TR-20 Computer Maintenance Series
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COMPUTER
M aintenance oO) erves
© ELECTRONIC ASSOCIATES, INC. 1966 @ PRINTED IN U.S.A. @ PUBL. NO. 00 800.2006-0 @® AUGUST 1967
RELATED PUBLICATIONS
The table below lists other publications which may be of interest to the readers of this manual.
Unless otherwise indicated by title or footnote, all are maintenance handbooks. Note that main-
tenance handbooks directly applicable to a particular system are normally supplied with the sys-
tem.
Title Publication Number
Handbook of Analog Computation 00 800. 0001-3
TR-20 Computer Operators Reference Handbook 00 800. 2003-1
Sine-Cosine Diode Function Generators, Models 16.313 and 16.314 00 800, 2005-0
TR-20 Maintenance Manual 00 800. 2006-0
Transport Delay Simulator, Type 2.448 00 800. 2009-0
Reactor Kinetics Group, Type 2. 475 00 800. 2010-0
Dual DC Amplifier, Model 6. 282 00 800. 2011-0
Quarter-Square Multiplier 7.045 00 800. 2013-0
Dual x? Diode Function Generator 16,101 00 800. 2016-0
Dual Log X Diode Function Generator 16.126 00 800. 2017-0
Dual One-Half Log X Diode Function Generator 16.133 00 800. 2018-0
Variable Diode Function Generator 00 800. 2019-0
Variable Diode Function Generator 16.156 00 800. 2020-0
Signal Comparator 6.143 00 800. 2023-0
Repetitive Operation Display Unit 34.034 and 34. 035 00 800. 2024-1
Dual Coefficient Attenuators 42.183, 42.187 and 42.188 00 800. 2025-0
Reference Regulator 43. 037 00 800. 2027-0
Bi-Polar Multiplier, Models 7.117 and 7.137 00 800. 2038-0
NOTICE
In order to enable us to process your requests for spare parts and replacement items quickly
and efficiently, we request your conformance with the following procedure:
1. Please specify the type number and serial number of
the basic unit as well as the EAI part number and de-
scription of the part when inquiring about replacement
items such as potentiometer assemblies or cups, re-
lays, transformers, precision resistors, etc.
2. When inquiring about items as servo multipliers, re-
solvers, networks, printed circuit assemblies, etc.,
please specify the serial numbers of the major equip-
ment with which the units are to be used, such as:
Console, Type 8811, Memory Module, Type 4. 204,
Serial No. 000, etc. If at all possible, please in-
clude the purchase order or the EAI project number
under which the equipment was originally procured.
Your cooperation in supplying the required information will speed the processing of your requests
and aid in assuring that the correct items are supplied.
It is the policy of Electronic Associates, Inc. to supply equipment patterned as closely as possi-
ble to the requirements of the individual customer. This is accomplished, without incurring the
prohibitive costs of custom design, by substituting new components, modifying standard com-
bonents, etc., wherever necessary to expedite conformance with requirements, As a result,
this instruction manual, which has been written to cover standard equipment, may not entirely
concur in its content with the equipment supplied. It is felt, however, that a technically quali-
fied person will find the manual a fully adequate guide in understanding, operating, and main-
taining the equipment actually supplied.
Electronic Associates, Inc. reserves
the right to make changes in design,
or to make additions to or improve-
ments in its product without imposing
any obligation upon itself to install
them on products previously manufac-
tured.
M226-3 PRINTED IN U.SoAc
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Princeton, New Jersey: U.S. Route No. 1, P.O. Box 582, Princeton, New Jersey 08541, Telephone: 609-452-2900
Resident Field Engineers: Bedford, Mass./Florham Park, N. J./Washington, D.C./Baltimore, Md./Eatontown, N. J.
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Cleveland District Office: 6741 Ridge Road, Parma, Ohio 44129, Telephcne: 216-842-1840
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SOUTHERN REGION
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Telephone: 205-881-7031
Field Engi San Antonio, Texas/A do, New Mexico/Tulsa, Oklahoma/Houston, Texas
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Western U.S. Headquarters: CUSTOMER REPAIR FACILITY, 1500 East Imperial Highway, E) Segundo, California 90245,
Telephone: 213-322-3220, TWX 910-348-6284
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Telephone: 213-322-3220, TWX 910-348-6284
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Resident Field Engineers: Edwards, California/Pasadena, California/Moffet Field, California/Martin Marietta Corp., Denver,
Colorado/Ryan Aeronautical, San Diego, California
CANADA
Toronto Office: Allan Crawford Associates, Ltd., 65 Martin Ross Avenue, Downsview Ontario, Canada, Tel: 416-636-4910
ANALYSIS AND COMPUTATION CENTERS
peineeten Analysis and Camputation Center: U.S. Route No, 1, P.O. Box 582, Princeton, New Jersey 08541, Telephone: 609-
452-
Los Angeles Analysis and Computation Center: 1500 East Imperial Highway, El Segundo, California 90245, Telephone: 213-
322-3220, TWX 910-348-6284
San Francisco Analysis and Computation Center: 4151 Middiefield Road, Palo Alto, California 94303, Tel: 415-321-0363,
TWX 910-373-1241
i D.C. A is and ion Center: 12260 Wilkins Avenue, Rockville, Maryland 20852, Tel: 301-933-4100
ysis and Pp ion Center: 7007 Gulf Freeway, Room 128, Houston, Texas 77017, Tel: 713 Ml 4-3678
Engineering and Manufacturing Division
Engineering Department: West Long Branch, N. 4. 07764, Tel: 201-229-1100, TWX 710-722-6597, Telex 01-26655, Cable:
PACE West Long Branch, N. J. 07764
Manufacturing De attments West Long Branch, N. J, 07764, Tel: 201-229-1100, TWX 710-722-6597, Telex 01-26655, Cable:
PACE West Long Branch, N. J. 07764
Other Departments, Divisions and Subsidiaries
Ee rament Division: Long Branch, N. J. 07740, Tel, 201-229-4400, TWX 710-722-6597, Cable: PACE West Long Branch, N. J.
Pacific Data Systems, Inc.: 644 Young Street, Santa Ana, California 92705, Tel, 714-540-3610, TWX 714.546-3049
Scientific instruments Department: 4151 Middlefield Road, Palo Alto, California 94303, Tel: 415-321-7801, TWX 910-373-1241
INTERNATIONAL SALES & CUSTOMER SERVICES OFFICES
UNITED KINGDOM & SCANDINAVIA
Electronic Associates, Ltd.: Burgess Hill, Sussex, England, Tel; Burgess Hill (Sussex) 5101-10, 5201-5, Telex: 87183, Cable:
PACE Burgess Hill
Northern Area Office: Roberts House, Manchester Road, Altrincham, Cheshire, Tel: Altrincham 5426
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10064, Cable: PACE STOCKHOLM
EUROPEAN CONTINENT
EAE { Office: Centre International, 22nd Floor, Place Rogier, Brussels 1, Belgium, Tel: Brussels
18-40-04, Telex: 2.21-106, esgic! PACEBELG Brussels
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EAI Electronic Associates SARL: 72-74, rue de la Tombe Issoire, Paris 14e, France, Tel: 535,.01.07, Telex 27610
GERMANY
EAI-Electronic Associates GMBH: 5100 Aachen, Bergdriesch 37, West Germany, Tel: Aachen 2 60 42; 2 60 41, Telex 832.676 eai d
AUSTRALIA & NEW ZEALAND
EAI-Electronic Associates, Pty., Ltd.: 26 Albany St., Leonards, N.S.W. Australia, Tel: 43-7522, Cable: PACEAUS, Sydney
Victorian Office: 34 Queens Road, Melbourne S. C. 2, Australia, Tel: 26-1329, Cable: PACEAUS, Melbourne
JAPAN
EAI-Electronic Associates (Japan), Inc.: 9th Mori Building, 1-3 Shiba-Atago-cho, Minato-Ku, Tokyo, Japan, Tel: 433-4671,
Telex: 7814285, Cable: EAIJAPACE
ENGINEERING AND MANUFACTURING
Electronic Associates, Ltd.: Burgess Hill, Sussex, England, Tel: Burgess Hill (Sussex) 5101-10, 5201-5, Telex: 87183, Cable:
PACE BURGESS HILt
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PACEMEX
COMPUTATION CENTERS
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5101-10, Telex: 871-183, Cable: PACE BURGESS HILL
Australian Computation Center: 34 Queens Road, Melbourne S. C. 2, Australia, Tel: 26-1329, Cable: PACEAUS, Melbourne
©
EAI ELECTRONIC ASSOCIATES, INC. West Long Branch, New Jersey 07764
ADVANCED SYSTEMS ANALYSIS AND COMPUTATION SERVICES/ ANALOG COMPUTERS/DIGITAL COMPUTERS/HYBRLD ANALOG-DIGITAL COMPUTATION EQUIPMENT/ANALOG AND DIGITAL
PLOTTERS/SIMULATION SYSTEMS/SCIENTIFIC AND LABORATORY INSTRUMENTS/ INDUSTRIAL PROCESS CONTROL SYSTEMS / PHOTOGRAMMETRIC EQUIPMENT/ RANGE INSTRUMENTA- '
TION SYSTEMS/TEST AND CHECK-OUT SYSTEMS/MILITARY AND INDUSTRIAL RESEARCH AND DEVELOPMENT SERVICES/FIELD ENGINEERING ANO EQUIPMENT MAINTENANCE SERVICES. Bulletin No. 1L-64104-10
Printed in U.S.A. July, 1967
CHAPTER
CONTENTS
I - THE TR-20 COMPUTER
GENERAL DESCRIPTION. .cccccccccccceccccccvcccccscssccsesscess
EQUIPMENT COMPLEMENT. ccccccceccvcces evcccccccccccccsccscees
OPERATING AND MAINTENANCE ACCESSORIES ....cccccccccceccccsses
PRELIMINARY CHECKOUT... ecccccccccccvcccccccccvcccssesscesese
e Visual INSPECtion..cocceccscressneesccccessccevesseresese
|m
jo
Insertion of Pre-Patch Panel. cosccccccccccvescsecscececes
Feedback for the Amplifiers. ccccccccvccccscccccccevescce
Ja
e
1A.
e
Application of Primary Power. ceccccccccescesccoseccccose
@. Operational Checks.scercccccccccccsccevccreevesesssccece
INSTALLATION OF PATCHING BLOCKS AND CONTACT SPRINGS.....0n0-
CHASSIS AND ETCHED CARD REMOVAL. ...cccccecsecevcvsssccsscvcs
OUTPUT DEVICES .ccccccc avec ccc ees cece ec ee een cess esveveepeoes
II - DUAL DC AMPLIFIER, MODEL 6.712
INTRODUCTION... ccccccceccccccecscece ec eeseesee esses eres enoeee
TECHNICAL DATA ,acsws cee cscs e cinevecenceneceensers esi seed sonies
OPERATING CONSIDERATIONS .. cocccccccccccccv ccc ccceseseoveccce
a. Patching cevcecvcccccccvecceresscvsseseccosevarescsesenes
b. Amplifier Balancing ceocccvccccsvccccececvoscecenseveseses
Cc. Overloads .crccccccccccccccccscecccccenccceeereereeeebere
CIRCUIT DESCRIPTION... ccccccccrccccccescceee esos oe ce eees eases
a. Basic Block Diagram. cccoccccossccsecccccscssereccsesseves
b. The DC Amplifier SECtLON, ecccccccceccvescoresccseseseese
Cc. The Stabilizer SECCLIONs peocceccccccecnsecesecsseeenrecos
11
11
11
Lo
15
15
15
15
17
18
18
18
20
23
TEST PROCEDURES, .
|@
CONTENTS (Cont)
ec@eoeeoceeeeoeveeoeneeeeoe eevee eeened
e Frequency RESPONSE, crvescerecceceveveasesecressesvcces
b. Offset MeASUTEMENt. .cccccarecccccccecrceccessccceavceecs
Cc. Noise Measurement, ..ccsccvccvevcccscsccevecevscesesseces
d, Output Current CapadLl sty ic ccovcctiew adds eves Cues atiesee
TROUBLESHOOTING... cc ccc ccc ccc ccccccccucseccevcccccssesecceve
a. Failure to Balance. .r.ceccccecvecssseccscersccscvsscceseses
ja jo |e
[o
DC Amplifier Section CHECK, sccwa cess weds s Ree e TRO wT ST ee
Stabilizer Check, .ccccccccvcvesccoececeecccescescesceces
Some Symptoms and Possible Remedies... ....sccceccccccess
. Amplifier Voltage and Resistance Checks.....ccsscscvcces
CHAPTER III - DUAL {NTEGRATOR NETWORK, MODEL 12,1116
6.
CHAPTER
il
GENERAL DESCRIPTION: o.s.cicesasineu we ee’ oe eteveeeseeww tees ieee ws
TECHNICAL DATA. ,cccrnccccccccevecccecvcvccseveseesccecececess
PATCHING «wc nce eee ene ea cee HKEET ENED SO EEN ERES OES HNHES ROR BE
CIRCUIT DESCRIPTION oo wceee queen UCU EMER RO TR REDE O EE HERD ®
TEST PROCEDURES... cc cccccccccscescccsces
a. Operational Check,,
c. Integrator Drift Rate... ..cccseeesceccescccecse
TROUBLESHOOTING....
b, Initial Condition Resistor Ratio... ..c.ecece
@eoogaeeaaeeoaeeoeoneeoaceeseoeoeeeee eee eoe
eooeveonovoeeseoeoo0eo0e FS Peeve Hee H OBO KR eFCHe HAH AYA
IV - QUARTER-SQUARE MULTIPLIER, MODEL 7.045
GENERAL DESCRIPTION
TECHNICAL DATA,
PATCHING. .....e000;
CIRCUIT DESCRIPTION
@eeowroevseonoeenoooes one eooeoeeeeooeeroeesceeeead
eeoeococmseeereveoceeeeeneoeeeCeneeoeevoeaenoeee0eove eee
eocoeeoooveeneaseoeeenneneneove ove
25
25
25
26
26
26
27
27
27
33
mR
33
33
35
35
35
35
37
39
39
39
41
CONTENTS (Cont)
Page
5. MAINTENANCE, .. cc ccccccccc cc ccc ccc ccc c ence reece cece aceccecccs 43
a. Error TOSt. ce cecccccc caren nscracsececerecsscscescecseecns 43
b. Adjustment Procedure... .csssecrecvecccccccvccccvcesovese 45
c. Troubleshooting. ..cccccccccccccscccccscceescssccessccens 45
CHAPTER v - x¢
DIODE FUNCTION GENERATOR, MODEL 16.101
1, GENERAL DESCRIPTION. .....cccccenccccncecseneccencesesssceses 47
2. TECHNICAL DATA... ..cccccccccccccccccccevcccssencssensesceess 47
BD, PATOHING..,ccsecctccnbassesdeegneussiseessvesscveseevestusen 47
4, CIRCUIT DESCRIPTION... ..ccccc cece cs cnccccscseecceecesnsesecs 49
5. MAINTENANCE, .ccceccccccccccwccccccrcccccccccceccccescscccces 49
a. Adjustment Procedure... ...ccccecvcecacccececsvecsscscece 49
b. Troubleshooting.....ccsececcecccccccccccccncccscvcccenes 52
CHAPTER VI - DUAL LOG X DFG, 16.126 AND DUAL 1/2 LOG X DFG, 16.133
1, GENERAL DESCRIPTION... ..ceccecccccncnccccccceveccecccssceces 53
2. TECHNICAL DATA... ..cceeccecccccccc sens ecccecsescscseessevces 53
3. PATCHING. ....cccecccnccccccccccnccscseecsessessscenseccceees 55
4, CIRCUIT DESCRIPTION. .... cece sec ce cc ceececcsserssccorvsssecs 55
5. MAINTENANCE, ...cccecsceec cscs ccccnerccceseceercsesersesseens 55
a. Adjustment Procedure... ..cccescssceccenevccccsveccecnceve 55
b. Troubleshooting... cc ccccccncccccvcsccrcvesvcsccssesevenes 58
CHAPTER VII - VARIABLE DIODE FUNCTION GENERATOR GROUPS 2,645 AND 2,713
1. GENERAL DESCRIPTION, .....cccceccccccccscccccsnsecscesceseces 59
2. TECHNICAL DATA... . ccc ccc eee nec ce cence ces esc ressecesevesces 61
3. OPERATING INCSTRUCTIONS ... cr cccccccc ccc evercesccescesesccees 61
{@
C) SCOPE . ccecon ce ws seb ha CSOSCETCEN ES COKE DSTO CHET O SW OO 8 61
[>
° PASC RLAS, on see e. UE ERROR EN SINESS UMKSN MESSRS SEM Se wR EO mY 62
Lii
CONTENTS (Cont)
CIRCULT DESCRIPTION. ...cccccaccccsctecves
a, Fixed Breakpoint VDFG.....
b. Variable Breakpoint VDFG........ccccccececas
MAINTENANCE, .
|»
. Fixed Breakpoint VDFG's..
b, Variable Breakpoint VDFG'S......eccceeseves
CHAPTER VIII - COEFFICIENT ATTENUATOR GROUPS
CHAPTER
iv
l,
GENERAL DESCRIPTION. .....ucccccececccecrccevssceersssececece
CIRCUIT DESORIPEION. osc 0008 iRe ae eee KNEE ED DEKE DROME wE
MATIITENANCE ccc oped es 004d REEEE DERM E eas G cree renee mhEEES
IX - SIGNAL COMPARATORS AND FUNCTION SWITCHES
RELAY COMPARATOR, MODEL Os14S cess cess cs aaeea METH RE TE HOD A Le
[»
General Description. ..c..eesoee
eee eeeeoeeeeoneseeeoeveeoeeene
Is
Technical Data,....
e@aceoeeevoevoveeeeeneeoeaeveeeveeeeoseeeev oe oen
Ke)
Circuit Description,
eeoeeeeeeoeveece erent oeoesoneeoseeeeereaevneees
}a.
°
Adjustment of Voltage Switching Level.........cccceceeee
e. Maintenance,...,
ELECTRONIC COMPARATOR, MODEL 40,538...
a. General Description......
b. Technical Data,........ TeTerretriT Cee ee ATS as WERE we
c. Block Diagram Analysis.......cceeeeee STTrrerTrrrerrrer Try
ad. Circuit Déseription, vice. sccews TerTTI TEC eerie weTrecty’
e. Maintenance,,.... errr rrr Tr rt de eewieneenwen eer rr <
Page
62
62
65
65
65
67
69
69
71
73
73
73
73
75
75
77
77
79
79
81
85
CONTENTS (Cont)
3. DUAL FUNCTION SWITCH GROUP ye i) rr 87
CHAPTER X - MANUAL MODE CONTROL, REPETITIVE OPERATION, AND MONITORING
CIRCUITS
1. READOUT FACILITIES... ccc ccc cc ccc crc erence ccccccesccesaccees 91
2. MANUAL MODE CONTROL. .....ccescevcoees
eeoeeoeereceoeeseeoeeeseeoeeeosene 91
BD. STAVING sco nccwesvess we
eoeeseeoeneeesceseeaeeeeeeeseeoeeeeeoveseeoeveos 93
4, REPETITIVE OPERATION GROUP 2.715... ..cscecscccccvcnccccccceess 95
|»
General Description... .....0020000000> PerVrrrrrry rrr re Tr ri 95
Is
e
Dual Integrator Network 12,1115 .... ccc ccs ccccccsscesccces 95
Jo
s
Repetitive Operation Control Panel 20.532......cccccvecees 96
fen
Timing Unit, Model 36,082... ...ccccccccecesccecrvcccecevens 96
e, Adjustment of Reset and Operate TimeS.......cccceesceseces 97
£. Repetitive Relay Checks... ..aseccseercsesvcsvcvcesccnvene 99
5. READOUT AND DISPLAY NETWORKS .,.......ccccccscccvevvacevvscsscees 101
& Model 12,987 Display Network. ...csccwnscasccwewncvensse ane 101
b. Model 40.538 Electronic Comparator.....ccccccccccsccncsecs 101
6. OVERLOAD INDICATORS... cc cccvcccnccccccccccccccncecessccccccens 103
a. Visual Overload Indicators... ...ccccccccccccccncccccccerce 103
b, Audio Overload Alarm, Model 13.017.......ccccccccesceccece 103
CHAPTER XI - POWER AND REFERENCE VOLTAGE SUPPLIES
ie)
General Description. ..ccwccsccccsccccvccvessssescesccevsers 107
Io
LECHHLCAL DAC. co ccvccves sees sees S TESS Sede es NESE wees 107
Ke)
e
Circuit Description...
ecoeeevvesevseeeeneeeeceeeneeeeseeseeeeoee 109
[a
Output Voltage Adjustment..........000-
cece cere ccesoccceee 110
1
e
Troubleshooting...
weeseeoewoeeseereoeereeeesees eevee eee eoeeeeeres 110
Bis
4,
APPENDIX
tbs
2.
APPENDIX
l,
2.
APPENDIX
APPENDIX
vi
CONTENTS (Cont)
REFERENCE REGULATOR, MODEL 43,037... .cccccccccccccccccccccces 111
a. General DeSCription., ...cccccccceccvccecccccacecsccecseces 111
b. Technical Dales ccwewcs ee Ke eeE TENE EMH OR TONER SMH ETE TES 111
ce Circuit DESCLIPtion...ccccceccsccccccccccccssccsccvcseces 111
Patching. .
@neeeeeseveeceseeeevreeveeeavpeeeeeseeneneenaeeoeeeeenee 113
Ja.
ie)
- Adjustments... ..cccccccccccwcccccccccccesccucecucescecacs 113
£. Troubleshooting. ....ccccccscccccccccccscvccscvecccsesecsece 114
POWER BUS BYPASS NETWORK. cee seenae ceed wees nerve cece sie ae 114
APPLICABLE DRAWINGS FOR THE POWER AND REFERENCE CIRCUITS..... 114
I - ELEMENTARY PRINCIPLES OF ANALOG DEVICES........cecceeces AI-1
THE DC AMPLIFIER, ...ccccnccccvcsccscscccccccccscsccccsccccene AI-2
DIODE FUNCTION GENERATORS AND QUARTER-SQUARE MULTIPLIERS..... AI-3
ZL - SERVICING TECHNIQUES ..0cas Ose e RN OREN WOweD OREO ORME AII-1
TRANSISTOR SERVICING AND TROUBLESHOOTING TECHNIQUES.......... AII-2
ETCHED CIRCUIT BOARD SOLDERING TECHNIQUES. ......ceccecceccere AII-3
IIL - REPLACEABLE PARTS LISTS.......cccueccccccceccceccceecees, AIII-1
IV - DRAWINGS ......0cccee
eevee enneereeoeseeveneseeeoesareeeeeeneone AIV-1
Figure
Number
la.
11.
12.
13.
14,
15.
16,
17.
18.
19,
ILLUSTRATIONS
Title
Typical TR-20 Computer, Front View ........
Typical TR-20 Computer, Rear View .......ee0-
Typical TR-20 Computing Components ........
Inserting the Pre-Patch Panel ..........66.
Amplifiers with Bottle Plugs in Place .....
Installation of Patch Blocks in Pre-Patch Panel .......
Dual DC Amplifier, Model 6.712 ............
Model 6.712, Patched as an Inverter .......
One Channel of Dual DC Amplifier, Model 6.7
Simplified Block Diagram .........cc00c8
eeoeeeevreevevee
12,
One Channel of the Model 6,712, Simplified Schematic ...
Frequency Response Test Circuit .....e..e0.
Test Circuit for Measuring Amplifier Offset ...
Test Circuit for Measuring Noise ..........
Output Current Test Circuit ..... cece eevee
Amplifier Troubleshooting Guide .........00.
eoevreeeeneseee
eocereeeeveevas
Stabilizer Section Test Circuit and Test Points ........
Symptoms and Possible Causes of Amplifier Malfunctions ,
Dual Integrator Network, Model 12,1116....
Patching an Amplifier to an Integrator, Showing Simpli-
fied Schematic of an Integrator Network
Block Diagram and Symbol for an Integrator
10
12
14
16
19
21
24
24
24
24
28
29
30
32
34
34
vii
Figure
Number
20,
21,
22.
220
24,
25
26,
21
28,
29
30.
31.
OZ.
33,
33a,
34,
35
36,
37.
38.
39,
40,
viii
ILLUSTRATIONS (Cont)
Title
Operational Check Circuit...........
Initial Condition Resistor Ratio Check Circuit........
Integrator Drift Rate Check Circuit,
Symptoms and Probable Causes of Some
ELUNCCLONS. ...cccceececscccceecece
Quarter-Square Multiplier Patching,..
@e@eeereecaoeseevroe coe
Integrator Mal-
eeeoeerereeeeoeveoe eos
e@owoeetoonseanceveeee
Quarter-Square Multiplier, Simplified Schematic.......
Error TOS oc vee ved cabs eeworecvneves
e@oecoeeeeeceveeosed
Quarter-Square Multiplier Adjustment........ccecccceee
x? DFG Patching. ....ceeseccccecseses
z* DFG, Simplified Schematic........
2
X” DFG Adjustment Information.......
Log X and 1/2 Log X DFG Patching....
e@eeeereeereoeoe eevee
ceneovoeseevoceeanooeen
+Input Log X DFG, Simplified Diagram.......cesccuccoes
Adjustment Information Log X DFG's,,
VDFG Mounting LocationS ..ccccccccccccccccccccccseseres
+VDFG Patching and Symbol.......c0c.
®oeecereocerosxecenreocne
+Fixed Breakpoint VDFG Unit, Simplified Schematic.....
+Variable Breakpoint VDFG Unit, Simplified Schematic..
VDFG Test Circuit......... ow emns PT TTCTR TTT TTT Cre TT
Attenuator Schematic.......... co ee crc ccc ceesencec asses
Schematics and Symbols for Attenuators..... SewER BERR S
Relay Comparator, Simplified Diagram
Page
36
36
36
38
40
42
44
46
48
50
51
54
56
57
60
63
64
66
68
70
70
74
Figure
Number
41.
42,
43,
Ah,
45,
46.
47.
48,
49,
50.
51.
52.
53.
54.
556
56,
57.
58.
596
60.
61.
62.
63.
64,
ILLUSTRATIONS (Cont)
Circuit for Setting Voltage Switching Level .....
Sensitivity and Switching Time Test Circuit .....
Test Waveform ..ccccccccccccccccccccccessccsscces
Model 40,538 Electronic Comparator ..c.cccccccccce
Comparator Unit, Functional Block Diagram .......
Electronic Switch Unit, Functional Block Diagram
Comparator, Simplified Schematic ....cccccccccoes
Electronic Switch, Simplified Schematic ,........
Gate Output Offset Test Patching ...cccccccsccece
Gate Junction Offset Test Patching ..cccccccccece
Control Area of the TR=-20 ..ccccsccccccccccscccecs
Readout Circuits, Simplified Schematics .........
Relay Bus Driver, Simplified Schematics ......e0c
Patching an Amplifier to a Rep-Op Integrator
Showing Simplified Schematic of Integrator
Network SCORCH HSHOHHSOCHEHOSSHEHEHHSHTHEOHHOHSHOEEEHHOHHHHEOHEH ES
Reset and Operate Time Adjustment ...cccccccccecs
Improper WaveformS .secececccccccovcccscccsccsccs
Locating an Integrator with an Average Start Time
Start Time Error TeSt..cccscccccvcsccccscccccvces
Simplified Diagram of Wiring for Display Networks
Overload Indicator, Simplified Schematic ........
Overload Indicators, Simplified Wiring Diagram ..
Power and Reference SupplieS ...csccccccceccceees
Reference Regulator, Model 43,037, Simplified
Schematic eeoecseeeaevoevnseeas eee een eanueereeaeeeoeeeeeoee
Reference Balance Test Circuit ccccccccccccccvcce
76
78
80
80
82
84
86
86
88
90
92
94
98
98
100
100
102
104
104
108
112
112
ix/x
INTRODUCTION
TR-20 MAINTENANCE MANUAL
An Operator's Reference Handbook and a Maintenance Manual are provided with each
TR-20. The Operator's Reference Handbook provides programming procedures, and
sufficient information on computer operation to enable the user to interconnect
computing components and to operate the computer without difficulty, This publica-
tion is the maintenance manual for the TR-20 and its contents have been arranged
in accordance with that use, The manual is divided into sections that describe
a particular computing component or a group of related circuits, A technically
qualified person will find the circuit descriptions an adequate guide in under-
standing the operation of the equipment, Persons who are not familiar with analog
devices are referred to Appendix I for a discussion of some elementary principles.
(Suggestions and techniques for servicing transistor circuits are included in
Appendix II to aid maintenance personnel who are not familiar with transistorized
equipment.) Where applicable, recommended test and adjustment procedures are
included. The test procedures selected are designed to provide a simple and
convenient means for monitoring the equipment on a regular basis. A replaceable
parts list and schematic and wiring diagrams for each unit are located in the
rear of the manual. A component location diagram has been placed near each sche-
matic diagram to facilitate maintenance,
xi
xt
COEFFICIENT ATTENUATORS
PATCHING AREA
| COEFFICIENT
ATTENUATORS
PRE-PATCH
PANEL
INTEGRATOR NETWORKS
AND NON-LINEAR
COMPONENTS
LZ
OPERATIONAL
AMPLIFIERS
PRE-PATCH PANEL
LOCKING LEVER
POWER ON-OFF
SWITCH VOLTMETER
COMPUTE TIME SWITCH
AMPLIFIER OVERLOAD
INDICATORS
COEFFICIENT
AMPLIFIER SELECTOR ATTENUATORS
SWITCH
-FUNCTION SWITCHES
NULL POT AND REF
SELECTOR SWITCH
MODE CONTROL SWITCH
VOLTMETER FUNCTION
VDFG UNITS
(BEHIND PANEL)
REPETITIVE OPERATION
SWITCH CONTROL PANEL
VOLTMETER RANGE SWITCH
Figure la. Typical TR-20 Computer, Front View
pc sus J *REF
#2
HQ GND
CRI AND CR2
-15V DC
DC BUS +I5V DC
pa +30VDC
+GND
HQ GND
POWER BUS BYPASS
NETWORK,NWI RELAY BUS DRIVER
DISPLAY CONNECTOR
POWER SUPPLY SLAVE eee
J3
AC POWER
CONNECTOR (AC)
TIMING UNIT FOR
REPETITIVE OPERATION
REFERENCE AMPLIFIERS REFERENCE
REGULATOR
Figure 1b. Typical TR-20 Computer, Rear View
—
CHAPTER I
THE TR-20 COMPUTER
1, GENERAL DESCRIPTION
The ee TR-20, Figure 1, is a general purpose analog computer designed and manu-
factured by Electronic Associates, Inc. Composed of solid-state computing components,
the TR-20 is compact in size, has low power requirements, and does not need special
cooling equipment in order to operate in normal office or classroom environments.
A fully expanded computer consumes less than 60 watts.
The computing components (see Figure 2) in the TR-20 occupy cradles above the slant-
ing control panel area. The cradle area is divided into three rows; the top row
contains the coefficient attenuators; the middle row houses the integrator networks,
comparators and other non-linear computing components; the bottom row provides space
for twenty (10 dual units) operational amplifiers.
The computing components are constructed on plug-in chassis, The front of each com-
puting component consists of a color-coded plastic patching block that contains the
input and output terminations for the unit. The computing components are inter-
connected by placing patch cords between the appropriate input and output termina-
tions. TR-20 Computers may be equipped with a removable pre-patch panel that allows
problem patching away from the computer. The pre-patch panel consists of a rigid
aluminum frame with individual rows that contain patching blocks identical to the
patching blocks that form the front panels of the components. Contact between the
pre-patch panel and the computing components is accomplished by means of gold plated
contact springs.
2. EQUIPMENT COMPLEMENT
The components contained in and available for the TR-20 Computer are listed in
Table I.
The TR-20 Computer cabinet accepts the plug-in computing components listed in
Table I in five areas as follows:
a. Attenuator Row
This is the top row of computing components, It is wired to accept a maximum
of 10 dual coefficient setting potentiometer plug-in modules (20 potentiometers).
b. Non-Linear Row
This is the middle row of computing components. It is wired to accept a variety
of interchangeable linear and non-linear computing components.
(a) 12,1116 Integrator Network
(0) 6.712 Dual DC Amplifier
(c) 16.306 Variable Diode Function Generator
Figure 2, Typical TR-20 Computing Components
c. Amplifier Row
This is the bottom row of computing components. It is wired to accept a maximum
of 10 dual amplifier modules (20 amplifiers).
d. Control Panel Area
This is the area on the right side of Control Panel 20.734. Three positions are
available (numbered left to right) to accept the following accessory equipment:
(1) Position CPl. High Speed Repetitive Operation Control Panel, 20.532.
(2) Position CP2. Type 20.366 Function Switch Assembly.
(3) Position CP3. Type 42.185 Quad Coefficient Setting Potentiometer Panel.
e. The VDFG Area
This area is located behind the hinged cover below the control panel. Space is pro-
vided for housing up to six VDFG units in slide-out trays. The slide-out feature
makes the adjustment pots readily accessible for function setup.
Certain TR-20's, such as those that are equipped with a Reactor Kinetics Network.
or a Transport Delay Simulator, will have different arrangements.
Non-Linear computing components (multiplier; DFG's, etc.) are housed in full-width
(1-1/2 inches) or half-width (3/4 inches), plug-in modules that are interchangeable
in the non-linear row. This row consists of twenty 3/4-inch positions numbered to
correspond to the numbering strip across the top of the row. It has the capacity
for mounting twenty half-width modules, or ten full-width modules, or any combina-
tion of both which does not exceed the total capacity of the row. Full-width
modules occupy adjacent odd and even numbered position pairs, i.e., 1 and 2, 5 and
6, etc,
The non-linear row makes provisions for the following inter-changeable components
in any combination (within the limitations described below), providing that the
total capacity of the row is not exceeded.
(1) Integratcr Networks. Up to nine Type 12,11160r Type12.1115 Dual
Networks can be accommodated in positions 1 through 18. Each dual network occupies
adjacent position pairs.
(2) Multipliers. Up to nine Type 7.045 Quarter-Square Multipliers or 7.117
Bi-Polar Quarter-Square Multipliers can be accommodated in positions 1 through 18.
Since the multiplier is housed in a full-width module it also occupies adjacent
position pairs.
TABLE I. TR-20 COMPONENTS
MODEL
GROUP COMPONENT NUMBER
COMPUTING COMPONENTS
1 Dual DC Amplifier 6,712
2a Dual Integrator Network (Non-Rep-Op) 12.1116
2b Dual Repetitive Operation Integrator Network 12.1115
3a Quarter-Square Multiplier 7.045
3b Bi-Polar Quarter-Square Multiplier 7.117*
4a x2 Diode Function Generacer 16.101
4b Log X Diode Function Generator 16.126
4c 1/2 Log X Diode Function Generator 16.133
4d Sine/Cosine Diode Function Generator 16.313*
5a Variable Diode Function Generator Group 2./713-0
Consists of:
-Variable Diode Function Generator 16,154-1
+Variable Diode Function Generator 16.156-1
+VDFG Readout Module 16.310
5b Variable Diode Function Generator Group 2.645
Consists of:
+Variable Diode Function Generator 16.304 -1
-Variable Diode Function Generator 16.306 -1
VDFG Readout Module 16.308
5c Variable Diode Function Generator Group 2.752
Consists of:
+Variable Diode Function Generator 16,165-1
VDFG Readout Module 16.310
——
MODEL
GROUP COMPONENT NUMBER
COMPUTING COMPONENTS (Cont)
6a Attenuator Group 42.183
6b Attenuator Group 42.187
6c Attenuator Group 42.188
6d Attenuator Group 2.128
Consists of;
Attenuator Panel 42.185
Readout Module 12.265
Ja Reference Network 12.266
7b Tiepoint Network 12.267
7c Dual Function Switch Group 2.127
Consists of:
Function Switch Assembly 20.366
Readout Module 12.264
8a Signal Comparator 6.143
8b Electronic Comparator 40.538
9 Regulated Power Supply 10.179
10 Reference Regulator 43.037
11 Dual DC Amplifier 6.282
OPTIONAL COMPONENTS AND ACCESSORY EQUIPMENT
12 Repetitive Operation Expansion Group 2.715
Consists Of:
High Speed Repetitive Operation Control Panel 20.532
Repetitive Operation Timing Unit 36.082
MODEL
GROUP COMPONENT NUMBER
OPTIONAL COMPONENTS AND ACCESSORY EQUIPMENT (Cont)
Dual Repetitive Operation Integrator Network 12.1115
13 Display Unit** 12.987
14 Reactor Kinetics Group 2.475%
15 Transport Delay Simulator 2.448%*
16 Audio Overload Alarm 13,017
17 Slave Cable 510.038
18 Patching Kit 100,007
19 Service Shelf 51.039
20 AC Power Cable 51.040
21 Pre-Patch Panel 5.235
22 Rep-Op Slave Panel 20.567
AUXILIARY EQUIPMENT
1 vanteveraes 1110
2 Repetitive Operation Display Unit 34.035*
(3) Variable DFG. The available models of the variable DFG can be
accommodated in any even numbered position with the exception of position 20,
(4) Fixed Diode Function Generators (Half Width). The Type 16.101 x?
Function Generator, the Model 16.126 Log X Diode Function Generator, and the
Model 16.133 1/2 Log X DFG are housed in half-width modules, and may be placed
in any even numbered position with the exception of position 20.
*xThese Components described in separate manuals,
*kThis component not required if the Electronic Comparator, Model 40.538 is provided.
—~
(5) Fixed Diode Function Generators (Full Width). The Model 16.313 Sine/
Cosine Diode Function Generator is housed in a full-width module, and may be located
in adjacent position pair 17-18 only.
(6) Reference Panel. The Type 12.266 Reference Panel can be positioned in
any even numbered position with the exception of position 20.
(7) Dual Tie Point Panel. This unit can be used in any position in the
non-linear row.
(8) Comparators. The Type 6.143 Relay Comparator may be used in position
18 only. The Type 40,538 Electronic Comparator may be used in adjacent position
pair 17-18 only.
(9) Function Switch Patching Module. The Type 12.264 Patching Module may
be mounted in position 19 only.
(10) Quad Potentiometer Patching Module. The Type 12.265 Patching Module
may be mounted in position 20 only.
(11) Display Module, This module is required only if the electronic
comparator is not supplied. It can be placed in position 17 only.
NOTE
The above assignment of computing components
applies to the standard TR-20 Computers.
Special computers may be supplied with pro-
visions for mounting DFG's or reference panels
in the odd numbered positions (with the
exception of position 1) or for accommodating
more than one comparator.
3. OPERATING AND MAINTENANCE ACCESSORIES
In addition to the components listed in the preceding paragraph, each TR-20 in-
cludes a group of operating and maintenance accessories. These items are listed
in Table I.
4. PRELIMINARY CHECKOUT
Each TR-20 is completely tested prior to shipment and should be ready for opera-
tion upon receipt. However, as a matter of good practice, it is recommended that
the procedures below be followed as a preliminary checkout,
a. Visual Inspection
Make a visual inspection of the computer. Lock for signs for shipping damage.
Become familiar with the location of all components (refer to Figure 1). Check
all plug-in units for proper seating. Verify that the patching blocks on the
Figure 3,
Inserting the Pre-Patch Panel
i
pre-patch panel are positioned in the same order as the computing components. The
switches in the control area should be positioned as follows:
Power ON-OFF Switch ..cc.cccseccee OFF
Mode Control Switch ..0..eese+e.ee++ RESET
Voltmeter Function Switch......+. VM
Voltmeter Range Switch .....ceee+ OFF
COMPUTE TIME MILLISEC Switch..... OFF
b. Insertion of Pre-Patch Panel
As shown in Figure 3, hold the pre-patch panel at a slight angle and place it in
the patch bay groove. Move the pre-patch panel to the right until it contacts
the right-hand side of the patch bay. Gently push the pre-patch panel forward
until it is flush with the computer. Turn the locking lever down (the pre-patch
panel will slide to the left).
c. Feedback for the Amplifiers
All operational amplifiers should be provided with feedback whenever the computer
is turned on. Connect bottle plugs or patch cords as shown in Figure 4.
d. Application of Primary Power
The TR-20 is designed to operate from a 50 to 60 cycle ac supply. The ac circuits
are factory-wired for 110 vac or 220 vac as specified in the purchase order for
the computer. (Drawings D010 179 OS and DO10 179 OW show the required changes
for converting from one power level to the other.) A three wire power cable is
furnished for connecting primary power to the TR-20. The power cable is terminated
in a parallel ground (3-prong, polarized) plug for connection to a parallel ground
receptacle. If the primary power line to which the computer is to be connected
is not equipped with such a receptacle, a parallel ground adapter (adapts 3 prong
appliance plugs for use in standard 2 prong outlets) must be used. In this case,
two precautions should be observed:
(1) The power cable should be connected so that the ground side of the
ac line is connected to the ac common line of the computer. The ac common line
is terminated on pin 1 of the ac power connector; see Drawings DO45 078 OW, Sheet
2 and BO45 078 OW, Sheet 3.
(2) The ground wire on the adapter must be connected to earth ground.
These precautions should be taken for safety reasons and also to prevent ex-
cessive noise in the amplifier outputs.
10
QUAL OC DUAL DC
AMPL 6.712 AMPL 6.712
Figure 4, Amplifiers with Bottle Plugs in Place
e. Operational Check
Place the power ON-OFF switch in the ON position. The amplifier overload indicators
will flicker briefly, then go out. If an overload indicator remains on, try to
balance the amplifier (see Chapter II).
Next, measure the power supply output voltages and adjust them if necessary. Balance
the amplifiers and verify that they will perform as inverters. (Place one end of
a patch cord into a minus reference voltage termination; connect the other end to
a l input of each amplifier. Connect a voltmeter to the O termination of the ampli-
fier; the output should measure +10 vdc. )
Check out all other computing components in turn by applying selected inputs and
observing the proper output. The sections of the manual that describe the patch-
ing for a component are helpful here since they show typical patching schemes.
If any difficulties arise, reference to the appropriate section of this manual
should help to clear them up.
5. INSTALLATION OF PATCHING BLOCKS AND CONTACT SPRINGS
T