherwise stated
TABLE 1-1
Electrical Characteristics
Characteristics Performance Requirement
Deflection Factor
Calibrated Range From 10 mV/div to 1V/div in 7switch positions using a
1-2-5 switching sequence.
Attenuator Accuracy All deflection factors within 2% with gain adjusted at
0.1 VOLTS/DIV when driven from a50 0source.
VARIABLE (VOLTS/DIV) Range At least 2.5:1 .See Figure 1-1 for effect on bandwidth
GAIN Range Adjustable to at least 3% from nominal at 01V/div.
1-2

General Information— 7A29
TABLE 1-1 (CONT.)
Electrical Characteristics
Characteristic Performance Requirement
Frequency Response (10 mV/DIV to 1V/DIV)
High Frequency, AC or DC Coupled When operated in the vertical compartment of the following
oscilloscope series 7100, 1GHz (0° to 35° C); 7900, 500 MHz
(0° to 30° C); 7800, 400 MHz (0° to 35° C); 7700, 175 MHz;
7600, 100 MHz. 7300, 25 MHz
NOTE
Use of the VARIABLE /Volts/Div) control affects
frequency response See Figure 1-1.
Low Frequency, AC Coupled 1kHz or less from a50 Osource; 200 Hz or less with a
10X 50 0probe
Maximum Input
DC Coupled 10 Vrms or 1-watt-second pulses not exceeding 50 Vpeak.
See Figure 1-2, and Detailed Operating Information, section 2.
AC Coupled 100 Vadditional dc component. Derate linearly to 0V
additional at 60 Hz
'CAUTION <
Signals of more than 50 Vpeak amplitude must be
connected with input switch in OFF position so that
input coupling capacitor is precharged.
Input Protection Disconnect Threshold 10 Vdc within 2Vdc. -10 Vdc within 2Vdc, or approximately
10Vrms up to 100 MHz
Input Protection Disconnect Time Less than 30 ms for 50 Vdc of either polarity. 40 ms to 150 ms
for 25 Vdc of either polarity.
Input Impedance
Resistance Dc coupled; 50 Owithin 1Cl Ac coupled: 50 0within 1O
in series with at least 16pf
Reflection Coefficient 0 05 or less in a1GHz +20% time domain reflectometer system.
VSWR (Except Option 4)
DC Coupled 1.4:1 at 10 mVOLTS/DIV 1.20:1 from 20 mVOLTS/DIV to
1VOLTS/DIV; dc to 1GHz.
AC Coupled 1.4 1at 10 mVOLTS/DIV. 1.20:1 from 20 mVOLTS/DIV to
1VOLTS/DIV; 1MHz to 1GHz
VSWR (Option 4)
DC Coupled 1.5:1 dc to 800 MHz
AC Coupled 1.5:1. 1MHz to 800 MHz.
Input Offset Current 50 pfk or less.
VARIABLE (VOLTS/DIV) Balance 0.2 div maximum trace shift.
1-3

General Information— 7A29
Characteristic
P0LARI1Y Balance
IDENTIFY
POSITION Range
DC Drift
Drift With Ambient Temperature
(Line Voltage Constant)
Delay Range (Option 4only)
Figure 1-1. VARIABLE (Voits/Div) control effect on bandwidth.
1-4

General Information—7A29
01 SEC 1SEC 1SEC
DURATION
2320-7
Figure 1-2. Maximum rms input voltage.
TABLE 1-2
Environmental Characteristics
Characteristic Performance Requirement
Temperature
Calibration +20° to +30°C (+68° to *86° F).
Operating 0° to 50° C(+32° to *122° F).
Storage -55° to *75° C(-67° to +167° F).
Altitude
Operating To 15.000 feet.
Storage To 50.000 feet
Transportation Qualified under National Safe Transit Committee Test
Procedure 1A, Category II.
1-5

General Information—7A29
TABLE 1-3
Physical Characteristics
Characteristic Performance Requirement
Overall Dimensions Compatible with all 7000-series plug-in compartments;
see Figure 1-3. for dimensional drawing
Net Weight
Standard Instrument Approximately 2lbs 8oz. (1.14 kg)
Option 4Instrument Approximately 3lbs 4oz. (1 .48 kg).
STANDARD ACCESSORIES
1ea Instruction Manual
RECOMMENDED ACCESSORIES
The following accessories have been selected from our
catalog specifically for your instrument. They are listed as
aconvenience to help you meet your measurement
needs For detailed information and prices, refer to a
Tektronix Products Catalog or contact your local Tektronix
Field Representative.
PROBES
P6056
The P6056 is apassive 10X attenuating probe with a
bandwidth of dc to 3.5 gigahertz, and a500 ohm input
resistance for use with 50 ohm inputs.
P6057
The P6057 is apassive 100X attenuating probe with a
bandwidth of dc to 14gigahertz and a5kilohm input
resistance for use with 50 ohm inputs.
P6201
The P6201 is an active (FET) nonattenuating probe
with abandwidth from dc to 900 megahertz, an input
impedance of 100 kilohms and 3picofarads (1
megohm and 1.5 picofarads with 10X and 100X
attenuating heads).
1-6

OVERALL
DIMENSIONS
(MEASURED
AT
MAXIMUM
POINTS*

Section 2—7A29
OPERATING INSTRUCTIONS
To use the 7A29 effectively, 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
CONTROLS AND CONNECTORS
CAUTION <
Before applying any signal in excess of 10
volts to the 7A29. refer to Detailed Operating
Information given later in this section of the
manual.
The 7A29 front panel is shown in Figure 2-1 Abrief,
functional description of each control and connector is
included in the illustration. Refer to Detailed Operating
Information for additional information
17000 series oscilloscope mainframe (e g7104, 7904,
or 7704A).
27B-series time base unit (e g7B10, 7B15, 7B80. or
7B85).
3. One bnc cable: 50-ohm coaxial. Tektronix Part 012-
0057-01
SETUP PROCEDURE
1With the 7000-series oscilloscope power switch in the
off position, connect the oscilloscope to asuitable power
source.
CHECKOUT PROCEDURE 2Install the 7A29 in the left vertical compartment
The following procedure can be used for incoming
inspection to verify proper operation, and may also be
used by the operator for instrument familiarization. Only
instrument functions (not measurement quantities or
specifications) are checked in the procedure, therefore, a
minimum amount of test equipment is required If
performing the Checkout Procedure reveals improper
performance or instrument malfunction, first check the
operation of associated equipment; then refer to qualified
service personnel for repair or adjustment of the
instrument.
NOTE
Refer qualified service personnel to the
Calibration section of this manual tor the
procedure to check the Option 4VARIABLE
DELAY control.
BEFORE YOU BEGIN:
Refer to the Change Information at the rear of this
manual for any modifications which may affect this
procedure.
3. Install the 7B-series time-base unit in the Bhorizontal
compartment.
4Set the front-panel controls as follows:
7A29 AMPLIFIER
VOLTS/DIV 0.1 V
VARIABLE (Volts/Div) CAL IN
POSITION Midrange
POLARITY +UP
AC-OFF DC OFF
Time-Base Unit:
Time/Div 1ms
Position Midrange
Magnifier XI
Triggering
Mode Auto
External Trigger In In
Coupling AC
Source Internal
TEST EQUIPMENT REQUIRED
The following test equipment was used in preparing the
Operators Checkout Procedure Other test equipment
which meets these requirements may be substituted
When other equipment is substituted, the control
settings or setup may need to be altered
Oscilloscope
Vertical Mode Left
Horizontal Mode B
BTrigger Source Vert Mode
Calibrator 4V
Aand BIntensity Counterclockwise
2-1

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Operating Instructions—7A29
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AMPLIFIER
AC-OFF-DC (Switch) —Selects signal input coupling mode
AC The ac component ol the signal is coupled to the amplifier input while the dc component is blocked
OFF Disconnects input signal, precharges input coupling capacitor, and resets input protection system when OVERLOAD light is on
DC Both ac and dc components of the signal are coupled to the amplifier input
OVERLOAD (Indicator)- When on, indicates that input signal exceeded the safe input level
POLARI fY (Switch) Provides ameans of inverting the display
•UP Apositive going signal at the INPUT connector deflecis the ctt display upward
INVERf Apositive going signal at the INPUT connector deflects the crt display downward
VARIABLE (Control) -Provides continuously variable deflection (actors between settings of the VOLTS/DIV switch.
VOLTS/DIV (Switch) —Selects calibrated deflection factors from 10 mV/Div to 1V/Div; 7steps in a1-2 5sequence
IDENTIFY (Switch) -Deflects the trace about 02division for trace identification In instruments with readout, also replaces readout with
the word "IDENTIFY"
POSITION (Control) Controls the vertical position of the trace
GAIN (Control) Screwdriver adjustment permits calibration ol deflection factor
Option 4VARIABLE DELAY (Control) Delays the signal up to •and 500 picoseconds by using acalibrated 10 turn dial (deleted on the
standard 7A29I
INPUT (Connector) -Provides ameans lor connecting asignal
2320 3
Figure 2-1 .Front-panel controls, connectors and indicators.
2-2

Operating Instructions—7A29
5. Set the oscilloscope's power switch on and allow at
least 20 minutes warmup.
AMPLIFIER FUNCTIONS
1. Connect abnc cable from the oscilloscope's calibrator
output connector to the 7A29 INPUT connector
2Rotate the Bintensity control clockwise until the trace
is just visible.
3. Set the 7A29 AC-OFF-DC switch to DC
4. With the POSITION control, align the display with the
center 4divisions of the graticule area Adjust the GAIN
(screwdriver adjustment) for 4divisions of display
5With the POSITION control, align the bottom of the
displayed signal with the center horizontal graticule line
6Set the AC-OFF-DC switch to AC Notice that the
displayed signal shifts downward approximately 2
divisions, and that the tops of the waveforms are tilted
7. Set the AC-OFF-DC switch to DC With the POSITION
control, align the trace with the center and top-most
graticule lines.
8Set the POLARITY switch to the INVERT position.
Notice that the displayed signal is now inverted, being
roughly aligned with the center and bottom graticule
lines.
9 Set the POLARITY switch to the *UP position.
10. Rotate the POSITION control fully counterclockwise
and notice that the displayed signal can be positioned off
the graticule area at the bottom of the crt.
11 Set the POLARITY switch to INVERT.
12 Rotate the POSITION control fully clockwise, and
notice that the displayed signal can be positioned off the
graticule area at the top of the crt
13 Return the POLARITY switch to the +UP position.
Position the display to the center 4divisions of the
graticule area.
14 Press to release the VARIABLE (Volts/Div) control
Rotate the VARIABLE (Volts/Div) control fully
counterclockwise and notice approximately 16divisions
of displayed signal. Rotate the VARIABLE (Volts/Div)
control fully clockwise and notice at least 4divisions of
displayed signal
15 Press the VARIABLE (Volts/Div) control in
16 Set the AC-OFF-DC switch to the OFF position and
notice that no signal is displayed on the crt.
17
Press the IDENTIFY button. Notice that the displayed
trace is deflected upward approximately 025 division
and. in oscilloscope mainframes equipped with readout,
notice that the 7A29 readout display is replaced with the
word "IDENTIFY".
18
Rotate the VOLfS/DIV control through each position
and note that the 7A29 readout display corresponds with
the front-panel nomenclature Change the POLARITY
switch to INVERT. Rotate the VOLTS/DIV control through
each position. Again note that the 7A29 readout display
corresponds with the front panel nomenclature Note
additionally that a downward-pointing arrow appears
within the readout display
19. Press and release the VARIABLE (Volts/Div) control
Note that a">" symbol appears in the readout display
between the downward pointing arrow and the deflection
factor information
20 Change the POLARITY switch to +UP Note the
disappearance of the "1" symbol. Press and latch the
VARIABLE (Volts/Div) control. Note the disappearance of
the ">" symbol
21 Disconnect the bnc cable from the INPUT connector
of the 7A29.
22. Connect a10X readout-encoded probe to the INPUT
connector and note the corresponding change in the
deflection factor of the displayed readout Repeat with
100X probe
NOTE
Readout encoding is accomplished by
connecting aresistance from the outer ring of
the 7A29 INPUT connector to ground The
following gives the resistance value
necessary to simulate aprobe, and may be
used in place of an actual probe
Function Resistance
XI Open circuit
XI 011 KO. within 5%
XI 00 62kO. within 5%
IDENTIFY 0ohms
23 This completes the Operators Checkout Procedure.
2-3

Operating Instructions --7A29
DETAILED OPERATING
INFORMATION
PROBES
Probes recommended for use with the 7A29 are the
P6056 (10X) or P6057 (100X) Both probes are
compatible with 50 ohm systems, and will allow good
frequency response These probes also contain trace
IDENTIFY and readout encoding functions
If the P6201 Probe is used, aone megohm input
impedance may be achieved (with some loss in
bandwidth). Consult your local Tektronix Field Engineer
or Representative for further information
VERTICAL GAIN CHECK AND ADJUSTMENT
To check the gain of the 7A29. set the VOLTS/DIV
switch to 01Vand connect a04V. 1kHz signal from
the oscilloscope mainframe calibrator to the 7A29 INPUT
connector
NOTE
Oscilloscope calibrators typically have an
output impedance of either 50 Oor 450 Cl.
The 50- ohm input impedance of the 7A29
forms avoltage divider with the calibrator
output impedance, reducing the voltage to the
7A29 by aprecise factor of 2(for 50- ohm
calibrators) or 10 (for 450-ohm Calibrators).
Thus the 4 V calibrator output of the 7104
and 7904 must be selected for an output
voltage of 04volts.
The vertical deflection should be exactly four divisions. If
not. adjust the front-panel GAIN adjustment for exactly
four vertical divisions.
INPUT COUPLING
The AC-OFF-DC switch allows achoice 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 signals with frequencies below about 1
kHz the DC coupling position is necessary to avoid signal
attenuation
In the AC coupling position the dc component of the
Signal is blocked by a2microfarad capacitor in the input
circuit. The AC coupling position provides the best display
of signals with adc component much larger than the ac
component.
In the OFF position of the input coupling switch, the
signal path of the amplifier is interrupted so that there is
no displayed signal However, asignal connected to the
INPUT connector will be loaded by approximately 390
kilohms dc, or by 195 kilohms ac. At extremely high
frequencies a small portion of the input signal will still be
displayed. For example, the signal attenuation in the OFF
position is about 32 dB at 1gigahertz.
The OVERLOAD protection feature of the 7A29 activates
when asignal capable of causing damage (to 7A29
internal circuitry) is applied to the INPUT connector To
reset the 7A29. turn the AC-OFF-DC switch to the OFF
position and remove the cause of overloading The 7A29
is then ready for normal operation
The 7A29 is capable of withstanding short term
overloads in excess of its continuous rating of 10 Vrms.
Thus, it is possible to apply 50 Vpeak (the same as 50 V
rms for asingle pulse) for 20 ms, or a20 Vrms signal for
125 ms. The 7A29 integrates the rms input power and
disconnects the signal before damage can occur.
Generally speaking, the 7A29 will protect itself from
excessive (damaging) signals; however, there are
exceptions. Continuous wave or pulsed radio frequency
signals above 100 MHz are not sensed by the input
protection circuitry and may cause damage to the input
attenuator if in excess of the 10 Vrms. 50 Vpeak, rating.
The relay contacts which disconnect the 7A29 from
excessive voltages may themselves be damaged by
arcing. If the contacts open with asignal greater than 50
Vapplied to the INPUT, the contacts may be permanently
damaged.
The ac coupling capacitor used in the AC position of the
AC-OFF-DC switch is rated at 100 Vdc Since the input
protection circuitry is located after the ac coupling
capacitor, application of up to 100 Vdc to the INPUT is
possible in the AC coupled mode. However, in order to
avoid afast-rise pulse being sent to the 7A29 from a
signal in excess of 50 Vdc. turn the AC-OFF DC switch
to OFF before connecting such asignal to the 7A29
INPUT In the OFF position, the ac coupling capacitor is
safely precharged to the average dc voltage
Figure 1-2 in section 1shows the maximum rms
amplitude which may safely be applied to the 7A29
INPUT Figure 1-2 also corresponds approximately to the
rms voltage the 7A29 will accept without automatically
disconnecting itself Acomplex pulse, whose rms value is
equal to the amount shown in Figure 1-2. is safe if it is
also less than 50 Vpeak.
For example, a30 Vrms sinusoid may be applied for up
to 55 ms. but a36 Vrms sinusoid may not be applied
because the peak voltage exceeds 50 VThe 7A29 INPUT
may be connected to a50 Vpower supply for up to 20 ms
because the rms and peak values of the resulting pulse
are both 50 V
2-4

Operating Instructions 7A29
VOLTS/DIV SWITCH
The amount of deflection produced by a signal is
determined by the signal amplitude, the attenuation
factor of the probe, and the setting of the VOLTS/DIV
switch. Calibrated deflection factors represented by the
VOLTS/DIV switch apply only: (1) When the probe
attenuation is XI or when the input signal is appreciably
above 1kHz with AC coupling (the dc blocking capacitor
attenuates signals below 1kHz), and (2) when the
VARIABLE (Volts/Div) control is in the CAL IN position.
POLARITY SWITCH
The POLARITY switch provides ameans of inverting the
displayed signal With the POLARITY switch set to *UP. a
positive going signal at the INPUT produces an upward
deflection on the crt display With the POLARITY switch
set to INVERT, apositive going signal will produce a
downward deflection on the crt display
TRACE IDENTIFICATION AND READOUT
FUNCTIONS
When the IDENTIFY button is pressed, the trace is
deflected upward about 0.25 division to identify the 7A29
trace. This feature is particularly useful when multiple
traces are displayed on the crt. In oscilloscope
mainframes with readout, the IDENTIFY button also
replaces the 7A29's deflection factor readout display
with the word "IDENTIFY". The 7A29 is equipped with
probe encoding circuitry that, when used with acoded
probe, corrects the deflection factor readout.
VARIABLE DELAY (OPTION 4)
The option VARIABLE DELAY line provides ameans for
delaying the signal applied to the INPUT connector up to
t500 picoseconds relative to another 7A29. a7A19, or
7A19 Option 4When the Option 4instrument is used
with astandard 7A29 (which has afixed delay) the
VARIABLE DELAY control can be used to match the
signal delay time of both units.
MATCHING DELAY TIMES USING TWO 7A29
UNITS, 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
With high speed signals, the delay times of the probes
and amplifiers can distort the true time relationship of
the two signals By using the VARIABLE DELAY (Option
4). the delay times between the two units can be
matched to within afew picoseconds, thus giving atrue
time relationship of the signals being viewed.
For matching delay times of two 7A29 units with probes,
proceed as follows
1Install the standard 7A29 in the left vertical plug-in
compartment of the oscilloscope.
2. Install the 7A29 Option 4in the right vertical plug-in
compartment.
3Connect both 7A29 INPUT connectors to one of the
signal sources and adjust the time-base unit for the
fastest convenient sweep available
4Set the oscilloscope's trigger source switch to Left
Vert, and verticial mode switch to Alternate.
5. Set both 7A29 units to the same deflection factor
settings
6. Center both displays vertically.
7. Adjust the front-panel VARIABLE DELAY knob so that
the two displays are superimposed The delay times of
both units and the associated cables (or probes) are now
matched
2-5