Tektronix 7904 Instruction Manual Download

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Summary of Contents for 7904

Page 1: ...CHECK SCR CHANGE INPCRMATION AT THE READ C THIS MANUAL CILL COP SN E260000 UP IN F U IUN MANUAL_ Tektronix Inc P O Box 500 Beaverton Oregon 97077 Serial Number ____ 070 2390 00 First Printing SEP 1977 Product Group 42 Revised MAY 1983 ...

Page 2: ...ry Operation 2 1 Plug In Units 2 1 Installation of Plug In Units 2 1 Controls and Connectors 2 1 Functional Check 2 4 Set Up Information 2 4 Display Focus 2 4 Trace Alignment 2 4 Graticule Illumination 2 4 Controllllumination 2 5 Vertical Deflection System 2 5 Horizontal Deflection System 2 5 Triggering 2 7 Readout 2 7 Beam Finder 2 7 Calibrator 2 8 Z Axislnput 2 8 Simplified Operating Instruction...

Page 3: ...sity Modulation 2 21 Raster Display 2 22 Calibrator 2 22 Signal Outputs 2 23 Probe Power Connectors 2 23 Applications 2 24 THE REMAINING PORTION OF THIS TABLE OF CONTENTS LISTS THE SERVICING INSTRUC TIONS THESE SERVICING INSTRUCTIONS ARE FOR USE BY QUALIFIED SERVICE PERSONNEL ONLY TO AVOID ELECTRIC SHOCK OR OTHER PERSONAL INJURY DO NOT PERFORM ANY SERVICING OTHER THAN THAT DESCRIBED IN THE OPERATO...

Page 4: ...eshooting the High Efficiency Power Supply Unit 4 8 Corrective Maintenance 4 13 Obtaining Replacement Parts 4 13 Soldering Techniques 4 73 Component Removal and Replacement 4 14 Adjustment After Repair 4 27 SECTION 5 PERFORMANCE CHECK AND ADJUSTMENT Preliminary Information 5 1 Adjustment Interval 5 1 Using this Procedure 5 1 Test Equipment Required 5 1 Test Equipment Alternatives 5 2 Performance C...

Page 5: ...rounding connec tion must be made before making connection to the instrument s input or output terminals The following safety symbols may appear on the equipment CAUTION Refer to manual DANGER High voltage Protective ground earth terminal Do Not Remove Instrument Covers To avoid electric shock hazard operating personnel must not remove the protective instrument covers Com ponent replacement and in...

Page 6: ...ely bright sharply focused dot exists on the crt Also remember that fhe light filter reduces the apparent light output from the crt Prevent Instrument Damage A Type Slow blow fast blow etc B Voltage rating 250 V etc C Current rating Plug in units should not be installed or removed without first turning the instrument power off to prevent instrument damage Operating Power Consideration To prevent d...

Page 7: ...ly discharged before attempting any repairs or ohmic measurements A warning indicator neon bulb located on the Power Supply Inverter board flashes when this storage voltage exceeds about 80 volts However simply because the neon bulb is not flashing does not mean that the capacitors are fully discharged Disconnect Instrument Power To avoid electric shock hazard always disconnect the 7904 from the p...

Page 8: ...due type of cleaner preferably isopropyl alcohol totally denatured ethyl alcohol or TP35 Before using any other type of cleaner consult your Tektronix Service Center or representative Do Not Use Pin Sockets for Connection Points Exercise Care When Handling CRfi Anode Lead Do not touch any components with the crt anode lead until it is fully discharged The spring Pension of the pin sockets ensures ...

Page 9: ...ize and high writing rate Graticule area is 8 X 10 cm Additionally the instrument includes a readout system providing crt display of alphanumeric information from the plug ins including deflectior7 factor sweep rate and other encoded parameters The instrument s high vertical bandwidth 500 MHz and four plug in compartments which accept 7 series plug in units form a highly flexible measurement syste...

Page 10: ...heck and Adjustment con tains procedures to check the operational performance and electrical characteristics of the instrument Procedures also include methods for adjustment of the instrument to meet specifications Section 6 Instrument Options contains a description of available options and locations of incorporated infor mation for those options To prevent damage to the instrument always check th...

Page 11: ...rce Table 1 1 POWER CORD CONDUCTOR IDENTIFICATION Conductor Ungrou nded Line _ _Gr_o_un ded _ Neutral Grounded Earthing Color Alternate Color Brown _Blue_ _ _ Green Yellow B lac k__ ____ ______ White ______ __ Green Yellow 2 Loosen the two captive screws which hold the cover onto the selector assembly then pull to remove the cover 3 To convert from 115 V to 230 Vnominal line voltage or vice versa ...

Page 12: ...e service required Operating Temperature The 7904 can be operated where the ambient air temperature is between 0 C and X50 C This instrument can be stored in ambient temperatures between 55 C and i 75 C After storage at temperatures beyond the operating limits allow the chassis temperature to come within the operating limits before power is applied The 7904 is cooled by convection air flow through...

Page 13: ...L CHARACTERISTICS Performance Requirement Supplemental Information VERTICAL SYSTEM Compatible with all 7 series plug in units lTi_ Less than 1 difference between vertical compartments 0 1 div or less compression or ex pansion of a center screen two division signal when positioned anywhere vertically within the graticule area Varies with amplifier plug in selected See Table 1 7 Vertical System Spec...

Page 14: ...rence between _ _ compartments 0 1 div or less error at each graticule line after adjusting for no error at the second and tenth graticule lines do to at least 1 MHz 0 5 ns div A horizontal unit only Dual sweep alternates between hori zontal units With 7B92A time base unit only A Other 7B series units are uncal ibrated for first 60 ns of sweep time when used with 7904 Selected by front panel HORIZ...

Page 15: ... Open circuit 4 mV 40 mV 0 4 V 4 V 40 V _____ __ Into 50 ohms __ 2 mV 20 mV 0 2 V 0 4 _ __ _ Output Curren 40 mA through front panel current loop _ Amplitude Accuracy Voltag and Current 15 C to 35 C Within 1 0 C to 50 C Within 2 _ __ Repetition Rates 1 kHz Selected by front panel RATE switch 1 2 repetition rate of B Sweep gate Dc 1 kHz Accuracy Voltage and Current 15 C to 35 C Within 0 25 0 C to 5...

Page 16: ...tensity range Positive going signal decreases trace intensity negative going signal increases trace intensity A HORIZ time base unit or B HORIZ time base unit Supplemental Information Approximately 0 V input produces no intensity change Dc Approximately 10 ns Approximately 20 ns Approximately 25 ns Approximately 50 ns Approximately 0 ns 500 f2 f10 15 V dc peak ac Selected by internal Sweep switch ...

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Page 18: ...thode Ray Tube Graticule Type DISPLAY Internal illuminated with variable edge lighting Area Standard instrument 8 div vertical by 10 div horizontal Each division equals 1 cm Option 4 8 div vertical by 10 div horizontal Each division equals 0 5 cm Phosphor Beam Finder Minimum Photographic Writing Speed with Polaroide Type 410 Film without film fogging techniques Standard instrument Tektronix C 51 R...

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Page 20: ...cooling Automatic resetting thermal cutout protects instrument from overheating 20 minutes for rated accuracy Anodized front and rear panel with blue vinyl painted aluminum cabinet Height 13 5 in Width 34 2 cm 12 0 in Length Net Weight Instrument Only 30 5 cm 23 8 in 69 5 cm 30 0 lbs 13 5 kg NOTE DIMENSIONS ARE GIVEN WITH TOP FIGURE IN INCHES AND BOTTOM FIGURE IN CENTIMETERS Fig 1 2 7904 dimension...

Page 21: ...it type number identifies a unit not equipped with the circuitry necessary to encode data for the 7000 series readout system The second letter describes the purpose of the plug in unit Table 1 7 lists the vertical specifications which are system dependent For more complete specifications on plug in units for the 7000 Series Oscilloscope System refer to the Tektronix Products catalog A Amplifier L ...

Page 22: ...g an external calibrator whose accuracy is within 0 25 INT CAL 15 C to 35 C Plug in gain set while operating within a temperature range of 15 C to I 35 C using the oscilloscope calibrator INT CAL 0 C to 50 C Plug in gain set using the oscilloscope calibrator within 10 C of the operating temperature In a temperature range between 0 C and 50 C 67A18 Opt 6 offset version Add 1 to accuracy figures whe...

Page 23: ...Preamplifier 100 kHz to 1 7 GHz Spectrum Analyzer 1 kHz to 1 8 GHz Spectrum Analyzer Dual Delay Line Readout Access Unit Accepts Plug In Sampling Heads Time Domain Reflectometer and Sampling Applications Dual Trace Delayed Sweep Sampler Random or Sequential equivalent or Real Time Sampling STANCARD ACCESSORIES leach Instruction Manual 2 each Lead Test bnc red 18 inch long leach Adapter conn female...

Page 24: ...ecked when installed to verify theiraccuracy referto the operating instructions in the plug in manual The 7904 accepts up to four Tektronix 7000 Series plug in units This feature allows selection of bandwidth sensitivity display mode etc and provides for future expa sion of the system CONTROLS AND CONNECTORS The overall capabilities of the system are mainly determined by the characteristics of the...

Page 25: ...Operating Instructions 7904 SN 8260000 UP 2390 01 Fig 2 1 Fron4 and rear panel controls connectors and indicators 2 2 ...

Page 26: ...time base unit GATE Output signal derived from A Gate B Gate or A Dly d Gate CAL VOLTS Square wave output signal used for application to external equipment 16 Ground not labeled Binding post for use as chassis ground SIG OUT Output signal derived from vertical signal as selected by A TRIGGER SOURCE switch 18 B TRIGGER SOURCE Selects internal trigger source for B HORIZ plug in 19 Current loop not l...

Page 27: ... control so the top and bottom of the displayed square wave are as thin as possible but not elongated Set the ASTIG adjustment so the top and bottom of the displayed square wave are as thin as possible Repeat the adjustments for best overall focus NOTE This instrument contains circuitry to automatically protect the crt phosphor against damage due to excessive crt beam current If the A or 8INTENSIT...

Page 28: ...ther vertical unit moves the display Return the VERTICAL MODE switch to the LEFT position 15 Notice that the position control of only the left vertical unit has any effect on the vertical position of the displayed trace Position the trace to the upper half of the graticule with the left vertical unit position control Horizontal Deflection System 22 Notice that the position control of only the A ti...

Page 29: ...n the sweep rate switches of both time base units throughout their range Notice that two traces are displayed on the crt atall sweep rates Also notice that when both time base un its are set to a slow sweep rate 50 milliseconds division or slower both traces are visible on the crt at the same time Return the sweep rate switches of both time base units to 0 5 millisecond division 30 Set the CALIBRA...

Page 30: ... of the VERTICAL MODE switch buttons and the HORIZONTAL MODE buttons Notice that the readout from a particular plug in occupies a specific location on the display area If either of the vertical plug in units is a dual trace unit notice that the readout for channel 2 appears within the lower division of the crt Return the VERTICAL MODE switch to LEFT VERT 36 The B TRIGGER SOURCE switch operates in ...

Page 31: ...ot explained here or operations which need further explanation are discussed under Detailed Operating Information SIMPLIFIED OPERATING INSTRUCTIONS General The following information is provided to aid in quickly obtaining the correct setting for the 7904 controls to present a display The operator should be familiar with the complete function and operation of this instrument as described in this se...

Page 32: ...st the time base position control so the dis play begins at the farthest left vertical line of the graticule Set the time base sweep rate to display the desired number of cycles 11 Set the left vertical unit deflection factor for a display about four divisions in amplitude Adjust the vertical position control to move this display to the top of the graticule area Dual Trace Display The following pr...

Page 33: ...ect to the trace produced by the A time base unit 7 Connect the signal to the input connector of the vertical unit Dual Trace Dual Sweep Display 8 Set the vertical unit for ac input coupling and calibrated deflection factors The following procedure will provide a dual trace dual sweep display of two single trace vertical units against two time base units four traces displayed on crt 9 Set both tim...

Page 34: ...lay The following procedure will provide a dual trace dual sweep display where the left vertical unit is displayed only at the sweep rate of the B time base unit and the right vertical unit is displayed only at the sweep rate of the A time base unit 1 Follow steps 1 through 19 of the previous procedure for Dual Trace Dual Sweep displays 2 Press the ALT button of the VERTICAL MODE switch 14 Press t...

Page 35: ...dure will provide a delayed sweep display of two single trace vertical units four traces displayed on screen 1 Install 7A series amplifier units in both the LEFT VERT and the A HORIZ compartments 1 Follow the complete procedure given under Dual Trace Displays 2 Press the LEFT button of the VERTICAL MODE switch and the A button of the HORIZONTAL MODE switch 2 Be sure the time base unit installed in...

Page 36: ...n an X Y mode orifeitheroneofthe time base units is set to a slow sweep rate even if the time base unit with slow sweep rate is not selected for display by the HORIZONTAL MODE switch 1 his reduces the danger of damaging the crt phosphor with a stationary or slowly moving spot Since beam current limiting does not take effect until after about ten milliseconds the full display intensity capability o...

Page 37: ... Option 3 This filter provides shielding against radiated EMI electro magnetic in terference from the face of the crt It also serves as a light filter to make the trace more visible under high ambient light conditions The mesh filter fits in place of the plastic crt mask and the tinted filter Figure 2 3 shows the oscilloscope graticule and defines the various measurement lines The terminology defi...

Page 38: ...re the readout from each plug in unit and channel is displayed Notice that the readout from channel 1 of each plug in unit is displayed within the top division of the graticule and the readout from channel 2 is displayed directly below within the bottom division of the graticule Only the readout from plug ins or channels which are selected for display by the VERTICAL MODE or HORIZONTAL MODE switch...

Page 39: ...omplete frame Rate of change must be at least 0 1 V s Maximum current 3 mA requ ired Maximum open 10 V circuit voltage Maximum safe _ 10 V 5 V dc peak ac input voltage The READOUT control determines the intensity of only the readout portion of the display independent of the other traces The Readout System is inoperative in the fully counterclockwise OFF position This may be desirable when the top ...

Page 40: ...e vertical unit can be used in either of the two single channel modes in either dual trace mode or added algebraically a delaying time base may be used either for a normal sweep or for delayed sweep Therefore it is difficult to list all of the display combinations which can occur using the plug in units which are available since the display combinations possible are dictated by the specific com bi...

Page 41: ...sweep operation is used under this condition a different sequence of display occurs First the leftvertical unit is displayed at the sweep rate of the time base unit in the A HORIZ compartment delaying sweep and then at the sweep rate of the time base unit in the B HORIZ compartment delayed sweep The vertical display then shifts to the right vertical unit and it is displayed con secutively at the d...

Page 42: ...es between time base units after each sweep on the crt Although the ALT horizontal mode can be used at all sweep rates the CHOP horizontal mode provides a more satisfactory display at sweep rates below about 20 milliseconds division At slower sweep rates the switching between the alternate mode traces becomes apparent and may interfere with correct analysis of the display NOTE The A and B INTENSIT...

Page 43: ...DE and the actual internal trigger source obtained as a result of the VERTICAL and HORIZONI AL MODE switch settings and operating mode of the time base units LEFT VERT or RIGHT VERT Table 2 3 Trigger Source VERTICAL MODE Trigger Source for Switch Position A and B HORIZ units LEFT ALT ADD CHOP RIGHT VERT MODE Table 2 2 LEFT VERT unit only Determined by HORIZONTAL MODE Switch see Table 2 3 Algebraic...

Page 44: ... listed under Applications provide information on X Y measurements and interpreting the resultant lissajous displays While the X Y delay compensation network provides minimum phase shift between theXand Y portions of an X Y display it adds negative preshoot distortion and some corner rounding to fast step functions An internal Delay Disable switch see Fig 2 6 is provided for both the A and B delay...

Page 45: ...t in the vertical compartment special connections must be made from this time base unit to the blanking network for further information see the instruction manual for the applicable time base unit Calibrator General The internal calibrator provides a convenient signal source for checking basic vertical gain and sweep timing The calibrator output signal is also very useful for adjusting probe compe...

Page 46: ...rtical unit except for delayed sweep operation then the output signal is the same as in the A or B positions The LEFT VERT and RIGHT VERT positions of the B TRIGGER SOURCE switch provide the vertical output signal only from the selected vertical unit even when it is not selected for display The output voltage into a 50 f2 load is about 25 millivolts division of crt display and about 0 5 volt divis...

Page 47: ... reset operation The remote ready lights are optional and can be used with an active or passive system whenever it is necessary to provide an indication at the remote location that reset has occurred Normally open relay or pushbutton switch Remote A Ready Fig 2 8 Typical circuit for remote single sweep reset operation Maximum current 10 mA requ ired Minimum pulse 10 Ns at 50 amplitude width points...

Page 48: ... JOE CiY UA F 4 PEF df l NC_Y iQ AtJC ID PER i af i v i 3RY U iW i P RFC R uI At Y SER lGW C CEO C C H fir C C 3TACNEv f Pc Fi a TC 1C 1 R t Ci Ufi CV ES J Y J R A iC iFC l Lai REFER TQ JPEC AiC ETY i Rl r C iD SER 1Li E SAFE_s 5 sfi l A r Y rC F i ...

Page 49: ......

Page 50: ...ck diagrams give the names of the individual stages within the major circuits and show how they are connected togethertoform the major circuit 1 he block diagrams also show the inputs and outputs for each circuit and the relationship of the front panel controls to the individual stages The circuit diagrams from which the detailed block diagrams are derived are shown in the Diagrams section Symb Is...

Page 51: ...ersthat specific part of the instrument BLOCK IAGRAM The Logic circuit develops control signals for use in other circuits within this instrument and the plug in units These control signals automatically determine the correct instrument operation in relation to the plug in units installed or selected plug in control settings and 7904 control settings The crt circuit contains the Z Axis Amplifier wh...

Page 52: ... a E t7 c v c C d A 7 3 O i d d tj W V 0 0 o ro _N W Fig 3 1 Basic block diagram of the 7904 Oscilloscope J Y h QE of E A o c a o 0 0 0 o c c a o H E y V e U V Of G v _7 a C y C C y a y V _ _ _ y i in 07 7 7 m 3 t C V N z a u a W z Q E O 3 3 O C ai o 7 a C Q1 C y o N E io COi O N R E V r U c O _ O 7 7 ova O C c N ti 07 C 5 m m a aE O oE N O J O W O j F N U ...

Page 53: ... J CCF OI OZOMN 2 ipJ 0 Z nN QM U d QNC MM FMcn00 N W XC7 MNN NJO add W F N U O O U ZSUaY n O C7 w T U J m R Fig 3 2 Detailed block diagram of Logic circuit F fn 1 U UU mU U yO ZQ Q UO o d a ZO O Zo g 2 ZffQ QZ Z d a ua U wOp j0 jl y wm ti S wm v m rnQ Q QX2 a NJQ aUO aQU D O U Q 2 m Z F V1 Nfn y W J _O Q wU J dd ...

Page 54: ...ld be noted that these logic diagrams are not an exact represen tation of the internal structure ofthe integrated circuit but are only a logic diagram of the function performed by the stage An input output table is given where applicable for use along with the circuit description and logic diagram These input output tables document the combination of input conditions that are of importance to perf...

Page 55: ...sables the A sweep while the B sweep is being displayed in the ALT horizontal mode both units must be in time base mode if non delayed opera tion is being used The second combination disables the A sweep during delayed sweep operation so that the B sweep can complete its holdoff before the next A sweep begins As shown by Fig 3 5B the output of this stage is HI only under one set of input condition...

Page 56: ...e produced at the end of the sweep by the respective time base unit is differentiated by either C311 or C309 to provide a positive going pulse to pin 6 or 9 An Alternate Pulse is produced at the end of each A sweep when the HORIZONTAL MODE switch is set to the A position 2 B ONLY MODE In the B position of the HORIZONTAL MODE switch an Alternate Pulse is produced at the end of each B sweep A time b...

Page 57: ... B WITH VERTICAL UNIT IN A COMPARTMENT m _ ___ _ _ ____ _ _______ e_ _ _y NO OUTPUT PULSE LO AT OUTPUT HAS NO EFFECT IN THIS CASE POSITIVE GOING PULSE WHERE BOTH A AND B HOLDOFF ARE REQUIRED TO BE HI A HI AT EITHER INPUT PRODUCES AN ALTERNATE PULSE NEGATIVE GOING PULSE iissa Fig 3 6 A Logic diagram for Alternate Pulse Generator stage B Table of Input output combinations 3 8 ...

Page 58: ...nk the crt display for vertical chopping horizontal chopping or during a readout display Figure 3 7 identifies the inputs to the Z Axis Logic stage This circuit is current driven at all inputs except pins 5 and 15 1 he current at pins 1 2 9 and 16 is variable from zero to four milliamperes and is determined by the applicable current source to control the output current at pin 8 The Vertical Choppi...

Page 59: ... an excessive voltage is applied to the Z AXIS INPUT connec tor The A INTENSITY control sets the output current level when the A Gate at pin 14 is HI and the Display B Command at pin 15 is LO Whenever the AGate level goes LO indicating that the A sweep is complete or the Display B Command goes HI indicating that the B sweep is being displayed the A INTENSITY current is blocked The current from the...

Page 60: ...INIMUM VOLTAGE OR CURRENT CURRENT LEVEL L0 0 mA HI MAXIMUM VOLTAGE OR CURRENT HI VARIABLE FROM 0 TO 4 mA iiss s 4 HAS NO EFFECT IN THIS CASE CURRENT CAN BE ADDED OR SUBTRACTED FOR INTENSITY MODULATION Fig 3 S A Logic diagram for Z Axis Logic stage B fiable of Input output combinations 3 1 1 ...

Page 61: ... vertical unit being displayed first against the A time base unit delaying then the B time base unit delayed before the display is switched to the other vertical unit In the CHOP position of the HORIZONTAL MODE switch the Display B Command switches between the HI and LO levels to produce a display that switches between the A and B HORIZ units at a 0 2 megahertz rate The repetition rate of the Disp...

Page 62: ...ETITION RATE ONE HALF HORIZONTAL CHOPPED BLANKING RATE B 3 REPETITION RATE ONE HALF ALTERNATE PULSE RATE Fig 3 10 A Logic diagram for Horizontal Binary stage B Table of Input output combinations 0 2 p O Q Q v0 C9 O Q Ow m O Oiv m O Oiu tt Q Q 2w 4J v C V OZ O cS0 w ti O y Q Q O VO c4 1 3 4 7 8 10 6 HORIZONTAL DISPLAY HI LO LO LO _ LO A HORIZONTAL UNIT LO HI HI LO HI B HORIZONTAL UN IT LO LO LO LO ...

Page 63: ...operations of the Vertical Binary stage in relation to the modes of operation that can occur NOTE Although the output at pin 6 of 0275 is always controlled by the HORIZONTAL MODE switch as described here this level determines the Vertical Mode Control level at the collector of Q296 only in the ALT position of the VERTICAL MODE switch due to AND gate CR201 CR204 See the discussion on the Vertical M...

Page 64: ...SLAVING HAS NO EFFECT IN THIS CASE n 1 1F OUTPUT IS LO PRIOR TO LO IT GOES HI AND VICE VERSA ACTUATED BY NEGATIVE GOING EDGE REPETITION RATE ONE HALF ALTERNATE PULSE RATE 3 REPE1 ITION RATE ONE HALF DISPLAY B RATE 1195 13 Fig 3 12 A Logic diagram for Vertical Binary stage B Table of Input output combinations ...

Page 65: ...e vertical and time base units The resultant crt presenta tion when the dual trace unit is set foralternate operation displays the Channel 1 trace at the sweep rate of the B time base unit and the Channel 2 trace at the sweep rate of the A time base unit Input conditions fora LO output level so that Channel 1 of the vertical plug in can be displayed at the B sweep rate are A logic diagram of the V...

Page 66: ...unit 4 Channel 2 of RIGHT VERT unit at sweep rate of A time base unit Notice that under these conditions both channels of the LEFT VERT unit are displayed at the B sweep rate and that both channels of the RIGHT VERT unit are displayed at the A sweep rate The repetition rate at the output of this stage is one half the Display Right Command rate Input conditions when the VERTICAL MODE switch is set ...

Page 67: ... it Therefore C213 can begin to discharge through R214 The emitter level of Q2 follows the discharge of C213 until it reaches a level about 0 6 volt more negative than its base Then Q2 is forward biased and its collector drops negative to reverse bias Q1 The level at pin 14 drops negative also to complete the cycle Once again C213 begins to charge through R212 R213 to start the second cycle Two ou...

Page 68: ...ased upon the operating mode of the vertical system or the plug in units dual trace units only Vertical Chopped Blanking pulses are produced if 1 VERTICAL MODE switch is set to CHOP 2 Dual trace vertical unit is operating in the chopped mode and that unit is being displayed 3 Dual trace vertical unit operating in the chopped mode with the VEki f ICAL MODE switch set to ADD The repetition rate of t...

Page 69: ...tage 0255 produces the Vertical Chopping signal the Plug In Chop Command and the Horizontal Chopped Blanking signal The Clock pulse produced by the Clock Generator stage provides the timing signal for this stage The functions of the input and output pins for the Chop Counter IC U225 are identified in Fig 3 18A Idealized waveforms showing the timing relationship between the input and output signals...

Page 70: ... Blanking stage CHOP MODE HORIZ CLOCK 10 VERTICAL CHOPPING SIGNAL HORIZONTAL CHOPPED BLANKING PLUG IN CHOP COMMAND VERTICAL CHOPPING SIGNAL PIN 1 PLUG IN CHOP COMMAND PIN 8 CHOP MODE HORIZI PIN 6 HORIZONTAL CHOPPED BLANKING PIN 4 VERTICAL CHOPPED BLANKING PIN 4 OF U215B Iel 1195 19 Fig 3 18 A Input and output pins for Chop Counter IC U225 B Idealized waveforms for Chop Counter stage ...

Page 71: ...IGHT a HI level is connected to the base of 0292 through R204 This forward biases 0292 and the positive going level at its emitter is connected to the emitter of 0296 The collector of 0296 goes HI to indicate that the R I GHT VERT unit is to be displayed For the CHOP position of the VERTICAL MODE switch a HI level is applied to the anodes of CR202 CR203 through R202 Both diodes are forward biased ...

Page 72: ...T TRACE SEPARATION B control The current from the VERT TRACE SEPARATION B control is switched so that the Trace Separation output is provided only when the B sweep is being displayed in the ALT or CHOP horizontal modes and not when B sweep only is being displayed nor for independent pairs operation sweep slaving Opera tion of this stage is as follows The VER r TRACE SEPARATION B control provides c...

Page 73: ...endent pairs operation sweep slaving is selected The output of this stage is determined by the Horizontal Slave Enable level from the Logic circuit and by the VERTICAL MODE switch For further information on independent pairs operation and the Horizontal Enable level see the description of the Vertical Binarystage in the Logic circuit When independent pairs operation is selected the output of the S...

Page 74: ...ach com bination of the Horizontal Slave Enable level the setting of the VERTICAL MODE switch and the setting of the trigger The A and B Trigger Channel Switch stages determine which input signal provides the internal trigger signal to the horizontal units as controlled by the trigger Right and Add signals from the trigger select logic stages S455 A TRIGGER SOURCE A TRIGGER OUTPUT AMPLIFIER FROM A...

Page 75: ... 100 f2 differential load for the trigger outputs of the vertical plug in units and establish the input resistance of the trigger channel switch stages The A and B Trigger Channel Switch stages are made up primarily of integrated circuits 05502 05510 and 05530 for the A Trigger and 05602 05610 and 05630 for the B Trigger The operation of the A and B Trigger Channel Switch is similar Therefore only...

Page 76: ...R5574 and R5576 The B Trigger Level Shifter circuit operates in a similar manner Signal Out Amplifier T he signal out amplifier stage 05679 receives trigger signals by the selection of the B TRIGGER SOURCE switch and provides a sample of the trigger signal to a front panel connector Resistor R5678 biases Q5679 and 05650 Resistors R5682 R5683 and R5684 set the base bias voltage of Q5679 Signal Out ...

Page 77: ...ter Selection Matrix for 7904 Readout System F X W F F Z O F F a 7 OC O U O y a W w O w w O F U Z a O OC y a L a U a F W W a F a O _ w U o w O w w w w J W F a a w oC tri O a Z U O_ a F F J Z_ U Z O O O a a a _ w y w U O v 0 w M _N 47 N N 3 28 REV OCT 1981 ...

Page 78: ...feach stage to the operation of the overall Readout System Detailed information on circuit operation is given later The key block in the Readout System is the Timer stage This stage produces the basic signals that establish the timing sequences within the Readout System Period of the timing signal is about 250 microseconds drops to about 210 microseconds when Display Skip is received see detailed ...

Page 79: ...N COM i PARTMENTS DATA ENCODED BY RESISTORS IN PLUG IN UNITS ROW ANALOG DATA IN FROM PLUG IN COM PARTMENTS SKIP IF NO COLUMN DATA ENCODED IN THIS TIMESLOT 1 Fig 3 26 Detailed block diagram of Readout System CONTROL PULSES TO VERT AMP HORIZ AMP LOGIC AND CRT CIRCIJITS SKIP IF W DISPLAY DATA SKIP1 ENCODED IN TS 1 TIME MULTIPLEXED ANALOG VOLTAGES 1195 27 3 30 ...

Page 80: ...F LINES WHERE NO NUMBER APPEARS THERE IS ONE LINE DECIMAL POINT LOGIC AND CHARACTER POSITION COUNTER 1195 28 Fig 3 26 cont CHARACTER GENERATOR FIFTY CHARACTER MATRIX U2270 U2272 U2274 U2276 U227B Y SIGNAL TO VERTICAL AMPLIFIER X SIGNAL TO HORIZONTAL AMPLIFIER 3 31 ...

Page 81: ...Horizontal Amplifierand Vertical Amplifierthrough the X and Y Buffer stages Also the Zeros Logic and Memory stage produces the IDENTIFY function When time slot 1 is encoded for IDENTIFY column 10 row 3 this stage produces an output level which connects the Column Data Switch and Row Data Switch to a coding network within the Readout System Then during time slots 2 through 9 an analog current outpu...

Page 82: ... of the Strobe pulse collector of 02138 negative and diverts the output current of Row Decoder U2185 to row 2 1 he purpose of this configuration is to prevent the Zeros Logic and Memory stage U2232 from storing incorrect data during the quiescent period of the Strobe pulse When the Strobe pulse goes positive CR2140 is reverse biased to disconnect 02138 from U2272 and allow the Row Decoder to opera...

Page 83: ...n trol also provides a means of turning the Readout System off when a readout display is not desired When 82124 is turned fully counterclockwise the switch in series with the Readout Intensity line opens The current to pin 11 of U2126 is interrupted and at the same time a positive voltage is applied to pin 4 through CR2124 The positive voltage switches the stage to the same conditions as were pres...

Page 84: ...I NIM a n cc nlool ail j I I i r I I I I I I I i r r t 1 Fig 3 29 Timer stage operation when Display Skip condition Fig 3 30 Time relationship of the time slot TS pulses produced occurs by U2159 TIMESLOT PULSE 5 PIN 10 TIMESLOT PULSE 6 PIN 9 TIMESLOT PULSE 7 PIN 7 TIMESLOT PULSE 8 PIN 6 TIMESLOT PULSE 9 PIN 5 TIMESLOT PULSE 10 PIN 4 r ai ii i M 1 F 1 fi OV OV OV OV OV OV FOV OV OV OV NOrE TEST OSC...

Page 85: ...e Single Shot Lockout stage This stage allows a single readout frame eight complete words to be displayed on the crt after which the Readout System is locked out so further readout displays are not presented until the circuit is reset 021208 and U2120C are connected to form a bistable flip flop For normal operation pin 8 of U2120C is pulled HI through R2108 This activates U2120C to result in a LO ...

Page 86: ... the column current and the row current corresponding to the column and row of the matrix The column and row data is encoded by program ming the plug in units Figure 3 31 shows a typical encoding scheme using resistors for a voltage sensing amplifier plug in unit Notice that the 10 time slots TS pulses produced by the Time Slot Counter stage are connected to the plug in unit However time slots 5 6...

Page 87: ...o display on the crt See Display Skip Generator for further information C 1 C 3 C 4 C 5 C 6 C 7 ___ c s C 9 C 10 _ PROGRAM FOR 100 uV INVERTED CALIBRATED UNCALIB IBI RATED OPERATION SHOWN BY SHADED AREA 1195 34 Fig 3 32 Idealized current waveforms of A Row analog data B Column analog data be displayed Time slot 10 is not encoded in accordance with the Standard Readout Format The resultant crt read...

Page 88: ...bit lines are LO only when the associated plug in unit has been selected for display When a unit is not selected the respective line is HI to forward bias the associated diodes CR2162 CR2163 CR2166 CR2167 CR2170 CR2171 or CR2174 CR2175 The forward biased diodes cause the channel switches to bypass the encoded data from the inhibited channel However since it may be desired to display information fr...

Page 89: ...The column and row data is also used throughout the Readout System to perform other func tions The input current at pin 9 of the Column Decoder stage is steered to only one of the ten Column Digital Data outputs When a Display Skip signal is present collector of 02225 HI pin 9 is pulled HI through CR2226 This ensures that no current is connected to the Character Generator stage under this conditio...

Page 90: ...he plug in unit along with row 3 during time slot 1 the Zeros Logic and Memory produces a negative going output pulse at pin 1 to switch the Column Data Switch and Row Data Switch to the ninth channel Then time slot pulses 2 through 9 encode an output current through resistors R2191 R2199 for column data and R2201 R2209 for row data This provides the currents necessary to display the word IDEN T I...

Page 91: ...ich generate the X horizontal and Y vertical outputs at pins 16 and 1 respectively to produce thecharacterdisplayon the crt Each integrated circuit can produce 10 individual characters U2270 designated Numerals can produce the numerals 0 through 9 shown in row 1 of the Character Selection Matrix Fig 3 24 U2272 can produce the symbols shown in row 2 of the Character Selection Matrix and U2274 produ...

Page 92: ...ms two functions The first function is to add a staricase current to the X horizontal signal to space the characters horizontally on the crt After each character is generated the negative going edge of the Ready signal at pin 5 advances the Character Position Counter This produces a current step output at pin 3 which when added to the X signal causes the next character to be displayed one characte...

Page 93: ...the top and bottom of the graticule area The X and Y deflection signals produced by the Character Generator stage are connected to pins 2 and 7 respectively of Format Generator U2284 The Channel Address Code from the Channel Counter is also con nected to pins 1 8 and 15 of this stage The Channel Address Code directs the format Generator to add current to the X and Y signals to deflect the crt beam...

Page 94: ...Circuit Description 7904 SN 8260000 UP y w Y a J WJp W Wy C7 OF a w O X2a y ZD O r 1195 38 Fig 3 36 Flow chart for character generation by the Readout System 3 45 ...

Page 95: ...ertical Mode Command from the Logic circuit This stage is made up primarily of integrated circuit 04625 and 04685 An input outputtable for these switches is shown in Fig 3 38 The positive and negative signal channels from the vertical plug in com partments are connected to the inputs of U4625 and U4685 through 50 SZ coaxial cables Each coaxial cable is terminated in its characteristic impendance b...

Page 96: ...INPUT AMPLIFIER 0694 0698 0705 0710 0716723 0728 DELAY LINE OMPENSATION 1 195 2390 05 Fig 3 37 Vertical Amplifier detailed block diagram INPUT OUTPUT OUTPUT SIGNAL LEFT VERTICAL SIGNAL NEITHER BLOCKED BY READOUT SYSTEM Q HAS NO EFFECT IN THIS CASE 1195 ao 5125 Fig 3 38 Input output table for Vertical Channel Switch IC 04625 04685 VERTICAL MODE COMMAND FROM LOGIC CIRCUIT 04625 04685 ADD MODE FROM V...

Page 97: ...rcuitry of U685 is represented in Fig 3 39 Terminals to the emitters of the input transistors of 0685 at pins 5 6 and 11 12 permit the quiescent operating conditions of the stage to be set by discrete components R682 and R689 set the quiescent operating level R684 and R688 are selected to accurately set the gain of the differential channels These emitter inputs also provide a means of injecting th...

Page 98: ...rizontal X signal portion of an X Y display to match the delay of the vertical Y signal due to the Delay Line The Horizontal Channel Switch portion of the circuit selects the horizontal deflection signal from the output of the A HORIZ and B HORIZ plug in unit The Main Horizontal Amplifier circuit amplifies the push pull horizontal deflection signal from the Horizontal Channel Switch forapplication...

Page 99: ...ntal Amplifier detailed block diagram T J w u O oc c7 x 3 50 REV A OCT 1979 Circuit Description 7904 SN 8260000 UP JZ Z HOO Oti JZ FOO Uw o OUJ UO OUQWaU Jai N NWaF WW Nw ZO W p Z Q OW WJa Ow NWH W _ fHpO Y fn QG U O J N Z J J ZOt J GN wa ag aC inao a0 DU ...

Page 100: ...dless of the setting of the positioning controls or signal amplitude Left and Right Driver Amplifiers The Left and Right Driver Amplifiers are current driven shunt feedback amplifiers consisting of 04901 and 04911 and feedback resistors R4889 and R4899 Tran sistors 04905 and 04915 are emitter followers that drive the capacitive load that is presented by the output stage Input Amplifier The Input A...

Page 101: ...ier The output signal at the front panel GATE connector J1089 is selected from three input gate signals by Gate switch S1065 In the A position the A Gate signal from the A time base unit is connected to the base of emitter follower 01069 through R1067 The base of 01073 is connected to ground by S1065 in this position so it operates as a common base stage 01069 provides a high input impedance for t...

Page 102: ... through 01111 and its collector goes positive again to complete the square wave Once again C1108 begins to charge through R1109 to start the second cycle The signal produced at the collector of 01111 is a two kilohertz square wave C1114 differentiates this signal to produce positive and negative going output pulses coincident with the rise and fall ofthe square wave which provides negative going ...

Page 103: ...bridge rectifier and the voltage across C1216 C1217 will be the peak value approximate ly of the line voltage As a result the output voltage applied to the Inverter stage is about the same for either 115 V or 230 V operation Thermistor R1209 limits the surge current demanded by the power supply when it is first turned on After the instrument is in operation the resistance of the thermistor drops s...

Page 104: ...Circuit Description p 7904 SN 8260000 UP a N O7 Fig 3 44 Detailed block diagram of Converter Rectifier circuit 3 55 ...

Page 105: ...nant network of L1237 C1237 Diodes CR1234 and CR1241 provide reverse conduction paths across 01234 and 01241 respectively when these transistors are held off for pre regulation To aid in understanding circuit operation Fig 3 45A shows a representation of the Inverter stage with a do input voltage equal to E The three possible states of the Inverter are depicted by the three possible positions of s...

Page 106: ...le pulse width monostable multivibrator which is initally triggered by current phase information fed back from the Inverter The charge ramp for the multivibrator is available at pin 12 of 01275 R1300 C1300 determine the rate of rise of the charge ramp The sensing inputs to 01275 determine the pulse width of the charge ramp i e th8 multivibrator on time The pulse width of the charge ramp correspond...

Page 107: ...s determined by the voltage level at the E Sense input at pin 15 If this voltage level is low the duration is short As this voltage level increases the duration increases Balance The Balance portion of 01275 provides over load protection for the Low and High Voltage Rectifiers by sensing a malfunction in these circuits Beam I current Sense and I current sense inputs from the crt circuit and output...

Page 108: ... as follows If the output level of this supply decreases becomes less negative due to an increase in load or a decrease in input voltage as a result of line voltage changes or ripple the voltage across divider R1512 R1513 R1514 decreases also This results in a more positive level at the base of Q1508B than that established by the 50 V Reference stage at the base of Q1508A Since the transistor with...

Page 109: ...ERIES REGULATOR 01428 50 V 50 VOLT FEEDBACK AMPLIFIER 01409 07415 01425 E 50 VOLT CURRENT LIMITING 01418 SEMI REGULATED 17 VOLTS R 1457 15 VOLT SERIES REGULATOR 01458 15 VOLT FEEDBACK AMPLIFIER 01436 01451 n1455 Fig 3 46 Detailed block diagram of Low Voltage Regulators circuit 3 60 ...

Page 110: ...Circuit Description 7904 SN B260000 UP a 50 V 50 VOLT CURRENT LIMITING 01526 R 1537 GRAT ILLUM 1195 49 Fig 3 46 coot 3 61 50 VOLT FEE BACK 50 VOLT AMPLIFIER REFERENCE 01508 VR 1505 01522 01534 ...

Page 111: ...s more negative than the base of 01576A Now 015768 is cut off and 01576A conducts The collector current of 01576A forward biases CR1576 and decreases the voltage on the base of 01582 This limits the conduction of 01588 to a safe current level F15 Volt Supply The 15 V Supply regulates in the same manner as the 50 V Supply current limiting operates in the manner described for the 5 V Supply The grou...

Page 112: ...Pl r r a aaaaa yf O y pZ w NZ 2 Fig 3 47 Detailed block diagram of the CRT Circuit 3 63 n W ttt _y ____ JO ay f 00 a ww w pt1 c c oCOC o oNa t0 J r a jj r t a 10 y U V vw W Oa OJ nn nn aa as _ ______ f yA U F M J ao 0w aCCd y _ aaa U wo ro Oa xw r U tr0 O tL y a h a O OF a O ao H r U a t w L p0 w U jWU ZJ w wW y zu w ZW boa JAG 000 a z z y QOU Ov OC g Z Z aw m CO ayW 9SU OU a m C ...

Page 113: ...nals to the Z Axis Amplifier The output of the Z Axis Amplifier provides the drive signal to control the crt intensity level through the Control Grid DC Restorer 1 he negative three kilovolt accelerating potential for the crt cathode is generated by a voltage doubter con sisting of CR1607 CR1608 C1607 C1608 High frequency filtering is accomplished by R1609 C1609 R1612 C1612 R1612 and C1612 also pr...

Page 114: ...rols these stages maintain optimum focusfor all portions of the display as it is switched between readout A Horizontal and B Horizontal displays Transistors 01740 01744 and 01746 select current from the A INTENSITY control B INTENSITY control or READOUT INTENSITY control inputs as determined by the Vertical and Horizontal OFF Command at the base of 01740 and the Display B Command at the base of 01...

Page 115: ...f the drive CR1655 charges the focus grid side of C1656 to a level more negative than the reference level The resulting focus grid voltage is more negative than the reference level by an amount equal to the difference between the x 130 V Supply and the Auto Focus Amplifier output level CRT Control Circuits hhe AS TIG adjustment R1733 used in conjunction with the FOCUS control to obtain a well defi...

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