Tektronix 7904A Instruction Manual Download

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Summary of Contents for 7904A

Page 1: ...ton Oregon 97077 Serial N umber COMMITTED TO EXCELLENCE PLEASE CHECK FOR CHANGE INFORMATION AT THE REAR OF THIS MANUAL 7904 OSCILLOSCOPE WITH OPTIONS I NST RU CTIO N MANUA L 070 4593 00 First Printing...

Page 2: ...ice change privileges are reserved INSTRUMENT SERIAL NUMBERS Each instrument has seri al number on panel insert tag or stamped on the chassis The first number or letter designates the country of manuf...

Page 3: ...15 OPERATORS CHECKO UT PROCE DURE 2 1 APPLICATIONS 2 15 TEST EQUI PMENT REQU IRED 2 1 VERTICA L AMPLI F I ER PLUG IN UN ITS 2 15 PRELI M INARY SETUP 2 5 SI NG LE TRACE 2 15 DISPLAY FOCUS 2 5 DUAL TRA...

Page 4: ...R GEN ER ATO RS 3 51 3 CH O P M ODE 3 12 OUTPUT A MPLI FI ER S 3 51 4 ALT MODE 3 12 SIGN ALS OUT I NTENSITY LI M ITER 3 51 VERTICAL BI NARY 3 13 SAWTOOTH AMPLI FI ER 3 51 1 0R MODE 3 13 GATE AMPLI F...

Page 5: ...PPLIES 4 10 SUPPLIES 3 63 STEP D CHEC K LINE INPUT CI R CU IT 4 11 50 V REGULATOR 3 63 STEP CHE CK CRT AN D HIGH VOLTAG E 15 V REGULATOR 3 64 CI RC U IT 4 12 5 V REGULATOR 3 64 STEP F CH EC K THE I NV...

Page 6: ...NATIVES 5 11 DIAGRAMS PART 1 PERFORMA NCE CHECK 5 14 I NTERCO NNECTI N G DIAGRAM 1 I NDEX TO PERFO RMANCE CH ECK PROCEDURE 5 14 MODE SW ITCH DIS PLAY CO NTROL CALI BRATO R 2 PERFO RMANC E CHECK POWER...

Page 7: ...Horizontal un its 5 3 Typ ical display whe n ch eck ing phase is disp layed 25 compen sation 5 60 3 11 Output waveforms of the Timer stage 3 26 5 4 Readout display with Q2225 removed 5 70 3 12 Detail...

Page 8: ...put Output Combinations for the Vertical Binary Stage 3 14 V1 LIST OF TABLES Table No Page 3 9 In put Out put Combinations for the Plug In Binary Stage 3 15 3 10 Input Output Combinations for the Vert...

Page 9: ...ower cord To avoid im mediately accessible as one reads the marking or electrical shoc k plug the mainframe power cord into hazard to property includi ng the equipment itself properly wired receptacle...

Page 10: ...llows d ual trace vertical and d ual sweep h orizontal disp lays The 7904 features incl ude an 8 cm 10 cm crt dis play area wi t h crt readout display of al p han umeric characters from the associated...

Page 11: ...ARNING mechanical parts and shows exploded drawings whic h identify assemblies THE FOLLO WIN G SERVICING INSTRUC TIONS ARE FOR USE BY QUALIFIED PERSONNEL ONL Y TO A VOID PERSONA L I N J UR Y DO NOT PE...

Page 12: ...e to the instrument always ch eck the settings of the LINE VOL TAG E SELECTOR switch located on th e rear panel of the 7904 Oscilloscope mainframe before connecting the instrument to the line voltage...

Page 13: ...used for this pu rpose Also if this instrume nt is to be shipp ed to Tektronix Service Center for service or re pair attach tag to the i nstrument showing the following Ow ner of the i nstrument with...

Page 14: ...it Rise time 10 to 90 with 7 29 Am p lifier Unit Isolation Between Vertical Compartme nts 8 Div Signal LEFT R IGHT A LT Mo des Differen ce in Signal Delay Between Vertical Co mp artments TABLE 1 3 Ele...

Page 15: ...G The VERT TRACE SEP 8 co ntrol is inoperative in slaved alternate mode and T R IGGER SOURCE Selected by front panel switch es Lig hts behind th e push buttons are illu m inated to ind icate th e trig...

Page 16: ...4 V 40 mA availa b le throug h CAL I BRATOR outp ut with option al bnc to curre nt loop adapter CAL I BRATOR switch mu st be set to 4 V for cali b rated ou tput Within 1 1 kH z within 0 25 49 to 50 2...

Page 17: ...See 7904 Oscilloscope Vertical System Specification in Table 1 7 0 V within 1 V into 1 MO READOUT DISPLAY I nte rnal switch on Readout Board must be in Free Run position Continuously displayed READOUT...

Page 18: ...of time base units installed in and HOR IZ comp artm ents Closure to grou nd or switching from the h ig h level 50 to 10 V sin k less than 40 I to the low level 0 5 V to 5 V sink less th an 12 mA in l...

Page 19: ...ar panel Dc Approximately 470 Less than 50 pF App roximately 0 V 15 V dc plus peak ac 1 MHz LI NE VOLTAGE S ELECTOR Selects 115 V or 230 V range Positive 2 V provi des complete blan ki ng from maximum...

Page 20: ...L 288000 Sect 4 5 5 3 1 Type Class 5 Style except 0 15 i nch amplitude Sect 4 5 5 3 1 c 55 Hz Resonance Dwell Sect 4 5 5 3 1 e 2 an d 20 to 55 Hz Frequency Increment Sect 4 5 5 3 1 e 2 Tested to MIL 2...

Page 21: ...1r 000 lot I F 01 1 L W Figure 1 1 7904 Dimensional Drawing General Information 7904A 0 W r h 3 20 aW U W D W 2 J z 02 LL W CE W F...

Page 22: ...ABLE 1 6 Plug In Incompatibilities Symptoms The th ird an d fou rt h digits of the plug in type number do not carry any special connotation suffix letter ad ded to the normal four digit type nu mber i...

Page 23: ...3 4 5 110 3 2 None 105 100 3 5 7A13 P6053B 3 5 1 5 2 5 3 5 100 3 5 6055 65 5 4 65 5 4 7A14 6021 55 6 4 2 3 4 50 7 0 6022 120 2 9 100 3 5 7 15 6 None 053 80 4 4 3 4 5 70 5 0 7 16 None 225 1 6 2 3 4 14...

Page 24: ...esistance 7512 Universal Counte r Timer Programmable Digitizer CATV Pream plifier TABLE 1 8 7904 Oscilloscope Horizontal System Specification Maxim um Performance Calibrated Feature Sweep Rate Perform...

Page 25: ...anual 1 ea Instruction Manual 1 ea Blue Faceplate Filter installed 1 ea Power Cord OPTIONAL ACC ESSORI ES not i ncl uded The following accessory is available for use with your 7904 Oscilloscope For mo...

Page 26: ...nt blocks have no functional assignment but I NSTALLATIO N OF PLUG IN UNITS indicate the relationship among controls and or connectors CAUTION 7 prevent instrument damage plug in units should not be...

Page 27: ...OSCILLOSCOPE 711 3 J J j OUT PU TS R Lrr W 14 j I J he T RIGGE R SO U RCE FOCUS TRACE F R 13 F S S CALIBRAT ED TI ElDIV 5 131 LEFT A LT 4 R G47 VERT HORIZONTAL MODE iW GATE 717 F RUN L 6 R 5 RR H iC3...

Page 28: ...p lay GRAT I LLUM MAN Switch when pressed actu ates READO U T I N TEN SITY Control to determi n e one graticule illumi n atio n brightness of readout d isplay Disables Readout System in co u ntercloc...

Page 29: ...ctive probe system SINGLE SWEEP READY Connector for output of single sweep ready s i gnal f rom time base unit in HORIZ com partment SINGLE SWEEP READY Connector for output of si ngle sweep ready sign...

Page 30: ...t the left am plifier unit deflection factor to display Type Used TEKTRONI X FG503 Functio n Generator signal am plitude of 2 divisions ce ntered on the requires 500 power modu le screen 4 Coaxial Cab...

Page 31: ...on of the overlap adjust the VERT TRAC E SEPARATIO N displayed trace Positio n t he trace to the upper half co ntrol to position one trace to the bottom of th e of the graticule graticule area Turn th...

Page 32: ...e A LT positio n the plug in unit Notice that the deflection factor HOR IZONTA L MOD E switch is in either the ALT or indicated by the readout is i ncreased by 10 times the CHOP position and the time...

Page 33: ...t reflections the amplifier unit deflection factor to 0 5 from the face of the crt to improve contrast when volts division four division display Now connect viewing the display under high am bient tig...

Page 34: ...o the HORIZ com partment The I NTENSITY control input of the amplifier unit Set the sine wave determi nes the brig htness of the display produced by generator repetition rate to 1 kilohertz and the th...

Page 35: ...e up to eig ht words of readout is R eadout System is obtained from the plug in units displayed The GATE switch determi nes whether installed in the plug in com partments Readout is displayed at the e...

Page 36: ...ombi nations which can occur dur ing use of the 7904 and availa ble plug i n units Table 2 1 lists the com bination of VERTICAL MOD E and HORIZONTAL MODE switc h positions availa ble and the type of d...

Page 37: ...n inputs and delayed sweep rates good rule is not to apply signal of more than about eight times the vertical deflection factor Larger Chopped Mode The CHOP positio n of the VERTICAL vo ltages may res...

Page 38: ...e ADD position and TRIGGER SO URCE switches Also see Vertical the VERTICAL MOD E switch since the internal trigger Trace Se paratio n for informatio n on positioni ng the signal i n t hese mo des is t...

Page 39: ...ERTICA L MOD E switch Wave Shape Probe Power The square wave output signal of the CALI BRATOR ca n The two PR OBE POWER connectors on the rear panel be used as reference wave shape when chec king or o...

Page 40: ...ntrols two volt peak to pea k signal will completely blank the display even at maximum intensity levels lower am plitu de sig nals can be used to change only the relative trace brightness Negative goi...

Page 41: ...artments suggested later i n th is section Dual trace sampli ng dis plays can also be made by NOTE 7512 in the mi ddle two compartments an d 7S11 in the The 7B50 series time base units are not LEFT VE...

Page 42: ...p h a n umeric test messages may be se nt or received via the front panel port Readout Access Plug in Unit The 7 13 READOUT plug in unit provides front panel keyboard operatio n for co nvenient access...

Page 43: ...t h vertically a nd horizontally by h orizontal deflection signal ca n be con nected eit h er to sawtoot h signals T h is is accom p lis hed in t he 7904 by an external in p ut connector on t h e time...

Page 44: ...is to use the Z AXIS INPUT to provide provided for the time base units when they are in the i nte nsity modulatio n for the display This ty pe of raster verticalcompartments external triggering must b...

Page 45: ...QUALI FI ED PERSONNEL ONLY AVOID PERSONAL INJURY DO NOT PERFORM ANY SERV ICI NG OTHER THAN THAT CONTAI NE D IN OPERATI NG I NSTRU CTIO NS UNLESS YO U ARE QUALIFI ED DO SO REFER OPERATORS SAFETY SUMMAR...

Page 46: ...void striking the crt on any object which mig ht cause it to crack or implode When storing USE CARE WHEN SERVICING WITH crt place it in protective carton or set it face down in POWER ON protected loca...

Page 47: ...ier Horizontal Channel Switch Horizontal Am plifier Focus Amplifier and Axis logic circuits Signals from the Readout System produce the al pha numeric display for the Vertical Horizontal and Axis Am p...

Page 48: ...TOR SIG OUT I CALIBRATOR I HORIZONTAL V D 6 w AMPLIFIER COMPENSATION SWITCH 1 11 READOUT SYSTEM X Y INHIBIT Z AXIS INHIBIT COM MAND AC LINE IN VERTICAL DELAY VERTICAL CHANNEL LINE AMPLIFIER SWITCH INT...

Page 49: ...All logic fun ctions are descri bed using the positive logic Digital logic techn i ques are used to perform ma ny convention Positive logic is system of notatio n where functio ns within the instrume...

Page 50: ...ice wit h one input one output The out put is always the opposite state of t he input device with two i nputs one out put F Negation small circle at t he i nput or output of symbol i ndicates that I n...

Page 51: ...When the C inp ut is LO t he J inputs are irrelevant L Q S Q J For devices wit h direct Set Rest inputs the indicated state at eit her of these inputs over rides all other inputs J inputs have no effe...

Page 52: ...h en using the current loop 3 adapter the Calibrator must be operated only in the 4 V switch position for stated output MAIN I NTERFACE Transistors Q376 an d Q382 form 1 kilohertz square wave oscillat...

Page 53: ...c j CD C Q L 3 n cc m g vi V J CC J c y m m 2 z J z V pt m CC Theory of Operation 7904A _ _ i 1 0 1 1 6 1 0 1 01 9...

Page 54: ...wee p operation logic fu nctions Sweep Locko ut Swee p Locko ut enabling the sweep to complete its holdoff before the and Alternate Pulse Generation The majority of the next sweep begins logic for the...

Page 55: ...The followi ng sections descri be the operation of the unit see mai n Interface diagram 3 Alternate Pulse Generator stage for the various com binatio ns of inp ut conditions shown in Table 3 5 The thi...

Page 56: ...ept for the readout dis play which is controlled by the R eadout System The output current at pin 8 is determined by the setti ng of the or INTENS ITY cont rols and the Auxiliary Axis in put The Auxil...

Page 57: ...tpu t com bi nations of the Axis readout display T he i nte nsity of the readout dis play is Logic stage determi ned by separate Readout intensity level con nected directly to the Axis Amplifier see C...

Page 58: ...g rate 3 R epetition rate one half alte rnate pulse rate 2 MOD E Selecting the horizontal mode provides description later in this section Each t i me the HI Display Command to all circuits Horizontal...

Page 59: ...layed base unit delayed before the dis play is switched to the swee p ot her vertical unit Pi n 7 HI The sweep is to be dis playe d Dis play The Vertical Alternate Command is used in the Plug In Comma...

Page 60: ...ONTA L MOD E switch set to any trace at the sweep rate of the time base unit positio n except or The Plug In Alternate Command switches from HI to LO as the Display Command from the Horizontal Binary...

Page 61: ...f Q1 pulls the emitter of Q2 positive Wit h Q2 reverse biased its col lector rises positive to produce Pin 4 LO VERTICAL M OD E switch set to ALT positive output level at pin 14 Pin 8 HI or LO Plug Al...

Page 62: ...Blan king pulse The slo pe of the of U4320 The output at pin 15 is positive goi ng clock negative going delay ramp is determined by the clock pulse with repetitio n rate of about two mega hertz gener...

Page 63: ...ANK I NG PULSES AT OU TPUT with t h e switch i ng between th e disp layed traces The Horizontal Ch op ped Blank ing signal The clock pu lse duty cycle of th e wi d e pulse train prod uced in th e cloc...

Page 64: ...ition rate of the Plug in Chop level Command at pin 8 is 0 5 megahertz one fourth clock rate Th is provides choppi ng signal that controls switching betwee n channels in dual trace vertical units This...

Page 65: ...same Vertical Alternate Comman d from pi n 6 of the Vertical time segment is displayed from the vertical signal Bi nary stage ca n pass to the base of Q4382 to determi ne source with or without Horizo...

Page 66: ...Display Comman d at its base is HI for this mode screen current associated wit h t hese bright spots can be Therefore the VERT TRACE SEP ARATIO N control large enough to enable the intensity limiter...

Page 67: ...signal at the collector of Q4492 is HI independent of other control inputs If diode CR4495 is This turns on Q4494 and the INTENSITY indicato r connected to ground by amplifier un it installed in the...

Page 68: ...discussio n of the Trigger Diagram 5 Am plifier is given Integrated Circuit U274 provides final amplifi cati on of the trigger sig nal Components R261 AND TRIGGER CHANNEL SWITCHES and R272 are bias re...

Page 69: ...t System provi des an alphanumeric display of informatio n encoded by the plug in units Th is display is presented on the crt and is written by the crt beam on time s hared basis with the analog wavef...

Page 70: ...Theory of Operation 7904A 3 24 _ z z J U _ 0 F z 4 F J _ Figu re 3 9 C haracter selection matrix fo r 7904 Readout System S N 031766 Below REV N OV 1985...

Page 71: ...S 8 Defi nes the prefix which modif ies The key block in the Readout System is the Timer Stage the units meas urement see schematic 6 This stage produces the basic sig nals that establis h the timi ng...

Page 72: ...sto red there during time slot 1 is transferred to the input of the Column Decoder stage to modify the analog data duri ng the applicable time slot Also the Zeros Logic and Memory stage produces the I...

Page 73: ...ed to the area of the crt associated the qu iescent period of the stro be pulse When the with th e plug in and chan nel originating the word see strobe pulse goes positive CR2140 is reverse biased to...

Page 74: ...h e Timer output signal When ch aracter is to be generated pin 4 is LO and the circ uit operates as just descri bed However when character is not to be displayed HI level is applied to pin 4 of U2126...

Page 75: ...he Time Slot Counter can be reset in th is manner only when J ump Command is received by U2155C and D see followi ng discussion WORD TRIGG ER The Word Trigger stage is made up of U2155A and Quiescentl...

Page 76: ...ces the Channel Add ress Code for the Column display word one This pulse is applied to pi n 3 of and Row Decoder stages an d the Format Ge nerator U2120A which produces at pin 6 of U2120B stage This c...

Page 77: ...co ntrol the row analog data which is connected back to analog data is connected bac k to the R eadout System the R eadout System Fig ure 3 16 shows an idealized via te rmi nal 837 of the plug in int...

Page 78: ...R 130 is not connected to the time slot encoded during time slot the zeros do not appear in 3 line si n ce the deflectio n factor is cali brated the display The crt readout will now be changed to 1 T...

Page 79: ...never any information appears at the output of gives the eight combi nations of the Chann el Address the Column Data Switch the base of 02215 is pulled Code an d the resultant chan nel selected with e...

Page 80: ...zed an d ca n be inspected This activates the Zeros to colum n 0 programs the Readout System to not Logic and Memory stage so that it can store the display character at this readout location encoded d...

Page 81: ...is activated For exam ple if some letters used as prefi xes shown in row 4 colum n 2 is encoded the five character Generators are I ntegrated circuits U2276 and U2278 produce the enabled so that eith...

Page 82: ...so be adva nced when Space in Fig ure 3 18 t h is dis plays decimal point after t he instruction is enco ded so space is left between the t hird c haracter that can be d is played on the crt T he dis...

Page 83: ...mbering system uses the numerals 0 through 9 and the letters DI SPLAY SEQUENCE through F to represent the sixteen possi ble cominations Fig ure 3 19 shows flow chart for the Readout System of four bin...

Page 84: ...Theory of Operation 7904A 3 38 Ln Cc Cc 0W0 r Q cc A F A J z Q z z z 10 LIZ 0 i ix CA 00 4 CC 0C s Qt 0 cc 0 LL z Figure 3 19 Flow chart for character ge neration by the Readout System d REV N OV 1985...

Page 85: ...during Slot End of Word channel REV Theory Two channel Data ing resultant that on corresponds tion information cial purpose readout manuals The selected stages from compartments age from Switch from D...

Page 86: ...Theory of Operation 7904A 3 4 Figu re 3 20 Character selection matrix for 7904 Reado ut System SN 031767 Above c i 13 Q REV NOV 1985...

Page 87: ...or plug in This Word Trigger stage can also be ad Each character displayed on the CRT consists of series of vanced to jump complete word or portion of word connected points within an 8 point by 8 poi...

Page 88: ...OM OUTPUT SIGNALS CIRCUIT JUMP SINGLE DISPLAY SKIP SHOT LOCKOUT 5 00 W CHANNEL COUNTER CODE WORD TRIGGE R CHANNEL COUNTER U21278 TS 2 TO TS 9 IDENTIFY NETWORK 3 CHANNEL COUNTER CODE COLUMN IDENTIF Y D...

Page 89: ...D CO NVERTER 22 ROW DECODER U2185 2 U2246 ROW DECIMAL TO BCD CONVERTER U2186 R 7 R 7 02131 02132 CHARACTE R GENERATOR HORIZONTAL CHARACTER POSITION 2202 2263 U2264 ENABLE C R OUTPUT GENERATOR AMPLIFIE...

Page 90: ...igure The R eadout output at pin 12 is produced next This cur 3 14 shows the time relationship of the time slot pulses No rent is connected to the CRT circuit to unblank the CRT to tice that only one...

Page 91: ...Figure 3 15 resistors R 10 through R90 con displays are not presented until the circuit is reset ante trol the row analog data which is connected back to the grated circuit U2120A and U2120B are conne...

Page 92: ...g data from each of the 8 In the above example the row analog data was pro data sources 2 channels from each of the 4 plug in grammed to define which row of the Character Selection compartments Matrix...

Page 93: ...sense the magnitude of the analog voltages at their in puts output is produced at pin 7 while the memories are being pin 10 and produce binary output on one of ten lines set This negative going pulse...

Page 94: ...Data Switch and Row Data Switch to the ninth channel Then time slot pulses 2 throug h 9 encode an output current throug h resistors R 2191 through R2199 for column data and enable pin 10 of U2186 Thi...

Page 95: ...t starts the oscillator and is The Character Generator s 8 bit output provides the i n clocked at pin 11 by the oscillator output from Q2153 formation necessary to move the instrument beam around Q220...

Page 96: ...acter Position Counter for the see Fig 3 18 The decimal location encoded by plug in next character within the readout word duri ng time slot one is achieved by adding positioning cur rent to the horiz...

Page 97: ...2 information from pin 3 of the Channel Counter U2127A is inverted by U2251 A and converted to current by R2252 and R2253 The Channel Counter pro d uces LO at pin 3 when t he readout word is to be di...

Page 98: ...is eit her terminate d wit hin the stage or cou pled t hroug h the stage as dete rmi ned by t h e Vertical C ha nnel Selector stage T he C hannel Switc h stage is made up primarily of i ntegrated cir...

Page 99: ...el off R IG HT VERT c ha nnel signals are VERTICAL amplified and fe d to t h e out puts LEFT VERT c han nel sig nals are terminated wit hi n U668 sc hematic diagram of t he Vertical Amplifi er is give...

Page 100: ...e on the collector of compensated signal from th e delay line compensation Q541 drops to zero wh ic h turns Q631 off an d turns 0630 stage at input pi ns 7 and 9 Variable resistor R211 on The Axis sig...

Page 101: ...he delay compensation networ k is actually two separate delay networks an network and The delay com pensation network may or may not be activated depen ding on the type of plug in in t he HOR IZ com p...

Page 102: ...ation of co mponents me ntioned here Su b hea dings in the left an d right Active Pea king circuits is i dentical only following discussion use the stage names to further discussion of the right Activ...

Page 103: ...t he voltage at the base of 068 as set by the Focus Output Level adjustment R70 The com pared signal is ADD NOV 1985 TABLE 3 14 Input O utput Relationships for the Auto Focus Channel Switch DATA OUT R...

Page 104: ...r driven by U123 to provide error correction to th e crt cathode supply 3 58 FOC US GRID DC RESTORER The operation of the Focus Gri d DC Restorer is similar to the operation of the Co ntrol Gri d DC R...

Page 105: ...t h e instrume nt an d to k eep the approximate 25 k ilo hertz Inverter sig n al from enteri n g t h e power line Com ponents R5 C5 and C6 sup p ress reverse recovery transients of C R 15 The LI NE V...

Page 106: ...ne frequencies that the vol tage at point is some voltage more positive This line frequency sig nal is also con nected to the than the negative supp l y voltage and th at 040 has just Inverter Control...

Page 107: ...ED DC INPUT 1 L37 VOLTAGE b C37 230 V 1 4 110 2 40 CR41 230 V CR34 3 PH AS E SEN SE TO U75 b 35 mom Theory of Operation 7904A b RE 0 V I _ _ 4 4553 70 Figure 3 24 Representation of Inverter stage Idea...

Page 108: ...to keep Q54 time However various fau lt conditions can affect hold and 052 turned on When the inverter restarts C54 is off time or stop the Inverter operation altoget her The recharged throug h CR59 a...

Page 109: ...ere o btained at t he s upply the voltage at the load wo uld not stay consta nt due to the i nhere nt resista nce of the interco nnecti ng cable betwee n t he supply a nd its load The se nse co nfigur...

Page 110: ...uld t he su pp ly be s horted to one of t he more positive su pplies s horte d to positive su pply Operational amplifier U84A provi des current limiting for 094 by monitoring t he voltage dro p across...

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