Tektronix 7B87 User manual

HaktfDnix-
CXDMMITTED TO EXCELLENCE
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF THIS MANUAL.
7B87
TIME BASE
WITH
PRETRIGGER
ACQUIRE CLOCK
INSTRUCTION MANUAL
Tektronix. Inc.
P.O. Box 500
Beaverton. Oregon 97077 Serial Number
070-2788-00
Product Group 42
First Printing APR 1980
Revised JAN 1986

Copyright -i' 1980 Tektronix. Inc. All rights reserved.
Contents of this publication may not be reproduced in any
form without the written permission of Tektronix. Inc.
Products of Tektronix. Inc. and its subsidiaries are covered
by U.S. and foreign patents and/or pending patents.
TEKTRONIX. TEK. SCOPE-MOBILE, and are
registered trademarks of Tektronix. Inc. TELEQUIPMENT
is aregistered trademark of Tektronix U.K. Limited.
Printed in U.S.A. Specification and price change privileges
are reserved.
INSTRUMENT SERIAL NUMBERS
Each instrument has aserial number on apahel insert, tag,
or stamped on the chassis. The first number or letter
designates the country of manufacture. The last five digits
of the serial number are assigned sequentially and are
unique to each instrument. Those manufactured in the
United States have six unique digits. The country of
manufacture is identified as follows:
BOOOOOO Tektronix. Inc.. Beaverton. Oregon, USA
100000 Tektronix Guernsey. Ltd., Channel Islands
200000 Tektronix United Kingdom. Ltd., London
300000 Sony/Tektronix. Japan
700000 Tektronix Holland. NV. Meerenveen,
The Netherlands

7B87 Instruction
TABLE OF CONTENTS
PAGE PAGE
LIST OF ILLUSTRATIONS
LIST OF TABLES iv
OPERATOfiS SAFETY SUMMARY w
SERVICING SAFETY SUMMARY, wit
SECTION 1OPERATING INSTRUCTIONS
INSTALLATION t-1
CONTROLS. CONNECTORS. AND INDICATORS 1-1
FUNCTIONAL CHECK 1-1
SETUP PROCEDURE 1-1
SWEEP FUNCTIONS 1-4
TRIGGERING FUNCTIONS 1-4
PRETRIGGER ACQUIRE CLOCK FUNCTIONS 1-S
GENERAL OPERATING INFORMATION 1-6
TRIGGERING SWITCH LOGIC 1-6
TRIGGERING MOOES 1-6
TRIGGER COUPLING 1-9
TRIGGER SOURCE 1-9
TRIGGER SLOPE 1-11
TRIGGER LEVEL 1-11
HORIZONTAL SWEEP RATES 1-11
TIME MEASUREMENT 1-11
SWEEP MAGNIFICATION 1-11
VARIABLE HOLD OFF 1-12
MAINFRAME OPERATING MOOES 1-12
APPLICATIONS 1-12
TIME INTERVAL MEASUREMENTS 1-12
PERIOD AND FREQUENCY MEASUREMENTS ...1-12
RISE TIME AND FALL-TIME MEASUREMENTS ..1-13
PULSE WIDTH MEASUREMENTS 1-14
SECTION 2SPECIFICATION
STANDARD ACCESSORIES 2-4
LmmIhmmJI
THE REMAINING PORTION OF THIS TABLE OF CONTENTS
LISTS SERVICING INSTRUCTIONS. THESE SERVICING
INSTRUCTIONS ARE FOR USE BY QUALIFIED PERSONNEL
ONLY. TO AVOID ELECTRICAL SHOCK. OO NOT PERFORM
ANY SERVICING OTHER THAN THAT CALLED OUT IN THE
OPERATING INSTRUCTIONS UNLESS QUALIFIED TO DO
SO.
SECTIONS THEORY OF OPERATION
BLOCK DIAGRAM DESCRIPTION 3-1
TRIGGER GENERATOR 3-1
SWFFP GENERATOR 3-1
PICKOFF AMPLIFIER AND DELAY GATE
GENERATOR 3-1
LOGIC 3-1
DIGITAL VOLTMETER 3-1
CLOCK GENERATOR 3-1
DETAILED CIRCUIT DESCRIPTION 3-1
FRONT-PANEL DISTRIBUTION .3-3
TRIGGER GENERATOR 3-3
EXTERNAL SOURCE 3-3
INTERNAL AND LINE SOURCE 3-3
TRIGGER SOURCE SELECTOR AND
AMPLIFIER 3-3
PEAK TO-PEAK AUTO 3-3
SLOPE SELECTOR AND TRIGGER
GENERATOR 3-5
GATE GENERATOR 3-5
LOGIC 3-5
SWEEP MOOES 3-5
HOLD OFF TIMING 3-6
LOCKOUT BUFFER AMPLIFIER 3-7
HOLD OFF OUTPUT AMPLIFIER 3-7
SWEEP GENERATOR 3-7
TIMING CURRENT SOURCE 3-7
RAMP GENERATOR 3-10
HORIZONTAL PREAMPLIFIER 3-10
SWEEP GATE GENERATOR 3-10
DVM 3-10
DELAY TIME COMPARATOR AND DELAY
GATE GENERATOR 3-10
OIGHAL VOLTMETER 3-11
DELAY COMPARISON VOLTAGE-TO RAMP
CONVERTER 3-12
COMPARATOR 3-12
REFERENCE CURRENT SOURCE 3-12
REFERENCE CURRENT INVERTER 312
COUNTER AND ENCODER 3-12
CLOCK GENERATOR 3-12
CONTROL LOGIC 3-13
OSCILLATOR 3-13
FIRST DIVIDER 3-15
XI X10MULTIPIEXER 3-15
DECADE DIVIDER 3-15
INTERNAL CLOCK MULTIPLEXER 3-15
OUTPUT CLOCK MULTIPLEXER 3-15
INTENSIFY CIRCUIT 3-15
7B87 IN AHORIZ PLUG-IN COMPARTMENT 316
IN1FRNAL BUTTON PRESSED 3-16
7B87 IN BHORIZ PLUG IN COMPARTMENT 3-16
INTERNAL BUnON PRESSED 316
TIME DIVISION AND READOUT SWITCHING 3-17
BASIC READOUT SYSTEM 3-17
TIME DIVISION READOUT 3-17
ACOUIRE-STOP DELAY TIME READOUT 3-17
INTERFACE CONNECTIONS AND POWER
SUPPLY 3-17
SECTION 4MAINTENANCE
PREVENTIVE MAINTENANCE 4-1
CLEANING 41
EXTERIOR 4-1
INTERIOR 41
SWITCH CONTACTS 4-1
REV JUN 1981

7B87 Instruction
TABLE OF CONTENTS (CONT)
PAGE
VISUAL INSPECTION 4-1
LUBRICATION 4-1
CAM SWITCH LUBRICATION 4-2
SEMICONDUCTOR CHECKS 4-2
ADJUSTMENT AUER REPAIR 4-2
TROUBLESHOOlING 4-2
TROUBLESHOOTING AIDS 4-2
DIAGRAMS 4-2
VOLTAGES AND WAVEFORMS 4-2
CIRCUIT-BOARD ILLUSTRATIONS 4-2
SWITCH CAM IDENTIFICATION 4-4
DIODE COLOR CODE 4-4
WIRING COLOR CODE 4-4
SEMICONDUCTOR LEAD CONFIGURATIONS 4-4
IN TER BOARD PIN CONNECTOR
IDENTIFICATION 44
MULTI-PIN CONNECTOR IDENTIFICATION 4-4
INTERFACE CONNECTOR PIN LOCATIONS 45
PERFORMANCE CHECK AND ADJUSTMENT 4-5
STATIC SENSITIVE DEVICES 45
TROUBLESHOOTING EQUIPMENT 4-6
TROUBLESHOOTING TECHNIQUES 4-6
TROUBLESHOOTING PROCEDURE 4-6
CORRECTIVE MAINTENANCE 4-8
OBTAINING REPLACEABLE PARTS 4-8
SOLDERING TECHNIQUES 4-9
COMPONENT REMOVAL AND REPLACEMENT 4-10
CIRCUIT BOARDS 410
SWITCHES 4-12
SEMICONDUCTORS 415
INTERCONNECTING PINS 4-15
CIRCUIT-BOARD PINS 415
FRONT-PANEL LIGHTS 4-16
ADJUSTMENT AFTER REPAIR 4 16
INSTRUMENT REPACKAGING 416
PAGE
SECTION 5PERFORMANCE CHECK AND
ADJUSTMENT
PRELIMINARY INFORMATION 5-1
ADJUSTMENT INTERVAL 5-1
TEKTRONIX FIELD SERVICE 51
USING THIS PROCEDURE 5-1
TEST EQUIPMENT REQUIRED 5-1
SPECIAL FIXTURES 51
TEST EQUIPMENT ALTERNATIVES 51
INDEX TO PERFORMANCE CHECK AND
ADJUSTMENT PROCEDURE 5 4
PRELIMINARY PROCEDURE 5-4
ATRIGGERING SYSTEM 5-5
BHORIZONTAL 'AQS SYSTEM 5-10
SECTION 6-INSTRUMENT OPTIONS
SECTION 7REPLACEABLE ELECTRICAL PARTS
SECTION 8DIAGRAMS AND CIRCUIT BOARD
ILLUSTRATIONS
SECTION 9REPLACEABLE MECHANICAL PARTS
CHANGE INFORMATION
ii REV JUN 1981

7B87 Instruction
LIST OF ILLUSTRATIONS
FIG PAGE
NO
Frontis
piece 7B87 Features vni
1-
1Location of release latch 1-1
I2Front panel controls, connectors, and
indicators 1-2
13Single Sweep Accguisilion 15
14Effect of LEVEL control and SLOPE switch
on cri display 1-10
15Area of graticule used for most accurate
time measurements 1-11
1-6 Operation of sweep magnifier 1-12
17Measuring the period and determining the
frequency of adisplayed waveform 1-13
18Measuring the rise time and fall time of
a displayed waveform 1-14
19Measuring the poise width of adisplayed
waveform 1-14
2-
17887 dimensional drawing 2-5
3-
1Basic block diagram of the 7687 Delaying
Time Base Unit 3-2
3-2 Detailed block diagram of Trigger Generator 3-4
33Timing diagram for Gate Generator stage
(092, Q96, Q98) 3-6
3-4 Detailed block diagram of Logic circuit 3-7
3-5 Detailed block diagram of Sweep Generator 3-8
3-
6Timing of events that form the Delay
Gate signal 3-11
4-
1Lubrication procedure for atypical
cam switch 4-2
42Semiconductor lead configuration 43
4-3 Inter-board mulli-pin connector assembly 44
FIG. PAGE
NO
4-4 End-lead mulli-pm connector assembly 4 4
4-5 Location of pin numbers on Interface
connector 4-5
4-6 7B87 troubleshooting chart 47
4-7 fteadoiii board removal procedure 4-10
4-8 Coaxial end lead connector assembly 4-11
49Location of securing screws and inier-board
multi-pin connectors on clock circuit hoard 4-12
4-10 Cam switch removal procedure 4-13
41 1 Removal procedure lor typical pushbutton
switch 4-14
4-12 Exploded view ol circuit-board pin and
ferrule 4-16
4-13 Front-panel light socket assembly 4-16
The illusiralions in Section 8are located near their associated
diagrams on the foldoul pages.
8-1 Semiconductor Lead Configurations
8-2 Locations of circuit boards in the 7B87.
8-3 A2 Trigger circuit board assembly
6-4 A1 -Interface circuit board assembly
8-5 A1 -Interface circuit board assembly.
8-6 A1 -Interface circuit board assembly
8-7 A4 Clock circuit board assembly
8-8 A4-Clock circuit board assembly
89A3 Readout circuit board assembly.
8-10 A1 -Interface circuit board assembly
8-1 1Test Point and Adjustment Locations.
REV JUN1981 Ml

7687 Instruction
LIST OF TABLES
TABLE PAGE
NO.
1-1 TIME/OIV Setting Relationship To 7B87
Internal Acquire Clock Rep Rate 1-7
2-1 Elecirical Characteristics 2-1
2-2 Mainframe Horizontal Compatibililv 2-3
2-3 Environmental Characteristics 2-4
2-
4Physical Characteristics 2-4
3-
tTruth Table. TIME/OIV Setting vs Strobes
lor U637 andU638 3-13
3-2 Selected Inputs or XI and X10 Mulliploxers 3-14
3-3 Operation of Output Multiplexer U6S5 3-15
3-4 Current in CHI Readout Line vs Acquire
Clock Mode. During TS10 3-16
3-
5Readout Character Selection 3-18
4-
1Relative Susceptibility 4-5
5-
1Test Equipment 5-2
5-2 Acquire Clock Repetition Rale Output 5-11
5-3 Delay Time Linearity 5-12
5-4 Acquire-Stop Delay Accuracy 5-13
5-5 Sweep Timing 5-14
5-6 Magnified Sweep Timing 5-15
IV

7B67 instruction
OPERATORS SAFETY SUMMARY
The general safety information in this part of the summary is for both operating and servicing personnel. Specific
warnings and cautions will be found throughout the manual where they apply, but may not appear in this summary.
TERMS
IN THIS MANUAL
CAUTION statements identify conditions or practices that could result in damage to the equipment or other property.
WARNING statements identify conditions or practices that could result in personal injury or loss of life.
AS MARKED ON EQUIPMENT
CAUTION indicates apersonal injury hazard not immediately accessible as one reads the marking, or ahazard to
property including the equipment itself
DANGER indicates apersonal injury hazard immediately accessible as one reads the marking.
SYMBOLS
IN THIS MANUAL
Static-Sensitive Devces.
AThis symbol indicates where applicable cautionary or other information is to be found.
AS MARKED ON EQUIPMENT
DANGER High voltage.
Protective ground (earth) terminal
ATTENTION -refer to manual
WARNINGS
POWER SOURCE
This product is intended to operate in amainframe connected to apower source that will not apply more than 250 volts
rms between the supply conductors or between either supply conductor and grourtd. Aprotective ground connection by
way of the grounding conductor in the mainframe power cord is essential for safe operation
GROUNDING THE PRODUCT
This product is grounded through the grounding conductor of the mainframe power cord To avoid electrical shock, plug
the mainframe power cord into aproperly wired receptacle before connecting to the product input or output terminals A
protective ground connection by way of the grounding conductor in the mainframe power cord is essential for safe
operation.
V

7B87 Instruction
DANGER ARISING FROM LOSS OP GROUND
Upon loss of the protective-ground connection, all accessible conductive parts (including knobs and controls that may
appear to be insulating), can render an electric shock
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERES
To avoid explosion, do not operate this product in an atmosphere of explosive gases unless it has been specifically
certified for such operation.
DO NOT OPERATE PLUG-IN UNIT WITHOUT COVERS
To avoid personal injury, do not operate this product without covers or panels installed Do not apply power to the plug-in
unit via aplug-in extender
VI

7B87 Instruction
SERVICING SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL ONLY
Refer also to the preceding Operators Safety Summary
DO NOT SERVICE ALONE
Do not perform internal service or adjustment of this product unless another person capable of rendering first aid and
resuscitation is present.
USE CARE WHEN SERVICING WITH POWER ON
Dangerous voltages exist at several points mthis product. To avoid personal injury, do not touch exposed connections
and components while power is on.
Disconnect power before removing protective panels, soldering, or replacing components.
POWER SOURCE
This product is intended to operate in amainframe connected to a power source that will not apply more than 250 volts
rms between the supply conductors or between either supply conductor and ground. Aprotective ground connection by
way of the grounding conductor in the mainframe power cord is essential for safe operation.
VII

7B87 Instruction
}TM )
7B87 FEATURES
The 7B87 Time-Base unit Preuigger Acquire Clock provides calibrated sweep rales from Sseconds to 10 nanoseconds andiriggering to 400
megahertz for 7000-Series Oscilloscopes AX10 Magnifier increases each sweep rate by afactor of 10 anda VAflIABLE TIME/DIV control
provides continuously-variable sweep rates between calibrated steps Variable holdoff and alphanumeric readout are provided Also, when
operating in the AUTO TRIGGERING MODE, abright baseliite trace is displayed in the absence of atrigger signal The 7B67 can be operated
as an independent time base or as a delayed-sweep unit with acompanion delaying time-base unit Sweep mode is determined by the
companion delaying time base
The7B87 also feat uresaninternally-gerteraied clock andan external clock input lor sequential single sweep acquisition when operating in a
7000-series digitizing oscilloscope The frequency range of the internally gerteraied clock is 20 46 mHz {millihertzl to 20 48 MHz as
determined by the TIME OlV, X10 MAG, aitd INT -1000 switches Also, an ACQUIRE-STOP DECAY function varies delay pickoff, ornl
therefore pretrigger time, in compatible digitizing plug-m oscilloscopes The portion of the oscilloscope real-time display between tbe
triggering event and the end of delay lime is intensified The exact delay lime is displayed on the cri readout
viii

Section 17B87
OPERATING INSTRUCTIONS
The 7B87 Time-Base unit operates with aTektronix 7700-. 7800-, or 7900-senes oscilloscope mainframe and a7A-
series amplifier unit to form acomplete oscilloscope system. This section describes the operation of the front-panel
controls and connectors, provides general operating information, afunctional check procedure, and basic applications for
this instrument.
INSTALLATION
The time-base unit operates in the horizontal plug-in
compartment of the mainframe When used for single
sweep acquisition with aTektronix 7000-series digitizing
oscilloscope (7854) the 7B87 must be installed in the B
horizontal compartment of the mainframe. This
instrument can also be installed in avertical plug-in
compartment to provide avertical sweep on the crt.
However, when used in this manner, there are no
internal triggering or retrace blanking provisions, and the
unit may not meet the specifications given in Section 2.
Specification.
To install the unit in aplug-in compartment, push it in
until it fits firmly into the compartment The front panel
of the unit should be flush with the front panel of the
mainframe Even though the gain of the mainframe is
standardized, the sweep calibration of the unit should be
checked when installed. The procedure for checking the
unit is given under Sweep Functions in the Functional
Check procedure in this section.
To remove the unit, first turn the power off, then pull the
release latch (see Fig. 1-1) to disengage the unit from the
mainframe, and pull it out of the plug-in compartment.
CONTROLS. CONNECTORS. AND
INDICATORS
AM controls, connectors, and indicators required for the
operation of the time-base unit are located on the front
panel. Figure 1-2 shows and provides abrief description
of all front-panel controls, connectors, and indicators
More detailed information is given in the General
Operating Instructions
FUNCTIONAL CHECK
The following procedures are provided for checking basic
instrument functions. Refer to the description of the
controls, connectors, and indicators while performing
this procedure. If performing the functional check
procedure reveals amalfunction or possible improper
adjustment, first check the operation of the associated
plug-in units, then refer to the instruction manual for
maintenance and adjustment procedures.
SETUP PROCEDURE
1. Install the lime-base unit in the Ahorizontal
compartment of the mainframe
2. Install an amplifier plug-in unit in avertical
compartment.
3. Set the time-base unit controls as follows:
SLOPE (+)
MODE P-P AUTO
COUPLING AC
SOURCE INT
POSITION Midrange
TIME/DIV 1ms
VARIABLE (CAL IN) Calibrated (Pushed in)
HOLD OFF MIN (fully counterclockwise)
MAG XI (pushed in)
Figure t-1. Location of release latch.
1-1

Operating Instructions 7B87
Figure 1-2. Front-panel controls, connectors, and indicators.

Operating Instructions 7B87
TRIGGERING
©
©
©
©
©
©
©
LEVEL Control Selects 3oomi on ihc trigger signal where triggering occurs
SLOPE Switch Permits sweep to be triggered on negative- or positive-going portions of the trigger signal
READY indicator Illuminates when sweep circuit is armed (SINGLE SWEEP Mode)
TRIC'D Indicator Illuminates when the displav >s triggered
MODE Pushbuttons Selects the operating mode of the triggering circuit
COUPLING Pushbuttons Selects the method of coupling the trigger signal to triggering circuit.
SOURCE Selects source of the trigger signal
SWEEP
POSITION Control Provides horizontal positioning.
FINE Control Provides precise horizontal positioning
MAG Pushbutton Selects magnified X10 or unmagnified sweep
HOLD OFF Control -Permits hold off period lobe varied to improve trigger stability on repetitive, complex waveforms.
TIME/DIV Selector-- Selects the sweep rale of the sweep generator.
(13 )VARIABLE Control and CAL Switch Selects calibrated or uncalibraied sweep rates. Uncalibraied sweep rates can be
continuously reduced to at least the sweep rate of the next slower position
SWP CAL Adjustment -Compensates for basic timing changes due to the differences in sensitivity of mainframes.
EXTERNAL TRIGGER INPUT
EXT TRIG AT1 ENUATOR -Selects attenuation factor for external trigger signals
16^ EXT TRIG IN Connector Connector (BNC type) provides input for external trigger signals
PRETRIGGER ACQUIRE CLOCK
AOS (acquire single shot) CLOCK/AQR {acquire repetitive) Selects the source of clock pulses from the 7887 to
the 7854 digitizing plug-in oscilloscope (7867 must be installed in Bhorizontal compartment of companion
oscilloscope mainframe).
ACQUIRE-STOP DELAY Control Avariable delay gate lunciion that allows pretrigger lime lobe varied in compatible
7000 series digitizing oscilloscopes Exact delay time is displayed on oscilloscope ert readout
EXT CLOCK IN Connector Provides input for external TTL clock signals
?7B8 3B
Figure 1-2 (cont). Front-panel controls, conrtectors. and indicators.
1-3

operating ln$tructions -7B87
4.
Turn on the meinframe and allow at least 20 minutes
warmup
5Set the mainframe vertical and horizontal modes to
display the plug-in units used and adjust the intensity
and focus for awell-defined display. See the oscilloscope
mainframe and amplifier unit instruction manuals for
detailed operating instructions.
SWEEP FUNCTIONS
NORMAL SWEEP. Perform the following procedure to
obtain anormal sweep and to demonstrate the function
of the related controls:
1. Perform the preceding Setup Procedure.
2. Connect a0.4-volt, 1-kilohertz signal from the
mainframe calibrator to the amplifier unit input.
3. Set the amplifier unit deflection factor for 4divisions
of display.
4Adjust the LEVEL control for astable display.
5. Turn the POSITION control and note that the trace
moves horizontally.
6. Turn the FINE control and note that the display can be
precisely positioned horizontally.
7. Check the display for one complete cycle per division.
If necessary, adjust the front-panel SWP CAL screwdriver
adjustment for one complete cycle per division over the
center 8graticule divisions. Be sure that the timing of the
mainframe calibrator signal is accurate to within 0.25%
(+20° to *30° C).
8. Press to release the VARIABLE (CAL IN) control- Turn
the VARIABLE (CAL IN) control fully counterclockwise
and note that the displayed sweep rate changes to at
least the next slower TIME/DIV switch setting (i.e., 2
milliseconds/division). Press the VARIABLE (CAL IN)
knob in (to the calibrated position)
MAGNIFIED SWEEP. Perform the following procedure
to obtain a X10 magnified display and to demonstrate the
function of the related controls:
1.Obtain aone cycle per division display as described in
the preceding Normal Sweep procedure.
2. Press to release the MAG button (X10). Note that the
unmagnified display within the center division of the
graticule is magnified to about 10 divisions.
3. Press the MAG button (XI).
TRIGGERING FUNCTIONS
Perform the following procedure to obtain atriggered
sweep and to demonstrate the functions of the related
controls;
1. Obtain adisplay as described in the preceding Normal
Sweep procedure.
2. Press the AUTO MODE button and turn the LEVEL
control fully counterclockwise to obtain afree-running
sweep.
3Slowly turn the HOLD OFF control clockwise and note
that astable display can be obtained at several positions
of the HOLD OFF control. Return the HOLD OFF control
to the fully counterclockwise (MIN) position.
NOTE
The HOLD OFF control varies the sweep hold-
off time which effectively changes the
repetition-rate of the horizontal sweep signal.
However, its primary function is to obtain a
stable display of complex waveforms which
are otherwise difficult to trigger.
4.
Press the AC. AC HF REJ, and DC COUPLING buttons
for both the +and -positions of the SLOPE switch and
check for astable display (LEVEL control may be
adjusted, if necessary, to obtain astable display).
5- Apply the 0-4-volt, 1-kilohertz signal from the
mainframe calibrator to the amplifier unit and to the EXT
TRIG IN connector.
6Press the EXT SOURCE button and set the amplifier
unit deflection factor for a4-division display.
7. Press the AC. AC HF REJ. and DC COUPLING buttons
for both the *and -positions of the SLOPE switch and
check for astable display (LEVEL control may be
adjusted, if necessary, for astable display).
8. Press the AC COUPLING. INT SOURCE, and NORM
MODE buttons. Adjust the LEVEL control for astable
display.
9. Press the AUTO MODE button and adjust the LEVEL
control for afree-running display
10. Press the NORM MODE button and check for no
display.
11. Adjust the LEVEL control for astable display and
press the SINGLE SWP MODE button.
12- Note that one trace occurs when the RESET MODE
button is pressed.
13. Disconnect the mainframe calibrator signal from the
amplifier unit input and press the RESET MODE button.
Check for no display and note that the READY indicator is
lit.
1-4

Operating lnstructions~7B87
14. Note that one trace occurs and that the READY
indicator extinguishes when the mainframe calibrator
signal is reconnected to the amplifier unit input
PRETRIGGER ACQUIRE CLOCK FUNCTIONS
NOTE
The following procedure must be performed
with the 7B87 installed in the Bhorizontal
compartment of aTektronix 7854
Oscilloscope.
NOTE
Four divisions of intensified display at 1
ms/div relates to delay-time readout of
approximately 4ms.
9. Set the amplifier unit input coupling switch to off or
ground. Set the 7B87 to SINGLE SWEEP MODE and
press the RESET pushbutton so that READY light is on.
10. Set the 7854 to Stored CRT Display and then to
Acquire Single-Shot Waveform Acquisition (AQS).
1. Install the 7887 in the 7854 Oscilloscope 8horizontal
compartment and install an amplifier unit in the
mainframe left vertical compartment. Turn on
oscilloscope power. See Tektronix 7854 Oscilloscope
Operators Manual for detailed operating information.
2. Set the time-base unit controls as follows;
SLOPE (+)
MODE AUTO
COUPLING AC
SOURCE INT
POSITION Midrange
TIME/DIV 1ms
VARIABLE Calibrated (CAL IN)
HOLOOFF MIN (fully counterclockwise)
MAG XI (pushed in)
AOS CLOCK/AQR INTERNAL
ACQUIRE STOP DELAY Midrange
3Set the 7854 vertical and horizontal modes to display
the plug-in units and set WFM ACQUISITION to SCOPE
Set the intensity and focus for awell-defined, intensified
display.
4Connect the 0.4-volt. 1-kilohertz signal from the
mainframe calibrator to the amplifier unit input.
5. Set the amplifier unit deflection factor for 4divisions
of display.
6. Set the TRIGGERING MODE to NORM and adjust the
LEVEL control for astable display (TRIG'O light on).
7. Rotate the ACQUIRE-STOP DELAY control fully
counterclockwise Notice that delay-time readout (located
in the lower right-hand corner of the crt) is near 0.2 ms.
(Zero delay time means that (he acquired signal occurred
prior to the triggering event.)
8. Rotate the ACOUIRE-STOP DELAY control until the
delay-time readout is approximately 4ms. Notice that the
first four divisions of squarewave display are intensified.
The 4ms intensified display relates to four divisions of
post-trigger in the subsequent single-sweep display
Therefore, the remaining 6divisions in the subsequent
display would be pre-trigger (see Fig. 1-3).
INTENSIFIED ZONE
IMPOST-TRIGGER.^
rTIME \
SCOPE (REAL-TIME) MODE
SWEEP SPEED
TRIGGER
POINT STOP
ACQUIRE-STOP DELAY 1
-^(POST-TRIGGER TIME)
(A) 7854 REAL-TIME DISPLAY (SCOPE MODE)
PRE-TRIGGER TIME IN
THE 7887 INTERNAL
AOS CLOCK MODE
POST-TRIGGER
TIME
SINGLE SWEEP ACQUIRE
TRIGGER POINT
(8) 7854 STORED SINGLE SWEEP DISPLAY.
r*
IE V
1
.
--1
)1
1
r
1;
i
1
——
4E^L*sJta!_
Figure 1-3. Single Sweep Acquisition.
1-5

operating Instructions 7B87
11.To trigger the single-sweep display, set the amplifier
unit input coupling to dc. Triggering occurs when the
amplifier coupling switch is set to dc. The first six
milliseconds of the display is pretrigger. (Noise in the
Stored Single Sweep may be displayed at the Single
Sweep Trigger Point as aresult of the coupling switch
contact closure.)
GENERAL OPERATING
INFORMATION
TRIGGERING SWITCH LOGIC
The MODE, COUPLING, and SOURCE pushbuttons of the
TRIGGERING switches are arranged in asequence which
places the most-often used position at the top of each
series of pushbuttons With this arrangement, astable
display can usually be obtained by pressing the top
pushbuttons; P-P AUTO, AC, INT. When an adequate
trigger signal is applied and the LEVEL control is correctly
set. the unit is triggered as indicated by the illuminated
TRIG'D light. If the TRIG'D light is not on. the LEVEL
control is either at asetting outside the range of the
trigger signal applied to this unit from the vertical unit,
the trigger signal amplitude is inadequate, or its
frequency is below the lower frequency limit of the AC
COUPLING switch position. If the desired display is not
obtained with these buttons pushed in. other selections
must be made. Refer to the following discussions or the
instruction manuals for the associated oscilloscope
mainframe and vertical unit(s) for more information.
TRIGGERING MODES
The MODE pushbutton switches select the mode in
which the sweep is triggered.
P-P AUTO. The P-P AUTO MODE provides atriggered
display at any setting of the LEVEL control whenever an
adequate trigger signal is applied. The range of the
LEVEL control in the P-P AUTO MODE is between
approximately 10% and 90% of the peak-to-peak
amplitude of the trigger signal. The LEVEL control can be
set so that the displayed waveform starts at any point
within this range on either slope The trigger circuits
automatically compensate for achange in trigger signal
amplitude. Therefore, if the LEVEL control is set to start
the waveform display at acertain percentage point on the
leading edge of alow-amplitude signal, it also triggers at
the same percentage point on the leading edge of ahigh-
amplitude signal, if the LEVEL control is not changed
When the trigger repetition rate is outside the parameter
given in the Specification section, or when the trigger
signal is inadequate, the sweep free runs at the rate
indicated by the TIME/DIV switch to produce abright
base-line, reference trace (TRIG'D light off) When an
adequate trigger signal is again applied, the free-running
condition ends and atriggered display is presented
The P-P AUTO MODE is particularly useful when
observing aseries of waveforms, since it is not necessary
to reset the LEVEL control for each observation. The P-P
AUTO MODE is used for most applications because of the
ease of obtaining atriggered display. The AUTO, NORM,
and SINGLE-SWP MODE settings may be used for
special applications.
AUTO. The AUTO MODE provides atriggered display
with the correct setting of the LEVEL control whenever
an adequate trigger signal is applied (see Trigger Level
discussions). The TRIG'D light indicates when the display
is triggered
When the trigger repetition rate is outside the frequency
range selected by the COUPLING switch or the trigger
signal IS inadequate, the sweep free runs at the rate
indicated by the TIME/DIV switch (TRIG'D indicator off).
An adequate trigger signal ends the free-running
condition and atriggered display is presented The sweep
also free runs at the rate indicated by the TIME/DIV
switch when the LEVEL control is at asetting outside the
amplitude range of the trigger signal. 1his type of free-
running display is useful when it is desired to measure
only the peak-to-peak amplitude of asignal without
observing the waveshape (such as bandwidth
measurements).
NORMAL. The NORM MODE provides atriggered
display with the correct setting of the LEVEL control
whenever an adequate trigger signal is applied. The
TRIG'D light indicates when the display is triggered.
The normal trigger mode must be used to produce
triggered displays with trigger repetition rates below
about 30 hertz. When the TRIG'D light is off. no trace is
displayed.
SINGLE-SWEEP OPERATION. The 7B87 single-sweep
function can be used with both digitizing and non-
digitizing oscilloscopes. Adiscussion of each follows:
Non-Oigitizing Oscilloscope Single Sweep. When the
signal to be displayed is not repetitive or varies in
amplitude, waveshape, or repetition rate, aconventional
repetitive type display may produce an unstable
presentation Under these circumstances, astable
display can often be obtained by using the single-sweep
feature of this unit. The single-sweep mode is useful to
photgraph non-repetitive or unstable displays.
To obtain asingle-sweep display of arepetitive signal,
first obtain the best possible display in the NORM MODE
Then, without changing the other TRIGGERING controls,
press the SINGLE SWP RESET button. Asingle trace is
presented each time this button is pressed. Further
sweeps cannot be presented until the SINGLE SWP
RESET button is pressed again. If the display signal is a
complex waveform composed of varying amplitude
pulses, successive single sweep displays may not start at
the same point on the waveform. To avoid confusion due
to the ert persistance, allow the display to disappear
before pressing the SINGLE SWP RESET button again. At
fast sweep rates, it may be difficult to view the single-
sweep display. The apparent trace intensity can be
increased by reducing the ambient light level or by using
aviewing hood as recommended in the mainframe
instruction manual.
1-6

operating Instructions— 7B87
When using the single-sweep mode to photograph
waveforms, the graticule may have to be photographed
separately in the normal manner to prevent over
exposing the film. Be sure the camera system $well
protected against stray light, or operate the system in a
darkened room. For repetitive waveforms, press the
SINGLE SWP RESET button only once for each waveform
unless the signal is completely symmetrical. Otherwise,
multiple waveforms may appear on the film. For random
signals, the camera shutter can be left open until the
signal triggers the unit Further information on
photographic techniques is given in the appropriate
camera instruction manual.
Single-Sweep Acquisition Using a76S4 Oscilloscope.
The ACQUIRE-STOP DELAY control and AOS CLOCK
switches function only with the 7B87 installed in the
7854 Oscilloscope BHoriz compartment. The 7854
requires asequential clock signal to acquire asingle-
sweep display this is provided by the 7B87 time-base
unit with the AOS CLOCK/AOR clock switch in the
INTERNAL or INT 1000 positions or externally through
the EX1 CLOCK IN. when in the EXT/AOR position.
Table 1-1 shows the internal clock frequencies at
different TIME/OIV switch settings, at X10MAG settings
and at the INTERNAL and INT -1000 settings of the AOS
Cl.OCK/AOR switches
The AOS CLOCK.''AOR switches select three clock
operating modes
1. INTERNAL The clock is generated internally, with the
clock frequency determined by the TIME/DIV and MAG
settings (see Table 1-1).
The ACOUIRE-STOP DELAY control varies the allocation
of pretrigger and post-trigger time in the subsequent
stored single-sweep display. The post-trigger portion is
intensified in the real-time display and the exact time is
displayed by CRT readout (see Fig. 1-3).
NOTE
Occasionally, when using the 7887/7854. the first
point of single-shot acquiredfAQSJ waveform will be
displayed at the end of the trace (extrema right) and
will appear that the waveform has made atransition
on the last point. To determine if the last point is
erroneous, check that the first and last points have
nearly the same vertical value at any setting of the
7887 ACQUIRE-STOP DELAY control.
2. INT -1000 In this AOS CLOCK mode the internal
clock frequency is divided by 1.000 (see Table 1-1). The
real-time display is the same as the internal mode with
the intensified zone and associated ACOUIRE-STOP
DELAY readout corresponding to post-trigger time in the
subsequent stored single-sweep display.
TABLE 1-1
TIME/DIV Setting Relationship To
7B87 Internal Acquire Clock Rep Rate
TIME/DIV MAG XI 1000 X10 -1000XI X10
5s20 48 Hz 204.8 Hz .02048 Hz .2048 Hz
2s51.2 Hz 512 Hz .0512 Hz .512 Hz
1s102 4 Hz 1024 Hz .1024 Hz 1024 Hz
5s204 8Hz 2048 kHz .2048 Hz 2048 Hz
.2 s512 Hz 5.12 kHz .512 Hz 5 12 Hz
1s1.024 kHz 10.24 kHz 1024 Hz 10.24 Hz
50 ms 2048 kHz 20.48 kHz 2.048 Hz 20 48 Hz
20 ms 5.12 kHz 51.2 kHz 5.12 Hz 51.2 Hz
10 ms 10.24 kHz 102 4 kHz 10 24 Hz 102 4Hz
5ms 20.48 kHz 2(M.8 kHz 20 48 Hz 204.8 Hz
2ms 51.2 kHz 512 kHz 51.2 Hz 512 Hz
1ms 102.4 kHz 1024 MHz '102 4 Hz 1.024 kHz
.5 ms 204 8kHz 2.048 MHz 204 8Hz 2048 kHz
2ms 512 kHz 5.12 MHz '512 Hz 5.12 kHz
1ms 1.024 MHz 10.24 MHz 1024 kHz 10.24 kHz
50 pS 2048 MHz 2.048 kHz 20.48 kHz
20 pS 5.12 kHz
10 pS 1
10.24 MHz 10 24 kHz
REV AMAR 1981 1-7

Operating Instructions- 7B87
The AQS stored single-sweep display is effectively 1000
times slower than the real-time display; however, the
ACOUIRE-STOP DELAY tirrte (post-trigger time) remains
unchanged and becomes insignificant compared to the
digitized sweep Therefore, the stored single-sweep
display is for practical purposes all pretrigger.
NOTE
During single-shot aeguisition with an external dock
input the 7854 may not necessarily sample one data
point for each dock pulse, as shown below:
P/W (Points/ dock Pulses
Waveform) Required
1024 1
512
1
2
256 4
128 8
3- EXT/AQR (EXT CLOCK INh This mode connects the
external TTL compatible clock signal, applied to the front-
panel EXT CLOCK IN connector, to the companion
digitizing oscilloscope mainframe (7854).
The real-time display is the same as the internal mode
with the intensified zone and associated ACQUIRE-STOP
DELAY readout corresponding to post-trigger time in the
subsequent stored single-sweep display When the AQS
(acquire single-shot) display is stored, the ACQUIRE-
STOP DELAY time is as displayed on the readout but the
effective TIME/DtV of the display changes at arate
determined by the frequency of the external clock signal
The resulting TIME/OIV for the stored single-sweep
display acquired in the external clock mode can be
determined by (he following formula.
EXT TIME/DIV =102.4 xExternal Clock Period
or
102.4 XCLOCk"FREQUENCY
NOTE
The 7854 maynot return from the acquire single-shot
(AQSl mode if the acquire-stop occurs before the
memory is filled once. This is most noticeable at slow
sweep speeds, especially in the internal -i- 7000 dock
mode. When the 7864 AQS button is pressed, the
7854 begins to sample the waveform and fill the
memory. The acquire-stop signal occurs at aset
interval after the 7B87 is triggered: this intervalis the
acquire-stop delay time. If the acquire-stop is
generated before the 7854 has filled the memory
once lone digital sweep) the 7854 will not recognize
it. and the system will keep on digitizing.
When the 7854 is used for non-single sweep acquisition
(AQR). the 7B87 clock should be disabled by selecting the
EXT/AQR pushbutton and removing any connection from
the EXT CLOCK IN connector. This prevents the 7887
clock signal from interfering with the 7854 acquisition
mode.
To obtain a stored single-sweep display of arepetitive
signal with a7854 digitizing oscilloscope, first obtain a
real-time display (7854 set to Scope CRT Display Mode)
in the NORM TRIGGERING MODE Then select the
portion of pretrigger and post-trigger desired for the
subsequent stored single-sweep display with the
ACQUIRE-STOP DELAY control. The displayed intensified
zone relates to the portion of the single- sweep displayed
after the single-sweep trigger event (post-trigger) and the
non-intensified zone relates to the portion of single-
sweep displayed before the single-sweep trigger event
1-8 REV AMAR 1981

operating instructions -7B87
occurs (pretrigger— see Fig. 1-3). The exact amount of the
post-trigger display is indicated by the CRT readout.
Then, without changing other triggering controls, select
the single-sweep mode by pressing the SINGLE SWP
RESET pushbutton. Set the 7854 to the Stored CRT
Display mode and to the AQS (acquire single-shot) WFM
Acquisition mode. When the AQS button is presed. the
7854 will respond by lighting the "Busy" LED and
blanking the entire screen. Arm the single-sweep
function by pressing the SINGLE SWP RESET pushbutton
again. After the trigger event occurs, the stored
waveform will be displayed on screen. Asingle stored
trace is displayed each time the 7854 AQS function is
selected and the 7B87 SINGLE SWP RESET pushbutton
is pressed.
If an Error message is displayed at the bottom of the CRT.
the 7887 clock is running faster than the 7854 can
digitize, and the single sweep will not be acquired. To
remedy this error condition, select aslower TIME/DIV
setting and re-acquire the single-sweep display until the
Error message disappears and the single-sweep display
is stored. If the 7854 does not return from the "Busy"
state or if it is desired to abort the AQS before the trigger
event has occurred, press Slop Ext Acquire button on the
7854 rear panel.
TRIGGER COUPLING
The TRIGGERING COUPLING pushbuttons select the
method in which the trigger signal is connected to the
trigger circuits. Each position permits selection or
rejection of some frequency components of the signal
which triggers the sweep.
AC. AC COUPLING blocks the dc component of the
trigger signal. Signals with low-frequency components
below about 30 hertz are attenuated In general, AC
COUPLING can be used for most applications. However,
if the signal contains unwanted frequency components or
if the sweep is to be triggered at alow repetition rate or a
dc level, one of the other COUPLING switch positions will
provide abetter display.
AC LF REJ. AC LF REJ COUPLING rejects dc. and
attenuates tow-frequency trigger signals below about 30
kilohertz. Therefore, the sweep is triggered only by the
higher-frequency components of the trigger signal. This
position is particularly useful for providing stable
triggering if the trigger signal contains line-frequency
components. Also, the AC LF REJ position provides the
best alternate-mode vertical displays at fast sweep rates
when comparing two or more unrelated signals.
AC HF REJ. AC HF REJ COUPLING passes all low-
frequency signals between about 30 hertz and 50
kilohertz Dc is rejected and signals outside the above
range are attenuated When triggering from complex
waveforms, this position is useful to provide astable
display of the low-frequency components.
DC. DC COUPLING can be used to provide stable
triggering from low-frequency signals which would be
attenuated in other COUPLING switch positions. DC
COUPLING can be used to trigger the sweep when the
trigger signal reaches adc level set by the LEVEL control.
When using internal triggering, the setting of the vertical
unit position control affects the triggering point.
TRIGGER SOURCE
The TRIGGERING SOURCE pushbuttons select the
source of the trigger signal which is connected to the
trigger circuits.
INTERNAL. The INT position causes the 7887 to trigger
on the trigger signal from the vertical plug-in unit.
Further selection of the internal trigger signal may be
provided by the vertical plug-in unit or by the mainframe;
see the instruction manuals for these instruments for
more information For most applications, the internal
source can be used However, some applications require
special triggering which cannot be obtained in the INF
position. In such cases, the LINE or EXT positions of the
SOURCE switches must be used.
REV AMAR 1981 1-9

Operating Instructions— 7B87
(LEVEL)
CRT DISPLAY
OBTAINED WITH
SLOPE SWITCH
SET TO POSITIVEIi-l
CRT DISPLAY
OBTAINED WITH
SLOPE SWITCH
SET TO NEGATIVE (-)
figure 1
C19S8-7
4. Effect of LEVEL corttrol and SLOPE switch on crt display.
1-10 REV AMAR 1981