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TM 11-6625-2749-14&P
OPERATOR'S, ORGANIZATIONAL, DIRECT SUPPORT, AND GENERAL SUPPORT
MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS)
FOR
DIFFERENTIAL AMPLIFIER AM-6786/U
(TEKTRONIX TYPE 7A22, VERTICAL PLUG-IN UNIT)
(NSN 6625-00-478-0597)
H E A D Q U A R T E R S , D E P A R T M E N T O F T H E A R M Y
OCTOBER 1979
CLEANING THE INTERIOR
Use an eye-shield when cleaning with pressurized air. Hardened dirt can be
removed with a paint brush, cotton tipped swab or cloth dampened with a
water and mild detergent solution. Avoid the use of chemical cleaning agents
that might damage the plastic parts.
SPECIFIC COMPONENT REPLACEMENT INFORMATION
Disconnect the instrument from the power source before removing or replac-
ing components.
The pushbutton switches are not repairable and should be replaced if defec-
tive. Components which are mounted on the circuit board associated with the
pushbutton switch can be replaced using the normal replacement procedure.
See the information under Light-Bulb Replacement for bulb replacement.
TM 11-6625-2749-14&P
This manual contains copyright material reproduced by permission of Tektronix, Incorporated.
T ECHNICAL M a n u a l HEADQUARTERS
DEPARTMENT OF THE ARMY
No. 11-6625-2749-14&P Washington, DC, 10 October 1979
OPERATOR'S, ORGANIZATIONAL, DIRECT SUPPORT, AND GENERAL SUPPORT
MAINTENANCE MANUAL
(INCLUDING REPAIR PARTS AND SPECIAL TOOLS LISTS)
FOR
DIFFERENTIAL AMPLIFIER AM-6786/U
(TEKTRONIX TYPE 7A22, VERTICAL PLUG-IN UNIT)
NSN 6625-00-478-0597)
Current as of 20 March 1979
REPORTING OF ERRORS
You can improve this manual by recommending improvements using DA Form 2028-2 located in
the back of the manual. Simply tear out the self-addressed form, fill it out as shown on the sample, fold
it where shown, and drop it in the mail.
If there are no blank DA Forms 2028-2 in the back of your manual, use the standard DA Form
2028 (Recommended Changes to Publications and Blank Forms) and forward to the Commander, US
Army Communications and Electronics Materiel Readiness Command, ATTN: DRSEL-ME -MQ, Fort
Monmouth, NJ 07703.
In either case, a reply will be furnished direct to you.
This manual is an authentication of the manufacturer's commercial literature which, through usage,
has been found to cover the data required to operate and maintain this equipment. Since the manual
was not prepared in accordance with military specifications, the format has not been structured to
consider levels of maintenance.
i-0.1
TM 11-6625-2749-14&P
TABLE OF CONTENTS
Page
SECTION O
Introduction . . . . . . . . . . . . . . . . . . . 0-1 `age
SECTION 1 SPECIFICATION Input Gate Current . . . . . . . . . . . . . 2-4
Introduction . . . . . . . . . . . . . . . . . . . . 1-1 Voltage Measurement . . . . . . . . . . . 2-4
Electrical Characteristics . . . . . . . . . . . 1-1 Signal Input Connectors . . . . . . . . . 2-4
Deflection Factor . . . . . . . . . . . . . . . 1-1 High Input Impedance . . . . . . . . . . . 2-5
Gain . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Display Polarity . . . . . . . . . . . . . . . 2-5
Differential Dynamic Range . . . . . . 1-1 Deflection Factor . . . . . . . . . . . . . . 2-5
DC Offset . . . . . . . . . . . . . . . . . . . . 1-1 Bandwidth Selection . . . . . . . . . . . . 2-5
Frequency Response . . . . . . . . . . . . 1-1 Voltage Comparison Measurements 2-10
Bandwidth limit . . . . . . . . . . . . . . . 1-1 Differential Operation . . . . . . . . . . 2-10
Recovery Time . . . . . . . . . . . . . . . . 1-1 DC Offset Operation . . . . . . . . . . . . 2-11
Common-Mode Signal Range . . . . 1-1 Input Overdrive Indicator . . . . . . . . 2-12
Common-mode Rejection Ratio . . . . 1-1 Readout . . . . . . . . . . . . . . . . . . ...2-12
Maximum input Voltage . . . . . . . . 1-3 Trace Identify . . . . . . . . . . . . . . . 2-13
Input Rand C . . . . . . . . . . . . . . . . . 1-3
Maximum Input Gate Current . . . . 1-3
Variable Balance . . . . . . . . . . . . . . 1-3 SECTION 3 CIRCUIT DESCRIPTION
Step Attenuator DC Balance . . . . . . 1-3 Introduction . . . . . . . . . . . . . . . . . . . . 3-1
Displayed Noise Block Diagram Description . . . . . . . . . 3-1
(Tangentially Measured) . . . . . . . 1-3
Input Coupling . . . . . . . . . . . . . . . . 3-1
DC Drift . . . . . . . . . . . . . . . . . . . . . 1-3 3-1
Input Attenuators . . . . . . . . . . . . . .
Isolation between + and -- Inputs 1-3 3-1
Preamp . . . . . . . . . . . . . . . . . . . . . .
Environmental Characteristics . . . . . . . 1-3 3-1
L F -3 dB Point . . . . . . . . . . . . . . .
Altitude . . . . . . . . . . . . . . . . . . . . . 1-3 . . . . . . . . . . . . . . 3-2
Output Amplifier
Transportation . . . . . . . . . . . . . . . . 1-3
H F -3 dB Point . . . . . . . . . . . . . . 3-2
Physical Characteristics . . . . . . . . . . . . 1-3 3-2
General Information . . . . . . . . . . . . . .
Finish . . . . . . . . . . . . . . . . . . . . . . . 1-3
Feedback Amplifiers . . . . . . . . . . . . 3-2
Dimensions . . . . . . . . . . . . . . . . . . . 1-3 Differential Configuration . . . . . . . 3-3
Weight . . . . . . . . . . . . . . . . . . . . . . 1-3
Detailed Circuit Description . . . . . . . . 3-3
Input Coupling . . . . . . . . . . . . . . . . 3-3
SECTION 2 OPERATING INSTRUC- Input Attenuators . . . . . . . . . . . . . . 3-4
TIONS Gate Current Compensation . . . . . . 3-4
Introduction . . . . . . . . . . . . . . . . . . . . 2-1 Input Amplifier . . . . . . . . . . . . . . . . 3-4
Front Panel Controls and Connectors . 2-1 X15 Preamp . . . . . . . . . . . . . . . . . 3-4
Operating Instructions . . . . . . . . . . . . . 2-2 DC Balance . . . . . . . . . . . . . . . . 3-4
First Time Operation . . . . . . . . . . . 2-2 Floating Power Supply . . . . . . . . 3-5
General Operating Information . . . . . 2-4 Common-Mode Rejection . . . . . . 3-5
Trace Drift . . . . . . . . . . . . . . . . . . . . 2-4 Cross Neutralization . . . . . . . . . . 3-6
i
TM 11-6625-2749-14&P
TABLE OF CONTENTS
Page Page
Input Overdrive Protection . . . . . 3-7 Detailed Troubleshooting . . . . . . . . . . 4-4
DC Off set . . . . . . . . . . . . ...... 3-7 General . . . . . . . . . . . . . . . . . 4-4
Offset Generator . . . . . . . . . . . . 3-7 Test Equipment Recommended . . . . 4-4
Input Overdrive Indicator . . . . . . 3-8 DC Balance Check . . . . . . . . . . . . . 4-4
L F -3 dB Point Selector . . . . . . 3-9 Troubleshooting by Direct
Output Amplifier . . . . . . . . . . . . . . 3-9 Replacement . . . . . . . . . . . . . . . . 4-5
Gain Switching Amplifier . . . . . . 3-9 Component Checks . . . . . . . . . . . . . 4-6
Variable Output Stage . . . . . . . . . 3-11 Transistors . . . . . . . . . . . . . . . . . 4-6
Signal Output Amplifier . . . . . . . 3-11 Diodes . . . . . . . . . . . . . . . . . . . . 4-6
Trigger Output Amplifier . . . . . . . 3-11 Resistors . . . . . . . . . . . . . . . . . . . 4-6
Indicator Oscilloscope Readout . . . . 3-11 Capacitors . . . . . . . . . . . . . . . . . 4-7
Probe Sensing . . . . . . . . . . . . . . . 3-11
SECTION 5 PERFORMANCE CHECK/
Trace Identify . . . . . . . . . . . . . . 3-11
CALIBRATION PROCEDURE
Introduction . . . . . . . . . . . . . . . . . ... 5-1
SECTION 4 MAINTENANCE Test Equipment Required . . . . . . . . . . . 5-1
Introduction . . . . . . . . . . . . . . . . . . . . 4-1 General . . . . . . . . . . . . . . . . . . . . . 5-1
Preventive Maintenance . . . . . . . . . . . 4-1
Short Form Procedure . . . . . . . . . . . . . 5-2
General . . . . . . . . . . . . . . . . . . . . . 4-1
Performance Check/Calibration
Cleaning Front Panel . . . . . . . . . . . . 4-1 Procedure . . . . . . . . . . . . . . . . . , . . 5-3
Cleaning Interior . . . . . . . . . . . . . . . 4-1 General . . . . . . . . . . . . . . . . . . . . . 5-3
Visual Inspection . . . . . . . . . . . . . . 4-1 Preliminary . . . . . . . . . . . . . . . . . . . 5-3
Transistor Checks . . . . . . . . . . . . . . 4-1 Check or Adjust . . . . . . . . . . . . . . . 5-4
Calibration . . . . . . . . . . . . . . . . . . . 4-1 AC Atten Balance . . . . . . . . . . . . 5-4
Corrective Maintenance . . . . . . . . . . . . 4-1 Variable Balance . . . . . . . . . . . . 5-4
General . . . . . . . . . . . . . . . . . . . . . 4-1 Coarse DC Balance. . . . . . . . . . 5-4
Obtaining Replacement Parts . . . . . 4-2 + Gate Current Zero . . . . . . . . 5-5
Special Parts . . . . . . . . . . . . . . . . . . 4-2 - Gate Current Zero . . . . . . . 5-5
Soldering Techniques . . . . . . . . . . . 4-2 GAIN . . . . . . . . . . . . . . . . . . . . . 5-5
Component Replacement Information 4-3 VARIABLE Control Ratio . . . . . 5-5
Troubleshooting . . . . . . . . . . . . . . . . . 4-3 VOLTS/DIV Gain Switching . . . . 5-5
Introduction . . . . . . . . . . . . . . . . . . 4-3 Isolation between + and -
Indicator Oscilloscope . . . . . . . . . . . 4-4 Inputs . . . . . . . . . . . . . . . . . . . 5-7
Operating Procedure and Total DC Offset Range . . . . . . . . 5-7
Control Settings . . . . . . . . . . . . . 4-4 C241 + Cross Neutralization . . . 5-7
Trouble Symptoms .............. 4-4 C141 - Cross Neutralization . . . 5-8
Visual Inspection . . . . . . . . . . . . . . . 4-4 Cl 15 Xl +Input Atten Time
Calibration Check . . . . . . . . . . . . . . 4-4 Constant . . . . . . . . . . . . . . . . . 5-8
ii
TM 11-6625-2749-14&P
TABLE OF CONTENTS
Page SECTION 6 ELECTRICAL PARTS LIST
C215 x1 - Input Atten Time Abbreviations and Symbols
Constant . . . . . . . . . . . . . . . . . 5-8 Parts Ordering Information
Input Atten Accuracy . . . . . . . . . 5-9 Index of Electrical Parts List
Input Atten Differential Balance . 5-9 Electrical Parts List
+ Input Atten S e r i e s
Compensation . . . . . . . . . . . . . 5-10
- Input Atten Compensation . . . 5-10
SECTION 7 DIAGRAMS AND ME-
CHANICAL PARTS ILLUSTRATIONS
-input A t t e n S h u n t
Compensation . . . . . . . . . . . . . 5-11 Diagrams
H F -3dB Point . . . . . . . . . . . . 5-12 Mechanical Parts Illustrations
L F -3dB Point . . . . . . . . . . . . . . . . . . . . . . .5- 12
CMRR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .5-13 SECTION 8 MECHANICAL PARTS
Input Overdrive Indicator . . . . . . 5-13 LIST
Differential Dynamic Range . . . . 5 - 1 4 Mechanical Parts list Information
Overall Noise Level Index of Mechanical Parts Illustrations
(Measured Tangentially) . . . . . 5-15 Mechanical Parts List
Overdrive Recovery Time . . . . . . 5-15
SECTION 10 CALIBRATION TEST SECTION 9 PART NUMBER-NATIONAL STOCK
EQUIPMENT REPLACEMENT NUMBER CROSS REFERENCE INDEX.
APPENDIX A. REFERENCES A- 1
B. COMPONENTS OF END ITEM LIST (Not Applicable)
C. ADDITIONAL AUTHORIZATION LIST (Not Applicable)
D. MAINTENANCE ALLOCATION
Section I. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1
II. Maintenance Allocation Chart for Differential Amplifier
AM-6786/U D-4
III. Tool and Test Equipment Requirements for Differential
Amplifier AM-6786/U . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-5
APPENDIX E. EXPENDABLE SUPPLIES AND MATERIALS LIST (Not Applicable)
iii
TM 11-6625-2749-14&P
LIST OF ILLUSTRATIONS
Figure Page
1-1 Type 7A22 Differential Amplifier. . . . . . . . . . . . . . . . . A
1-2 CMRR vs Frequency for signal not exceeding Common Mode
Signal Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
2-1 Signals applied to the + INPUT Connector Produce an
Upright Display, while signals applied to the - INPUT
are inverted . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2-2 Location of AC ATTEN BAL Control . . . . . . . . . . . . . . . . 2-3
2-3 Location of wire strap between input line and internal
gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2-4A 7A22 CMRR at 10 uV/Div to 10 mV/Div. Inputs DC Coupled.
Worst-case degradation due to source resistance . . . . . . . . 2-6
2-4B 7A22 Bandwidth and VOLTS/DIV Error as functions of Source
Resistance . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2-5 7A22 FREQUENCY RESPONSE as a function of LF -3 dB POINT
SETTING (HF-3 dB POINT at l MHz) . . . . . . . . . . . . . 2-8
2-6
7A22 FREQUENCY RESPONSE as a function of HF -3 dB POINT
settings (LF -3 dB POINT of DC). . . . . . . . . . . . . . . . . . . . . . . . 2-9
2-7 Improving signal-to-noise ratio by setting bandwidth . . . . . 2-10
2-8 Waveforms showing differential rejection of a common-mode
signal ............................................. 2-11
2-9 Connecting a differential amplifier across a circuit . . . . . 2-12
3-1 Generalized feedback system showing the relation between
input and output . . . . . . . . . . . . . . . . . . . . . . 3-2
3-2 Feedback amplifier (Single-ended version). . . . . . . . . . . . . . . . 3-2
3-3 Feedback amplifier (Differential configuration). . . . . . . . . . 3-3
3-4 Gate Current Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3-5 Common-mode Rejection using floating power supply . . . . . . . . 3-5
3-6 Input cross neutralization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3-7 Effects of high impedance to ground in the - INPUT . . . . . . . 3-7
iv
TM 11-6625-2749-14&P
Figure Page
3-8 (A) Overdrive Protection System showing current paths.
(B, C) Sequence of events leading to excessive
overdrive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
3-9 Offset system showing (A) Conditions with zero offset, (B)
0.25V DC offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
3-10 Functional arrangement of the offset generator . . . . . . . . . . . 3-10
3-11 Partial Low Frequency -3 dB Point selector for + Input
amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
4-1 Removing or replacing component on circuit board . . . . . . . . . 4-2
4-2 Transistor junction-voltage measurements . . . . . . . . . . . . . . . . . 4-6
4-3 Transistor base pin and socket arrangement . . . . . . . . . . . . . . . 4-7
4-4 Diode polarity and color code . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
4-5 Color code for resistors and ceramic capacitors . . . . . . . . . . 4-8
4-6 Plain circuit board (components) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-10
4-7 Main circuit board (wire color code) . . . . . . . . . . . . . . . . . . . . . 4-11
4-8 Bandwidth circuit board (components and wire color code) . 4-12
5-1 Left side of the 7A22 showing adjustment locations . . . . . . . 5-4
5-2 Equipment required for steps 6 through 19 . . . . . . . . . . . . . . . . 5-6
5-3 Typical waveform showing (A) Cross neutralization properly
adjusted, (B) incorrectly adjusted . . . . . . . . . . . . . . . . . . . . . 5-7
5-4 Typical waveform showing (A) Correct adjustment of Input
Attenuator Time Constant. (B) and (C) incorrect
adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-8
5-5 Typical display obtained when Input Attenuators are
adjusted for optimum differential balance . . . . . . . . . . . . . . 5-9
5-6 Typical display obtained with - Input attenuator adjusted
for optimum Common-Mode signal rejection. (A) C208C
adjusted properly (B) C209C adjusted properly . . . . . . . . . . 5-10
5-7 Equipment required for steps 20 through 24 . . . . . . . . . . . . . . . 5-11
5-8 Right side of Type 7A22 showing location of adjustments . . 5-12
v
TM 11-6625-2749-14&P
Figure Page
5-9 Equipment required for step 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14
5-10 Typical display showing (A) two noise bands and (B) merging
noise bands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15
5-11 Equipment required for step 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-16
5-12 Typical waveform showing overdrive recovery time . . . . . 5-16
vi
TM 11-6625-2749-14&P
Fig. 1-1. Type 7A22 Differential Amplifier.
Type 7A22
TM 11-6625-2749-14&P
SECTION 0
INTRODUCTION
0-1. SCOPE
This manual describes Vertical Plug-In Unit, Differential Amplifier AM-
6786/U and provides instructions for operation and maintenance. Throughout
this manual, the AM-6786/U is referred to as Tektronix Type 7A22 Differential
Amplifier. The maintenance allocation chart appears in appendix D. Also,
included is a repair parts list.
0-2. INDEXES OF PUBLICATIONS
a. DA Pam 310-4. Refer to the latest issue of DA Pam 310-4 to determine
whether there are new editions, changes, or additional publications pertaining
to the equipment.
b. DA Pam 310-7. Refer to DA Pam 310-7 to determine whether there are
modification work orders (MWO'S) pertaining to the equipment.
0-3. FORMS AND RECORDS
Reports of Maintenance and Unsatisfactory Equipment. Maintenance
forms, records, and reports which are to be used by maintenance personnel
at all maintenance levels are listed in and prescribed by TM 38-750.
b. Report of Packaging and Handling Deficiencies. Fill out and forward
DD Form 6 (Packaging Improvement Report) as prescribed in AR 700-58/NAVSUPINST
4030.29/AFR 71-13/MCO P4030.29A and DLAR 4145.8.
Discrepancy in Shipment Report (DISREP) (SF 361). Fill out and for-
ward Discrepancy in Shipment Report (DISREP) (SF 361) as prescribed in AR
55-38/NAVSUPINST 4610.33B/AFR 75-18/MCO P461O.19C and DLAR 4500.15.
0-4. REPORTING EQUIPMENT IMPROVEMENT RECOMMENDATIONS (EIR)
EIR's will be prepared using DA Form 2407, Maintenance Request. Instruc-
tions for preparing EIR's are provided in TM 38-750, The Army Maintenance
Management System. EIR's should be mailed direct to Commander, US Army
Communications and Electronics Materiel Readiness Command; ATTN: DRSEL-ME-MQ,
Fort Monmouth, NJ 07703. A reply will be furnished directly to you.
0-5. ADMINISTRATIVE STORAGE
Administrative storage of equipment issued to and used by Army activities
shall be in accordance with TM 750-244-2.
0-6. DESTRUCTION OF ARMY ELECTRONICS MATERIEL
Destruction of Army electronics materiel to prevent enemy use shall be
in accordance with TM 750-244-2.
0-1
TM 11-6625-2749-14&P
SECTION 1
SPECIFICATION
Introduction DC OFFSET
h Type 7A22 Vertical Plug-in is a DC coupled differ- COARSE Range from
enticd amplifier with excellent common-mode reiection char- Electrical Zero
acteristics and high gain for low level applications. 10 pV/Div to At least +1 V to ◦ Jabse Service Manual Search 2024 ◦ Jabse Pravopis ◦ onTap.bg ◦ Other service manual resources online : Fixya ◦ eServiceinfo