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PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF THIS MANUAL.
LIFI
103000-UP
INSTRUCTION MANUAL.
Tektronix, Inc .
P.O. Box 500
Beaverton, Oregon 97077 Serial Number
070-2391-00 First Printing SEP 1977
Product Group 42 Revised AUG 1986
Copyright (~' 1977 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 U are
registered trademarks of Tektronix, Inc . TELEDUIPMENT
is a registered trademark of Tektronix U.K. Limited .
Printed in U .S .A . Specification and price change privileges
are reserved.
INSTRUMENT SERIAL NUMBERS
Each instrument has a serial number on a parcel 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 :
13000000 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, Heerenveen,
The Netherlands
7A24 (SN B103000 & UP)
PAGE PAGE
LIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii SECTION 4 MAINTENANCE
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii PREVENTIVE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
SAFETY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
CLEANING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
SECTION 1 OPERATING INSTRUCTIONS
LUBRICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1
CONTROLS AND CONNECTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
TROUBLESHOOTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3
FUNCTIONAL CHECK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-3
SETUP PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-1
TROUBLESHOOTING AIDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
CHECKOUT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3 TROUBLESHOOTING EQUIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . .4-4
DETAILED OPERATING INFORMATION . . . . . . . . . . . . . . . . . . . .1-3 TROUBLESHOOTING PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3
CORRECTIVE MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
SIGNAL CONNECTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-3 GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
VERTICAL GAIN CHECK AND ADJUSTMENT . . . . . . .1-3 OBTAINING REPLACEMENT PARTS . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
INPUT COUPLING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3 SOLDERING TECHNIQUES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-6
INPUT PROTECTION FUSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4 COMPONENT REPLACEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7
VERTICAL DEFLECTION FACTOR . . . . . . . . . . . . . . . . . . . . . . . .1-4 FUSE AND ATTENUATOR REPLACEMENT . . . . . . . . . . .4-7
POLARITY SWITCHING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4 SEMICONDUCTOR REPLACEMENT . . . . . . . . . . . . . . . . . . . . . . 4-7
DISPLAY MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-4 CIRCUIT BOARD REMOVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-7
TRIGGER MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 INTERCONNECTING PINS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8
TRACE IDENTIFICATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5 SWITCH REPLACEMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-8
BASIC APPLICATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 READJUSTMENT AFTER REPAIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
GENERAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-5
REPACKAGING FOR SHIPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-9
PEAK-TO-PEAK VOLTAGE MEASUREMENTS . . . . . . . 1-5
INSTANTANEOUS VOLTAGE MEASUREMENTS . . . . 1-6
COMPARISON MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . .1-6
DUAL TRACE PHASE DIFFERENCE
MEASUREMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-7 SECTION 6 PERFORMANCE CHECK AND ADJUSTMENT
HIGH RESOLUTION PHASE MEASUREMENTS . . . . .1-8 PRELIMINARY INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
COMMON MODE REJECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-8 ADJUSTMENT INTERVAL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
TEKTRONIX FIELD SERVICE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
SECTION 2 SPECIFICATION
USING THIS PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-1
TEST EQUIPMENT REQUIRED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1
Environmental . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2
SPECIAL CALIBRATION FIXTURES . . . . . . . . . . . . . . . . . . . . . .5-1
Physical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-2
TEST EQUIPMENT ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . 5-1
---------- ------ -
PRELIMINARY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-4
INDEX TO PERFORMANCE CHECK AND
ADJUSTMENT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
LOW FREQUENCY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-5
THE REMAINING PORTION OF THIS TABLE OF CONTENTS
LISTS THE SERVICING INSTRUCTIONS . THESE HIGH FREQUENCY PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-8
SERVICING INSTRUCTIONS ARE FOR USE BY QUALIFIED
PERSONNEL ONLY . T O AVOID ELECTRICAL SHOCK, DO
NOT PERFORM ANY SERVICING OTHER THAN THAT
CALLED OUT IN THE OPERATING INSTRUCTIONS UNLESS
QUALIFIED TO DO SO .
SECTION 6 INSTRUMENT OPTIONS
SECTION 3 THEORY OF OPERATION
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-1 SECTION 7 REPLACEABLE ELECTRICAL PARTS
BLOCK DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 SECTION 8 DIAGRAMS AND CIRCUIT BOARD
CH 1 AND CH 2 ATTENUATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 ILLUSTRATIONS
CH 1 AND CH 2 AMPLIFIERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
SECTION 9 REPLACEABLE MECHANICAL PARTS
DISPLAY SWITCHING AND OUTPUT . . . . . . . . . . . . . . . . . . . . . . . . 3-2
CH 1 AND CH 2 READOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3-3 CHANGE INFORMATION
7A24 (SN B103000 & UP)
ILLU
Figure
No . PAGE
1-1 7A24 Dual-Trace Amplifier . . . . . . . . . . . . . . . . . iv
1-2 Release Latch . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1-3 7A24 Front-Panel Controls and Connectors . . . . . 1-2
1-4 Measuring the peak-to-peak voltage
of a waveform . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1-5 Measuring instantaneous voltage with
respect to some reference . . . . . . . . . . . . . . . . . 1-6
1-6 Measuring phase difference between two signals . 1-8
1-7 High resolution phase measurement using
time-base magnifier . . . . . . . . . . . . . . . . . . . . . 1-8
1-8 Using the ADD mode for common-mode
rejection . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1-9
2-1 7A24 dimensional drawing . . . . . . . . . . . . . . . . . 2-2
4-1 Lubrication procedure for a typical cam switch . . . 4-1
4-2 Color code for resistors and capacitors . . . . . . . . . 4-2
4-3 Semiconductor electrode configurations . . . . . . . . 4-3
4-4 Orientation of multi-connector holders . . . . . . . . . 4-4
4-5 Coaxial end-lead connector assembly . . . . . . . . . 4-8
4-6 Exploded view of circuit-board pin and ferrule . . . 4-9
5-1 Test circuit for Input Resistance Check/Adjust
step . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
5-2 Approximately 2 .5 division pulse obtained
in step 11f . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
5-3 Short pulse before cancellation . . . . . . . . . . . . . . 5-9
The illustrations in Section 8 are located near their associated
diagrams on foldout pages .
8-1 Circuit board locator .
8-2 Semiconductor lead configurations .
8-3 A1 and A3 Attenuator circuit board assembly.
8-4 A5 and A6 Amplifier circuit board assembly .
8-5 A5 and A6 Amplifier circuit board assembly .
8-6 A2 and A4 Readout circuit board assembly.
8-7 7A24 Adjustment locations .
8-8 7A24 Troubleshooting chart .
Table
No. PAGE
1-1 Trigger Signal Source . . . . . . . . . . . . . . . . . . . . 1-5
2-1 Electrical Specifications . . . . . . . . . . . . . . . . . . . 2-1
2-2 Environmental Specifications . . . . . . . . . . . . . . . 2-2
2-3 Physical Specifications . . . . . . . . . . . . . . . . . . . . 2-2
5-1 Test Equipment . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5-2 Attenuator Accuracy . . . . . . . . . . . . . . . . . . . . . 5-7
ii REV A SEP 1980
7A24 (SN B103000 & UP)
This manual contains safety information which the user must follow to ensure safe operation of this instrument .
WARNING information is intended to protect the operator ; CAUTION information is intended to protect the
instrument . The following are general safety precautions that must be observed during all phases of operation and
maintenance.
WARNING
GROUND THE INSTRUMENT
To reduce electrical-shock hazard, the mainframe (oscilloscope) chassis must be grounded. Refer to the mainframe
manual for grounding information.
DO NOT OPERATE IN EXPLOSIVE ATMOSPHERE
Do not operate this instrument in an area where flammable gases or fumes are present. Such operation could
cause an explosion.
AVOID LIVE CIRCUITS
Electrical-shock hazards are present in this instrument. The protective instrument covers must not be removed by
operating personnel. Component replacement and internal adjustments must be referred to qualified service
personnel.
DO NOT SERVICE OR ADJUST ALONE
Do not service or make internal adjustments to this instrument unless another person, capable of giving first aid
and resuscitation, is present.
WARNING STATEMENTS
Warning statements accompany potentially dangerous procedures in this manual . The following warnings appear in
this manual and are listed here for additional emphasis .
To avoid electric-shock hazard, disconnect the instrument from the power source before soldering.
To avoid electric-shock hazard, disconnect the instrument from the power source before replacing components.
7A24 (SN 6103000 & UP)
7A24 FEATURES
The 7A24 is a dual-channel, wide-bandwidth amplifier plug-in unit designed for use with Tektronix 7000-series Oscillo-
scopes . Each channel has an input impedance of 50 ohms and is internally fused . Internal attenuators and gain circuits
are switched to correspond to the settings of the VOLT/DIV switches . Channel 2 can be inverted and added to channel 1
for differential measurements .
Figure 1-1 . 7A24 Dual-Trace Amplifier .
iv
Section 1-7A24 (SN B103000 & UP)
The 7A24 Vertical Amplifier unit operates with any Tektronix 7000-series oscilloscope mainframe and any 78-
series time-base unit to form a complete oscilloscope system . This section of the manual describes the operation
of the front-panel controls and connectors, provides a functional check procedure, detailed operating information,
and basic applications for this instrument .
INSTALLATION panel controls and connectors . See Detailed Operating
Instructions for more information .
The 7A24 is calibrated and ready for use as received .
It can be installed in any compartment of Tektronix FUNCTIONAL CHECK
7000-series oscilloscopes, but is principally used in
vertical plug-in compartments . To install, align the The following procedures are provided for checking
upper and lower rails of the 7A24 with the basic instrument functions. Refer to the description of
oscilloscope tracks and fully insert it . The 7A24 is the controls and connectors while performing this
fully inserted when the front is flush with the front of procedure. If performing the functional check
the oscilloscope and the latch at the bottom-left corner procedure reveals a malfunction or possible incorrect
of the 7A24 is in place against the front panel. See adjustment, first check the operation of the associated
Figure 1-2 for the latch location . oscilloscope and plug-in units, then refer to the
instruction manual for maintenance and adjustment
To remove the 7A24, pull on the latch (which is procedures.
inscribed with the unit identification "7A24") and the
7A24 will unlatch. Continue pulling on the latch to SETUP PROCEDURE
slide the 7A24 out of the oscilloscope .
1 . Insert the 7A24 into the left vertical plug-in
compartment of a 7000-series oscilloscope mainframe.
2. Insert a 7000-series time-base unit into the B hori-
zontal plug-in compartment.
3. Set the controls as follows :
7A24 Vertical Amplifier
CH 1, CH 2 POSITION . . . . . . .Midrange
CH 2 POLARITY . . . . . . . . . . . . . . . . . +UP
CH 1, CH 2 VOLTS/DIV . . . . . 10 mV
CH 1, CH 2 INPUT
COUPLING . . . . . . . . . . . . . . . . . . . . . . . .DC
CH 1, CH 2 VARIABLE . . . . . . .CAL IN
DISPLAY MODE . . . . . . . . . . . . . . . . .CH 1
TRIGGER SOURCE . . . . . . . . . . . . . MODE
Time Base
Level/Slope . . . . . . . . . . . . . . . . . . . . . . .Centered on positive
slope
Figure 1-2. Release Latch. Triggering Mode . . . . . . . . . . . . . . . .P-P Auto or Auto
Coupling . . . . . . . . . . . . . . . . . . . . . . . . . . .AC
Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Int
CONTROLS AND CONNECTORS Time/Div . . . . . . . . . . . . . . . . . . . . . . . . . .1 ms
Variable . . . . . . . . . . . . . . . . . . . . . . . . . . . .Cal In
All controls and connectors required for operation of Magnifier . . . . . . . . . . . . . . . . . . . . . . . . . .In
the Vertical Amplifier are located on the front panel .
Figure 1-3 provides a brief description of all front- Position . . . . . . . . . . . . . . . . . . . . . . . . . . . .Midrange
Operating Instructions--7A24 (SN B103000 & UP)
GAIN adjustment
VARIABLE -VOLTS/DIV -~- When the VARIABL F control is
Provides continuously variable pushed in, it becomes n front-parcel
uncalibrated settings between cal- screwdriver adjustment for calibra
tion of deflection facto
.-_..
Cfi 1 POSITION ----~_-------
Controls position of the CH 1 trace L
I and ADD display mode trace . VOLTS/DIV
Selects calibrated deflection factors
IDENTIFY from 5 mV/div to 1 V/div; eight
Deflects trace about 0.3 division for steps in a 1-2-b sequence .
trace identification, in instruments
with readout also replaces readout
with the word IDENTIFY .
Input Coupling
Selects signal input mod e.
C: F' 1~input connector
Provides siynai connection to CH 1 .
TRIGGER SOURCE
Selects souce of the trigger signal
H 2 Pc7LARITY
Provides rneans of inverting the CH -= DISPLAY MODE
Selects the mode of operation.
CH L POSTTION
Controls the pusition of the CH 2~r
trace only . Di sabled in Add .
FITT input corm
Provides signal connection to CH 2 .1
Figure 1-3. 7A24 Front-Panel controls and connectors .
Operating Instructions--7A24 (SIN B103000 & UP)
Mainframe This completes the basic operating procedure for the
Vertical Mode . . . . . . . . . . . . . . . . . . . . Left 7A24 . Instrument operation not explained here or
operation which needs further explanation is discussed
Horizontal Mode . . . . . . . . . . . . . . . .B under Detailed Operating Information .
Intensity . . . . . . . . . . . . . . . . . . . . . . . . . . . .CCW
Calibrator . . . . . . . . . . . . . . . . . . . . . . . . . .1 kHz, 40 mV under load
Trigger Source . . . . . . . . . . . . . . . . . . . Left Vert
4. Connect the mainframe to a power source which
meets the voltage and frequency requirements of the
mainframe power supply . DETAILED OPERATING
INFORMATION
5. Turn the mainframe power on and allow about five
minutes warmup . INTRODUCTION
For single-trace operation, either of the two identical
6. Advance the Intensity until a free-running trace is amplifier channels can be used independently by
observed . Adjust the position controls to center the setting the DISPLAY MODE and TRIGGER SOURCE
trace on the crt. switches to CH 1 or CH 2 and connecting the signal
to be observed to the appropriate Input . In the
7. Connect the mainframe calibrator output to the discussions to follow, single-trace operations using CH
7A24 CH 1 Input connector . 1 only apply equally to CH 2 only .
SIGNAL CONNECTIONS
CHECKOUT PROCEDURE
The 50-ohm input impedance of the 7A24 is ideally
8. Check the crt display for four divisions of vertical
suited for making waveform measurements on 50-ohm
deflection . If necessary, push in the CH 1 VARIABLE
systems, in that 50-ohm coaxial cables can be
control with a screwdriver and adjust the vertical gain
connected directly to the Input of the 7A24 . The
for exactly four divisions.
7A24, however, should not be connected directly to a
power supply, power line, or other voltage source that
9. Press the IDENTIFY button and check that the would exceed the input voltage limits of the 7A24 (see
display moves upward about 0.3 divisions . Also check Specification section, Table 2-1) . Probes recommended
that the readout information on the crt is replaced by for use with the 7A24 are the P6056 (10X) and
the word "IDENTIFY" . P605,7 (100X) . Both probes are compatible with'50-
ohm systems, and will allow optimum frequency
10 . Press and release the CH 1 VARIABLE control to response . These probes also contain trace IDENTIFY
its outward position . Turn the VARIABLE control fully and readout encoding functions. A one-megohm input
counterclockwise and check for 1 .6 divisions or less impedance may be achieved by using the P6201 FET
display amplitude . Press the VARIABLE control to the Probe.
CAL IN position .
VERTICAL GAIN CHECK AND ADJUSTMENT
11 . Change the 7A24 Vertical Amplifier CH 1 To check the gain of either channel, set the VOLTS/DIV
VOLTS/DIV to 0.1 V, the mainframe calibrator volts to switch to 50 mV and connect a 0.4 V (under load), one-
0.4 V (0 .2 V), and the time-base Triggering Source to kilohertz signal from the oscilloscope calibrator to the
Ext. Connect the calibrator output through a BNC T Input connector of the channel being checked. The vertical
connector to the time-base Ext Trig In and the 7A24 deflection should be exactly four divisions . If not, adjust
CH 2 Input. Set the POLARITY switch to INVERT to the front-panel GAIN for exactly fourdivisions of deflection .
display the opposite polarity of the square wave . The GAIN adjustment is engaged by pressing in the GAIN
control knob and turning the knob with a narrow-blade
12 . Return the POLARITY switch to +UP and set the screwdriver (see Fig. 1-3, Front Panel Controls and Connect-
TRIGGER SOURCE to CH 1 . Change the time-base ors) . Turn the knob clockwise, then counterclockwise, until
Triggering Source to Int and observe that the trace is the GAIN control is engaged . When the GAIN control is
no longer triggered. engaged, the vertical deflection will change as the knob is
turned . Turn the GAIN control knob with the screwdriver
13 . Return the TRIGGER SOURCE to MODE and set until the deflection is set to exactly four divisions, then
the DISPLAY MODE to ADD. Observe that only the CH remove the screwdriver . -.
1 POSITION control moves the trace.
14 . Set the DISPLAY MODE to CHOP . Observe that INPUT COUPLING
the channel one trace is controlled by the CH 1
POSITION control and the channel two signal is The Channel 1 and Channel 2 Input Coupling (OFF-
controlled by the CH 2 POSITION control . DC) switches select the signal input coupling mode .
REV A MAR 1980
Operating Instructions--7A24 (SN B103000 & UP)
DC To display a signal in one channel independently
The DC position couples both ac and do components when a signal is also applied to the other channel,
of the signal into the input amplifier . A 50-ohm simply select the desired channel by setting the
impedance is presented to the signal source . DISPLAY MODE switch to the appropriate CH 1 or CH
2 position .
OFF
Alternate Mode
The OFF position disconnects the signal source from
the amplifier and connects it to a resistive 50-ohm The ALT position of the DISPLAY MODE switch
termination . produces a display which alternates between Channel
1 and Channel 2 with each sweep on the crt.
INPUT PROTECTION FUSE
Although the ALT mode can be used at all sweep
A fuse in the input of each channel protects the 7A24 rates, the CHOP mode provides a more satisfactory
from damage due to excessive signal voltages . If this display at sweep rates below about 0.5 millisecond/
fuse is open, no display can be obtained . division . At slow sweep rates, alternate mode
switching becomes visually perceptible .
If no waveform can be displayed, but the POSITION
control will move the trace on the crt, the condition of Add Mode
the fuse should be checked by a qualified service
technician . The ADD position of the DISPLAY MODE switch can
be used to display the sum or difference of two
signals, for common-mode rejection to remove an
VERTICAL DEFLECTION FACTOR undesired signal, or for do offset (applying a do voltage
The amount of vertical deflection produced by a signal to one channel to offset the do component of a signal
is determined by the signal amplitude, the attenuation on the other channel). The overall deflection factor in
factor of the probe, the setting of the VOLTS/DIV the ADD mode with both VOLTS/DIV switches set to
switch, and the setting of the VARIABLE control . Cali- the same position is the deflection factor indicated by
brated deflection factors indicated by the settings of either VOLTS/DIV switch . However, if the CH 1 and
the VOLTS/DIV switch apply only when the VARIABLE CH 2 VOLTS/DIV switches are set to different
control is in the calibrated (CAL IN) position . deflection factors, the resultant amplitude is difficult to
determine from the crt display. In this case, the
voltage amplitude of the resultant display can be
The VARIABLE control provides variable, uncalibrated determined accurately only if the amplitude of the
settings between the calibrated steps of the signal applied to one channel is known. In the ADD
VOLTS/DIV switch . With the VARIABLE control fully mode, positioning of the trace is controlled by the
counterclockwise and the VOLTS/DIV switch set to 1 Channel 1 POSITION control only.
volt/division the uncalibrated vertical deflection factor
is extended to at least 2 .5 volts/division . By applying Chop Mode
a calibrated voltage source to the Input connector, any The CHOP position of the DISPLAY MODE switch
specific deflection factor can be set within the range
produces a display which is electronically switched
of the VARIABLE control . between channels at approximately a 500 kilohertz
rate (controlled by mainframe). In general the CHOP
POLARITY SWITCHING mode provides the best display at sweep rates slower
The CH 2 POLARITY switch may be used to invert the than about 0.5 millisecond/division or whenever dual-
displayed waveform of the signal applied to the CH 2 trace, non-repetitive phenomena is to be displayed.
Input. This is particularly useful in added-mode
operation of the 7A24 when differential measurements TRIGGER MODES
are to be made . The CH 2 POLARITY switch has two
positions, +UP and INVERT . In the +UP position, the CH 1
displayed waveform will have the same polarity as the The CH 1 position of the TRIGGER SOURCE switch
applied signal and a positive do voltage will move the provides a trigger signal obtained from the signal
crt trace up . In the INVERT position, a waveform at applied to the CH 1 Input connector. This provides a
the CH 2 Input will be displayed on the crt in inverted stable display of the signal applied to the CH 1 Input
form and a positive do voltage will move the trace connector.
down .
CH 2
DISPLAY MODES The CH 2 position of the TRIGGER SOURCE switch
For single-trace operation, apply the signal either to provides a trigger signal obtained from the signal
the CH 1 Input or the CH 2 Input and set the applied to the CH 2 Input connector . This provides a
DISPLAY MODE switch to the corresponding position : stable display of the signal applied to the CH 2 Input
CH 1 or CH 2. connector .
Operating Instructions-7A24 (SN B103000 & UP)
MODE 6. Turn the 7A24 POSITION control so the lower
In this position of the TRIGGER SOURCE switch, the portion of the waveform coincides with one of the
trigger signal for the time-base unit is dependent on graticule lines below the center horizontal line, and
the setting of the DISPLAY MODE switch . The trigger the top of the waveform is within the viewing area .
source for each position of the DISPLAY MODE switch With the time-base Position control, move the display
is shown in Table 1-1 . so one of the upper peaks lies near the center vertical
line (see Fig . 1-4) .
TABLE 1-1
Trigger Mode Sources
Mode Trigger Signal Source
CH 1, ^ Channel_ .1
CH 2 __ Channel 2
ADD ~_ - Algebraic sum . of . Channel ,1_ . _and_Channel 2
CHOP Algebraic sum of Channel 1 and _ Channell_2
ALT Alternates between Channel 1~and Channel 2
TRACE IDENTIFICATION
When the IDENTIFY button is pressed, the trace is
deflected about 0.3 division to identify the 7A24 trace .
This feature is particularly useful when multiple traces
are displayed . In instruments with readout, pressing
the IDENTIFY button also replaces the deflection factor 2391-10
readout with the word "IDENTIFY" .
Figure 1-4. Measuring the peak-to-peak voltage of a
BASIC APPLICATIONS waveform .
GENERAL
The following information describes the procedures 7. Measure the divisions of vertical deflection peak-to-
and techniques for making basic measurements with a peak . Check that the VARIABLE (VOLTS/DIV) control is
7A24 and the associated Tektronix oscilloscope and in the CAL IN position .
time base . These applications are not described in
detail since each application must be adapted to the NOTE
requirements of the individual measurements . This
instrument can also be used for many applications not This technique can also be used to make
measurements between two points on the
described in this manual . Contact your local Tektronix
waveform, rather than peak-to-peak .
Field Office or representative for assistance in making
specific measurements with this instrument .
8. Multiply the deflection measured in step 7 by the
VOLTS/DIV switch setting . Include the attenuation
PEAK-TO-PEAK VOLTAGE MEASUREMENTS
factor of the probe, if used .
To make peak-to-peak voltage measurements, use the
following procedure: EXAMPLE: Assume that the peak-to-peak vertical
1 . Apply the signal to either Input connector. deflection is 4.5 divisions (see Fig. 1-4) using a 10X
attenuator probe, and the VOLTS/DIV switch is set to
1 V.
2. Set the DISPLAY MODE and TRIGGER SOURCE
switches to display the channel used .
Volts vertical probe
Peak-to- = deflection X VOLTS/ X attenuation
3. Set the Input Coupling switch to DC . Peak (divisions) DIV setting factor
4. Set the VOLTS/DIV switch to display about five Substituting the given values :
vertical divisions of the waveform .
Volts Peak-to-Peak = 4.5 X 1 X 10
5. Set the time-base Triggering controls for a stable
display. Set the time-base unit to a sweep rate that
displays several cycles of the waveform . The peak-to-peak voltage is 45 volts.
Operating Instructions-7A24 (SN B103000 & UP)
INSTANTANEOUS VOLTAGE MEASUREMENTS Substituting the given values :
To measure the do level at a given point on a
waveform, proceed as follows: Instantaneous
Voltage = 3.6 X +1 X 0.5 V X 10
1 . Connect the signal to either Input connector.
2. Set the DISPLAY MODE and TRIGGER SOURCE The instantaneous voltage is 18 volts .
switches to display the channel used .
3. Set the VOLTS/DIV switch to display about five
divisions of the waveform .
COMPARISON MEASUREMENTS
4 . Set the Input Coupling switch to OFF and position In some applications it may be desirable to establish
the trace to the bottom graticule line or another arbitrary units of measurement other than those
reference line . If the voltage is negative with respect indicated by the VOLTS/DIV switch . This is particularly
to ground, position the trace to the top graticule line . useful when comparing unknown signals to a
Do not move the POSITION control after this reference reference amplitude. One use for the comparison-
line has been established . measurement technique is to facilitate calibration of
equipment where the desired amplitude does not
NOTE produce an exact number of divisions of deflection .
The adjustment will be easier and more accurate if
To measure a voltage level with respect to arbitrary units of measurement are established so that
a voltage other than ground, make the the correct adjustment is indicated by an exact
following changes to step 4: Set the Input number of divisions of deflection . The following
Coupling switch to DC and apply the procedure describes how to establish arbitrary units of
reference voltage to the Input connector, measure for comparison measurements .
then position the trace to the reference
line .
To establish an arbitrary vertical deflection factor
5. Set the Input Coupling switch to DC . The ground based upon a specific reference amplitude, proceed as
reference line can be checked at any time by follows :
switching to the OFF position . 1 . Connect the reference signal to the Input connec-
tor . Set the time-base unit sweep rate to display
6. Set the time-base Triggering controls for a stable several cycles of the signal .
display. Set the time-base sweep rate for an optimum
display of the waveform . 2. Set the VOLTS/DIV switch and the VARIABLE
control to produce a display which is an exact number
7. Measure the distance in divisions between the of vertical divisions in amplitude. Do not change the
reference line and the point on the waveform at VARIABLE control after obtaining the desired
which the do level is to be measured . For example, in deflection .
Figure 1-5 the measurement is between the reference
line and point A.
8. Establish the polarity of the waveform . With the
CH 2 POLARITY switch in the +UP position, any point
above the reference line is positive .
9. Multiply the distance measured in step 7 by the
VOLTS/DIV setting . Include the attenuation factor of
the probe, if used .
EXAMPLE : Assume the vertical distance measured is
3.6 divisions (see Fig . 1-5) and the waveform is above
the reference line using a 1OX probe with a
VOLTS/DIV setting of .5 V.
Using the formula:
Instan- vertical VOLTS/ probe 2391-11
taneous = distance X polarity X DIV X attenua-
Voltage (divi- setting tion
sions) factor Figure 1-5. Measuring instantaneous voltage with respect
to some reference.
Operating Instructions-7A24 (SN B103000 & UP)
3. To establish an arbitrary vertical deflection factor so DUAL-TRACE PHASE DIFFERENCE
that the amplitude of an unknown signal can be MEASUREMENTS
measured accurately at any setting of the VOLTS/DIV
switch, the amplitude of the reference signal must be Phase comparison between two signals of the same
known . If it is not known, it can be measured before frequency can be made using the dual-trace feature of
the VARIABLE VOLTS/DIV control is set in step 2. the 7A24. This method of phase-difference
measurement can be used up to the frequency limit of
the oscilloscope system . To make the comparison, use
4. Divide the amplitude of the reference signal (volts) the following procedure:
by the product of the vertical deflection (divisions)
established in step 2 and the setting of the
VOLTS/DIV switch . This is the vertical conversion
factor . 1 . Set the CH 1 and CH 2 Input Coupling switches to
DC .
reference signal 2. Set the DISPLAY MODE to ALT or CHOP . In
Vertical amplitude (volts) general, CHOP is more suitable for low frequencies
Conversion and ALT is more suitable for high frequencies . Set the
Factor vertical VOLTS/DIV TRIGGER SOURCE to CH 1 .
deflection X switch
(divisions) setting
3. Connect the reference signal to the CH 1 Input and the
comparison signal to the CH 2 Input. Use coaxial cables or
5. To measure the amplitude of an unknown signal, probes which have similar time-delay characteristics to
disconnect the reference signal and connect the connect the signals to the input connectors .
unknown signal to the Input connector. Set the
VOLTS/DIV switch to a setting that provides sufficient
vertical deflection to make an accurate measurement . 4. If the signals are of opposite polarity, set the CH 2
Do not readjust the VARIABLE control. POLARITY switch to invert the Channel 2 display.
(Signals may be of opposite polarity due to 180
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