Tektronix AA 501A User manual

- --
COMMITTEDTO EXCELLENCE
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF THIS MANUAL.
AA 501A
DISTORTION
ANALYZER
WITH OPTIONS 01 AND 02
INSTRUCTION MANUAL
I ,,,
i
Tektronix, Inc.
P.O. Box 500
Beaverton, Oregon 97077
070-6592-00
Product Group76
Serial Number
First Printing JULY 1987

Copyright 1987 Tektronix, Inc. All rights reserved.
Contentsof this publicationmay not
be reproduced in any form
without the written permissionof Tektronix, Inc.
Products of Tektronix, Inc. and its subsidiaries are covered by
U.S. and foreign patentsand/or pending patents.
TEKTRONIX, TEK, SCOPE-MOBILE, and
@ are registered
trademarks of Tektronix, Inc. TELEQUIPMENT is a registered
trademark of Tektronix, 1nc.TELEQUIPMENT is a registered
trademark of Tketronix U.K. Limited.

TABLE OF CONTENTS
Page
.....................
LIST OF ILLUSTRATIONS iii
............................
LIST OF TABLES iv
.............
OPERATOR'S SAFETY SUMMARY v
.................
SERVICE SAFETY SUMMARY vi
Section 1 SPECIFICATION
.............. Instrument Description 1-1
PerformanceConditions
............. 1-1
ElectricalCharacteristics
............. 1-2
EnvironmentalCharacteristics
........ 1-8
PhysicalCharacteristics
............. 1-8
Section
2 OPERATING INSTRUCTIONS
Preparation for Use
................
Repackaging Information ............
Controls. Connectors. and Indicators ...
Instrument Connections .............
Level Measurements ................
Distortion Measurements ............
Distortion Measurement Procedure ....
High Distortion Measurement Limitations 2-8
IM Distortion Measurements(Option 01
....................
and Option 02) 2-8
IM Distortion Measurement Procedure
........... (Option 01 and Option 02) 2-10
...........................
Filters 2-11
..........................
Displays 2-13
........................
Monitoring 2-13
THE FOLLOWING SERVICING INSTRUC-
TIONS ARE FOR USE BY QUALIFIED PER-
SONNEL ONLY
. TO AVOID PERSONAL INJU-
RY. DO NOT PERFORM ANY SERVICING
OTHER THAN THAT CONTAINED IN OPER-
ATING INSTRUCTIONS UNLESS YOU ARE
QUALIFIED TO DO SO
. REFER TO OPERA-
TORS SAFETY SUMMARY AND SERVICE
SAFETY SUMMARY PRIOR TO PERFORM-
ING ANY SERVICE
.
Section 3 THEORY OF OPERATION
.......................
Introduction 3-1
.....................
Input Amplifier 3-1
.............
Automatic Gain Control 3-2
.......................
Notch Filter 3-2
........
Frequency Band Discriminator 3-3
Notch Filter Control
................. 3-5
Distortion Amplifier
................. 3-5
Filters and AC-DC Converters
(Standard and Option 01 Instruments
............................
Only) 3-6
Filters and AC-DC Converters
.........
(Option 02 Instruments Only) 3-7
dB Converter
...................... 3-7
................
dB Offset Generator 3-8
dB Ratio Circuitry
..................
6 V Reference .....................
DVMIlnterface .....................
.....................
Display Board
Logic Circuitry
.....................
Power Supplies ....................
IM Analyzer (Option 01 and 02 only) ...
Section 4 CALIBRATION
PERFORMANCECHECK
Introduction
.................... 4-1
........
Performance Check Interval 4-1
...............
Services Available 4-1
Test Equipment Required
.......... 4-1
......... Performance Check Steps 4-2
AA 501A Performance Check
......................
Summary 4-3
...................
PROCEDURE 4-7
ADJUSTMENT PROCEDURE
....................
Introduction 4-19
Test Equipment Required
.......... 4-19
.....................
Preparation 4-19
...................
PROCEDURE 4-19

TABLE OF CONTENTS (cont)
Section 5 MAINTENANCE
Introduction .
.. .. . ... .. .. .. . . ... . . . .
Preparation For Use ... .. .. .. .. .. . . .
On-board Jumpers . ... ...... . .. . .
REAR INTERFACE INFORMATION
Functions Available at Rear Connector. .
+ and - lnput connectors(28B,28A)
lnput Common (27B,27A) . . .. . . .. .
Auxiliary lnput (25B).... . ...... .. .
Auxiliary lnput Ground (268) ... . ...
Function Output (238) .. . ... ......
FunctionOutput Ground (248) .. .. ..
lnput Monitor (24A) . . . .. . ... .... .
lnput Monitor Ground (23A) .. .. . ...
Converter Output (20A) ..... ..... .
dB Converter Output (19B) . .. . . ...
dB Converter Output Ground (20B) ..
General Maintenance Information ... ...
Troubleshooting Aids .. . . .. . . . ....
Diagrams ... . ... .. . .... .... . .
Circuit Board Illustrations ..... ..
Calibration Fixtures .. . . . . . .. . . . ..
Troubleshooting Equipment .. . . ....
Static-SensitiveComponents .......
Obtaining Replacement Parts . ... . .
Circuit Board Removal . . . . . ... . .. .
1. Top Cover Removal ... . . . . . .
2. Bottom and Back Covers
Removal
. . . . .. . .... . .. . .. .
3. Main (A15), InputINotch(A1 4),
and IMD (Option01 and Option
Section
5 MAINTENANCE (cont)
02 Only (A13) Boards Removal
4. Control Logic (A12) and DVM/
Interface(A16) Boards Removal
5. Display Board (A10) Removal
.
Magnetic Shield ...... . . ..... . . ..
Soldering Techniques . . . .. . . .. . ...
Semiconductors ... .. . . . . .. . .....
CoaxialCables .. .. ... .. ... . .. ...
Exterior Cleaning . . ..... . . . .... . .
Chassis .....................
Front Panel . . . . .. . . . . . . . .... .
InteriorCleaning . . .. . . . ... . . . ... .
Troubleshooting High Residual
Distortion Problems
. ... . . . .. . .. ..
Section 6 OPTIONS
Section 7 REPLACEABLE ELECTRICAL PARTS
Section
8 DIAGRAMSAND CIRCUIT BOARD
ILLUSTRATIONS
Section
9 REPLACEABLE MECHANICAL PARTS
CHANGE INFORMATION

LIST OF ILLUSTRATIONS
Fig.
No.
Page
Installationand removal . ....... . . .. .. ..
Front panelcontrols and connectors . .....
Typical connections for distortion
measurements.
... .... ... .... . .... ...
Block diagram of a basic harmonic distortion
analyzer
............................
Transfer characteristicsof an audio device
THD test of transfer characteristics
. .. . ..
Block diagram of basic IM analyzer .... ..
IMtest of transfer characteristicsin time and
frequency domain
.... .. .. . . .. .. . . .. . .
Responsecurves for AA 501A filters . .. . .
Oscilloscopedisplay of deviationfrom
linearity
. . . . . . ... . . ..... . . ......... ..
3-1
Simplified notch filter . . . .. . . . . . . . .. .. . . 3-2
3-2
Frequency banddiscriminator .. . . . . . . . . . 3-4
3-3
Intermodulationdistortion analyzer block
diagram
. . . .. .. .... . . ... . . .. . . . . . . .. 3-11
4-1 AA 501A
grounded unbalancedinput
connection
. ... . . .. . . . ... .. . .. . . ..... 4-7
4-2
. AA 501A common mode input connection 4-8
4-3 AA 501A
checkladjust step .. . . .. . ... . . .
4-13
4-4
SMPTE residual intermodulation
distortion checkladjust
.. . . . . .... .. . . . . . 4-15
4-5
Total harmonic SMPTE and CClF distortion
and CClFresidual
IM distortion checkladjust 4-16
4-6 AA 501A
top cover adjustmentsaccess ...
4-19
5-1
Main board rear interface connector
assignments..
. .. .. . ....... . .. .. . . ... 5-3
5-2
Circuit boards and connectors pictorial (top
view).
. . . . . . .. .. . . . ... ... .. ... . . . . .. 5-6
5-3
Latch assembly pictorial
...... .. .. . . .. . 5-7
iii

LIST OF TABLES
Table
No. Page
1-1 ELECTRICAL CHARACTERISTICS . . . . .. 1-2
1-2 ENVIRONMENTAL CHARACTERISTICS
. . 1-7
1-3 PHYSICAL CHARACTERISTICS
. . . . .... 1-7
2-1 Gains from INPUT terminals to FUNCTION
OUTPUT connector for various settings of
the INPUT LEVEL RANGE control
.. ... .. 2-14
3-1 TRUTH TABLE FOR U2042 OUTPUTS
. . . 3-3
3-2 INTERNAL CONNECTIONS IN U1010
DEPENDING ON LOGIC STATES OF PINS
10AND 11
.......................... 3-5
3-3 GAIN AND SWITCHING THROUGH U2031 3-6
3-4 TRUTH TABLE FOR U1021
.. . ... . ..... 3-6
4-1 Suggested Test Equipment
. . ... . . .. .... 4-2
4-2 Common Mode Rejection CHECK
.... .. . 4-9
4-3 Level Function Volts Accuracy
.. .. .. .... 4-9
4-4 Total Harmonic Distortion Accuracy CHECK 4-13
5-1 RELATIVE SUSCEPTIBILITY TO STATIC
DISCHARGE DAMAGE
. . . .. . ..... . .. . .
5-4
5-2 HIGH DISTORTION/NOISE SYMPTOMS
AND PROBABLE CAUSES
.... . ........
5-10

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OPERATORS SAFETY SUMMARY
\.
This general safety information 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 Grounding the Product
In This Manual
This product is grounded through the grounding conductor
of the power module power cord. To avoid electrical shock,
CAUTION statements identify conditions or practices that
plug the power cord into a properly wired receptacle before
can result in damage to the equipment or other property. connecting to the product input or output terminals. A pro-
tective groundconnection by way of the grounding conduc-
tor in the power cord is essential for safe operation.
WARNING statements identify conditions or practices that
can result in personal injury or loss of life.
Danger Arising From Loss of Ground
As Marked on Equipment
Upon loss of the protective-groundconnection, all accessi-
bleconductiveparts (includingknobs and controls that may
CAUTION indicates a personal injury hazard not immedi-
appear to be insulating) can render an electric shock.
ately accessible as one reads the marking, or a hazard to
property including the equipment itself.
Use the Proper Power Cord
DANGER indicates a personalinjuryhazardimmediatelyac- Use only the power cord and connector specified for your
cessible as one reads the marking. product.
Use only a power cord that is in good condition.
SYMBOLS
Refer cord and connector changes to qualified service
personnel.
In This Manual Use the Proper Fuse
indicates where applicable To avoid fire hazard, use only the fuses specified in the
cautionaryor other information is to be found. parts list for your product, and which is identical in type,
@ Protectiveground (earth)terminal. voltage rating and current rating.
ATTENTION-refer to manual.
0 Refer to manual.
Power Source
Refer fuse replacementto qualified service personnel.
Do Not Operate in Explosive Atmospheres
To avoidexplosion, do not operatethis product in an atmo-
sphere of explosive gases unless it has been specifically
certifiedfor such operation.
This product is designed to operate from a power module
that does not apply more than
250 volts rms between the
Do
Operate Plug-in Unit Without Covers
supply conductors or between either supply conductor and
ground. A protective ground connection by way of the To avoid personal injury, do not operate this product with-
grounding conductor in the power cord is essential for safe out covers or panels installed. Do not apply power to the
operation. plug-in via a plug-inextender.

SERVICING SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL OM Y
Refer also to thepreceding Operators Safety Summary
Do Not Service Alone Do Not Wear Jewelry
Do not perform internalservice or adjustment of this prod- Remove jewelry prior to servicing. Rings, necklaces, and
uct unlessanother personcapable of renderingfirst aid and other metallic objects could come into contact with danger-
resuscitationis present. ous voltages and currents.
Use Care When Servicing With Power On Power Source
Dangerousvoltages may exist at several points inthis prod- This product is intended to operate from a power module
uct.To avoid personal injury,do not touch exposedconnec- that will not apply more than
250 volts rms between the
tions and components while power is on. supply conductors or between either supply conductor and
ground.
A protective ground connection by way of the
grounding conductor in the power cord is essential for safe
Disconnect power before removing protective panels, sol- operation.
dering, or replacing components.

Section 1-AA 501A
SPECIFICATION
Instrument Description
The AA 501A is a fully automatic distortion analyzer
packaged as a two-wide TM 500 plug-in. Total harmonic
distortion is measuredwith the standard instrument.Option
01 instruments also measure SMPTEIDIN intermodulation
distortion and CClF two-tone difference frequency distor-
tion. In addition, Option 02 instruments permit noise mea-
surements in accordancewith CClR recommendation468-2
or DIN 45405.
Distortion set level, frequency tuning and nulling are fully
automatic, requiring no operator adjustment. Input level
range and distortion measurement rangeselections are fully
automatic or may be manually selected. Distortion readout
is provided in percent or dB.
The AA 501A is also a high sensitivity, autoranging, au-
dio frequency voltmeter. Readingsmay be in volts, dBm, or
dB relativeto any arbitrary reference.
Filters are includedwhich allow measurement of noiseto
IHF and FCC specifications. Option 02 instrumentsprovide
a quasi-peak detector for noise measurements in accor-
dance with CClR or DIN standards. A hum rejectionfilter is
providedas are provisionsfor externalfilters.
All readings are displayed on a
3 112 digit readout. An
uncalibratedanalog readoutis also provided to aid in nulling
and peakingapplications.
Ac to dc conversion is either average or true rms re-
sponding, allowing conformance with most standards. Op-
tion 02 instruements provide quasi-peak or true rms
detection. This feature permits compariston with readings
obtainedon other instruments.
Ac input and output connections are available on both
the front panel and the rear interface. Dc signals, cor-
responding to the displayed reading, are available through
the rear interface. This allows flexibility in interconnection
with other instrumentssuch as filters, chart recorders, spec-
trum analyzers, oscilloscopes, etc.
Performance Conditions
Theelectrical characteristicsinthis specification are valid
only if the AA 501A has been adjusted at an ambient tem-
perature between +20°C and +30°C. The instrument
must be in a noncondensing environment whose limits are
described underthe environment section. Allow twenty min-
uteswarm-uptimefor operationto specified accuracy; sixty
minutes afterexposureto or storagein a highhumidity (con-
densing) environment. Any conditions that are unique to a
particularcharacteristicare expressly stated as part of that
characteristic.
The electrical and environmental performance limits, to-
gether with their related validation procedures, comprise a
completestatementof the electrical and environmental per-
formance of a calibratedinstrument.
ltems listed in the Performance Requirements column of
the Electrical Characteristicsare verified by completingthe
Performance Check in the Calibration section of this man-
ual. ltems listedin the Supplemental Informationcolumn are
not verified in this manual.

Table 1-1
ELECTRICAL CHARACTERISTICS
Characteristics
INPUT (all functions)
Impedance
Input ranges
Maximum input voltage
Common mode rejection
(inputsshorted)
LEVEL FUNCTION
Modes
Accuracy Vi, in
2 100pV
(-78 dBm) with level ranging
indicatorsextinguished
(T<+40°C)
20 Hz to 20 kHz
10 Hz to 20 Hz and 20 kHz to
100kHz
Bandwidth
(nofilters selected)
Supplemental Information
Fulldifferential. Each side ac coupled through 1 pF
and shunted to ground by approximately200 pF.
Dualbananajack connectorsat 0.750 inchspacing
with groundconnector additionally provided.
2-6 sequence from 200 pV to 200 V Range
selectionis manualor automatic. Autoranging time
is typically
< 1 second. Separate increase range
and decrease range indicators illuminatewhenever
input level does not fall within optimumwindow for
selected range.-For specified instrument
performancebothindicatorsmust beextinguished.
300 V peak, 200 V rms either input to ground or
differentially. Will recover without damage from
continuous overloadsof 120 V rrns or 200 V rrns
for 30 minutes on all ranges. For linear response,
peak inputvoltage must notexceed
3 times INPUT
LEVEL RANGE setting.
Typically 240dB to 300 kHz.
Volts, dBm (600 R), or dB ratio with push to set 0
dB reference. lnput rangedetermines display
range. Singleeffective range in dB modes with
0.1
dB resolution. Stored 0 dB referenceis unaffected
by subsequentchanges in mode or function.
Performance Requirement
100 k R k2%,each side to
ground
200 pV to 200 V in 10steps
250dB at 50 or 60 Hz for
common mode signals up to
one-half of selected input
range or 50 mV, whichever is
greater.
VOLTS
Within
k(2%+1
count)
Within
~(4%+2
counts)
dBm OR dB
RATIO
k0.3 dB
k0.5°/o~f
reading
+ 0.5 dB
At least 300 kHz