Manual / Guide · c. 1970

Monroe 920 Service Manual

The 116-page service manual for the Monroe 920 electronic calculator.

Author: Monroe
Year: c. 1970
Type: Manual / Guide
Credit: Scan: Rick Bensene, Old Calculator Web Museum, oldcalculatormuseum.com.

Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 PREFACE This manual is the guide for service after sales with the main purpose of quality performance of products and is also useful for marketing promotion as well as repair ser- vice. It consists of seven sections, i.e., General; Basic Circuit; Operation Principle; Operation Procedure; How To Repair; Parts Catalog and Service Manual Report. It is necessary that the operation features and basic circuits of the Monroe 920 should be fully understood in the following sections of General & Basic Circuit, that the principles and the theorem should be also done of Operation Principle and Operation Procedure, and that the proper service should be done by referring to How To Repair and Parts Catalog. Order repair parts by proper part number from Orange. Part numbers are contained in both the ''How To Repair", and ''Parts Catalog" sections of this manual. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 HOW TO USE THE SERVICE MANUAL This manual consists of seven sections, i.e., General; Basic Circuit; Operation Principle; Operation Procedure; How To Repair; Parts Catalog and Service Manual Report. General Specifications and operation features are described, and also the manual operations with their precautions are explainded details. If this chapter is thoroughly understood, it will be basically in the servicing Basic Circuit By using Integrated Circuit, Delay Line, Crystal Oscillator, Nixie Tube and Reed Switch, the electronic circuits are simplified with higher reliability and stability. It is very important to master these Basic Circuits before understanding Operation Principle and Operation Procedure. Operation Principle Principle of operation calculation is classified in addition & subtraction, multiplication, division and square root with detail descriptions concerning about each data, decimal point and sign respectively. It is necessary to understand the fundamental working operation of these electronic calcu- lations. Operation Procedure The actual operation of each calculation is described which is based on Operation Principle, according to Flow Chart and Timing Chart, so that the structural and operational movements can be easily understood. How To Repair Operation Check Program; Adjustments; Trouble-Shooting and Wiring Diagrams & Tables necessary for actual repairs and maintenance are explained with important point to localize the faults or defects. Parts Catalog Assembly Units are listed in this section and the diagrams should be used in locating the physical defects for repair & maintenance. When parts are ordered, it is important to always to write the complete parts number. Service Manual Report Reports of any modifications which should be known by all service personnels and agencies will be issued and forwarded as soon as published. It is important to keep them, so they should be filed in this section for future reference. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 CONTENTS I. GENERAL 4. [troduction 126,635 SEO Vss RUROINI TE Rs TING em cteoe a Ss ree avers 1 2. SpOGHCAtiONs 2.nre.e s.09 spies maEe nie ee MS INOS HOR e WSiGyewiaGe ayaa arin Stange SO 1 2.1 General Specifications, 6.005 bese ees eels Gls Wy oe eaieleles Sata slale wee eee oe 1 Od Rrmbient COmdHtior onc.0ase.coscece wcbosie, Ej8 ee hzG MS HET INTS ROA IG ES BSS Sac 2 2.3: Physical Features: .......0.0.05 0.00 veisiee die n)8l So Nie pele wie Wie SIR Sleielee 9G Sleeve 2 2.4: Kéyboard isecive cies SOE RESTON WARE Se Selene 2 ka ©) 9-1-1 (0) | PC 4 341 Special Features sia ceaguw-s aernawanun wemere naman’ mois equa mM 4 Std: Overflow Lamp. sivicvicccmencncs seman anne neM RIS Hees 4 3.2: Registration = so. Fes4 Wee BOTT a ie eae aS Cee eee Sea See we Misael ele Hea 4 3:2-1 Entry. 2c ie. oes ceuieileia AURORE A EWG eee aTeG Le 4 3.2-2 Clearing of the Indicator 2. ..s.se esc ee eee eee cee eal eee eee wets ws 4 3°93: Calculation Overflow csesk owssaaamsuanesan tasinza CON Roe RBEN es 5 3.2-4 Decimal Point Switch and Registration 0.0.6.6... 6666s e eee eens 5 53: Addition a: Subtraction) “i caeawscawsts a wires qian aioara occa wraes WeeremiNre ae 5 3.3-1 Negative Value 2... sec e ence e ene tee ee teen teense ere eneene 5 3.3-2 Overflow of Decimal Point Coordination ...... 0.0.00 eee ee ee eee eee 6 33:3 Calculared Result so secarBaee sowiaGaie SwReORaEN Ue oaeas 6 3.3-4 Changing the Affixed Decimal Point Position ..........0+0seeeeee ees 6 3A Multiplication 3 scieiiie wed ilns Ces wie ewes Seas Cece as ae eee wm 7 3.4-1 Negative Value Multiplication ........ 0. eee e eee eee e eee eens 7 3.4-2 Multiplication Capacity 6.6... sce eee eee n nance eee e nee ee 8 3.4-3 Correction of Order Key wives vias cee eane eee vie sine eee seein 10 $5 “Division 7 wiss0es aera aR ea ieck, Weve a vantaNee pee RS ee TEM ION ea Hannes 11 3.5-1 Negative Division... . 0. ss eevee eee ete teen e eee ee eee e reer eee 11 3.5-2 Calculation Capacity . ios ciesiees cei cine cue e eee cee eee nee nee 11 3.5-3 Correction of Order Key s e.ecses cvencee cee ewewens cave cee e renee 14 C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 3.6 Constant Multiplication or Division 2... 66. cece eee reece reer n ene e tenes 14 3.6-1 Constant Multiplication ........ee cence eee eect erent eee eene 14 3-629: IConstan€ DIViStON: siscoganerecone wrececmrecere wneuenenenene exeuiecelisim enpsai= Satie SSE ELM OSS © 14 3.6-3 Correction of Order Key .....escece cence ee enneeeneeeeseenenerees 15 3.7 Square Calculation .......cseeee rescence e etna een n eee e teenie eene serene 15 3.7-1 Square Calcualtion ........ sees cence sent e nee e tent e nee e een enes 15 SIF2D POWEES — sce carasccoaunna sana rerecosevexsmoipvena ee corerenevenoe vw: eeiacenmneie Winseveuaysit Bel 8y 2 o 55 3.8 Summary of Overflow ... 0... c sce e cence een ene e renee nen e teen en een ens 16 3.8-1 Registration... sees eee e eee e eee eee teen enn en nee ene neees 16 3,8-2 Decimal Point Coordination «6 osc 00 owe seis eee ee ee cn eeieiee ne ee 16 33:3: Calculation: Overflow: svi aierezeurive scaceraiceeys svernyereseceperpiajesersiessiacmelaeecwiele tye 16 FHA Pecinial PomvOver HOw — crcasea ly weecdiereseconconmmmsecmnacsecoemvensy samperrcns ee 16 3.8-5 Overflow by Changing the Affixed Decimal Point Position ........+++++- 16 SAG) Gverflow Position Releases Snesessvenwsscrerareseseraleuaceieseeice eimenacmsain mmenasnacera une 16 3.9 Summary of the Function Key .......0see secre cence eer e nent nee enes 16 ll. BASIC CIRCUITS 1, Integrated Circuit 2... 06sec cree cece cece eee e eee e teen ener ee ens n enon eeseenes 1 1.1 Types of Integrated Circuit... 1... 0. sees e reser eet eee e teen ener eeees 1 VEVER WET, cocccecesecaqe wyececovecore eipcajenersvie: execeuareroray oes Steere eee wee aes Niepeleleie el aaa 1 T2920 SET cacecenecraie vamaeriacece opeceievepere ecouerenenecaneversuenesteyeivin Hiei elnece sieie wimatel elare 1 AES “AOS ccssorsrece visvanersszsn euarazeceseserenouer peecenesee, 9 t-8s8 9 Sie Bie eC MIETOe Gitey Bemnere BIE 2 TENA TORHEES a erracannrcorese peroveseere ererereceecareiene waldo PALS wile Oe Gin HES OR AON INe WieNNS 2 1.2 DTL Circuit & Characteristics .......cc cc cew cece eee e ee eee eres ones scenes 2 1.2-1 Improved DTL ..... cee eee cece etree ere ener een e eaten ne eeeeees 2 1.2-2 Three Input NAND Gate... se esse cree eee teen eee tenn e ees 4 1.2-3. Four Input NAND Gate... eee e cere eee eee teen teen nents 4 LIZA BUC GCC E coocere sicererouaiereso9.0.0/ki0ie Sa)e LOCA ENTRAR ORE ealrate 4 1.2-5 Integrated Circuit ..... 66s eee e eee cence eee eee e eee teen en aees 5 1.3 Logic of Integrated Circuit ©... 0.0 e eevee cece eee tent ee eee nee e eee ees 5 4.331 “SNAND SUNORE nnocco.c cicteje Aas ECS Were STOR e OSS Wize ta ata ae pl elas SEES Is 5 BSD “WC COR VAL ANDY oienie cpeseve dbce. aiebe este oe el eenecal eile GUPLUCEiala Rate IE Ree eiw irs 6 1.4 R.S Flip-flop attached Resistors & Condensers .....++es+sereeeereeeeeeeeeee 7 165 Flip-AGp (2) .conee sienna mines maenet OES We ARE REC SO HERR F 8 C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 1.6 DType Flip-flop ...... cece e eee e eee e ence een nent en ener eee eneen en enes 8 EF FEB ASP (A): corinne wnncnsicnennenemnenace nememne ieveeneailne cede eet eee 9 2. Timing Pulse Generators .....++++++++ A ese See HAASE eee AEN OSI aaa neers 11 DEG BIG CHS! scecereconsreresere arecorewreve siewneracaie nsereseseseca niece Skee Saw Oe USN Sid) HeLa Oey ass 11 2.2 Timing Counters .......eseeeeeere cece en nee nene eee eeee ee enereereneaas 11 DOA “Bit COUnter: ccsyierecovsseses wrersisieowce eceieveca arene mavecemsoce euprarpueesn oF OEM OF 11 B99. "TS Counter: ciaserarscwiesesre mereraraieiernierarecmyace esecereverevqueese wyaareneseseiszpceiere er 9/18)5 13 2.2-3 Digit Counter ....... cscs eeee reece cree eee e ene n nen ee ence scenes 13 DOA: “Poimn€ Counter. sate cians cece-5seresaratacerarete:e wreree)e ete mienenvanceyee exeicavecaicoxeser eral gyeseseee 14 2.3 Delay Line and Circuit...... 00 csee cece cence eee e ence ene renee ee nen nn eens 15 BFA “Date PGW: ciostwsss awossis sutatacescome nemesis eespernieam wraedesenesereieceircere 15 2.4 Write Amplifier ......0.. sees ceeee reece eee ee en ener eee eeeneeneneneg nee 16 2.5 Read Amplifier ... vonucsEGiechawonsdiice devas emeseeuiemancenseie ExROURE eS 17 Ill. OPERATION PRINCIPLE 1. Outline of Operation Principle .. 2.6... - eee e eee eee eee eee teen eee e tenes 1 1.1 Special Features of Operation ..... 66. e eee e nee e erent eee e nee nn nen n ees 1 1.2 Outline of Addition & Subtraction®. 0... 05:6 6 esc e ccee meee wee eee meee 1 VOT) Céereeal ccs cers orursiaiats macaace scoresiauere worsen pie tieresee wipmenerazeseueene prerere 1 122:9 Sabtrastion sxx crecumreces scoreratavacarmelererscecacecmce srateneanvane eysarermuarennsexe mise 4 1.3 Outline of Multiplication .. 0... c cece n ee cee ene eee ener enn nn ee meee 3 FEST General sea sriecsecovsransvcssratarerarase Weaatereeve pMacaiereieorw a fonere ahaietiens enenareeerrere en wiece 3 1.3-2 Decimal Point in Multiplication .......0eee cece eee eee eee eens 4 1A: (Outline of Division: scicirccvore wsewvece wie wrae re Minis taieye cave ores nb peranaare WORN sree LeLETe Me 5 TAS: Genretal cccvawsiracacrarciae awximscavevelevereslacsew'e ls otareyiaitanp con dtteraitecoeneceussepseienaianmuee 5 42: Decimal Point cevsewrccin scenes rau wrecvesiae erasavaens re sueaeieneengemieue weereonneaeveye 6 2. Operation Principle 2.0... .cce ces eens eben eee ewe eee rene ee rene nneeen en nns 7 Bt RAaleon Be Subtracti OM eve: doscscscersce wuxcewarosnae cere erase Suet ane wrote ernzesm edwin erenranenaneracecexess | QE ‘Binary: Code sasicsascnwws sewage asmaaae verstrems walecersieepenie weiss 7 2.1-2 Discrimination of Sign for Calculated Result .......0+eeee cece reece es 8 C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 2A-3: ‘Overflow of Calculated Result ipssessrserxarereareceinwrererniewiness murerererere wysiienere 9 DAA, Data BNO ww isscesseya wicna cove a ywracwecerenariontave'se:-anayw ta (ececa ons ieia(e os} ensiece warare re ave wierasy 9 2.1-5 Registration of Numerals ....... 00sec eee eee ene nee n nee eee eeeee 10 2.1-6 Data Flow of Addition or Subtraction 1... 0.0006. seeceeevcesentceres 10 2.1-7 Decimal Point Coordination in B Register «1.0... 0s cece cece eee eee 11 2.1-8 Operation 20... cee eee been ee meee a ene ee ee ee meee n ens 11 2:2, Multiplication 2 sissies cows camianas aiererarwinne Vaieieieieia stata wince oiwremrerncaie e18 ace 11 2.2-1 Outline of Operation System... eee ee eee eee eee eee een eer ee es 11 22.9. “Bata PlOW:. coxcsva pixswidta, Ser aresasate Wie eaaNe arene aera se reelw a ETHIOTS a MLENRW TANS os 1] 2.2-3. Registration 6.0... eee eee eee ene eee ne eee nee tener ee cern ene oe 14 2.2-4 Multiplication Operation ....... ces eee e seen e eee een erence enna 15 DiS: PGSM co eieia. 65 o Re SOR re CM RUIN SIGIR gates WESTON SieezareE erninetaree me 17 AB Daca Blow: ssa carewyeta wetiels aarraewicre aotaretcein eevee oearal a lenarveve rere 17 2.3-2 Decimal Point Counter and Operation Ending Method: sesaiassceccesstetenw sraweonts 18 2.3-3 Registration System 1.06.6... e eee n eens 19 2.3-4 Division Operation ©... 0. cee cee cece cee eee eee eee eee e eens 19 IV. OPERATION PROCEDURES 1. Explanation of Blocks .......6cs bs ee cee eect ete ene e eee e tence ene e ee neon nes 1 1.1. Input Blocks. 66:54 seeedias wee e dae eee eee eee eae ete dete lee eee 1 TGA) Rey Circuit siexccusnonse versccd eran scranminnemeenns 1 135 Bey OR Gealit sex saresa7 sexi ecrwence eomesvanawescnin exencea 1 Li9z3 ‘Start: Circuit: 56.6555 BRC CNG laceew Sara eraiats em ee rare Wi Wie teicataltn SateTR 2 1.1-4 Registration Circuit 2... cece cee eee eee eee eee eee e eee e nen ees 3 1.2 Output Blocks .......cceeee cere eee nee ene e nee nett eee nee eeenee eens 3 1.2-1 Digit Selection Circuit ......6 ces e ese eee eee eee enn eee eee eens 3 1.2:2 Numeral Selection Circuit (62 0000i becca Cee eee eee wee eee Hee wees 4 1.3 Operation Blocks ......-.seece cere renee eens e nent eee eee nee e nee tenes 6 1.3-1 REPIStErS 2. .enceeercancing ne sehen sees eiea sie eeeeesins a eeeinaeeeeies 6 1.32 “Data Gates: o creressrecene 0,8 4 bets oi eieeeie eel alale ae Wee STs sliaieeNene-e ainielere 6 4.323 “Ball A der: oo-o-0.0:056,628)5 ORG SUTTON ele BUND SMeianeoeraerece are 9 4,34 ‘Decimal Point Counter? csniesywisg siosiesiaie nese emer snares ee 11 4:4 Control Blocks gni6' oixc5 SSeS Sala Mma aaa s TaN sar ear sae a Naa ale RNa STE DO AID TO Hie 13 1.4-1 Order Flip-flops ......ce cs ces ence renee acne eee seen eee en enn e noes 13 1.4-2 Discrimination Flip-flops «0.6... e scence eee ee eee nee n een ees 14 2. Explanation of Operation Procedure ......0sseeee reer eee eens rs erste re seeeees 15 C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 2.1 Entry of Numeric .......:es cece eee e nee e een cence ese e ee ee tense ees 15 2.1-1 Numeral KeyS ......eeeceec creer eee eres e eter eee eneeeneeeeenes 15 V. HOW TO REPAIR 1. Operation Check Programs... cee e ener eect te eee n ener n nen eter e renee tenes 1 9 Gkrouite: sacs eee reiraiaias areca Mekereranaia Rai MMNOTS NOMOe RATE mETNwEOIE SeMPye ee recerelece 3 2:1 Precaution se:gcccawialernintenscwnaiei ae Se ee eee 3 2.2. Integrated Circuit 6.0. 6s cess sede eee cana ee eee teeta nt eae cee renee 3 2.3 Crystal Oscillator .... sees cece e eee eee renee ee rte e ree ease eee nes tenes 4 2.4 Delay Line, Read and Write Amplifier «1... 60.000 s sees eee e reese eee e eens 5 2:5. Indication’ Gireults meesiiss swcavensen waiwmrwnewce are vaNeLeTe Hierro em eRe teem celine Hine 6 2.6 Power Supply Circuit 2.0.06. css cece eee etree nen eee e ener teenie ens 6 2.7 Keyboards sivisiin sees cadicinn caine nee eeeaies meine nes tems nee mees et 7 2:8 “Decimal Point Switelis scsi siwscarnannwe-owiotere accesses srerwieimnereemnesereceieecole wrens ied !s 8 3. Trouble Shooting 0.0... .s secre cece sent eee ee een ee nee eens nest enn eenenes 9 3.1 Initial Checking Points 2.6.6... 6 cece eee ener e tenet n ence tenner enene es 9 $3 Wndicator saissciccascaars eeare ncaa miemerwince eens (emai ac lemceusanans mina coreunre nea erenece 9 3:3 iDatas soaicavie Ga Meats HEA PARI ERIM SHOOK eRe HERE 9 4. Wiring Diagram Power Supply Circuit (UL) Power Supply Circuit (Except UL) Power Supply Wiring Diagram Transformer Wiring ‘Termianl Destinations (Arithmetic Card<* Indication Card) Termianl Destinations (Arithmetic Card+> Keyboard) Power Supply Assembly Indication Unit Assembly C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 VI. PARTS CATALOG Ug Oy BR a eae: See Tt eee en Cee Ba cy BL cy Pas ioraycicre ase cae CNIS WEEMS 2 Be BHCC LINIG! Fn ceceseso erecenenovesereceumsoresnissanauenerscasan tl enacqne/eaelennouesereceese A tetereut ein nee consoe 4 PAT CATHIE hw. soyanier serv pene foncseqeinr sussys=siavaeaue ha teyenenrie Teese a Pate ot tenet RTT oes 7 BE POWEPSUODIE CREA —sierenesmnescosrecersmuacenuteratmuns eeaHisbeietie eniera recente tocomeroxenetaesavetearasayate 7) Be PIM GISS HOT ORT a cera,cox ef ucwsncoveserce wunnseronaterrenncie He eRaeaTronanitases er arovers wre eoecnar aa hea vaTa ION 10 SiS! JAPCHTIOHCGRER! sorecscecg mcnceresnstio VOreserscene RISO SISONERRURS KER ERIC CNROTNTNRD KN 12 VII. SERVICE MANUAL REPORT C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 1 1. Introduction Monroe 920 is the most compact type of Monroe series with very simple calculation operations having high reliability and stability. 2. Specifications 2.1 General Specifications Type: Electronic Desk-top Calculator Calculation Ability: Addition, Subtraction, Multiplication, Accumulative Multiplication or Divi- sion, Constant Multiplication or Division, Square and Powers, Mixed or App- lied Calculation. Indicator: 12 digits Decimal Point: Registration: Floating decimal point until it coordinates to the affixed decimal point posi- tion. Result: Fixed decimal point system Affixed decimal point position: 2, 3 or 4 (The position cannot be changed during calculation.) Calculation Capacity: Operation Result Addition or Subtraction: 12 digits 12 digits 12 digits Multiplication: 12 12: * 12) * Division: 12 2 12) * 12 Calculation Time: Addition or Subtraction: 0.02 sec (max.) Multiplication: 0.35 sec (max.) Division: 0.35 sec (max.) Special Features: Negative Numeric: When there is negative registration or negative result , a comple- ment numeric is indicated. Overflow Indicator: When the undermentioned conditions occur, then overflow lamp lights up and all registration stops; 1) Registration overflow 2) Calculated result overflow Order Key Correction: When { or §) order key has been mistakenly pressed, it can be corrected, if the proper order key is pressed immediately after it. Key: Reed switch C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 2 Indicator: Nixie tube Indication system: Dynamic lighting up system Code: 2'-4-2-1 binary code Circuit elements: | DTL monolithic IC TTL monolithic IC Transistors & Diodes Register Element: Delay line A register ..... 3 words Bregister ..... 1 word Oscillator: Crystal oscillator 2MHz Clock Pulse Frequency: Arithmetic 125 KHz Delay line 1 MHz DC Power Supply: 1€: +5.3V Read amplifier: +5.3V, -4.5V Neon lamp: +120V Nixie tube: +200V 2.2 Ambient Condition AC allowable voltage fluctuation: AC voltage, -15% ~ +10% Ambient temperature: 0~104° F Storage temperature: 40 ~+158° F Humidity: 95% Power: 8W AC Power: 115, 220 or 240 V 2.3. Physical Features Dimension: 10.4 (W) x 12,8 (D) x 4.0 (H) in. Weight: 8.8 lbs 2.4 Keyboard {0} ~ [9] Numeral key: (J Decimal point key: _ Affixed decimal point system. Clear key: Clears the indication register, accumulation register and control circuits. co Clear Indicator key: _ Clears indication register. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 Multiplication key: 4 Division key: = Equal key: €a Negative equal key: R Constant key: C.S.B. No. ED9—505 GENERAL 3 For multiplication For division Also used for plus key in addition. Also used for entering of negative value in the calculation. Lock key for constant multiplication division. Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 5 3. Operation 3.1 Special Features 3.1-1 Overflow lamp This lamp lights up when a numeral enters the 13th digit position. It can be released by pressing |«1 or [© key. 3.1-2 In multiplication or division, the calculation of 12 digits 412 digits can be done and its result is registered in the indicator according to the affixed gecimal point position. 3.2 Registration 3.2-1 Entry of registration is freely done until it matches the affixed decimal point position. Ex. 1-1 45 6.7 8 9 3 withdial at D@=2 press indicator 4 [010 [o fo fo fo Jo [0 [o [0 fo [4,} 5 [oTo [o Jo fo Joo fo Jo [o [4 [5] 6 [oTo To Jo fo JoJo }o jo [4 ]5 jo 7 [oToTo Jo fo Jo lolo|4 {5 [6.17] 8 [Lolo To To Jo fo fo]4 [5 {6.]7 [8] Overflow 9 @[OTOTOTOTOTOT4T5 16171819] Registration stops 3 Q@OTOTOTO TO TOT4 75 [61718 19) Error Correction in Registration Ex. 1-2 1:2. 4.=* 123 press indicator c ofofofo]}ojolo,] BY “of ofo] oj ojo] & o]ofolo]o}1{2.) 3 _ofofofoj1[2]3,} In numeral or numeric correction, or [ci] key must always be pressed as shown in Ex. 1-2. 3,2-2 Clearing of Indicator (1) [€!|key clears all numerals registered in the indicator. (2) After &) or (4 key is pressed in multiplication or division and when |(ci|key is pressed before the registration of multiplier or divisor, only numeric are cleared. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com GENERAL 6 MONROE 920 3.2-3 Calculation Overflow When a numeric is more than 12 digits in the registration cycle, the 13th digit registers with the overflow lamp lighting up and no other digit or digits can be registered. 3.2-4 Decimal point switch and registration (1) Decimal point switch always must be set before any calculation is started and cannot be changed during calculation. (2) Number of fractional digits of the numeric to be entered must equal to or be less than the affixed decimal point position. 3) Decimal point is a floating system until it coordinates to the affixed decimal point & Sy P position. (4) After the decimal point has coordinated, the overflow lamp lights up when the next digit enters in a registration. Ex, 1-3 12 3:4 5.6 7.8 9 112 3:(D£= 2) @ (olols [2 [3 [415 [o[7Jslolij2 3 Overflow lamp lights up f Registration stops (5) However, in the registration of a multiplier or divisor when [K) key is not locked, the floating system is not concerned to the affixed decimal point position. 3.3. Addition & Subtraction Ex. 1-4 a+tbt+c-d= press Ce a [=] a be atb cB) atbtc d 8) atbte -d 3.3-1 Negative value When a negative numeric is registered or there is a negative result, the complement numeric appears in the indicator and it must be converted to its true value by pressing Elkey. Ex. 1-5 atbe=c press a Floating numerals until numeric coordinates to the affixed decimal position. C.§.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 3.3-2 3.3-3 3.3-4 GENERAL 7 Shifts to the affixed decimal position. b Floating numerals until numeric coordinates to the affixed decimal position. cl Coordinates to the affixed decimal position with the correct answer, but if —a>b, the complement answer is indicated. a-(-b)=c This equation of calculation also can be done as follows; press a Floating numerals until numeric coordinates to the affixed decimal position. Complement indicated. b Floating numerals until numeric coordinates to the affixed decimal positon. a Complement indicated a Converts to true value. Overflow of Decimal Point Coordination (1) In the decimal point coordination cycle, if the number of integral digits of registered numeric is greater than 12 minus the affixed decimal point position, then the overtlow lamp lights up. Ex. 1-6 DL=4 12:3 45678 9:0 112 @ AlziTs lel Is 19 loft 1210) Calculated result enters the 13th digit position. When the sum of the 12th digit of atb or-a-b enters the 13th position, then the over- flow lamp lights up. Place 1 to the indicated numeric and it will be the correct answer. Ex. 1-7 Di=4 987654320000 + 123456780000 @ ALLL hf fofofofofo} Overflow Changing Affixed Decimal Point Position During Calculation. If the affixed decimal point position is changed during calculation, then a mis-calcula- tion will occur. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 8 Ex. 1-8 1, 2 3 (DL=4) + 1 2. 3 (D£=2).... mis-calculation press indicator 1. 2 3 (DL=4) 10|0}0 jo{o folo{o Jo ]1.J2]3] &l [0/0/00 [o[0o{o]1.J213 ]o fo] 1 2. 3 (DL=2) {o[o[o Jofo [o[o fo [0 Ji [2]3] a (0 |o}0 folo fofo]1 [3 [5]3]o] Ex. 1-9 1 2. 3 (DL=4) + 1. 2 3 (DL=2)..... mis-calculation press indicator 1 2. 3 (D£=4) Lofolololofolo[o]oyi [23] = (0{o]0[o]o[o]1[2[3]o [oo] 1. 2 3 (DL=2) Lolo]ololo[o]o[ofo]1J2]3] iS {o]o[o]olo[o]1[2[3]1.J273] (1) When [) or & key is pressed after the addend or subtrahend was registered, the affixed decimal point position can be changed only to an upper position and then =] or & key must be pressed again; but it cannot be changed to a lower position, because if the affixed decimal point position is changed to a lower position the indicator clears with overflow lamp lighting up when (=| or key is pressed again. 3.4. Multiplication axb=c aki bel | ae Fixed decimal point. Floating decimal point (Multiplier) Floating numerals until numeric coordinates to the affixed decimal position. (Multiplicand) axbxc=d a&Xbel Rc as Both numerics [b] & [c] are floating decimal points. In continuous multiplication, [x] & [) key must always be pressed for each calculation and the multipliers have always floating decimal points. 3.4-1 Negative value multiplication Since the negative value is indicated by its complement, then it must be converted to it true value; so a negative sign must always be added to the result by the operator as follows; «. 1-10 2x 123 =-2 4 6 (DL=4) C.$.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 9 press indicator 2 [o[oJolojololololololo|2.) [olol9[9[9[9 [9] 8jo]o}olo} [9T9T9T9 1919 T9[8Jolololo} 123 fololofolofofofolo]1]2]3.) =) fololofolofofolo.jo[ol1|2 | ... mis-calculation Even though, it is a mis-calculation, the overflow lamp does not light up; so the comp- lement can be converted to its true value with the calculation continuing. Correct operation 2x123—~5%28123 8 246 (D£ =4) Ex. 1-11 2 [oJo[o]o{olololololo fo |2.) ea [o[o[o]o]o]o}o]2Jo[o fo fo] 123 lololo}olololo}o{oj1 }2 |3,) a [o[o/o[o[o]2]4|6.Jo]o[o fo] Answer -2 4 6 : Place a negative sign to the result. Therefore, it is to ignore the negative sign in the operation, but place it to the result. 3.4-2 Multiplication Capacity This calculator can calculate 12 digits x 12 digits at one time, but the sum of the inte- grals and fractions totalling 12 digits will be registered in the indicator with all other nume- rals being eliminated; thus, when multiplying large numbers, the position of the decimal point position (D £ ) is very important. When D £=0, the total maximum number of the integral digits of the multiplicand and multiplier can only be 12 or a true result will not be shown, and when D £=4, the maximum fractional digits can only total 4 as shown in the following examples: (1) D£=0 a x b = c¢ | 4 toss Total Be digits x tk digit 12 digits — = 99999999999 x 9 = 899999999991 a 6°" 12 " —* 999999 x 999999 = 999998000001 1 34 146° #12 " — 9x 99999999999 = 899999999991 C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com GENERAL 10 MONROE 920 (2) DL=4 a x b =c | | Total Indicator 7+4* 1+4* 16 digits 12 digits * the number of fractional digits. Ex. 1-9 1 23 4.5 6 7. 8°9 & 7x99 99 9 = 402 394 5:5 & Su8 370 2: 1:0 1.3 t cut off The total digits of the calculation figures are 16, but the upper 12 digits of the result are indicated due to the decimal point coordination with the lower 4 digits being cut off. (3) Large Numeric Multiplication When the integral figures of the multiplicand and multiplier are both 12 digits each; first, set the switch at 0, then enter the numerics and calculate. Record the result which is the least significant 12 digits of the correct answer. Then, set the switch at any position; but, be sure that a decimal point is entered into the multiplicand and multiplier, so that the sum of the integral figures will total to the amount of the difference between the switch set position to 12 and the maximum total digits is 23 digits as follows: Ex. 1-12 1 223 4:5 6: 7:8 O98 716 xm 99 OE9 9: 919 ONO BO =123456783987476543210124 (1) DL=0 123456789876x99999999999 =12345678987 [4]7|6[5/4[3]2[/1]0[1|2/4} ae and cut off L Overlaps (2) DL=4 1 2 3.24 Sib F 829: BF Gx 0.909 9°9 9 99 9°79 TY = [fij2[al4[slel7 [8 Jolst7]4]76543210124 * Overlaps Connect the overlapping numeral for the correct answer, so the method to calcu- late large numerics is: (1) First, set the decimal point switch at 0, so that the lower 12 digits of the calcula- tion will be indicated. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 11 (2) Then set the decimal point switch at 4 and place a decimal point in the multipli- cand (4), so that the upper 12 digits will appear in the indicator. Then connect the overlapping numeral or numerals. Ex, 1-13 12304 3S: Gu? 629 8 7 x 959 909 9 99 949 959 1234 5:6 7.8 9 8:6 8:7 6.5 4 3:21:01 3 " @i2345678987x99999999999 123456789 8(6|8]7 [6]5]4]3[2[1 [o/1[3] Overflows Tas off — overlaps Overflows with overflow lamp lights up (2) De=4 1234567.83987x9999999999 9 =(1]2]3]4[5 ]o]7[8.Jo[s[ols] 7654321013 L overlaps [ cut off 3.43 Correction of the order key 1) tn multiplication, if [4 key was pressed by mistake, it can be corrected by immediately pressing the correct key [¥ as follows; Ex. 1-14 ax b=c ate] Xl b (=) / (Correction method is the same for division.) “correction Ex, 1-15 axbxc=d a &) bl Ric (FI tg 2) Clearing registration or order key correction i) a (c}] Clears a ii) afdle) Clearsa iii) afdb\e} Clears only b C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 92G GENERAL 12 3.5 Divison at b=c abe | L Calculated result appears at the affixed decimal point position. Floating decimal point system when [K) key is not locked. Floating numerals until the numeric coordinates to the affixed decimal point position. a+ b+c =d aWbe &c L Both numerics b & c are floating system when [Kl key is not locked. In continuous division, [=] key must be pressed every time before a division takes place. 3.5-1 Negative Division The negative sign principle is exactly the same as in negative multiplication where the operator calculates with both as positive values and then attaches the negative sign to the result, because when negative © key is pressed after the numeric, it is instantly converted to its complement, giving an incorrect answer; Ex. 1-16 —144 + 12=-12(D£=4) If pressed accordingly to the equation, there will be a wrong answer. 144 Lolololololofofo loli[4]4] re) 1919/9] 9/9[8[5[6Jo[o[olo] a 19191919 ]9[8[5]6.JoTo[olo] 12 {o{olofolofofofo Jololi]2] S| @ 3BBBBBBRE BBB) (mis-calculation) 3.5-2 Calculation Capacity In division calculation, the calculation capacity is decided by the black region of the Vector Chart as follows; for instance, Ex. 1-17 LASS TVT EW VVAASEV Sea iO a = Pp=4 (decimal point position) D=8 (number of digits) so the above equation can expressed as follows; N=D-x 10? C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 13 12 ll 10 9 pit ® YY at i I 6 5 (2, 6) 4 3 2 WML) O °F: 2: 5 4: § 6 7:6 2M 10 Tl ————— P Ml IV Fig. 1-1 Registration Allowance Region (a) In registration of dividend, it must be within the black region of the first quadrant Ex. 1-18 9:8 7 16..5 4 -— = 4 “ft P=2 oof N=(P,D) = (2, 6) (b) In registration of divisor, since the decimal point is a floating system when key is not locked, then it must be within the region of (0, 0), (11, 0), (11, 12) and (0, 12) as shown in Fig. 1-1. Ex,.1-19 9876564321012 ' ' t——— p=7 (No concern with the decimal point position when [K) key is not D=12 _ locked.) C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 14 (c) In case of quotient, it is the same as dividend. Ex. 1-20 5361625+ 234.3 Thus, 5361625x104 + 2343x10'=22883x1 04 a b (DL=4) Therefore, a= (4, 7) b=(1, 4) So, calculation capacity is; = (Number of digits of dividend) - (That of divisor) + 1 When the value of the dividend is larger than that of the divisor, which is the same number of digits from the most significant digit, 1 must be added. This can be calculated as Vector Calculation as follows: 7-4+(1)=4..... Number of digits of the quotient... D=4 (3, 4) (-4)- (1) =-3..... Decimal point position of the P=3 quotient However, the quotient coordinates to the affixed decimal point position as follows: N = (3, 4) + (4, 5) Shifts one digit to the left. It is shown in following figure. a(4.7) Dividend b(1,4) (4.5) won. Quotient (Decimal point coordination ) (3, 4) ....441) (3, 3) oc me rPwWEUNDR 2 Dw + . A 12345678 910 —- p Fig. 1-2 Vector Calculation of Quotient C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 15 Calculation capacity can be obtained as follows; I (a) (b) (c) (a) Calculate the simple vector calculation. If the value of the dividend is larger than that of divisor which is the comparison of the value of the same number of digits from the most significant digit except 0, then 1 is added to D. It shifts to the decimal point position. After the operation of (a), (b) & (c), if the result is outside the black region in the first quadrant, then the calculation overflows. 3.5-3 Correction of Order key This is excatly the same as that of multiplication. 3.6 Constant Multiplication or Division Simple constant calculation is operated by using [KI key. 3.6-1 Constant Multiplication 1) 2) Kxa= {kK} lock K Kia E) Kxb= bel Kxc= ce K: Multiplicand (Constant) a,b &c: Multiplier Multiplicand is the constant When there is a negative multiplication, calculate it as a positive value and then the operator should write the minus sign to it. 3.6-2 Constant Division 1) 2) a+K= [Rllock aWMKe& b+K= b I c+K= c &l K: Divisor (Constant) a,b&c: Dividend Divisor is the constant. Negative division calculation is the same as that of multiplication. C.§.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com GENERAL 16 3.6-3 {Ki key 1) [K) key can be locked any time before =) or @ key is pressed. 2) Ordinary calculation can be done as soon as [Ki key is released. MONROE 920 3) Individual addition, subtraction, multiplication or division can be done even though key is locked. 3.7 Square Calculation 3.7-1 3.7-2 Square Calculation a ae 1) In square calculation, it does not matter whether {K] key is locked or not. 2) ‘ta’ can be either an entered numeric or a calculated result indicated in the indicator. Powers 3 335338 iou uw i SwNnNe Sy ' = 83353 8 “it uw ot wWnNne Oo = a) key locked RIE... a2 El... a? fe] 5.5.5 4% El--- as B a key locked or not EI a2 Xl =) at : a8 ql6 =] a2! key locked He a° Doo cy fi. . ». C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 GENERAL 17 3.8 Summary of Overflow 3.8-1 Registration 1) When a numeral enters the 13th digit position in registration the lamp lights up and registration stops. 2) When the decimal point position of multiplicand or dividend is more than the affixed decimal point position the lamp lights up. 3.8-2 Decimal Point Coordination When the resultant numeric of the result overflows during the decimal point coordina- tion, the overflow lamp lights up. 3.8-3 Calculation Overflow 1) Since the calculated result is a fixed decimal point system, so when it enters into the 13th digit, the lamp lights up and all calculation stops. 3.8-4 Decimal Point Overflow 1) In registration of addition, subtraction, multiplicand or dividend, when the decimal point position of the numeric is larger than DZ position, the overflow lamp lights up. 3.8-5 Overflow by changing the affixed decimal point position during calculation. 1) If the affixed decimal point position is changed to an upper position, then the decimal point coordination can be done, when any order key is depressed. 2) If the affixed decimal point position is changed to a lower position, then the overflow lamp lights up when any order key is pressed. 3.8-6 Overflow Release 1) When © or (i key is pressed, then indicator clears with the overflow lamp being extinguished. 3.9 Summary of the funciton key 1) © or fer] cavecesorornane Clears the indicator or all other circuits. 2) ©) or BO ceeeeeee For completion of the calculation; but when these keys are pressed again, the calculation will not continue except for power calculation. 3) BW or BH sewavaies If and & keys are pressed continuously, then only the latter order key will be in effect. C.$.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 BASIC CIRCUITS 14 1. Integrated Circuit 1.1 Types of Integrated Circuit 1.1-1 DTL (Diode Transistor Logic) In Fig. 2-1(a), diode D1 & D2 which is the AND gate that makes the transistor T1 operate to invert and amplify the given signals, so the equivalent logic is as shown in Fig. 2-1(c) which is a positive logic. The diode D3 & D4 in Fig. 2-1(a) is the Level Shift Diode which makes the Noise Margin larger by lowering the signal about 0.6V, lower by each diode. The circuit of Fig. 2-1(b) is an improved one to that of 2-1(a), where one level-shift diode is replaced by a transistor which operates not only as level-shift diode but also as an Emitter Follower. The advantages are that a large output is obtained and operates at a higher speed. Sinc? DTL has a larger Noise Margin and Fan-Out (number of output loads at one time) than that of RTL, so it was adopted in Monroe 950 or 990. J ty b +V s D ] D3 Da C=AB obs 7 oat — hoe—4 Te = D2 Da . ia Ti Bo—t¢ Th IT (a) Basic DTL (b) Improved DTL (c) Equivalent Circuit Fig. 2-1 DTL Circuit 1.1-2 TTL (Tansistor Transistor Logic) Recently TTL is been used in the place of DTL because it has a smaller output impe- dance and a larger noise margin. The difference between DTL and TTL is that the diodes are replaced by a transistor with an emitter follower T2 attached to the cirucit. C.S.B. No. ED9—505 Scan Courtesy The Old Calculator Museum, http://oldcalculatormuseum.com MONROE 920 BASIC CIRCUITS 2 T2 T, Ts T1 Fig. 2-2. TTL Circuit 1,1-3 MOS (Metal Oxide Semiconductor) In MOS integrated circuit, FET (Field Effect Transistor) is used which has a large input impedance while epitaxial transistor is used for DTL & TTL. Though the switching speed in MOS integrated circuit is a little lower than that of DTL & TTL, the noise margin and integration are much larger than them. Even now, 100-bit shift registers have been developed and are put into practical usage. Ye L Ao Bo—-+ Fig. 2-3 MOS Circuit 1.1-4 Others Extra-high-speed integrated circuits such as CTL (Complementary Transistor Logic) & CML (Current Mode Logic) which are improved circuits of TTL, have been developed to meet the requirements for extra-high-speed computers. 1.2 DTL Circuits and Its Characteristics 1.2-1_ Improved DTL The improved DTL, mentioned in 1.1-1(b) is adopted in Monroe 990. DTL is divided into two main circuits NAND gate and Master-Slave flip-flop. NAND gate is divided into three groups according to the number of input of