HP Sprinkler 181A User's Manual
Contents
1. OPERATING AND SERVICE MANUAL MODEL 181A AR OSCILLOSCOPE i l l SERIALS PREFIXED 840 See Section VII for Instruments With Other Serial Prefixes Copyright HEWLETT PACKARD COMPANY COLORADO SPRINGS DIVISION 1947 1900 GARDEN OF THE GODS ROAD COLORADO SPRINGS COLORADO U S A 02612 4 NN PRINTED APR 1969 Section I T ble 1 1 HORIZONTAL AMPLIFIER External Input Bandwidth dc cpie dc to 5 MHz ac coupled 5 Hz to 5 MHz Deflection Factor sensitivity 1 v div 5 on Xi 0 2 v div 5 on X5 0 1 v div 5 on X10 vernier provides continuous adjustment between ranges Dynamic range 5 v Input RC 1 megohm shunted by ABPEeseiuasely 30 pf Sweep Magnifier X1 X5 X10 magnified sweep accuracy x5 6b CALIBRATOR Type approximately 1 kHz square wave less than 3 psec rise time Voltage 10v peak to peak 1 CATHODE RAY TUBE AND CONTROLS Type post accelerator storage tube 8 5 kv ac celerating potential aluminized P31 phosphor Graticule 8 x 10 division parallax free internal graticule marked in 95 centimeter squares Subdivisions of 0 2 div on major axes Front panel recessed TRACE ALIGN alignstrace with graticule Y axis may be aligned to be perpen dicular with X axis with internal control for ac curate rise time measurements Writing Rate Write mode 20 cm msec Max write mode 1 cm sec Erase push button erasure takes approximately 300 ms2. 4 50 15 VOLT SUPPLY The 15 volt supply is sim ilar to the 12 6v supply except that changes in the output are applied tothe base of A8Q6 and inverted be fore being coupled through A8Q4 tothe series regula tor A8Q2 4 51 PLUG IN POWER 4 52 Table 4 1 lists the current available from each power supply for use by the vertical and horizontal plug ins Users desiring to design special purpose circuits should not exceed the capabilities shown in the table Thereisno minimum current requirement for any supply Table 4 1 LVPS Current Capabilities Power Supply l Maximum Safe Current Available 100 VDC 15 VDC 12 6 VDC 100 VDC 4 53 CALIBRATOR 4 54 The calibrator circuit performs a dual function it provides a 1kHz output signal of 10v pk pk 1 for calibration purposes and a lkHz 100v signal for the storage pulse circuit see Figure 8 15 A1Q6 and A1lQ7 areusedina free running multivibrator circuit Diodes A1CR12 and A1CR14 provide voltage protection to the transistors The collector of A1Q is discon HV OSCILLATOR 35KHZ HV XFMR 100V REGULATOR l E HV ADJUST Model 181A AR nectedfrom A1C15 by AIC R13 as A1Q7 turns off pro vidinga faster pulse rise time AlL2andA1C 16 isolate the multivibrator from the 100v supply while A1R31 and A1C17 isolate it from the 15v supply The 10v square wave output is applied to a front panel connec tor foruse inpro
3. The storage mesh of the CRT is not easily damaged however a high intensity repetitive trace or spot writ ten on the screen for an extended time may not erase completely To prevent CRT damage use minimum INTENSITY which will give the desired display for a given PERSISTENCE setting 3 40 PRESENTATION SELECTION Push button controls select the mode in which the CRT functions With ERASE push button depressed the other three functions are disconnectedandall stored and persist ing displays are removed from the CRT The WRITE and MAX W modes are the only conditions in which a display may be written on the CRT screen The STORE mode disconnects the WRITE and ERASE func tions and retains written displays at reduced intens ity on the CRT INTENSITY PERSISTENCE and ERASE do not function in the STORE mode The VIEW mode intensifies the stored dispiay to a set brightness and again INTENSITY PERSISTENCE and ERASE do not affect the display 3 41 MAX WRITE When MAX W push buttonis de pressedandthen the ERASE push button is depressed and released the storage surface is erased and then primed or pre fogged to allow much faster writing on the storage surface The display however has reduced contrast and fades positive more rapidly The contrast and storage time are also reduced in this mode 3 42 OPERATING TIPS 3 43 This information is provided toaidthe operator in becoming familiar with the Model 181A AR control
4. STORE IBiA C i Figure 4 5 Overali Block Diagram 4 4 02612 2 Model 181A AR 4 31 The internal sweep from the Horizontal Plug In is coupled through the HORIZONTAL DISPLAY switch to the horizontal output amplifier Here it is converted to a differential signal amplified and ap plied to the CRT horizontal deflection plates 4 32 EXTERNAL 4 33 Positioning the HORIZONTAL DISPLAY switch _to EXT removes the internal display voltage from the Horizontal Plug In The unblanking gate and the in ternal sweep are therefore not generated by the plug in 4 34 Gate amplifier operation and thus CRT intens ification is determined by an externally applied Z Axis Input signal the chopped blanking signal from the Vertical Plug In and an unblanking signal from the storage pulsecircuit Whenin EXT the gate amp lifier will produce an alternate trigger only if the ex ternal input signal is similar to the normal unblanking gate 4 35 The externally applied horizontal deflection sig nal is preamplified coupled to the output amplifier converted to a differential output and applied to the CRT horizontal deflection plates 4 36 CIRCUIT DESCRIPTION 4 31 The following paragraphs area detailed descrip tion of the circuits andtheir functions in the Model 181 A AR Oscilloscope 4 38 LOW VOLTAGE POWER SUPPLY LVPS 4 39 The low voltage power supply produces six dc voltages plus the CRT write and flood
5. 3 25 REAR PANEL 3 26 OUTPUTS Main and delayed sweep and gate signals are available at rear panel BNC connectors of the Model 181A AR These outputs are providedfrom separate isolationamplifiers which can supply 3 ma and will drive impedances as low as 1000 ohms without distortion The plug ins used in the Model 181A AR and the control settings employed deter mine the out put signals available 3 27 Z AXIS INPUT Anexternal signal can be util izedfor control of CRT intensity A rear panel mounted BNC connector permits a direct connectionto the CRT intensity gate amplifier A signal of approximately 42v dcto 15 MHz isrequired to blank a beam of nor mal intensity Input of a negative signal c can be used for beam intensification 3 28 AC LINE INPUT A three conductor ac input jack is providedfor power input Also located on the rear panelis the 115 230v slide switch andthe required fuses for 115 vac and 230 vac operation 3 29 INTERNAL 3 30 PHASE BANDWIDTH TheModel181A AR can also be usedfor phase measurements Positioning the PHASE BANDWIDTH switch to PHASE causes the horizontal input signal to be delayedthe same amount of time as the vertical input signal NOTE Make certain the control is returned to the Bandwidth position after making phase measurements i 3 31 PLUG IN UNITS 3 32 The Model 181A AR Oscilloscope requires hori zontaland vertical plug ins The deflection sensitivity of the CRT may
6. The basis for storage of information onthe non conductive material is the secondary emission ratio curve shown in Figure 4 2 Thiscurve shows the ratio of the number of electrons leaving the surface to the energy of the electrons striking the surface At an energy of about 40 electron voits ev the number of electrons leaving the surface is equal to the number arriving The point where the secondary emission ratio is equal to unity is called first crossover If the surface is bombarded with electrons with more than 40 ev of energy the surface potential rises because more electrons are leavingthanarriving If the sur face is bombarded with electrons with less than 40ev of energy the surface potential decreases because fewer electrons are leaving than arriving e E d x e e e iad gt a x e Zz o o id qi 41440 STORAGE MESH POTENTIAL IN VOLTS EISE IBIA A 8 Figure 4 2 Secondary Emission Ratio 4 10 When the ERASE push button is pressed the storage mesh is changed to the same potential as the collector mesh 156v The storage surface is also changed to nearly this same potential by capacitive coupling Since the surface is then being bombarded by electrons with energies much higher than first cross over energy the entire storage potential becomes equal to 156 volts The surface potential cannot in crease beyond 156 volts because the collector mesh would then repel the emitted electron
7. conducting The result ing 4 7v negative step at the collector of A6Q11 is differentiated by A6R26 A6C5 and applied to the base of A6Q7 turning it off A6Q7 will be nonconducting for approximately 200 milliseconds while A6QT is off The current flow through A6R25 A6R39 and A6Q14 causes the CRT write gun to remain blanked Also the current flow through A6R24 into the base of A6Q6 drives it into conduction effectively grounding the base of A6Q4 With A6Q4 in an off condition for the 200 millisecond period the CRT storage mesh rises to about 13 3v when operating in the WRITE mode and to about 7 5v in the MAX WRITE mode 4 91 Whenthe 200 millisecond interval is terminated A6Q7 again conducts and turns off A6Q6 This allows currenttoflowthrough A6R13 A6CR8 and the base of A6Q4 turning it on and reducing the storage mesh to the 3 3v level Variable width erase pulses are again applied to the storage mesh at the 1 kHz rate 4 92 Itis desirable to provide for inhibiting the CRT WRITE functionfor a short intervalafter erasing The Model 181A AR discharging time constant of A1C6 A1R10 through A1Q1 accomplishes this and keeps the write gun turned off momentarily 4 93 STORAGE PROTECTION Itispossible to ma nipulate the operating mode selector switch so that multiple functions or nofunctionatallmay be selected This switch is interconnectedtoprovide several oper ationalfeatures which protect the stored dis
8. ears in both steps since pressure on the outer edge tends to cause a swivel action defeating the purpose and subjecting the ears to possible damage Figure 2 2 Bezel Removal 02612 3 Model 181A AR Section HI Paragraphs 3 1 to 3 16 SECTION Ili OPERATION 3 1 INTRODUCTION 3 2 The Model 181A AR is a light weight variable persistence storage oscilloscope using plug in vertical andhorizontal modules Both highand low voltage pow er supplies a calibrator the CRT and circuitry for the variable persistence and storage operationare con tained in the Model 181A AR A compartment for the horizontal and vertical plug ins is locatedinthe lower portion of the Model 181A and in the right hand portion of the Model 181AR In both models the compartment is designed to accept the vertical plug in on the left side and the horizontal plug in on the right The plug in units must be locked together before being inserted into the compartment see plug in manuals 3 3 OPERATING CONSIDERATIONS 3 4 Prior to operating the Model 181A AR the oper ator must have a thorough understanding of instrument operation and control functions This section should be readinits entirety before attempting to operate the instrument To avoid CRT damage the following pro cedure should be followed every time the instrument is operated 3 5 The following are steps that must betakenprior toapplying power tothe Model 181A AR Oscillo
9. gun filament power The 100 12 6 15 100 and 156 volt supplies are regulated and used throughout the Model 181A AR and the plug in units An unregulated 423v is produced for use by the High Voltage Power Supply HVPS and the pilot lamp A regulated 105v is also produced for use only within the LVPS 4 40 Figure 4 6 illustrates a basic regulated power supply The series regulator and the parallel combi nation of the loadandthe sensing device divide the en tireapplied voltage Ifthe loadchanges thus changing the voltage drop across the load the sensing device will detect it and cause the resistance of the series regulator to change in the required manner to restore the output to the desired voltage level 4 41 Refer to the schematic diagram of the LVPS Figure 8 21 Theclosing of S5 supplies power to the primary of Ti The dual primary windings of T1 may be connected in series for 230v operation or in para llel for 115v operation 6 located on the rear panel of the instrument switches these windings for 115v or 230v operation 4 42 The ac voltages developed by the secondary wind ings of T1 are bridge rectified filtered fused and applied to the regulatingcircuits Decoupling RC and LC filter networks are employed for circuit isolation where required 02612 2 Section IV Paragraphs 4 31 to 4 48 4 43 The 100v output is used as a reference for the other regulating circuits It must be adjusted first since
10. in the series The serial number appears on a plate located on the rear panel All correspondence with a Hewlett Packard Sales Service Office inregardto an instrument should reference the complete serial number 1 23 SCOPE OF MANUAL 1 24 This manual provides operating and service in formation for the hp Model 181A AR Oscilloscope Information and operation of plug ins is contained in appropriate plug in manuals Information in this manual applies directly to instruments as manufac tured with serial numbers prefixed by the three digits indicated on the title page If the serial prefix of the instrument is different from that on the title page a Manual Changes sheet supplied or Section VII of this manual will describe changes which will adapt this manual to provide correct coverage Technical corrections if any to this manual due to known errors in print are called Errata and are shown on the change sheet For information on manual cover age of any hpinstrument contact the nearest hp Sales Service Office addresses are listed at the rear of this manual 02612 2 m U Model 181 A AR Section H Paragraphs 2 1 to 2 17 SECTION Hi INSTALLATION 2 1 INITIAL INSPECTION 2 2 MECHANICAL CHECK Check the shipping carton for damage immediately after receipt If itis damaged ask the carrier s agent to be present when the instrument is unpacked Inspect the Model 181A AR for phy
11. is determined by the setting of A6R42 whichis in series with ASR and the 100v supply Stray ac signals on the flood gun grid lead are decoupled from the flood gun by A6C4 4 87 ERASE The push button operating mode selec tor switch does not permit energizing the erase cir cuitry unless the WRITE or MAX WRITE mode of operating has been selected Activationof the ERASE switch S7 refer to Figure 8 12 in either of these modes applies 156v tothe CRT storage meshandto the junc tion of A6R36 and A6CR6 The diode A6CR6 prevents application of this 156vtothe collector of A6Q4 during ERASE while A6CR4 prevents the collector from ris ing above 15v because of the 100v applied through the voltage divider formed by A6R15 A6CR5 A6R16 and A6R19 Normally nonc onducting A6Q13 is turned on by application of the 156v which in turn shuts off A6Q12 Thispermits A6C6to charge positive through A6R33 and A6R37 to about 44 7v Theresultant cur rentthrough A6R37 causes A6Q14 toconduct and A6Q15 to cease conduction Currentflowingthrough A6R43 A1CR15 AIR10 and into the emitter of A1Q1 causes the Gate Amplifier to operate so as to blank the CRT write gun A clean erasure of the storage mesh is thereby assured since no writing of an input signal can take place during erasure 4 88 Releasingthe ERASE switch removes the 156v fromthe CRT storage meshand from A6R36 Current no longer flowsthroughthe base of A6Q13 and conduc t
12. its output will affect all other regulated LVPS outputs 4 44 100 VOLT SUPPLY A portion of the de volt age from the 100v rectifier filter circuit is dropped across ATR5 and series regulator Q4 The remainder is dropped across the voltage divider network A8R35 A8R36 and A8R37 If the 100v supply were to de crease in amplitude a small portion of the positive going change would be felt on the base of A8Q12 This change would be coupled through A8V2 and A8Q11 to the emitter of A8Q12 The differencebetween the in puts to A8Q12 a positive going signal is coupled throughcurrentamplifier A8Q10 tothe base of series regulator Q4 Less voltage is dropped by Q4 and the 100v supply increasestonormal A8C8 and A8R29 prevent high frequency oscillation of the series regu lator ABCR8 and A8CRO9 protect A8Q11 and A8Q12 respectively from reverse voltage breakdown in case the output voltage is shorted AS8CR iO acis to prevent reverse charging of A8C10 in the event F6 opens A8CR12 protects A8Q10 and A8Q4 from reverse volt age breakdown during instrument turn on 4 48 100 VOLT SUPPLY Operation of the 100v supply is similar to the 100v supply except that the base of A8Q2 is held at a constant voltage by A8V1 Any variations in the output are felt only on the base of A8Q3 and inverted prior to coupling throteh A8Q1 to the series regulator Q1 4 46 105 VOLT SUPPLY Afiltereddc voltage from A CRi 4andA7Ciis applied a
13. minimum usable in tensity 3 15 NORMAL Selection of this operating mode dis ables the variable persistence and storage features of the instrument Itwillnowfunctionasa conventional general purpose oscilloscope The PERSISTENCE control does not function in this mode Always adjust INTENSITY in WRITE mode with minimum PERSIS TENCE then switch to NORMAL 3 16 WRITE Depressing the WRITE push button 3 1 Section HI Figure 3 1 Note 1 FOCUS Controls sharpness of writing beam 2 STORE Retains displayed signal at reduced intensity for long time storage 3 VIEW Intensifies stored display to brightness level for viewing 4 NORMAL Selects operation as standard oscil loscope 5 WRITE Operates CRT at normal writing rate with variable persistence 6 MAX WRITE Operates CRT at maximum writing rate with variable persistence ERASE Removes stored or written displays 8 PERSISTENCE Controls endurance time of displayed signal 9 ASTIGMATISM Adjust roundness of writing beam 10 TRACE ALIGN Rotates trace around center of CRT face 11 FIND BEAM Returns display to CRT 12 INTENSITY Controls brightness of display 13 POSITION Coarse adjustment of display s horizontal position 14 FINE Fine adjustment of display s horizontal position l 15 MAGNIFIER Magnifies horizontal display 16 PHASE BANDWIDTH Selects between nor mal operation BANDWIDTH and XY opera tion PHASE Located inside
14. on board Figure 3 1 3 2 roo om H 18 19 20 21 K Model 181A AR Xo 0 OCC HA BIA A 11A Models181A and 181AR differ only in power module location Allcontrolsare identical See Fig 1 1 DISPLAY Selects source of horizontal input signal AC DC Selects AC or DC coupling of an ex ternal horizontal input signal EXT INPUT BNC connector for coupling an external horizontal input signal to oscilloscope POWER Push button switch with indicator light for turning oscilloscope on and off CALIBRATOR Provides a 1 kKHz square wave signal at 10v pk pk l REAR PANEL AC INPUT 3 wire ac power line input jack MAIN GATE OUTPUT BNC for connecting main gate to external equipment DELAYED GATE OUTPUT BNC for connect ing delayed gate to external equipment DELAYED SWEEP OUTPUT BNC for con necting delayed sweep to external equipment MAIN SWEEP OUTPUT BNC for connecting main sweep to external equipment Z AXIS INPUT BNC for connecting external intensification or blanking signal FUSE AC line fuse for 230vac operation FUSE AC line fuse for 115vac operation LINE SWITCH Input power switch for selec tion of 115vac or 230vac operation GROUNDING CONNECTOR 3 way connector jack for instrument grounding Front and Rear Panel Controls and Connectors 02612 2 Model 181A AR establishes the CRT in a condition for variable per sistence display of a signal which can l
15. Q16 and A6Q17 is used 4 19 Whenthe MAX W pushbutton is depressed one side of the multivibrator conducts Current flow through A6R47 and A6R46 holds A6Q16 on and A6Q17 off Thus the MAX WRITE ADJ pot A6R17 is para lleled with WRITE ADJ Atthe same time A6R9 is disabledand MAX WRITE COLLIMA TION ADJ A6R29 is enabled The multivibrator is necessary so that proper collimation voltage is retained when the VIEW or STORE mode is selected 4 80 The setting of the WRITE adjust A6R18 adjusts the positive pulse level at the collector of A6Q4 when operating in the WRITE mode while A6R18 in parallel with the MAX WRITE adjust A6R17 adjusts the level in the MAX WRITE mode Pulse level control of the 1 kHz pulsestothe storage mesh affords depth of eras ure control which directly affects writing rate In other words the more negative the storage surface becomes the longer it will take ittobuilduptoa level high enough to store a trace refer to Figure 4 4 4 81 STORE When the STORE function is selected the base of A6Q1 is grounded turning it off This allows the current flow through A6R2 and A6CRI to turn A6Q2 on Meanwhile the 15v square wave sig nalatthecollector of A6Q3 is differentiated by A6C1 A6R2 and applied to the base of A6Q2 through A6CR1 Thus A6Q2 hasa negative voltage developed at its base during the charging time of A6C1 which turns it off The time constant of AGCI A6R2 is such that A6Q2 is off for about 50 micro
16. SITY is the best approach The amp litude of the phenomena and the sweep time required todisplay itwillaffectthe persistence For example with maximum PERSISTENCE and some settings of INTENSITY a single shot straight line may bloom A single shot signal withamplitude variations may not cause bloom To determine the best INTENSITY set ting connect a signal which approximates the sweep time andamplitude of the single shot signalto be writ ten Set PERSISTENCE fully clockwise and trigger a single sweep ofthe test signal Set the INTENSITY as far as possible without causing blooming Repeat this procedure varying the INTENSITY until the proper display is obtained This setup should give maximum persistence to the single shot display After the sig nal has been written press the STORE push button to retain the display 3 46 Single shot signals which require a sweep time faster than 20 microseconds per division can be writ ten with more brightness by switching tothe Max Write mode The screen will be unevenly illuminated after erasing when in Max Write Figure 3 2B however IN TENSITY can be set high enough to make the display vis ible throughthe illumination A display writtenin Max Write will be more rapidly obscured by positive fading than a signal written in NORMAL 3 47 Single shot signals which require a sweep time between 200 and 20 microseconds per division may have low brightness at the center of the screen Fire a si
17. ac celerating them to strike the phosphor viewing screen thereby causing the phosphor to emit light Thusthe pattern of charge on the storage surface is made vis ible 4 14 The secondary electrons emitted by the storage surface where the write gun electrons strike must charge the surface from its erased potential to about 9 volts before floodelectrons can be captured by the RELEASE ERASE i56v 4 152e7V l42 7V Model 181A AR post accelerator Thus the writing speed of the CRT could be enhanced by erasing the surface to just below this cutoff level Thisis whatthe MAX WRITE mode does The disadvantages of operating inthis mode are reduced storage time and reducedcontrast ratio The cutoff potentials of various areas of the storage sur face may not be exactly the same Thus the back ground illumination may not be uniform when the storage Surface is erased in the MAX WRITE mode 4 15 VARIABLE PERSISTENCE 4 16 Figure 4 4 represents the method of obtaining variable persistence The unwritten storage surface after erasure is at approximately 10 volts Those areas of the storage surface which are struck by elec trons from the write gun become charged to near zero volts A 10 volt pulse applied to the storage mesh moves the unwritten areas of the storage surface to near zero voltsandthe writtenareastonear 10 volts While at this potential the written areas of the stor age surface attract and capture f
18. ater be stored Use the minimum INTENSITY and maximum PERSIS TENCE required to obtain the desired display 3 171 MAX WRITE Operation in the Max Write mode MAX W provides a more rapid build up and display of fast single shot signals Since the background il lumination also increases more rapidly the CRT con trast level and storage time are reduced 3 18 ERASE Depressingthe ERASE push button will remove stored signals from the CRT when either the WRITE or MAX W push buttonisdepressed Stored or written displays that remain visible after erasure may require the ERASE push button be held depress ed for approximately 30 seconds 3 19 PERSISTENCE ANDINTENSITY These controls determine the viewing time of a signal being displayed The INTENSITY sets the brightness of the trace as it is written The PERSISTENCE control is used to establishthe desired duration of signal viewing without rewriting Itaccomplishes this by varying the rate at Which the displayed signal is erased 3 20 TRACE ALIGN The TRACE ALIGN adjustment controlcompensates for external magnetic fields that may affect the alignment of the horizontal trace with the graticule Thealignment should be checked when the instrument is moved to a new location and the ad justment made whenever necessary 3 21 FIND BEAM Off screen positioning of the CRT beam may occur due to initial improper control set tings or a very high dc input signal The beam may be brought
19. back on screen by depressing the FIND BEAM push button Adjustthe horizontaland vertical position controls to center the beam refer to the plug in manuals Adjust the INTENSITY controlto obtain a visible trace 9 22 MAGNIFIER Whenthe DISPLAY control is set to EXT CAL the MAGNIFIER provides switched gain levels in the horizontal amplifier of X1 X5 or X10 In the X5 or X10 positions the horizontal gain is in creased to provide an amplified display of five or ten times respectively Theinsertion ofa 1v signal into the EXT INPUT jack will result ina 1 division deflec tionin X1 5 division in X5 anda 10 division deflec tion in the X10 position 8 23 DISPLAY This control determines the input signaltothe horizontalamplifier With the DISPLAY controlsetto EXT CAL the external horizontal input signal is coupled directly to the horizontal amplifier As the DISPLAY control is rotated counterclockwise the external signal is increasingly attenuated When the DISPLAY control is fully counterclockwise INT the externalinputsignalis disconnectedandthe inter nal sweep is coupled directly to the horizontal ampli fier 3 24 CALIBRATOR The 1 kHz square wave calibrator output signal of 10v can beused for vertical sensitivity calibration and for probe compensationadjustment The CALIBRATOR output amplitude is accurate within 1 Rise time of the square wave output is less than 3 u sec 02612 2 Section IH Paragraphs 3 17 to 3 37
20. be compensation and sensitivity cali bration and the 100v square wave output from the collector of A1Q6 is applied to the pulse circuit 4 55 OUTPUT ISOLATION AMPLIFIERS 4 56 Signals derivedfrom the Horizontal Plug In are coupled to rear panel BNC connectors J5 8 refer to Figure 8 7 Four emitter followers A2Q1 4 are employed as isolation amplifiers The signals actu ally developedare determined by the Horizontal Plug Inusedinthe instrument hence the signals available can be determined by referring to the Operating and Service Manual for the applicable plug in 4 57 HIGH VOLTAGE POWER SUPPLY HVPS 4 58 Three regulated voltages are produced by the HVPS 1440v 7kv and a control grid voltage of 1450v to 1500v refer to Figure 4 T A regulated oscillator isusedto develop the required high voltages in transformer A5T1 The 1440v supply is sampled to provide control of the osc illator output and thus reg ulate all three voltages 4 59 Unregulated 23v from the LVPS aroeiies pri mary power to oscillator Q5 operating at approximately 35kHz see Figure 8 18 The outputs from the high voltage transformer A5 T1 are coupledtotwo half wave rectifier filter circuits and to a voltage tripler filter circuit CRT control grid voltage is rectified by ASCR1 and filtered Th write gun cathode voltage is rectified by ASCR2 while A5R2 establishes the dc potential applied to its control grid Voltage regula tor
21. cross A7R2 A8R and breakdown diode A8VR1 Zener action keeps the top of A8VR1 five volts more positive than the bottom which is at 100v The 105v from A8VR1 is used to provide bias current for A8Q1 and A8Q3 4 41 4156 VOLT SUPPLY The rectifiedandfiltered voltage from A7CRi 4 and A7C1 is applied across ATRiand breakdown diode A7VR1 Zener actionkeeps the top of A7VR156 2 volts more positive than the bot tom which is at 100v The 156 volt potential at ATVRi is applied to the CRT collector mesh and is also used for the ERASE function 4 48 12 6 VOLT SUPPLY The voltage from the 12 6v rectifier filter is dropped across the series regulator Q3 A8R22 and the load Any variation in output is coupled through voltage amplifier A8Q9 and current amplifier A8Q7 to the base of the series regu lator Q3 A8C6 and A8R20 prevent high frequency oscillation of the regulator SERIES REGULATOR SENSING mE ammo t o G DEVICE m One OA AR A 6 Figure 4 6 Basic Regulated Power Supply 4 5 Section IV Paragraphs 4 49 to 4 59 4 49 The current limiter A8Q8 and A8R22 provide protection for the series regulator Q3 If the output becomes shorted the voltage drop across A8R22 turns on A8Q8 The negative signal from the collector of A8Q8 iscoupledthroughthe driver A8Q7 to the series regulator Q3 tending to turn it off Output current is thus limitedto onlythat required to keep A8Q8 con ducting
22. e through proper manipulation of the PERSISTENCE and INTENSITY controls Simply obtainthe desired mul tiple trace display in the WRITE mode then depress the STORE push button 3 12 A display stored on the CRT when power is re moved from the instrument will remain stored for Severaldays In order to observethis stored display depress the VIEW push button and turn the POSITION control on the Vertical Plug in counterclockwise prior to restoring power to the instrument This prevents a bright spot from being portrayed on the screen due to the initial surge from the CRT write gun 3 13 Several individual waveforms may also be stored eventhoughtheyare writtenatdifferenttimes Having storedatrace for instance the operator may choose to switch backto WRITE andrecordanothertrace etc prior to erasing And by turning the Model 181A AR power off as few as one trace a day can be recorded fora weekor more dependingontotaltime instrument is turned on as storage time would decrease accord ingly 3 14 VIEW To observe a previously stored display depress the VIEW push button The stored display will be intensified to a brightness level determined by the intensity and persistence values selected during the writeprocess Again theINTENSITY PERSISTENCE FOCUS ERASE and POSITION controls do not affect the display Excessive intensity for long duration may damage the CRT storage mesh The INTENSITY setting for any sweep speed should be
23. ec Brightness greater than 200 foot lamberts with entire screen faded positive Persistence continuously variable from less than 0 2 second to more than one minute or normal P31 persistence of approx 40 usec Storage Time MAX W Mode ten minutes is STORE mode ten seconds in VIEW mode l Beam finder pressing FIND BEAM control when operating in any mode except STORE or VIEW ting of horizontal or vertical controls Intensity Modulation approximately 2 volts dc to 15 MHz will blank trace of normal intensity Input resistance is 5100 ohms 1 0 GENERAL brings trace on CRT screen regardless of set Model 181A AR Table 1 1 Specifications OUTPUTS Four emitter follower outputs for mainanddelayed gates main and delayed sweeps Maximum cur rent available is t3 ma Outputs will drive imped ances down to 1k ohm without distortion Active Components all solid state no vacum tubes except CRT Environment Model 181A AR Oscilloscope with _ plug ins operates within specifications over the following ranges Temperature 0 C to 455 C Humidity to 95 relative humidity to 40 C Altitude to 15 000 ft Vibration vibrated i in three planes for 15 min each with 0 010 inch excursion 10 to 55 Hz Power 115 or 230 volts 210 50 400 Hz 100 watts at normal line convection cooled Dimensions cabinet overall dimensions 8 203 wide 11 280 h
24. ed from the Hori zontal Plug Into the gateamplifier where it is summed with the Z Axis Input chopped blanking signals and the unblanking signal from the storage pulse circuit The resulting signal is amplified coupled through the high voltage power supply and applied to the CRT write gun grid to control the display intensity 4 30 Each unblanking gate signal developed by the gate amplifier also generates analternate trigger sig nai This alternate trigger is directly coupled to the Vertical Plug In The Operatingand Service Manual for the Vertical Plug In unit employed should be re ferred to for the signal function 4 3 Section IV Model 181A AR Figure 4 5 l HORIZONTAL PRE AMP Position Q MAGNIFIER i t HORIZONTAL HORIZONTAL INTERNAL AMPLIFIER DEFLECTION SWEEP TT i 5 INTERNAL pe 2 O FIND BEAM DISPLAY NT t te KV HORIZONTAL 100V PLUG IN INTENSITY VERTICAL j DEFLECTION i UNBLANKING T HIGH GATE vertical f lt ieee GATE VOLTAGE om my PLUG IN S e CHOPPED AMPLIFIER POWER IZ AXIS BLANKING SUPPLY INPUT 7KV TO POST i ACCEL f O Focus ERASE UNBLANKING GATE 156V PULSER CIRCUIT AA CALIBRATOR EOSS i MAX WRITE 423V UNREG RON REAR LOW 156V HORIZONTAL PANEL VOLTAGE 4OOV PLUG IN SIGNALS POWER f ay 26V 100V
25. equired 2 8 The original shipping carton and packaging ma terials exceptfor the accordion pleated pads should be used for reshipment If they are not available or reusable the instrument should be repackaged with the following materials a A double walled carton refer to Tabie 2 1 for test strength required Table 2 1 Shipping Carton Test Strength Gross Weight ibs Carton Test Strength lbs up to 10 10 to 30 30 to 120 120 to 140 140 to 160 02612 3 b Heavy paper or sheets of cardboard to protect all instrument surfaces use a nonabrasive material such as polyurethane or cushioned paper such as Kimpak around all projecting parts C At least 4 inches of tightly packed industry approved shock absorbing material such as extra firm polyurethane foam d Heavy duty shipping tape to secure outside of carton 2 9 PREPARATION FOR USE 2 10 POWER REQUIREMENTS 2 11 The Model 181A AR requires either a 115 or 230 vac 10 single phase 50to 400 Hz power source that can deliver 100 watts a 115V OPERATION Thisinstrument as shipped is ready for operation on 115 vac See Step b below for 230 vac operation Before applying power check the rear panel slide switch for proper position 115 or 230 b 230V OPERATION If the instrument is to be operated on 230 vac setthe rear panel switch to 230 It is not necessary to replace the 115V fuse Position ing the 115 230 switch selects the pr
26. ese outputs are dependent upon the plug ins utilized the appropriate plug in Operating and Service Manual should be referred to for identification of the output signals available The output amplifiers can supply 3ma andwill drive impedances as low as 1000 ohms without distortion 1 9 A 1kHz square wave signal is available at the front panelfor calibration purposes Its amplitude of 10 volts peak to peakis accurate to 1 and it has a rise time of less than3u sec The signal may be used to adjust horizontal and vertical deflection factors and to compensate divider probes 1 10 CATHODE RAY TUBE 1 11 The Model 181A AR uses an internal graticule P31 aluminized phosphor CRT Special internal ele ments provide the variable persistence and storage features Parallax observation error is eliminated by use of the internalgraticule and a non glare safety face plate is bonded to the CRT 1 12 WARRANTY 1 13 This instrument is certified and warranted as described on the inside front cover of this manual The CRT is covered by a warranty separate from the rest of the instrument The CRT warranty and war ranty claim forms are located at the rear of this manual Should the CRT fail within the time specified on the warranty contact your nearest hp Sales Service Office and return the CRT with the warranty form completed i 1 14 ACCESSORIES FURNISHED 1 15 The standard Model 181A AR Oscilloscope is supplied with a mesh con
27. g metal but ton and sliding feet free b Remove aluminum trim stripfrom each side of instrument with a thin blade tool c Attach rack mounting flange in space from which trim strip was removed use screws provided with kit Large notch of flange should be positioned at bottom of instrument 2 17 INSTRUMENT COOLING 2 18 The Model 181A AR does not need forced air cooling when operated in an amibient temperature of 0 to 55 degrees centigrade Normal air circula tion wil maintain a reasonable temperature within the instrument 2 19 CONTRAST FILTER AND BEZEL REMOVAL 2 20 A contrast filter which also acts as an RFI Shield is located behind the bezel Use ofthe filter is recommended since it provides for comfortable viewingand RFI shielding In specificcases however such as when a camera is attached for use with the oscilloscope removal of the filter may be desirable To accomplish this merely remove the bezel as shown in Figure 2 2 slip the filter out and replace the bezel 2 21 To remove the bezel grasp it as shown in Figure 2 2A gently apply a downwardpressure with the index fingers until the bezel s upper ear is free of its slot pull slightly forward and release Next grasp the bezel as shown in Figure 2 2B apply an upward pressure with the thumbs until the bezel s 2 2 lower ear clears its slot pull forward and remove the bezel Be certain to apply pressure on the inner edge of the bezel to release the
28. ide storage and variable per sistence are located between the write gun andthe phos phor 4 1 The flood guns are physically located just out side the horizontal deflection plates A cloud of elec trons is emitted by each flood gun cathode These clouds are combined shaped and accelerated by two control grids It shouldbe noted that under certain con ditions the twoelectronclouds will appear as light areas onthe viewing screen when the instrument is first turned on The combinedcloud is further shapedandacceler ated by the collimator a coating on the inside of the funnel section of the glass The positive voltage on the collimator is adjusted so that the flood gun elec tron cloud just fills the CRT viewing screen The cloud is further accelerated toward the storage mesh and viewing screen by the collector mesh After pas sing through the collector mesh the flood electrons are further controlled by potentials on the storage mesh and sur ace l POST ACCELERATOR STORAGE FLOOD GUNS MESH PHOSPHOR VIEWING SCREEN DNE o WRITE GUN AQUADAG COLLIMATOR STORAGE COLLECTOR SURFACE MESH 18i A Figure 4 1 Simplified CRT Construction 02612 2 4 8 The storage mesh is located between the collector meshandthe phosphor The back side of this meshis coated with a layer of non conductive material The storage of information takes place on the surface of this non conductive material storage surface 4 0
29. igh 22 1 2 570 deep Rack DEnenetone Model 181AR NOTES Eben DIMENSIONS De INCHES AND MILAINETERS EIA RACK HEIGHT INCLUDING FILLER STRIP For ones NEIGHT INCLUDING FEET ADO E 8 Yo A MEAT REAR APRON RECESS al H IM i i t 3 wi Rii 75 asas 1493 Ll o mene FA 4831 Ds a BOA A IGOG Weight without plug zd Model 181A Net 24 lbs 10 9 kg Shipping 32 lbs 14 5 kg Model 181AR rack Net 26 Ibs 11 8 kg Shipping 35 lbs 15 9 kg Accessories Furnished mesh contrast filter de tachable power cord rack mounting hardware rack model only 02612 3 a Model 181A AR Section I Paragraphs 1 1 to 1 5 SECTION 1 GENERAL INFORMATION 1 1 DESCRIPTION 1 2 TheModeli81A AR Figure 1 1 isa lightweight general purpose variable persistence storage oscil loscope with plug in capability The Model 181A and the Model 181AR as shipped from the factory are in tended for bench use The Model 181AR may be rack mounted as described in Section II 1 3 Except for the CRT all active components are solid state devices The Model 181A AR is convec tion cooled and operates within specifications over a temperature range of 0 C to 55 C Figure 1 1 Model 181A and 181AR Oscilloscopes 02612 2 1 4 The variable persistence capability is especially useful for viewing slow speed signals Adjustment of persistence time can pro
30. intensity a stored display e ERASE To remove all displays and blooms which have been stored or written with persistence on the CRT f INTENSITY The brightness of a display as it is written on the CRT sereen PERSISTENCE and Sweep Time Constant g BLOOM A visible non symmetrical expan sion of a display written on the CRT screen LIB EAT A I2 Figure 3 2 Fade Positive and BackgroundIllumination 3 4 Model 181A AR h FADE POSITIVE Display obscured by slow blooming see Figure 3 2A i BACKGROUND ILLUMINATION A green cloud of illumination visible on the CRT screen see Figure 3 2B j SWEEP TIME The time inseconds millisec onds or microseconds required for the beam to move horizontally one unit of distance across the CRT screen when writing a display 3 38 CONTROL FUNCTIONS 3 39 PERSISTENCE ANDINTENSITY These controls contribute to the duration of afterglow ofadisplay The PERSISTENCE control sets the rate at which a display is erased INTENSITY sets the brightness of the trace as it is written With a given PERSISTENCE setting the actual duration of trace afterglow may be increased by increasing the INTENSITY Since the PERSISTENCE control sets the rate of erasing a written display it follows that a brighter trace will require more time to be erased Conversely a display of low intensity wil disappear more rapidly The same principle applies to a stored display of high and low intensity
31. ionceases This permits A6Q12to conduct due to the current flow through A6R34 into its base The result ing 4 7v negative step atthe collector of A6Q12 is dif ferentiated by A6C6 A6R32 and applied to the base of A6Q11 causing it to cease conduction As a result of the charging time constant of A6R32 and A6C6 A6Q11 will remain ina nonconducting state for approximately 100 milliseconds During this time A6C5 is being charged to 4 5 v through A6R31 AO6R38 and A6R2T Current flow through A6R38 and A6CRT7 causes the Blanking Control Amplifier A6Q14 A6Q15 and the Gate Amplifier to operate and blank the CRT write gun 4 89 Control of the voltage applied to the CRT colii mator is desired during storage mesh erasure A por tion of the current through A6R31 also flows through A6R27 placing A6Q8 in a conducting state and caus ing A6Q9 tocease conduction The voltage on the base of A6Q10 therefore rises to nearly 120v causing heavy conduction through A6Q10 This results in its emitter rising to about 120v due to the voltage drop across A6R30 Since the collimator is connected to the emitter of A6Q10 the 120v developed across A6R30 is appliedto the collimator while erasing This ensures a more uniform erasure of the storage mesh particularly of the periphery of the display area 4 9 Nein Section IV Paragraphs 4 90 to 4 95 4 90 At the end of the 100 millisecond initial erasing period AlQ11 again starts
32. lifier output to the CRT de flection plates to within 6vand 94v regardless of the amplitude of the input signal 4 11 Depressing FIND BEAM switch 83 disables lim iter ASCR7 CR8 andblocks the input signal to A3Q11 The differentialgainis effectively reduced by half and the electron beam is confined to the horizontal limits of the CRT screen 4 12 The gain of the complementary feedback ampli fier is made very stable by coupling a generous amount of negative feedback from the collectors of A3Q9 Q10 to the base of A3Q8 andfrom the collectors of A3Q12 Q13 to the base of A3Q11 The high frequency feed back of each amplifier is adjusted by A3C6 or A3C19 individually while A3C9 adjusts the feedback for both Diodes A3CR5 and A3CR9 provide temperature compen sation for A3Q10 and A3Q13 4 73 PULSE CIRCUIT 4 14 Pulses of adjustable level and width are used to controlthe variable persistence and storage capability of the Model 181A AR Oscilloscope They are ap plied to the CRT storage mesh when operating in the WRITE and MAX WRITE modes applied to the flood gun accelerator in the STORE mode and used to key the gate amplifier for CRT unblanking 4 75 VARIABLE PERSISTENCE The multivibrator circuit Figure 8 17 isthe source of a 1 kHz square This signal in turn is applied to the pulse circuit which modifies the width and level of the pulse A 100v square wave is obtainedfrom the junc tion of A1C14 and A1R28 and fed to
33. lood gun electrons whichtends to lower the potential of these areas When the storage mesh returns toits normal level the stor age surface drops 10 volts The unwritien areas of the storage surface return to a 10 volt potentialand the written areas return to a slightly negative poten tial somewhat lower more negative than their ini tial value This decrease in potential reduces the ability of the post accelerator potential to reach through and capture flood electrons thus reducing the trace brightness slightly STORAGE MESH POTENTIAL STORAGE SURFACE P POTENTIAL ESEE MEN IBIA B S Figure 4 3 Storage Mesh and Surface Potentials During Erasure 4 2 02612 1 Model 181A AR 4 17 If this procedure is repeated many times the Stored trace will eventually be erased The time re quired to accomplish this erasure is controlled by varying the duty cycle of the pulses applied to the stor age mesh or by varying the pulse width if the pulse repetition rate remains fixed l l 4 18 Duringthetime the storage mesh is pulsed pos itive floodelectrons are allowed through to the phos phor viewing screen Thusa light background glow is visible when the CRT is used in the variable persis tence mode 4 19 NORMAL 4 20 If the storage mesh potential is reduced to 25 volts it acts as a control grid to flood gun electrons andpreventsthem rom reaching the phosphor How ever it has little affect on write gun electro
34. ngle shot test signal with INTENSITY and PERSIST ENCE fully clockwise and press the WRITE push but ton If center screen brightness is low wait for one to three minutes for the low brightness areato become brighter Likewise if the entire display brightness appears below a usable level or the display is not visible at all waitforonetofive minutes for the dis play to appear 3 5 Model 181A AR Section IV Paragraphs 4 1to 4 11 SECTION IV PRINCIPLES OF OPERATION 4 1 INTRODUCTION 4 2 This section provides circuit theory analysis of the Model 181A AROscilloscope Since variable per sistence and storage techniques may be somewhat un familiar to the reader basic theory of operation will be explained first to aid in grasping these concepts An over all block diagram is explained next followed by a detailed description of the individual circuits 4 3 VAR PERSISTENCE amp STORAGE 4 4 STORAGE PRINCIPLES 4 5 The Model 181A AR Storage CRT consists mainly of a conventional electron gun with deflection plates write gun an aluminized phosphor viewing screen a pair of flood guns operated in parallel flood beam shaping and accelerating grids aflood beam collima tor a collector mesh and a storage mesh as shown in Figure 4 1 4 6 The write gun functions as a conventional elec trostatic deflection gun delivering high velocity elec trons to selected points on the phosphor viewing screen The elements which prov
35. ns allow ing many of them to reach the phosphor viewing screen Some of the write gun electrons strike the storage sur face charging it positive toward zero volts wherever they strike Thusthe CRT appearstoact as a conven tional CRT without variable persistence or storage However when the storage mesh is brought back to 3 3 volts those areas of the storage surface which have been struck by write gun electrons allow flood electrons to be captured by the post accelerator field and thus display the pattern that was written on the phosphor while the storage mesh was at 25 volts 4 21 In order to view a stored trace for one minute or more the storage mesh is held at a constant 3 3 volts This may be accomplished by reducing the width ofthe variable persistence erase pulses to zero corresponding to maximum persistence or by actu ally disconnecting the pulses from the storage mesh The write gun may be turned off if desired to prevent additional writing on the storage surface 4 22 The mechanism which limits viewing time is the fade positive of the storage surface entire Screen illuminated This is caused by positive ions reaching the storage surface and charging it positive The positive ions are generated by flood gun electrons striking residual gas molecules in the CRT To ob tain an extended storage time the flood guns should 02612 2 Figure 4 4 Variable Persistence Accomplishment Through Pulsed Erasure Sec
36. oper fuse forthe desired voltage 2 12 THREE CONDUCTOR POWER CABLE 2 13 The National Electrical Manufacturer s Associ ation NEMA recommends that the instrument panel and cabinet be grounded to protect the operating per sonnel The Model 181A AR is equipped with a de tachable three conductor power cord which when plugged into an appropriate outlet grounds the instru ment through the round offset pin When operating the Model 181A AR from a two contact outlet use a three conductor to two conductor adapter Preserve the safety feature by grounding the adapter lead A 3 way grounding terminal is also provided on the rear panel of the instrument 2 14 INSTRUMENT MOUNTING 2 15 BENCH USE Both the Model 181A and the Model 181AR as shipped from the factory are in tended for bench use The Model 181AR however may be rack mounted as described in Paragraph 2 16 2 16 RACK MOUNTING A kit for converting the Model 181AR to a rack mount is supplied with each instrument Instructions for making the conversion are given below Refer to Figure 2 1 for parts iden tification 2 1 Section II Paragraphs 2 18 to 2 22 BOTTOM PANEL iras TILT STAND d FOOT BUTTON PLASTIC FOOT TRIM STRIP Model 181A AR A ADHESIVE BACK d acm MOUNTING FLANGE TOOOHF 8 19 Figure 2 1 Bernch Rack Mount Conversion a Detach tilt stand by pressing itaway from front feet Remove all plastic feet by depressin
37. ore made equal to signal delay in the Vertical Plug In The vernier balance ASR is adjusted so that 0 vde appears across the HORIZONTAL DISPLAY control thus eliminating any horizontal dc shift as the control is operated 4 70 Input signals to A3Q3 are summed in the low im pedance emitter circuit with a current established by the setting of the POSITION controls A3R2 and A3R3 A3Q6 is driven by the low impedance of emitter fol lower 3Q4 The input signal to A3Q6 is coupled through the MAGNIFIER switch 4 tothe complemen tary driver A3Q7 S4 provides for selection of incre mental gain levels by selecting the amount of emitter degenerationemployed with A3Q6 and A3Q7 Increas ing degeneration decreases gain Adjustment A3R30 along with A3R31 controls the gain when in the X10 position A3R32 A3R33 control the X5 gain and A3R34 AS3R35determinethe X1 horizontal gain The dc bal ance of A3Q6 and A3Q7 is adjusted by A3R37 which controls the emitter potentials Transistor A3Q5 pro vides a low impedance voltage source for the base of ASQ The differential signalat the collectors of A3Q6 and A3Q7 is applied to the complementary feedback amplifiers current fed amplifiers A3Q8 Q10 and A8Q11 Q13 convertedtoa voltage and coupled to the horizontal deflection plates of the CRT A3CR3 pre vents A3Q6 from saturating while A3CR6 serves the same purpose for A8Q7 Diodes A3CR2 CR4 and 4 8 wave signal A3CR7 CR8 limit the amp
38. play from inadvertent erasure of overwriting For instance if no function is selected the CRT write gun is blanked and the PERSISTENCE control is inoperative 4 94 The write gun blanking is provided by current flow through A6R22 and A6R40 into the base of A6Q14 thus causing the Gate Amplifier toturn off the write gun 4 95 The disabling of the PERSISTENCE control is obtained by utilizing the current flowing through A6R22 and A6R23 into the base of A6Q4 This holds A6Q4 in conduction and keeps the storage meshat 3 3v Cur rent flowing intothe base of A6Q4 prevents the variable amplitude 1 kHz pulse from turning off A6Q4 A Table 5 1 Required Test Equipment Test Oscilloscope Recommended Type Test Equipment Model Required Characteristics Voltmeter hp Model 738AR 1 2 10v pk pk 0 2 Calibrator or 6920B i hp Model 180A AR w 1801A amp 1820A Sensitivity 1v div Sweep Speed lu sec Risetime 3u sec Sweep output 10 1 Divider Probe hp Model 10001A i300 l Constant Amplitude Tektronix Type 190B 50 kHz 50 MHz at i Signal Generator 10v pk pk 100 1 Divider Probe Square Wave Generator Current Source Oscillator Digital hp Model 3440A Voltmeter w 34444 hp Model 211A B 100vde x0 5 2 5 ma 206 hp Model 11044A 300vdc 200 kHz 1v pk pk Risetime 30 u sec a RM E 2 5 ma 30 hp Model 200CD 10 kHz 10v pk pk i 02612 2
39. s coupled to the complementary feedback amplifier a current fed operational amplifier A1Q2 A1Q4 where it is converted to a voltage and coupled to the control grid of the CRT write gun The large negative feed backfromthe collectors of A1Q3 and A1Q4 to the base of A1Q2 provides the complementary feedback ampli fier with a very stable gain Trimmer capacitors A1C8 and A1C9 adjust the high frequency feedback Diode A1CR6 provides temperature compensation for A1Q3 while AICR7 and A1CR8 protect A1Q3 and A1Q4 from voltage breakdown Diode A1CR10 and A1R5T isolate A1Q3 and A1Q4 from the high voltage inthe con trol grid circuit of the CRT write gun in the event of a grid or cathode short to ground The output from A1Q3andA1Q4 is differentiated by A1C13 A1R22 and A1R23 andcoupled through A1Q5 andthe positive clip per A CRi1i to the Vertical Plug In for alternate triggering purposes 4 65 HORIZONTAL AMPLIFIER 4 66 The block diagram Figure 4 9 illustrates the majorcircuitfunctions The horizontal amplifier can be driven by either an internally derived signal or by an external signal applied to the HORIZONTAL EXT INPUT front panel BNC jack Positioning the HORI ZONTAL DISPLAY controlto INT disconnects the ex ternal signal input and grounds the horizontal preamp lifier input The Internal Sweep signal is connected through the HORIZONTAL DISPLAY switch to the hor izontal output amplifier 4 67 The EXT INPUT BNC J4 i
40. s A1V1i and A1V2 limit the maximum potential difference between the control grid and the cathode to 140v The CRT focus voltage is obtained from the 1440 cathode voltage by a voltage divider network of which R5 the FOCUS control is a part Resistor VOLTAGE TRIPLER RECTIFIER amp FILTER RECTIFIER M l470V amp FILTER RECTIFIER amp FILTER BIA Bi Figure 4 7 HVPS Block Diagram 4 6 02612 1 Model 181A AR UNBLANKING GATE CHOPPED BLANKING Z AXIS INPUT PULSE INPUT 100V x INT DISPLAY 100V VERT BEAM FINDER FIND BEAM 26V INTENSITY 9l Section IV Paragraphs 4 60 to 4 67 AMPLIFIER UNBLANKING SIGNALS DIFFERENTIATOR ALTERNATE TRIGGER iBIA B 3A Figure 4 8 Gate Amplifier Block Diagram R6 maintainsthe write gun filamentat cathode poten tial The voltage tripler circuit of ASCR1 3and A9C1 4 is contained on Assembly A9 the output of which 7 kv is applied to the CRT post accelerator anode 4 60 Changes in output of the 1440vdc supply are de tected by the regulator A1Q8 A1Q10tochange the oper ating voltage of oscillator Q5 Assume that the 1440 supply voltage decreases goes positive Apositive going signal is applied through the regulator to the base of Q5 causing it to conduct for a greater portion oftheinputcycle The oscillation amplitude is there fore varied so as to oppose the original change in ou
41. s andtheir functions andtoserveas a guide for obtain ing the desired CRT display a For normal persistence operation depress WRITE push button and turn PERSISTENCE control 02612 3 Model 181A AR fully ecw Slowly rotate INTENSITY control cw to a point where no trace blooming appears Depress NORMAL push button do not increase INTENSITY while in NORMAL H sweepspeedis changed always check for proper intensity using the above procedure When not actively using the oscilloscope switch to STORE or VIEW mode thus turning off the write gun and eliminating the possibility of burningthe storage mesh Whenin WRITE NORM or MAX W mode any visible trace may cause permanent damage to the CRT if display is left for prolonged periods oftime Topreventthis from happening periodically erasethe dis play or switch to STORE mode if you wish to retain the image b For variable persistence operation press the WRITE push button Use minimum INTENSITY and maximum PERSISTENCE compatible with display c UseMAX WRITE mode only for fast sweeptime single shot display or to improve the uniformity of trace intensity The MAX W mode causes more rapid positive fading onthe CRT and persistence or storage time of the display is thus reduced d To store a display pressthe WRITE push but ton adjustthe INTENSITY and PERSISTENCE for the desired display and press the STORE push button e Toviewastoreddisplay press th VIEW push bu
42. s back to the storage surface tending to decrease the surface po tential l 4 11 When the ERASE push button is released see Figure 4 3 the storage mesh is now changed to 3 3 volts and the storage surface follows to the same po tential by capacitive coupling The surface potential 4 1 Section IV Paragraphs 4 12 to 4 16 then decays to zero volts by action of the flood gun electrons surface below first crossover brought to flood gun cathode potential After 100 milliseconds the storage mesh is raised to 13 3 volts and held there for 200 milliseconds The storage surface fol lows to 10 volts by capacitive coupling but immedi ately starts decaying toward zero volts by capturing flood gun electrons Atthe end of the 200 milliseconds the storage mesh is brought back to 3 3 volts The storage surface is consequently reduced from zero volts to 10 volts by capacitive coupling 4 12 Since the write gun electrons reach the storage surface withenergy much higher than first crossover energy they charge the surface in a positive direc tion wherever they strike This charge pattern on the storage surface remains for a considerable length of time since the storage material is a very good insula tor 4 13 Those areas of the storage surface which are charged to near zero volts allow the field created by the high positive potential on the post accelerator to reach through and capture flood gun electrons
43. s connected to the input of the preamplifier when either EXT SENS or EXT CAL is selected the preamplifier in turn is coupledtothe outputamplifier Selections of EXT SENS permits varying theamplitude of the preamplifier out put by adjustment of the HORIZONTAL DISPLAY con 4 7 Section IV Paragraphs 4 68 to 4 75 DISPLAY Model 1814 AR O t CRT HORIZONTAL DEFLECTION PLATES R3 o HORIZONTAL E POSITION I8LA B 2 Figure 4 9 Horizontal Amplifier Block Diagram trol When EXT CAL is selected this control Ri is shorted the output amplitude therefore is deter mined by the amplitude of the input signal 4 68 The signal selectedis fed into the output ampli fier where it is summed with a current established by the HORIZONTAL POSITION controls Theresultant current is converted to a differential signal ampli fied andappliedto the C RT horizontal deflection plates 4 69 External input signalsare preamplified by A3Q1 and A3Q2 refer to Figure 8 10 The high input im pedance of A3Q1 minimizes loading of the external in put source Diode A3CR1 protects A3Q1 from high level inputs A3Q2 has a low output impedance suit able for driving A3Q3 The BANDWIDTH PHASE Switch A3S1 would be positioned in PHASE when accu rate X Y measurement is desired In the PHASE position A3C2and A3C3 ar switched in decreasing the preamplifier bandwidth Thetotalhorizontalamp lifier signal delay is theref
44. scope a Depress WRITE push button pb Set PERSISTENCE control fully ecw c Set INTENSITY control fully cew d Apply power to Model 181A AR e After 3 minutes the entire CRT viewing area should be evenly flooded green l NOTE If there is no green illumination turn instrument off and check all CRT con nections 3 6 CONTROLS AND CONNECTORS 3 7 The location of operating controis andconnectors is shown in Figure 3 1 together witha brief explanation of their functions Additionai information regarding some of these controls and connectors is provided below 3 8 FRONT PANEL 3 9 FOCUS AND ASTIGMATISM These controls are providedtoassure uniform focus of the trace over the entire CRT screen To adjust set the Presentation Selector to WRITE center a low intensity spot on the CRT screen and adjust FOCUS and ASTIGMATISM 02612 2 controls for a small round sharply focused spot Readjustment of the ASTIGMATISM controlis seldom required except for example when the vertical plug in is changed 3 10 STORE In order to retain whatever is visible on the CRT depressthe STORE push button The sig nal will be stored at reduced intensity resulting in a storage time of greater than one hour The INTENSITY PERSISTENCE FOCUS ERASE and HORIZONTAL POSITION controls do not affectthe presentation in the STORE mode 3 11 In some applications it may be desirableto show several overlapping traces at once This is possibl
45. seconds each millisecond and only during this short interval will a positive poten tial be applied to the flood gun accelerator grid 4 82 While A6Q2 is on the flood gun accelerator voltage is established by voltage divider network A6R5 A6R6 at 9v With A6Q2 switched off by the differentiated 1 kHz pulse the accelerator voltage is 443v set by the divider network A6R4 and A6R6 4 83 With the accelerator grid held at 9v the flood gunelectronsarerepelled Thus when in the STORE mode the flood guns are always on but electronsare attracted to the storage mesh only when the acceler ator grid is at a positive potential about 5 of the time This reduces the display brightness and pro vides for greatly increased storage time 4 84 VIEW Depressing the VIEW push button allows viewing previously stored display at a brightness level determined by the intensity and persistence set tings duringthe writing process At least one minute 02612 2 Section IV Paragraphs 4 76 to 4 89 of aggregate viewing is available without trace degrad ation 4 85 When in VIEW NORMAL WRITE or MAX WRITE mode of operation A6Q1 is turned on by the currentflowthroughA6Rltoitsbase This effectively grounds the base of A6Q2 holding it off and keeping the flood gun accelerator potential at 43v 4 86 The flood gun grid levelis setto provide an op timum flood gun electron distribution at the storage mesh This is adjustable and
46. sical damage such as bent or broken parts and dents or scratches If damage is found refer to Paragraph 2 4 for recommended claim procedure H the Model 181A AR appears undamaged perform the electrical check Paragraph 2 3 Retain the pack aging material for possible future use 2 3 ELECTRICAL CHECK The performance check is given in Paragraphs 5 5 through 5 14 This check will determine whether or not the instrumentis still operating within its specifications as listed in Table 1 1 The initial performance and accuracy of this instrument are certified as stated on the inside front cover of this manual If the Model 181A AR does not operate as specified refer to Paragraph 2 4 for the recommended claim procedure Priortoiniti ating any performance check refer to Paragraphs 2 10 through 2 14 andthe operating guidance provided in Section HI 2 4 CLAIMS 2 5 H physical damage is found or if the instrument is not within specifications when received notify the carrier and the nearest Hewlett Packard Sales Service Office immediately The Sales Service Office will arrange for the repair or replacement of the instrument without waiting for a claim to be settled with the carrier 2 6 REPACKAGING FOR SHIPMENT 2 7 Hf the instrument is to be shipped to a Hewlett Packard Sales Service Office attach atagto it show ing owner and owner s address instrument s model number and 8 digit serial number and a description of service r
47. t put voltage This causes a voltage change to appear on the primary of A5T1 and increases the voltage of the secondary The steady state value of the CRT cathode voltage is established by A1R38 the High Voltage Adjust by setting the normal dc value on the base of the A1Q8 Inductor A4L1 suppresses any pos sible high frequency parasitic oscillation 4 61 GATE AMPLIFIER 4 62 The inputs to the gate amplifier refer to Fig ure 4 8 aretheunbianking gate the chopped blanking the Z AXIS INPUT andthe storage pulse circuit sig nals These four signals may be present either singly or simultaneously depending upon control settings They are summed with a current established by three front panel controls FIND BEAM INTENSITY and HORIZONTAL DISPLAY Depressing FIND BEAM shunts the normally adjustable INTENSITY control and supplies maximum currentfrom this source Set ting HORIZONTAL DISPLAY to EXT SENS or EXT CAL supplies additional current to brighten the beam 4 63 The gate amplifier A1Q1 A1Q4 senses the in put signal current convertsitto a voltage amplifies it and couples itto the control grid of the CRT write gun And in addition the output signal is also differ entiated clipped and coupled to the Vertical Plug In for use as a trigger signal if desired 02612 2 4 64 The input currents to the gate amplifier refer to Figure 8 7 are summed in the low impedance emitter circuit of A1lQ1 The resulting current i
48. the base of A6Q3 through A6R8 Inverted and level shifted by A6Q3 the resultant 15v square wave atthe collector of A6Q3 is applied through A6CR2 and differentiated byA6R13 A6C2 Applied to the base of A6Q4 through A6CR3 the amplitude of the pulse at the anode of AGCR3 is established by the ratio of AGR12 andthe PERSISTENCE control setting R9 Asaresult of the charging time constant of A6C2 A6R13 the variable amplitude sig nalisfeltas a variation in width i e duration at the base of A6Q4 By varyingtheconduction time of A6Q4 thetime requiredtoeraseatrace has been controlled In other words varying the erase time is essentially the same as varying the display time and this in turn is known as variable persistence 02612 2 Model 181A AR 4 76 NORMAL Selection of this mode permits the Model 181A AR tobe employedas a conventional oscil loscope With NORMAL activated the junction of A6R16 A6R19 is grounded and the storage mesh falls to 25v Because of this negative potential the vari able persistence and storage capabilities are therefore disabled 4 77 WRITE and MAX WRITE Operating in these modes allows normal viewing of the display and pre pares it for storing MAX WRITE is used only when necessary suchas in viewing fast single shot signals 4 78 To obtain display uniformity in the MAX WRITE mode the CRT collimator voltage should be readjusted in this mode Todo so a multivibrator consisting of A6
49. tion IV Paragraphs 4 17 to 4 30 STORAGE MESH POTENTIAL mp igla 8 4 be turned off Thisisdone in the STORE mode how ever thefloodgunsare turned on occasionally to per mit viewing of the stored trace at reduced intensity 4 23 OVER ALL DESCRIPTION 4 24 GENERAL 4 25 The Model 181A AR Oscilloscope consists of low voltage power supply a calibrator four external output isolation amplifiers a high voltage power sup ply a gate amplifier horizontal amplifier and storage and variable persistence puise circuitry Fig ure 4 5 shows the functional relationship of these cir cuits The instrument may be operated as a general purpose a variable persistence or a storage oscil loscope Circuitoperationin all three modes is des scribed in this section 4 26 Three input signals intensity horizontal de flection and vertieal deflection are necessary to obtain a usable display on the CRT The circuitry for the intensity and horizontal deflection signals is ex plained in the foliowing paragraphs which are refer enced to Figure 4 5 The vertical deflection signal is coupled to the CRT from the Vertical Plug In 4 27 INTERNAL 4 28 Horizontal deflection signals may be obtained from the Horizontal Plug In by positioning the HORI ZONTAL DISPLAY switch to INT Thisapplies 100 voltstothe plug in which produces an unbianking gate and generates an internal sweep signal 4 29 The unblanking gate is coupl
50. trast filter and a detachable Model 181A AR power cord Also included with the Model 181AR is a rack mounting kit 1 16 ACCESSORIES AVAILABLE 1 17 A mobile test stand for the cabinet Model 181A is available The Model 1118A Testmobile provides adjustable height tilt and rotation Equipped with locking wheels itis readily collapsible for transport Anadapter assembly available as hp Part No 01119 69501 permits the rack Model 181AR to be mounted on the Model 1119A Testmobile 1 18 A front panel cover of fiberglass material hp Model 10166A can beusedto provide front panel pro tection for the cabinet Model 181A and a cover for the rack Model 181AR is available as hp Part No 5060 0437 1 18 For ease of calibration and maintenance an hp Model 10407A Plug in Extender can be obtained It provides for removal of the plug ins from the main frame and exposes components and adjustments 1 20 Cameras probes viewing hoods terminations and other accessory items are available for special izedrequirements Informationonthese andthe above described accessories may be obtainedfrom hp Sales Service Offices listed in the rear of this manual 1 21 INSTRUMENT IDENTIFICATION 1 22 Hewlett Packarduses atwo section eight digit serial number to identify instruments The first three digits precedingthe dash are the serial prefix which identifies a series of instruments the last five digits identify a particular instrument
51. tton f Tostore more than one display press the WRITE push button set PERSISTENCE fully clockwise and INTENSITY as required allow first display to be writ tenontheC RT Set INTENSITY fully counterclockwise andconnect the second signaltobe stored Reset ver tical POSITION if second display is not to be super imposed onfirst Slowly rotate INTENSITY clockwise until second display appears Press theSTORE push button g A display which is stored when the Model 181 A AR power is turned off will remain stored for sev eral days To redisplay the stored waveform press the STORE pushbutton turn POSITION controls fully cew before turning power on Apply power to Model 181A ARandallow 5 minute warm up If stored sig 02612 4 Section HI Paragraphs 3 44 to 3 47 nal was written in WRITE mode depress WRITE pushbutton Ifstored in MAX W mode depress MAX W pushbutton Depress VIEW pushbutton to observe waveform h To eraseall persistent or stored displays set modetoWRITE or Max Write and then the ERASE push button for approximately 2 seconds thenrelease i If only a portion of a slow sweep display is de sired press the STORE push button when the trace has been writtentothe desired point the write gun is blanked and the written portion is stored j Use a viewing hood if desired to improve sereen display contrast 3 44 SINGLE SHOT OPERATION 3 45 To write or store single shot phenomena a trial setting of INTEN
52. vary slightly with differentunits Plug in units should be calibrated when first installed or when shifted between oscilloscopes The horizontal and vertical plug in units must be locked together prior to insertion into the Model 181A AR mainframe Con sult the respective plug in Operating andService Man ual for operation and capability information 3 33 MAGNETIC INTERFERENCE 3 34 The CRT is provided witha mu metal shield for protection against magnetic fields Duetothe sensi tivity ofthe CRT it is possible that the strong magnetic fieldfrom nearby motors ac linetransformers etc may still result in a noticeable beam deflection In this event reorient or relocate the instrument with respect to the interfering device l 3 35 OPERATING CONDITIONS 3 36 DEFINITIONS 3 37 Several words and phrases the definition of which may vary slightly from common usage are used 3 3 Section II Paragraphs 3 38 to 3 43 to describe the operation of the Model 181A AR The definitions ofthese words and phrases which apply to _the Model 181A AR are as follows a WRITE To transform an input signal into a visible display on the CRT screen b PERSISTENCE The iength of time a single Sweep written display remains visible on the CRT Screen INTENSITY and sweep time constant c STORE To retain at reducedintensity a dis piay which has been written on the CRT d VIEW To redisplay onthe CRT screen at nor mal
53. vide viewing of a complete trace with fading sufficient to prevent interference with the next trace The display persistence can read ily be adjusted to eliminate flicker and still provide high resolution 1 5 The storage feature of the hp Model 181A AR canbeusedto store single shot occurrences for later viewing or photographing Comparison of waveforms can be accomplished by storing several separate oc currences and later viewing them simultaneously Section I Paragraphs 1 6 to 1 24 1 6 The horizontal amplifier has a direct coupled bandwidth of dc to 5 MHz The ac coupled bandwidth is 5 Hz to 5 MHz With a dynamic range of 5 volts the amplifier has front panel selectable deflection ranges of 1 v div 0 2 v div and 0 1 v div A vernier controlprovides continuous adjustment between ranges A magnified sweep accuracy of 5 is maintained at selectable magnifications of X1 X5 or X10 and a front panel BNC connector permits the use of external de flection signals The external input has an input im pedance of 1 megohm shunted by approximately 30 pf 1 7 A rear panel BNC connector is provided for ex ternal control of CRT blanking A signal of approxi mately 42v from de to 15 MHz will blanka trace of normal intensity The input resistance is 5100 ohms 1 8 External outputs are provided through four rear panel mounted BNC connectors for coupling plug in derived signals to external equipment Since th
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