Home

HP 1123A User's Manual

Contents

1. Figure 4 7 AMPLIFIER ASSEMBLY CONSTANT VOLTAGE SOURCE COMPENSATION ADJUSTMENTS CONSTANT CURRENT SOURCE Q9 DC OFFSET R38 ADJ Functional Block Diagram OUTPUT 502 po 15V l20e6V COMMON 2 1 4 5 section V Model 1123A Table 5 1 Table 5 1 Required Test Equipment Recommended Instrument Required Characteristics Type Model DC Voltmeter HP 412A 100 mV 1 Oscilloscope HP 180A w 1801A or 005 V Div 2 usec Div 1802 and 1820A Square Wave HP 211A 500 Hz 10 kHz 160 mV Generator Power Supply HP 1122 12 6 V 120 mZ 15 V 150 mA Power Supply HP 6206A 10 5 V 20 mA Oscilloscope HP 140A w 1410A and 100 mV cm 2 usec cm 1424 Pulse Generator HP 213B 100 psec risetime 500 mV RX Meter HP 250B Measure 3 4 pF at 100 MHz VHF Signal Generator HP 608D 230 MHz 1 V pk pk Accessories Required 90 ohm Tee connectors HP Model 10221A BNC Tee connectors HP Part No 1250 0281 5 0 02632 1 Model 1123A Section V Paragraphs 5 1 to 5 15 SECTION V PERFORMANCE CHECK AND ADJUSTMENTS 3 1 INTRODUCTION 5 2 This section contains procedures for perform ance check and adjustments The purpose of this in formationis to deter mine whether or not the instrument is operating withinthe specifications as listed in Table 1 1 andif not howtocalibrate the instrument Physi cal location of all internal adjustments is shown in Fi
2. sion Due to the high input impedance of Ql the input resistance is established by R1 Output im pedance is determined by Q1 and Q2 Emitter fol lower Q2 connected to the source output furnishes additional current amplification thus reducing the output impedance even more The output impedance from emitter of Q2 to ground can be calculated using the equation shown in Figure 4 2 4 11 CONSTANT VOLTAGE SOURCE 4 12 As its name implies the constant voltage source supplies a constant voltage to the load This circuit is often used to prevent erroneous results caused by fluctuating supply voltages 4 13 Figure 4 3 shown one method of obtaining a constant voltage source Voltage divider R1 R2 es tablishes the desired voltage level at the base of Q1 4 1 Section IV Paragraphs 4 14 to 4 21 Since the voltage drop across the emitter base junc tion of Q1 remains relatively constant the voltage at the emitter is approximately 0 6 volts more positive than the base voltage This circuit is an emitter fol lower and as such has a low impedance output Es sentially this circuit approximates a voltage source whose source impedance is near zero calculate the output impedance usethe equation given in Figure 4 3 9 CONSTANT VOLTAGE be VARIABLE LOAD RESISTANCE Figure 4 3 Constant Voltage Source 4 14 CONSTANT CURRENT SOURCE 4 15 maintaina known current through a varying load a c
3. Check Test Set up Section V Paragraphs 5 16 and 5 17 SQUARE WAVE GENERATOR FREQUENCY cc ctt n v 500 Hz AMPLITUDE 89 Set for 8 div display c Repeat step b above with SWEEP TIME set to 20 usec with 5 kHz input and 5 usec with 10 kHz input d In each of the above conditions the output of the probe shall be within 1 x0 4 minor divisions of the input square wave 5 16 SINE WAVE COMPRESSION CHECK Note The DC Blocking Assembly used in this check allows the input signal to be super imposedona 0 5 volt level The DC Blocking Assembly must be assembledfor thistest see Figure 5 2 however care must be taken to minimize perturbations causedby the high frequency signal path LOW FREQUENCY 220UF HIGH FREQUENCY 2 21 Figure 5 2 DC Blocking Assembly Schematic a Connectthe equipmentas shown in Figure 5 3 b Set instrument controls as follows VERTICAL AMPLIFIER VOLTS DIV 2 er eee en ees 005 COUPLING 88 4 424 0 x AC VERNIER 2 eS ea fully ew TIME BASE SWEEP TIME 2 msec MODE AUTO SINE WAVE GENERA TOR FREQUENCY 2 kHz AMPLITUDE adjust for 8 div display c Adjust Power Supply output for 10 5 volts d Setswitch on DC Blocking Assembly to the OFF position e Display should be a sine wave 8 divisions in amplitude with no visible distortion f Set switch to plus position and then to mi
4. 4 3 2 ie 85 1 61 SP L 01 22 OsiUF i wo 1 pts E RIO CW 20K 200 20 gt ge MID FREQ MID FREQ 22 RESP 2 RESP 017 GND 1 l ov Au 3 6 Der V d 3 q 7 Zov Ex 45 464 75 1 2 15 014 1 x R44 i 33003 SEE NOTE2 ELO ov 2 6V RI3 e vivas 12 6 E cio Ad 4 44 Cll ostur T 648 UF 2 6 15 15 4 GAIN 2 50K 5 15 CURRENT SOURCE 2 99 OMV 24K F aA d R26 1600 62K ERROR CR2 AMPLIFIER 05 Q8AB QAB lt 2 6 71246 e 45V 15 a 6200 DIFFERENTIAL Sac Ok FEEDBACK Figure 8 5 Model 1123A Schematic Diagram 8 5 8 6 1123 Appendix I APPENDIX I ACCESSORIES MODEL 10214 10 1 DIVIDER 1 DESCRIPTION 2 The HP Model 10214A 10 1 Divider is a signal probing accessory for the HP Model 1425A 1410A oscilloscope samplingsystem The Model 10214 is illustrated in Figurel The divider offers essentially constant impedance to the probe regardless of the impedance t
5. Model 140 Series Sampling System For waveforms X8 and 557 use test set up and connections given in Paragraph 5 19 Any exceptions to these conditions are noted adja cent to the applicable waveform photo DC VOLTAGES The DC Voltage readings as given on the schematic diagram were taken with the Model 1123 discon nected from Oscilloscope with power applied Allvoltages are measured with reference to chassis ground Voltage readings are considered normal if within 10 of voltage given on schematic 02 V DIV 5 2 5 2138 PULSE IONSEC CM 02 V DIV SOMV CM 20 USEC IO NSEC CM 005W Div 02 V DIV 2 MSEC 2 MSEC 2 3 Figure 8 3 Waveforms at Test Points 02632 1 Model 1123A PRO GRID REF GRID REF GRID REF GRID REF GRID REF GRID REF GRID REF GRID 2 516_ LOC DESIG LOC DESIG Loc DESIG Loc DESIG LOC DESIG LOC DESIG LOC DESIG Loc R17 R19 R20 R21 R22 R23 R24 R25 R26 R28 C12 C13 C14 C15 C16 1 CR3 CR4 CRS R40 R41 Riz R43 R44 R45 R46 R46 VR2 524 R31 R32 R33 R34 R35 R36 R37 R38 R39 C3 C4 C5 C6 CT co C10 L3 14 15 L6 Ql Q2 Q3 Q4 Q5 R8 R9 R10 R11 R12 R13 R14 R15 R16 Qe qa Q10 Q11 RI R2 R3 R4 R5 i 1 i 1 1 i 1 L 1 LI V i 1 L i 1 i LI i 1 L 1
6. 005900 Be de ta ta Ca gomguommumgnng de Bo Go 4 C3 PA bd La tb Gee pmmmmmmmmutm d O Pd D mogomgmgomgmmm LO LO LO 53 1123 17 Figure 8 4 Component Identification Assy A2 02632 1 2 2 a ET mi AL Fm gt ea 1 7 ib TIP 3 4 sa io coms 8 1 F R SYMBOLS D CONVENTIONS COPYRIGHT 1968 BY HEWLETT PACKARD COs 1123A PROBE 827 s REFERENCE DESIGNATIONS NOTE 1 DENOTES FACTORY SELECTED ITEM MAY OMITTED NOTE 2 MAY VARY FROM 0 6 TO 1 4 Ji Relerence designations within assemblies are abbreviated Add assembly designation T as prefic to form complete designation Ri osa assembly 2 is 21 _ i DELETED RIB i 3 Section VIII Figures 8 4 and 8 5 AMPLIFIER 010 011 QIIB 0 SUPI COM 5 490 12 6 i2
7. 5 se ee ee INTERNAL DENSITY 4 6 44 de X d cw TIME SCALE MAGNIFIER X2 DELAY dx de ose De 24 ac required TIME 5 1 sec cm VERNIER c o 859 C or cc o c Aa A CAL MODE STABILITY adjust for stable triggering NORMAL TRIGGER SLOPE as required c Connect 50 ohm Load to 50 ohm Tee d Connect loaded 50 ohm Tee to Pulse Generator OUTPUT e Connect Oscilloscope CHANNEL A probe to 50 ohm Tee A 10 cm pulse should appear on the CRT f Insert Model 10214 10 1 Divider between probe and 50 ohm Tee andchange oscilloscope SENSITIVITY to 10 mv em 10 0 5 empulse should be obtained 2 REQUIRED CHARACTERISTICS 1 MHz repetition rate 0 5 usec pulse width 1 GHz Bandwidth 1 GHz Bandwidth 1 GHz Bandwidth 13 ADJUSTMENT PROCEDURE 14 The following procedure adjusts the probe for optimum capacity If the 10 1 division ratio is incor rect replace the divider Adjust the probe capacity as follows a Use the divider to monitor a 75 kHz square wave on the sampling oscilloscope b Adjusttheoscilloscopetoobtaina 10 centimeter display and optimize oscilloscope response The overshoot on the display should be 3 d If the overshoot is not 395 disconnect the di vider and adjust the slotted plate in the female con nector e Repeat steps b through d until the overshoot is 3 Keep
8. is connected to the probe by sliding the probe into the body portion of the blocking capacitor 5 USE WITH OTHER ACCESSORIES 6 The Model 10228 may be used in conjunction with the probe as described above or it may be used with the Model 10214 10 1 Divider the Model 10215A 100 1 Divider and the Model 10229A Hook Tip 7 CIRCUITS 8 schematic diagram of the Model 10228 is shown in Figure 2 The blocking capacitor C1 is 0 18uF low incuctance capacitor which is used to keep dc voltages in the circuit under test from reach ing the Vertical Amplifier Itis capable of blocking 90 volts dc from ground Inductor L1 is provided to dampen the lead inductance Capacitor C2 represents the stray circuit capacitance within the blocking Ca pacitor Assembly 9 MAINTENANCE 10 The only maintenance recommended is to run aperformance checkifoperation is improper There are no adjustments or replaceable parts except for the probe pin for the Model 10228A 11 PERFORMANCE CHECK 12 The following procedure may be used as an in coming quality assurance check or if the Blocking Capacitor is not functioning properly Test equipment required for the procedure is listed in Table 2 a Set Pulse Generator controls as follows gt rs 43 4 POS OUTPUT 3 4 6 em Soe x POS SENSITIVITY For triggered output 02632 1 Figure 1 Model 10228A b Set Sampling Oscilloscope controls a
9. 1123 Section Paragraphs 3 1 to 3 17 SECTION OPERATION 3 1 GENERAL 3 2 Thissectionfurnishes the information necessary tooperatethe Model 1123A Voltage Probe Eachcon nector adjustment andaccessory is explained briefly in Figure 3 1 Several operating set ups are given to show equipment versatility and to familiarize the operator with typical measurement operations 3 3 CONNECTORS AND ACCESSORIES 3 4 Although the functional descriptions in Figure 3 lare brief they provide a quick reference for the operator Some ofthe functional areas are explained herein more detail to ensure a thorough understand ing of their operation 3 5 OUTPUT CONNECTOR 3 6 Output signals from the Probe Amplifier are transferred to the BNC output connector from an emitter follower stage whose outputimpedance is main tained at 50 ohms Due to the high frequency capa bility of this instrument it is important to keep this output matched with a 50 ohm load e g the Model 1802 Dual Channel Vertical Amplifier 3 7 BLOCKING CAPACITOR TIPS 3 8 The Model 1123A Voltage Probe is dc coupled therefore when measuring small ac signals riding on large offset levels itisnecessaryto use a dc blocking capacitor Both Models 10217A for high frequencies and 10228A for low frequencies can be used with the Model 1123A Voltage Probe Do not apply steps or ac voltages larger than 50 volts peak as they will damage the input FET in t
10. 4 46 Transistor A2Q1 is temperature compensated by A2Q2 Careful examination shows the base emit ter junction of A2Q2 plus L1 and R1 are in parallel with the base emitter junction of A2Q1 plus R5 and R6 During normal operation the sum of the voltage drops across each of these strings is equal Since the change in voltage across these base emitter junc tions is equal they cancel each other and thus do not affect the output level of A2Q1 4 47 OUTPUT AMPLIFIER 4 48 Output Amplifier A2Q4 is an emitter follower which provides a low output impedance of 50 ohms for proper impedance matching This instrument ex hibits a 50 ohm source impedance and is designed to drive a 50 ohm load The source impedance looking into connector P1 consists of A2R45 added to the small internal emitter resistance of A2Q4 At high frequencies the internal resistance increases caus ing the output impedance to increase however due to capacitor A2C13 whose reactance decreases at highfrequencies and R46 C14 the output impedance remains relatively constant at 50 ohms 4 49 FEEDBACK TO MINIMIZE DC TEMPERATURE DRIFT 4 50 Since the temperature coefficient of the gate to source voltage of a FET is dependent on the bias current applied to the drain it is impossible to get 02632 1 ACTIVE PROBE ASSEMBLY Section IV Paragraphs 4 51 to 4 56
11. AMPLIFIER VOLTS DIV eee 50 mV Set for 10 display PULSE GENERATOR TRIGGER e e gt 0 43 9 we ano d 4 OUTPUT 54454684 SENSITIVITY Obtain Trigger Observearisetime of lessthan 1 6 Over shoot and ringing shall be less than 3 3 mm turbations shall be less than 6 6 mm pk pk SYNC PULSE OUTPUT ou se 140 OUTPUT 22 CABLE TRIGGER INPUT 502 TEE 502 LOAD 1123A e B Fuu H GR TON 500 900 c LOAD 16 Figure 5 6 Pulse Response Test Set up 5 20 BANDWIDTH CHECK a Connectthe equipmentas shown in Figure 5 7 b Set controls as follows SAMPLING TIME BASE TIME DIV rr n o nn 4 2 nsec TRIGGER ee ee INT SCANNING 555006 6 n n n NORMAL SAMPLING VERTICAL AMPLIFIER VOLTS DEV od no 100 mV 5 5 5 fully ew TRIGGER a 4 4 OSCILLA TOR FREQUENCY ete 220 MHz c Insert the Probe of Model 1410A into the con nector labeled B d Adjust Oscillator output for 10 cm display e Movethe Probe of Model 1410A to the connec tor labeled A and insert the Model 1123A Probe into the connector labeled B f Observe a signal of greater than 0 71 V pk pk 7 1 cm in amplitude 5 3 section V
12. GENERATOR PULSE TRIGGER 4 SENSITIVITY for triggered output c Adjust Power Supply output for 10 5 volts d Setthe switch on the DC Blocking Assembly to the OFF position e Amplitude of the pulse should be 10 cm Over shoot and ringing should be less than 6 6 mm f Set the polarity switch on the DC Blocking sembly to plus and then minus The pulse must be repositioned on screen each time g In each of the conditions in step f the pulse should be greater than 9 2 cminamplitude Overshoot andringing shouldbe lessthan 6 of signal amplitude 5 18 INPUT CAPACITANCE CHECK a Connect the equipment as shown in Figure 5 5 b Set Frequency of RX Meter to 100 MHz c Adjust DETECTOR TUNING and null RX Meter d Apply power to the probe and insert the probe tip into the adapter e Capacitance should be from 3 to 4 pF POWER CORD EXTENSION 2508 METER 1123 15 Figure 5 5 Input Capacitance Set up 5 19 PULSE RESPONSE CHECK a Connectthe equipment as shown in Figure 5 6 b Set controls as follows SAMPLING TIME BASE TIME DIV 10 115 MAGNIFIER 0 2 dau TUR 10 SYNC MODE 5 AUTO SYNC PULSE e s 404 SCANNING sc cc ttt NORMAL 02632 1 section V Paragraphs 5 18 to 5 20 SAMPLING VERTICAL
13. IO DBATTEN CHANNEL A PROBE TEE 50 LOAD INSERT 0228 0228 2 Figure 3 Test Set up 8 02632 1
14. MP P Q R ET meter mechanical part plug transistor resistor thermistor switch transformer terminal board test point vacuum tube neon bulb photocell etc voltage regulator diode cable Socket crystal ABBREVIATIONS amp ampl amperes amplifier glass grd ground ed h henries bp bandpass Hy mercury hr hour s carbon HP Hewlett Packard counterclockwise ceramic if coefficient ined composition incl connector ins cathode ray tube int clockwise Car CCW coef com comp conn crt cw intermediate freq impregnated incandescent include s insulation ed internal Ho H MH Ho dH Ho dw i k kilo 103 depc deposited carbon lin linear taper electrolytic log logarithmic taper encapsulated Ipf pass filter external elect encap ext m mili 1073 meg mega 107 metflm metal film met ox metal oxide mir manufacturer minat miniature mom momentary f farads fet field effect transistor fixed 1 F Ho H Kk germanium 02632 1 mtg my n n c ne n o npo mounting mylar radio frequency s b nano 10 9 Se normally closed sect neon semicon normally open 51 negative positive zero sil zero temperature si coefficient spl not separately replaceable Ta td order by description oxide Ti tol slow blow selenium section s semiconductor silicon sil
15. N channel o li Front panel marking Breakdown diode Rear panel marking Front panel control Tunnel diode T GG 0 Screwdriver adjustment Step recovery diode P O Panto Circuits or components drawn with dashed lines phantom show CW Clockwise end of vari function only and are not intended i ds P d to be complete The circuit or component is shown in detail on another schematic able resistor l b 1 NeCe No connection Il Unless otherwise indicated resistance in ohms V Waveform test point capacitance in picofarads with number inductance in microhenries V Common electrical point Wire colors are given by with letter not necessarily numbers in parentheses ground _ using resistor color code 925 is wht red grn gt gt Single pin connector d 2 7 Violet ene 3 Orange 8 Gray Pin of a plug in board 4 Yellow 9 White with letter or number Switch wafers are identified as follows Primary signal flow IF IR IR N o LL Secondary signal flow Optimum value selected at factory average value shown may have been omitted 2 2R 8 0 02632 1 Model 1123A Section VIII Paragraphs 8 1 to 8 14 SECTION SCHEMATICS AND TROUBLESHOOTING 8 1 INTRODUCTION 8 2 This section contains Model 1123A diagrams component locat
16. are intended to provide the operator with the necessary understanding to troubleshoot this instrument Many times suspected malfunctions are A2 ASSEMBLY Al SUB ASSE MBLY Figure 8 1 Unit System Reference Designation 02632 1 8 1 Section VIII Paragraphs 8 15 to 8 24 caused by improper control settings or system hook up Therefore it is recommended that the operator become as familiar as possible with the operation of the Model 1123A before troubleshooting 8 15 Tolocateatrouble start with a thorough visual inspection of front panel control settings and hook up Look for burned or loose components mis wiring or any condition which suggests a trouble Square pin wiring is shown on each component pictorial Refer tothese callouts after a board has been replaced to assure proper connections Correct any faults lo catedin instrument performance before continuing to troubleshoot Note Test point jacks shown on schematics are used in various checks and adjustments and do not correspond to waveform test points 8 16 The first electrical check should be to insure that proper voltages are coming on to the printed cir cuit boards Check the Low Voltage Power Supply LVPS to insure all voltages are correct Use the overallblock diagram Section IV the schematic dia grams andthe waveform photos adjacenttoeach sche matic This procedure will isolate the trouble to a particular circuit When trouble appears p
17. can be used with an instrument having a high input impedance 1 3 During operation the Model 1123A allows the operator toprobe circuits operating at relatively high frequencies without significant loading effects High input impedance is maintained by a field effect tran sistor FET mounted close to the probe tip 1 4 Power for the probe is provided by a connector on the front panel of the HP Model 1802A Dual Chan nel Vertical Amplifier plug in or the HP Model 676A Phase Amplitude Tracking Detector When operated with other instruments the Model 1122A Power Sup ply must be used to obtain power Refer to Table 1 1 for complete specifications on the Model 1123A Probe 1 5 WARRANTY 1 6 This instrument is certified and warranted as stated inside front cover of this manual Should afailure occur within the time stated on the warranty contact your nearest Sales Service Office immedi ately 1 7 ACCESSORIES SUPPLIED 1 8 standard 1123A Voltage Probeis sup plied with the following tips Model 10217A High SERIAL Figure 1 1 02632 1 H23A VOLTAGE PROBE HE 10 fa 35g t Frequency Blocking Capacitor Model 10228 Low Frequency Blocking Capacitor Model 10214A 10 1 Divider Model 10215 100 1 Divider and the Model 10229A Hook Tip 1 9 INSTRUMENT IDENTIFICATION 1 10 Hewlett Packard
18. f Perturbations should be less than 6 pk pk SENSITIVITY To obtain triggered output 3 minor divisions HIGH FREQ RESPONSE C4 HIGH FREQ PHASE NO I MID FREQ HIGH FREQ RESPONSE RIO RESPONSE 2 C3 INPUT BALANCE R32 DC OFFSET R38 R5 LOW FREQ GAIN C5 HIGH FREQ RESPONSE NO 3 DC GAIN R48 HIGH FREQ PHASE NO 2 R8 MID FREQ RESPONSE NO 2 2 22 Figure 5 9 Adjustment Location 02632 1 5 5 5 6 Model 1123 Performance Check Record PERFORMANCE CHECK RECORD 9 13 Input Balance step c None 5 14 DC Offset LL 5 15 Gain ___ Compression step i 1 4 div 0 V 1 mV 5 mV step e 5 18 5 19 8 Pulse Response step c Risetime None Overshoot None 4 Perturbations None 9 20 Bandwidth eb 5 21 Noise 1 2 Pulse Compression None 9 2 cm Input Capacitance 3 6 02632 1 5 7 5 8 Model 1123 Section VI Paragraphs 6 1 to 6 7 SECTION VI REPLACEABLE PARTS 6 1 INTRODUCTION 6 2 This section contains information for ordering replaceable parts for the instrument Table 6 2 lists the parts in alpha numerical order of their reference designations and provides the following information for each item a HP Part Number b Total quantity TQ used in instrument given only first time a part number is listed c Description of part see Table 6 1 for list of re
19. for a gain of one to minimize the Miller Effect Inductor A1L1 compensates for collector capacitance of A2Q3 and better terminates the sending end of the 100 ohm coaxial cable It also provides some high frequency compensation 4 38 Feedback from the output amplifier A2Q4 is applied to the base of A1Q4 This feedback signalis generated as a result of an offset or error between input and output levels detected at the base of A2Q8B the summing point for input and output currents When an error is detected it causes an increase or decrease inthe voltage difference between the base of A1Q3 and A1Q4 This error signal is fed through A2Q1and A2Q4 causing the output level to change until the resulting error signal at A2Q8B drops to zero Thus the feedback network maintains the desired level from input to output 4 39 INTERMEDIATE AMPLIFIER 4 40 Transistor A2Q1 receives the signal through cable Wi Resistor A2R1 terminates the cable with 100 ohms to provide impedance matching at its output end Inductor A2L1 compensates for loading caused by the input capacitance of 201 Common emitter stage A2Q1 provides a voltage gain of approximately 2 2 and contains both emitter and collector peaking networks for maintaining a flat frequency response Emitter peaking is accomplished by frequency com pensating adjustments C3 C4 C5 R5 R7 R8 R10 and R48 Collector peaking furnishes additional com pensation with L3 peaking medium freque
20. manufacturing may be noted brief expla nationis presented here for those unfamiliar with the designation system 8 10 Each component is identified by a letter number combination For example R1 R2 Cl C2 etc This letter number combination is the basic designa tionfor eachcomponent Components which are sepa rately replaceable and are part of an assembly have inadditiontothe basic designator a prefix designation which identifies the assembly on which the component is located Components not mounted on an assembly have only the basic reference designation 8 11 Figure8 lisusedasanexample The basic ref erence designationappearsthreetimes however each R1 is identified by a designation formed by combining component assembly and sub assembly designators Consider the R1 on sub assembly A1 The complete designation of that resistor is 2 Now R1 con nected between assembly A1 and the complete instru ment has only the designation R1 because it is not mounted on an assembly This system applies to all classes of components C CR Q etc 8 12 Assemblies are numberedfrom 1 consecutively If an assembly number is assigned and later deleted this number is not reused 8 13 TROUBLESHOOTING 8 14 The first and most important requirement for successfultroubleshooting isa thorough understanding of howthe instrument is designed to operate Section Operation and Section IV Theory of Operation of this manual
21. of Q1 through Cl thereby making 1 look like a large capacitance Negative feedback is produced by C1 consequently at high frequencies the capacitive reactance decreases caus ing amplifier gain to decrease At low frequencies the Miller Effect is insignificant due to the size of C1 which is usually a few picofarads 4 19 The effects of C1 can be reduced by two means 1 by making the source resistance low and 2 by having a low amplifier gain OUTPUT i SOURCE 5 Figure 4 5 Miller Effect 4 20 DIFFERENTIAL AMPLIFIER 4 21 Differential amplifiers come in a wide variety The one shown in Figure 4 6 will be used for ex planation because of its similarity to the ones used inthisinstrument Its ability to reject common mode signals e g noise or 60 Hz signals common to each 02632 1 is Model 1123A input while producing a differential output make it an excellent choice for many applications As its name suggests only the difference between the two inputs isamplified This makes the differential amplifier suitable for many comparator or control functions When used in power supply regulator circuits fixed reference at one input B can be compared to another voltage source at the other input The difference between the two inputs is amplified and the output C or complement D can then be used as a correction signal to bring one input into bal
22. terminated with 50 ohms at the load 2 Connect power connector to Model 1122A Power Supply 3 Select the necessary vertical sensitivity andhori zontal sweep to make desired measurements Note For high frequency measurements loss inthe 50 ohm cable must be considered Figure 3 3 Remote Operation 3 3 Section Model 1123 Figure 3 4 80A 8 Oooo m e I8OIA II22A 2 Whenthe Model 1123A Voltage Probe is used with vertical plug ins having high INPUT impedance itis necessary touse a 50 ohm feedthrough terminator such as an HP Model 10100 1 Using a 50 ohm feedthrough terminator connect the Voltage Probe output connector to INPUT of any vertical plug in whose inputimpedance is rela tively high e g the Model 1801A Vertical Plug in Connect power connector to appropriate supply Make oscilloscope settings insame manner as for any standard operation Figure 3 4 High Impedance Loads 3 4 02632 1 Model 1123A Section III Figure 3 5 08000 O N P 4 8 79 2 123 11 Note 6 Make necessary oscilloscope settings to obtain several cycles of square wave Calibrator sig Dynamic range of the HP Model 1123A nal Display should be five divisions high is 5 volts however i
23. versatility of the Model 1123A Voltage Probe Figures 3 2 through 3 7 have been added All figures contain an instru ment picture andrequired written steps to obtain pro per operating conditions Each control has a callout which corresponds to the step number of the proce dure It is assumed that the operator is familiar with the Model 180 Series Oscilloscope and knows how to obtain proper vertical and horizontal sweep settings For some of the following operations it is necessary to use AUTO SWEEP MODE and INT synchronization 3 1 Section Model 1123A Figure 3 2 II23A B 8 1 Connect the Model 1123A Voltage Probe in IN 9 Set DISPLAY to A PUT A of Model 1802A Dual Channel Vertical Amplifier 6 Position A trace on center horizontal graticule 2 Attach HP Model 1123A power connector to ap 3 2 propriate power jack Set Polarity switch to OFF Set VOLTS DIV selector to 01 Vernier in CAL 8 position 7 Set Polarity switch to on center horizontal graticule line Figure 3 2 Installation and Zero Adjustment Adjust ZERO ADJ potentiometer until trace is 02632 1 Model 1123 4 02632 1 Section Figure 3 3 180A 1821 9 1 Connecta 50 ohm coaxial cable between INPUT of a 180 Series Vertical Plug in and the output connector of the Model 1123A Voltage Probe Note When used in this manner the 50 ohm coaxial cable must be
24. 0 fxd cer 1 uf 50V 30 fxd cer 1 5 pF 500V 1 fxd cer 1 uf 50V 30 fxd ta 6 8 uf 35V 10 fxd Oluf 100V 80 20 fxd cer 3 6 pF 500V 1 fxd cer 4 7 pF 500V 1 fxd ta 1 uf 50V 20 fxd ta 1 uf 50V 20 fxd cer 01 uf 100V 80 20 fxd 075 uh fxd 10 uh 10 fxd 100 uh 10 fxd 1 2 uh 10 fxd 1 2 uh 10 fxd 1 2 uh 10 si PNP si PNP si NPN si NPN 82227 si PNP si PNP si PNP si NPN Dual si NPN si NPN si NPN Dual fxd metflm 100 ohms 1 1 8w fxd metox 1k ohm 2 1 4w fxd metox 1k ohm 2 1 4w fxd metox 100 ohms 2 1 4w var cer metflm 50 ohms 30 1 2w Model 1123A Description Part No 1 02632 1 Model 1123 Table 6 2 Replaceable Parts Cont d Section VI Table 6 2 HP Part No Description a Peano fra See Table 6 1 A2 Cont d 02632 1 0757 0397 2100 1788 2100 2030 0757 0911 2100 2030 0757 0282 0757 0936 0757 0968 0757 0405 0757 0928 0757 0296 0757 0075 0757 0957 0757 0912 0757 0929 0757 0958 0757 0972 0757 0955 0757 0972 0757 0967 0757 0975 0757 0458 0757 0459 0757 0967 0757 0958 2100 1788 0757 0920 0757 0920 0698 6994 0698 7077 0757 0941 2100 2610 0757 0458 0757 0943 0757 0976 0757 0459 2100 2031 0757 0470 0757 0393 0757 0398 0757 0408 2100 1788 1902 0799 1902 3203 01123 61301 01123 61302 01123 61601 01123 61603 20 00 00 Re R R R R
25. 1 volt signal can be observed without exceeding the 0 5 volt dynamic range of the probe DC gain of the feedback system is adjusted by A2R43 Section IV Paragraphs 4 34 to 4 50 into the desired operating range Diode A2CR2 tem perature compensates the current source A2Q9 keep ing the output current to A1Q1 constant 4 34 EMITTER FOLLOWER 4 35 Source Follower A1Q1 followed by emitter fol lower A1Q2 constitutes an impedance converter It accepts signals through its high impedance input and furnishes the signal to differential amplifier stage A1Q3 Q4 from its low impedance output As explained previously the low output impedance of emitter follower A1Q2 produces maximum bandwidth by mini mizing the effects of Miller capacitance in the follow ing stage A1Q3 Capacitor A1C4 bootstraps the source resistor of A1Q1 thus maintaining constant current biasing of A1Q1 and eliminating high frequency dis tortion High frequency stabilization is maintained by A1R4 and A1C2 4 36 DIFFERENTIAL AMPLIFIER 4 37 Differential Amplifier A1Q3 Q4 performs two important functions 1 it provides current amplifi cation which is required to drive the four foot 100 ohm coaxial cable W1 which connects the probe tip and amplifier assembly and 2 it provides the means for introducing a dc voltage to counteract variations in gate to source voltage of Q1 and therefore establish the probe dc level at the probe output The amplifier is designed
26. 4 3 7 9 SpecialInstruments 7 1 4 30 Source Follower 8998 4 3 4 32 Constant Current Source 4 3 VII SCHEMATICS AND TROUBLESHOOTING 8 1 4 34 Emitter Follower t 4 4 8 1 Introduction cc t ctc 7777 8 1 4 36 Differential Amplifier 4 4 8 3 Schematic Diagrams 8 1 4 39 Intermediate Amplifier 4 4 8 6 Component Identification 8 1 4 41 Intermediate Amplifier Gain 4 4 8 8 Reference Designation 8 1 4 43 Constant Voltage Source 4 4 8 13 Troubleshooting 50505007066 8 1 4 45 Temperature Compensation 4 4 8 17 Waveforms 777777 8 2 4 47 Output Amplifier 898999 4 4 8 19 DC Voltages 988985 8 2 4 49 Feedback to Minimize DC 8 21 Repair and Replacement 89 8 2 Temperature Drift 798 4 4 8 23 Servicing Printed Circuit 4 55 DC Gain and Offset Adjustment 4 5 Boards 4 s o e es gt 8 2 APPENDIXI rr tr t a gg t a IA 1 Model 10214A gt gt o s ros IA 1 Model 10215A ee 3 Model 10217A 5 Model 10228A TA 7 ii 02632 1 Model 1123A List of Illustrations LIST OF ILLUSTRATIONS Figure Title Page Figure Title Page 1 1 Model 1123A Voltage Probe 1 1 4 6 Differential Amplifier s resa 4 3 4 7 Functional Block Diagram 4 5 3 1 Model 1123A Voltage Probe and Accessories 3 0 5 1 Gain Check Test Set up 5 1 3 2 Installatio
27. 5 8 Theform may then be removed and filed in a safe place so that readings taken at a later date can be compared to the original readings 9 10 Itis recommended that the performance checks be done in the sequence given because succeeding steps dependupon control settings and results of pre vious steps If necessary steps may be done individu ally by referring to control settings and results prior to the desired step 5 11 PRELIMINARY SET UP 5 12 Connect the HP Model 1123 to an appropriate power source 02632 1 a Apply power and allow 5 minute warm up 5 13 INPUT BALANCE CHECK a Connect the Voltm ter to the probe tip pin b Connect the Voltmeter ground lead to probe ground c Observe a reading of 0 volts 1 mV 5 14 DC OFFSET CHECK a Connect a 50 ohm load and Tee connector to the output BNC b Connectthe Voltmeter to the center conductor of the Tee connector c Connect Voltmeter ground leadto probe ground d Observe a reading of 0 volts 5 mV 5 15 GAIN CHECK a Connectthe equipment as shown in Figure 5 1 b Set the controls as follows VERTICAL AMPLIFIER VOLTS DIV s gt rn n n 02 V DISPLAY E 2 ce AIT COUPLING n owe 2 DC TIME BASE SWEEP 5 2 msec TRIGGER 5 2 56 011 2902 AUTO E POWER CABLE EXTENSION 1123 14 Figure 5 1
28. ERING SLOPE required Connect 50 ohm load to 50 ohm tee d Connect loaded 50 ohm tee to pulse generator OUTPUT e Connect Model 10217A to oscilloscope CHAN NEL A probe and insert into 50 ohm tee f Adjust VERTICAL POSITION pulse generator DELAY and oscilloscope DELAY to observe a 10 cm pulse REQUIRED CHARACTERISTICS Risetime less than 100 ps 1 GHz Bandwidth 1 GHz Bandwidth 1 GHz Bandwidth g Change the system sensitivity to 10 mV cm and adjust VERTICAL POSITION to observe top of pulse on CRT Sag shall be less than 1 cm 13 REPLACEABLE PARTS 14 There is only one replaceable part in the Model 1021 probe pin HP Part No 5020 0457 Contact the nearest HP Sales Service Office for replacements If it is determined that blocking capacitor is faulty it must be replaced in its entirety 02632 1 Model 1123A Appendix I MODEL 10228A BLOCKING CAPACITOR 1 DESCRIPTION 2 The HP Model 10228A Blocking Capacitor is a signal probing accessory see Figure 1 The Model 10228A is used to isolate an instrument from dc po tentials present in the test circuit Specifications for the Model 10228 are listed in Table 1 Table 1 Specifications CAPACITANCE 0 180 MAXIMUM INPUT VOLTAGE when used with divider tip 50V dc 200 RISETIME Driven from 250 source lt 4 5 nsec SHUNT Less than 25 pF 3 CONNECTIONS 4 The Model 10228
29. Model 1021 is to run performance check if a malfunction is suspected 11 PERFORMANCE CHECK 12 Perform thefollowing procedure as an acceptance check or if a malfunction in the blocking capacitor is suspected Test equipment required for the perform ance check is listed in Table 2 a Set pulse generator controls as follows REP RATE 4 44 4 9 100k 1M VERNIER Set for 500 kHz output PULSE DELAY and VERNIER required PULSE WIDTH e c 9 9 9 9 5 5 VERNIER gt Set for exactly 1 usec output PULSE POLARITY e 9 9 t gt PULSE AMPLITUDE 998888 1 VERNIER Set for 1 volt output b Set oscilloscope controls as follows Function Selector CHANNEL A SENSITIVITY seses 100 mV cm CALIBRATED SMOOTHING NORMAL optimized SCANNING INTERNAL DENSITY 6 4 cw TIME SCALE MAGNIFIER X10 DELAY as required TIME SCALE 1 usec cm VERNIER 9 ee CAL IA 5 EX rine rig cae EL A ANN teh Appendix I Model 1123A Table 2 Test Equipment RECOMMENDED INSTRUMENT TYPE MODEL Pulse Generator HP 213B Sampling Oscilloscope HP 1425A 1410A 50 ohm Tee HP 10221A 50 ohm Load GR 874 W50 MODE STABILITY adjustfor stable triggering TRIGGERING NORMAL TRIGG
30. Paragraphs 5 21 to 5 30 _ CH B PROBE T1 1080 500 TEE 1123A A 18 Figure 5 7 Bandwidth Test set up 5 21 NOISE CHECK a Connect the equipment as shown in Figure 5 8 b Set controls as follows VERTICAL AMPLIFIER SYNC SOURCE 5 A VOLT DIV Both Channels 01 INPUTS DISPLAY e B TIME BASE TIME DIY e sens neds 1 usec TRIGGER s aa AUTO c Switch INPUT of both channels to UP d Noise should not increase by more than 300 p volts 0 3 divisions Note It may be necessary to shield the probe to prevent noise pick up PROBE H23A A 23 Figure 5 8 Noise Test Set up 5 22 ADJUSTMENTS 9 23 The purpose of the adjustment procedure is to establish proper calibration so the instrument will per form as indicated in the specifications given in Table 1 1 Physicallocation of all adjustments is shownin 5 4 Model 1123 Figure 5 9 Recommended test equipment is listed in Table 5 1 9 24 It is recommended that the adjustment proce dure be done in the sequence given because succeed ing steps depend upon control settings and results of previous steps 5 25 When internal adjustments are made a special cover HP Part No 01123 04102 should be used to maintain proper cover to circuit capacitance and oper ating temperature Ifthe cover is not used allow the circuit to reach operating temper
31. R R R R R R R R R R R R R R R R R R R R R R R R R fxd 68 1 ohms 1 1 8w var metflm 500 ohms 30 1 2w var metflm 20k ohms 30 1 2w fxd metox 300 ohms 2 1 4w var metflm 20k ohms 30 1 2w fxd metflm 221 ohms 1 1 8w fxd metox 3 3k ohms 2 1 4w fxd metox 68k ohms 2 1 4w fxd metflm 162 ohms 1 1 8w metflm 1 5k ohm 1 1 4w fxd metox 200 ohms 2 1 2w fxd metox 470 ohms 2 1 2w eleted fxd metox 24k ohms 2 1 4w fxd metox 330 ohms 2 1 4w fxd metox 1 6k ohm 2 1 4w fxd metox 27k ohms 2 1 4w fxd metox 100k ohms 2 1 4w fxd metox 20k ohms 2 1 4w fxd metox 100k ohms 2 1 4w fxd metox 62k ohms 2 1 4w fxd metox 130k ohms 2 1 4w fxd metflm 51 1k ohms 1 1 8w fxd metflm 56 2k ohms 1 1 8w metox 62k ohms 2 1 4w fxd metox 27k ohms 2 1 4w var cer metflm 500 ohms 30 1 2w fxd metox 680 ohms 2 1 4w fxd metox 680 ohms 2 1 4w fxd metox 30 ohms 2 1 4w fxd metox 15 ohms 2 1 4w fxd metox 5 1k ohms 2 1 4w var cer metflm 5k ohms 10 1 2w fxd metflm 51 1k ohms 1 1 8w fxd metox 6 2k ohms 206 1 4w fxd metox 150k ohms 2 1 4w fxd metflm 56 2k ohms 1 1 8w var cer metflm 50k ohms 30 1 2w fxd 162k ohms 1 1 8w fxd metflm 47 5k ohms 1 1 8w fxd 75 ohms 1 1 8w fxd metflm 243 ohms 1 1 8w var cer metflm 500 ohms 30 1 2w 7 5V zener 5 14 zener 5 400 mw inch ground lead 1 2 i
32. TSO ERATING AWD SERVICE MANUAL VOLTAGE PROBE 1123A HEWLETT PACKARD e dH n ul OPERATING AND SERVICE MANUAL MODEL 1123A VOLTAGE PROBE SERIALS PREFIXED 842 See Section VII for Instruments With Other Serial Prefixes Copyright HEWLETT PACKARD COMPANY COLORADO SPRINGS DIVISION 1968 1900 GARDEN OF THE GODS ROAD COLORADO SPRINGS COLORADO U 5 PRINTED DEC 1968 D 9 02632 1 Table of Contents Model 1123A TABLE OF CONTENTS Section Title Page Section Title Page I GENERAL INFORMA TION 1 1 V PERFORMANCE CHECK AND 1 1 Introduction 77 tcc 777 1 1 ADJUSTMENTS cc t tt t t es 5 1 1 5 Warranty S 4 99 ea we 1 1 5 1 Introduction rt te ee 5 1 1 7 Accessories Supplied 1 1 5 3 Test Equipment 5 1 1 9 Instrument Identification 1 1 5 5 Simplified Performance Check 5 1 1 11 Scope of Manual 9999998 1 1 5 7 Performance Check 4 4 5 1 5 11 Preliminary Set up 9999 5 1 INSTALLATION 99988996 2 1 5 13 Input Balance Check 9999 5 1 9 1 General 9 1 5 14 DC Offset Check 5 1 2 3 Initial Inspection 2 1 5 15 Gain Check 9 5 1 2 4 Mechanical Check 77 2 1 5 16 Sine Wave Compression 2 6 Electrical Check 2 1 Check 9 2 2 8 Claims 888898680 2 1 5 17 Pulse Compression Check 9 2 2 10 Repack
33. UIT BOARDS 8 24 Printed circuit boards in this instrument have components mounted on one side conductive surfaces on both sides and plated through component mounting holes Hewlett Packard Service Note M 20E contains useful infor mation on servicing and repair of printed circuit boards Some important considerations are as follows a Usea 37 to 47 5 watt chisel tip soldering iron with a tip diameter of 1 16 to 1 8 inch and a small diameter rosin core solder b Components may be removed by placing the soldering iron component leads on either side of the board If heat is applied to the component side of the board greater care is required so as not to damage components Extreme careis requiredtoavoid damage tosemiconductor devices Damage may be minimized by gripping component lead between soldering iron and the component using a pair of long nose pliers c If a component is obviously damaged or faulty clip the leads close to the component then unsolder the leads from the board d Large components such as potentiometers may be removed by rotating the iron from one leadto another while gently applying pressure to lift the com ponent from the board e Excessive heat or force will destroy the lami nate bond between the metal plated surface and the board this should occur the lifted conductor may be cemented down with a small amount of quick drying acetate base cement having good insulating properties If this r
34. aging for Shipment 2 1 9 18 Input Capacitance Check 9 3 2 13 Installation 9999998888 2 1 9 19 Pulse Response Check 9 3 9 20 Bandwidth Check s 7 9 3 OPERATION 3 1 5 21 Noise Check c 5 4 3 1 General 3 1 5 22 Adjustments 5 4 3 3 Connectors and Accessories 3 1 5 26 Preliminary Set up 5 4 3 5 Output Connector 3 1 5 28 Input Balance Adjust 5 4 8 1 Blocking Capacitor Tips 3 1 5 29 DC Offset Adjust 5 4 3 9 Divider Tips 3 1 9 30 Gain Adjustment 2 t c 5 4 3 13 Accessories c tct t t t ew 3 1 5 31 Pulse Response Adjustment 5 5 3 16 Operating Procedures 99999 3 1 IV PRINCIPLES OF OPERATION 4 1 VI REPLACEABLE PARTS 6 1 4 1 Introduction 4 1 6 1 Introduction r s sos s 6 1 4 3 Simplified Circuit Theory 4 1 6 4 Ordering Information 896 6 1 4 5 Attenuator Probe c 77 4 1 ae uo MANUAL CHANGES AND OPTIONS 7 1 4 11 Constant Voltage Source 4 1 7 1 M 7 1 4 14 Constant Current Source 4 2 7 Po c NND MES 1 3 Older Instruments 57 7 757777 1 1 FS 2 a 7 5 Newer Instruments 7 727777 7 1 4 20 Differential Amplifier 4 2 7 7 e Ex pus 7 4 24 Functional Description 4 3 1 a ou i hn 4 28 Detailed Theory of Operation
35. ance with the other DIFFERENTIAL OUTPUT 123A A 6 Figure 4 6 Differential Amplifier 4 22 With zero volts no signal applied to the inputs thecurrent through R2 divides equally through Q1 and Q2 Considering either transistor as a separate amplifier it can be seen that when the base of Q2 for example is at zero volts the current flowing through the forward biased emitter base junction clamps the top of R2at approximately 0 6 volts As long as the base of Q2 remains at zero volts a con stant current I3 will flow through R2 If the voltage applied to input goes slightly positive the current 11 through Q1 increases causing the voltage drop across R1 to increase Since R2 is a constant cur rent source when 11 increases 12 must decrease thereby decreasingthe voltage drop across R3 When the input voltage at input goes in a negative direc tion the opposite will happen i e I decreases and I2 increases causing the voltage across R1 and R3 to change in opposite directions These voltage changes are 180 out of phase therefore the output signal generated between points C and D is differential 4 23 Normally input A accepts the signal voltage and input B is the reference or ground signal Oc casionally long leads are required to connect one instrumentto another Consequently noise or 60 Hz pickup is often induced on the signal leads The differential amplifier only amplifies the difference 02632 1 S
36. ature then remove the cover and make the required adjustment Replace the cover and wait for circuit to reach operating tem perature again before checking the results of the ad justment 5 26 PRELIMINARY SET UP 5 27 Connect the HP Model 1123 to power source and allow a five minute warm up 5 28 INPUT BALANCE ADJUST a Connect the Voltmeter to the probe tip pin b Connect the Voltmeter ground lead to probe ground c SetInput Balance Adjust A2R32 for 0 volts 1 mV 5 29 DC OFFSET ADJUST a Connect a Tee connector and 50 ohm load to output BNC b Connecta Voltmeter to the center conductor of the Tee connector c Connect the Voltmeter ground lead to probe ground d Adjust A2R38 fully cw then fully ccw making sure adjustment range is greater than 0 5 volts to 0 5 volts e Set A2R38 for a reading of 0 volts 5 mV 5 30 GAIN ADJUSTMENT a Connect equipment as shown in Figure 5 1 b Set controls as follows SQUARE WAVE GENERATOR FREQUENCY omo 4 4 100 AMPLITUDE Set for 8 div display VERTICAL AMPLIFIER VOLTS DIV 02 DISPLAY 9 0 ALT COUPLING o9 e omae x 88805 8 DC TIME BASE t e eae 2 msec TRIGGER c Adjust A2R43 square wave output of probe is the same amplitude as input to the probe d Reset TIME DIV switch to 5 msec and adjust A2R5 to make
37. d by approximately 3 pF Increases input dynamic range to 5 V and maximum input voltage to 350 V peak ac Divider accuracy 5 MODEL 10215 100 1 DIVIDER Increases input impedance to 1 megohm shunted by approximately 3 pF Increases input dynamic range to 50 V and maximum input voltage to 500 V de peak ac Divider accuracy 4970 MODEL 10217A BLOCKING CAPACITOR Provides 0 001 uf ac coupling with lower cut off of 1 6 kHz or 160 Hz when using divider Adds less than 3 pF shunt capacitance maximum input voltage 50 V de peak or 200 V dc peak ac when using divider MODEL 10228A BLOCKING CAPACITOR Provides 0 18 ac coupling with lower cut off of 12 Hz or 1 2 Hz when using divider Adds less than 25 pF shunt capacitance maximum input volt age 50 V peak 200 V dc peak ac when using divider MODEL 10229A HOOK TIP May be used for circuit probing directly or with di viders and blocking capacitors 02632 1 aie e ee 8 ue Model 1123A section I Paragraphs 1 1 to 1 12 SECTION 1 GENERAL INFORMATION 1 1 INTRODUCTION 1 2 The HP Model 1123A Voltage Probe is shown in Figure 1 1 The probe provides low input capacitance high input impedance high current gain and wide bandpass Itis designed to operate with oscilloscopes or other measuring devices having 50 ohm inputs however when used with a 50 ohm feed through ter mination it
38. ection IV Paragraphs 4 22 to 4 33 between the two inputs therefore the undesirable common mode signal is rejected 4 24 FUNCTIONAL DESCRIPTION 4 25 Figure4 7 is a functional block diagram which shows the major stages of the Model 1123A Voltage Probe The high impedance and low capacitive input provides minimum loadingto circuits being examined The Impedance Converter functions basically as de scribedabove and provides the high to low impedance conversion The incoming signal is then applied to a Differential Amplifier which provides impedance matching to drive the 100 ohm coaxial cable keep signal losses to a minimum a Constant Current Source and Constant Voltage Source are used to supply power to part of the probe and amplifier circuitry 4 26 The incoming signal from the probe assembly is applied to an Intermediate Amplifier whose input impedance is matched to the cable An Output Amp lifier provides current gain and impedance matching to drive a 50 ohm load 4 27 To maintain low dc driftinthe probe assembly several amplifier stages are used in a closed loop feedback configuration The output of A2Q4 is summed with an amplified and inverted input at the Error Amplifier Any resulting offset is amplified and fed back to the probe This feedback signal controls the dc levelof the Differential Amplifier in the probe and causes the output to increase or decrease until the offsetatthe Error Amplifier is zero When the err
39. epair cannot be accomplished a section of good conducting wire may be soldered along the dam aged area f DBeforereplacinga component heat the remain ing solder in the component hole and clean it out with atoothpick or similar object Sharp pointed metallic toolsare not recommended because they may damage the plated through surface of the hole g Tin and shape leads of replacement component to fit existing holes h Install components in the same position as the original component refer to Paragraph 8 20 je Whenremovingor replacing square pin connec tings be sureto pull straight up for removal and re placement These connections can loosen and cause poor contact 02632 1 Model 1123 Figure 8 2 7 C6 RIO os 3 G er x M 8 1233 1 Figure 8 2 Component Identification Assy 1 02632 1 8 3 Section VIII Figure 8 3 and Table 8 2 WAVEFORMS The test point waveform as given in figures preced ing the schematic diagram were taken under the following conditions MODEL 180A AR TEST OSCILLOSCOPE 02 V DIV Ny 2 5 5K HZ INPUT 2005 v DIV 2 MSEC Table 8 2 Waveform and DC Voltage Measurement Conditions DISPLAY INT MAGNIFIER X1 HORIZON TAL PLUG IN TRIGGERING INT SLOPE SWEEP MODE AUTO VERTICAL PLUG IN Polarity UP DISPLAY A INPUT AC Model 1123A
40. es 7 1 8 1 Schematic Symbols and Conventions 8 0 8 2 Waveforms and DC Voltage Measurement Conditions s s e s s soss rrt t 8 4 02632 1 iii m Section I Model 1123A Table 1 1 Table 1 1 Specifications BANDWIDTH DC to greater than 220 MHz 3 dB down PULSE RESPONSE RISETIME Less than 1 6 ns 10 to 90 over full dynamic range OVERSHOOT RINGING PERTURBATIONS 4 pk pk with Model 1802A dc to 100 MHZ 6 pk pk with 1 GHz system probe must be properly terminated in 50 ohms GAIN Adjustable to X1 into 50 ohm load DYNAMIC RANGE OUTPUT 0 5 V peak INPUT 0 5 peak around reference voltage which can be offset with variable control from 0 to 0 5 Vdc NOISE Increases noise level by less than 300 uV pk pk when used with Model 1802A dc to 100 MHz DRIFT PROBE TIP ASSEMBLY Less than 100 p V AMPLIFIER ASSEMBLY Less than 1 mV INPUT IMPEDANCE 100k ohms shunted by approximately 3 5 pF OUTPUT IMPEDANCE 50 ohms MAXIMUM INPUT 50 V peak ac GENERAL WEIGHT Net 2 1 4 pounds 1 0 kg shipping 4 1 4 pounds 1 9 kg 1 0 POWER Supplied by Model 1802A plug in HP Model 1122A Power Supply may be used to power up to four Model 1123A Active Probes LENGTH Over all length is approximately 4 1 2 feet ACCESSORIES FURNISHED MODEL 10214 10 1 DIVIDER Increases input impedance to 1 megohm shunte
41. esonance at the divider input and output Capacitor C3 represents the stray capacitance present within the assembly 02632 1 Figure 1 Model 10214A 10 1 Divider 9 MAINTENANCE 10 The only maintenance recommended for the Model 10214 is to run a performance check if a malfunction is suspected and to adjust the capacity of C1 11 PERFORMANCE CHECK 12 Perform the following checkout procedure as an acceptance check or if a malfunction in the divider is suspected Test equipment required for the perform ance check is listed in Table 2 a Set Pulse Generator controls as follows REP RATE we odes 4 100 1M VERNIER Set to 500 kHz output PULSE DELAY and VERNIER as required PULSE WIDTH 5 5 VERNIER Set for exactly 1 usec output PULSE POLARITY gt s PULSE AMPLITUDE 1 VERNIER Set for 1 volt output SAMPLING C PROBE 10214 1 Figure 2 Model 10214 Divider Schematic Diagram Appendix I Model 1123A Table 2 Test Equipment RECOMMENDED INSTRUMENT TYPE Pulse HP 222A Generator Sampling HP 1425A Oscilloscope 1410A 50 ohm Tee HP10221A 50 ohm Load 874 W50 b Set Oscilloscope controls as follows Function Selector ssaa CHANNEL A 100 mv cm VERNIER CALIBRATED SMOOTHING NORMAL optimized SCANNING
42. feedback signalis connected to the base of A1Q4 Be causethis signal has increased in a positive direction it causes increased conduction A1Q4 Due to the differential connection of A1Q3 Q4 current in A1Q3 decreases Due to the decrease 103 collector current the collector voltage increases Transistor A2Q1invertsthis signal causing it to go less positive Consequently the output at A2Q4 goes negative bringing the signal back into balance at the summing point 4 54 It should be understood that this feedback amp lifier circuitry forms a closed loop around the probe amplifier and that operation is instantaneous When properly adjusted the instrument will track from in put to output providing a 1 1 dc output to any 50 ohm load The dc temperature drift characteristics are determinedby the feedback amplifier The only com ponent affecting temperature drift in the probe tip assembly is AiR2 In the amplifier assembly drift determined by A2Q8A B and A2Q11A B which are matched pairs Therefore there is almost no dc drift due to temperature changes 4 55 DC GAIN AND OFFSET ADJUSTMENT 4 56 Potentiometer 2638 and A2R41 apply a dc input signal to the feedback system which can be ad justedfor the desired dc output level If it is desired tolookataninput signal 0 volts to 1 volts the probe output can be adjustedto 0 5 volts thus when the in put signal goes to 1 volt the output goes to 0 5 volts In this manner
43. ference designators and abbreviations 6 3 Parts not identified by a reference designation are listed in Table 6 2 under miscellaneous 6 4 ORDERING INFORMATION 6 5 To order replacement parts from Hewlett Packard Company address the order or inquiry to the nearest HP Sales Service Office list at rear of manual and supply the following information Table a HP Part Number of item s b Modelnumber and eight digit serial number of instrument Quantity of parts required 6 6 To order a part not listed in the table provide the following information a Modelnumber and eight digit s rial number of instrument b Description of part including function and loca tion 6 7 Component descriptions given in Table 6 2 are as complete as possible to assist in obtaining replace ment parts from manufacturers other than HP How ever many parts are manufactured only by HP or are produced by other manufacturerstoHP proprietary specifications and are therefore available only from HP Actual manufacturer and manufacturers part number for non HP parts will be supplied upon request Contact the nearest HP Sales Service Office 6 1 Reference Designators And Abbreviations REFERENCE DESIGNATORS fuse filter hardware integrated circuit jack relay inductor Speaker assembly motor gt capacitor coupling diode delay line device signaling lamp misc electronic part 4o d How d M
44. gure 5 9 Troubleshooting information component andassembly locations and schematic diagrams are located in Section 5 3 TEST EQUIPMENT 5 4 Test equipment neededtocheck and maintain instrument is listedin Table 5 1 Similar or equiva lent test equipment may be usedif necessary Due to the unique design of this instrument some of the test equipment required is not commercially available Steps are given the performance check and adjust ment procedure to build the test fixture necessary to accomplishthe procedure When making adjustments a non metallic screwdriver or alignment tool should be used 5 5 SIMPLIFIED PERFORMANCE CHECK 9 6 A simplified performance check consisting of selected checks within the over all procedure is recommended as a quick check to ensure that the in strument is operating properly To accomplish the quick check steps 5 13 thru 5 15 and 5 19 should be performed If a thorough performance check is re quired allstepsin the procedure must be performed 5 7 PERFORMANCE CHECK 5 8 The purpose of this performance check is to de termine whether or not the instrument is operating within its listed specifications This check may be usedas part of an incoming quality control inspection aperiodic operational check or to check the calibra tion after repair and or adjustments are made 5 9 Enter the readings of the initial performance check on the Performance Check Record on Page 5 7
45. he probe 3 9 DIVIDER TIPS 3 10 900 ohm resistor inseries with the input pro duces a 10 1 attenuation in the Model 10214 Divider 02632 1 Tip since the input resistance of the probe is 100 ohms This tip contains a parallel capacitor for com pensation 3 11 The Model 10215A Divider Tip produces 100 1 attenuation and contains a manual compensation ad justment For theory of operation refer to Simpli fied Circuit Theory in Section IV 3 12 When divider tips are used in conjunction with the probe maximum input voltage is increased with each divider With the Model 10214A the maximum input voltage is 350V and with the Model 10215A it is 500V 3 13 ACCESSORIES 3 14 Allprobe adapter tips are designed to fit snuggly over the end of the Voltage Probe Combinations can be used to produce a desired result e g both a di vider tip and dc blocking tip can be used together When used together however the blocking capacitor must be used in front of the divider tip The hook tip can also be used with any of these combinations 3 15 The Model 1122A Power Supply produces suffi cient power to operate four HP Model 1123A Voltage Probes Byusingthis supply it is possible to operate uptofour active probes at remote locations Connect a 50 ohm coaxial cable from the oscilloscope input to the remote Voltage Probe andturn onthe power supply 3 16 OPERATING PROCEDURES 3 17 To familiarize the operator with the
46. he sampling probe from dc potentials present in the test circuit Specifications for the Model 10217A are listed in Table 1 3 CONNECTIONS 4 The Model 10217A is connected to the sampling probe by sliding the probe into the body portion of the blocking capacitor 5 USE WITH OTHER ACCESSORIES 6 The Model 10217A is used withthe sampling probe as described above It may also be used with the Model 10214A 10 1 Divider and the Model 10216A Isolator Table 1 Specifications CAPACITANCE 0 001 UF MAXIMUM INPUT VOLTAGE 50 Vdc 50V pk to pk ac x200V whenusedwith 10 1 Divider SAG 1 on 1 usec pulse 0 1 1 usec when Model 10214A 10 1 Divider is used SHUNT CAPACITANCE Less than 3 0 pF 7 CIRCUITS 8 The schematic of the Model 10217A is shown in Figure 2 The blocking capacitor is 0 001 low inductance capacitor which is used to keep dc poten tials inthe circuitundertest from reachingthe vertical amplifier Itis capable of blocking 100 volts dc from SAMPLING PROBE IOOK T 2 217 BLOCKING CAPACITOR 10217 1 Figure2 Modeli1021 7A Blocking Capacitor Schematic 02632 1 Figure 1 Model 10217A Blocking Capacitor ground Inductor 11 providedto damp any resonances that may be developed in the circuit and capacitor C2 represents the stray input capacitance present within the assembly 9 MAINTENANCE 10 Theonly maintenance recommended for the
47. ight digit serial number and a description of service required 2 12 The original shipping carton may beused any accordion pleated pads If original carton and packaging material are not available the follow ing materials should be used a A double walled carton refer to Table 2 1 for test strengths required Table 2 1 Shipping Carton Test Strengths Gross Weight 108 Carton Test Strength 105 Up to 10 10 to 30 30 to 120 120 to 140 140 to 160 b Heavy paper or sheets of cardboard to protect all instrument surfaces use a non abrasive material such as polyurethane or cushioned paper around all projecting parts c Atleast 4 inches of tightly packed industry ap proved shock absorbing material such as an extra firm polyurethane foam d Heavy duty shipping tape to secure outside of the carton 2 13 INSTALLATION 2 14 The Model 1123A Voltage Probe should be con nected as shown in Section III There are two nectors to attach a BNC at the input of the Vertical Amplifier plug in anda power connector for operating voltages Before use do the performance check in Section V to insure that the instrument is operating according to the specifications given in Table 1 1 2 1 Section III Figure 3 1 3 0 X2 IR Ko SER ka Power Connector Three pin connector accepts 15 volts 12 6 volts and power supply com mon Output Connect
48. ion pictorials troubleshooting infor mation and repair and replacement procedures 8 3 SCHEMATIC DIAGRAMS 8 4 Schematic diagrams appear on right hand pages that unfold outside the right edge of the manual These throw clear pages allow viewing the schematics while referring to another section can be fol lowed by unfolding the appropriate throw clear page 8 5 Schematics are drawn primarily to show the electronic function of an instrument A given sche matic may include all or part of several assemblies Schematics also include voltages and waveform measurement test points Waveforms applicable to each schematic are shown opposite that schematic DC voltage and waveform measurement conditions are shown in Table 8 2 Information about symbols and conventions used in these schematics is provided by Table 8 1 8 6 COMPONENT IDENTIFICATION 8 7 Chassis mounted parts not on an assembly are shown on a fold out page Assembly mounted compo nents are shown on page opposite the schematic When anassembly appears on more than one schematic all components are identified opposite the schematic on which the assembly first appears 8 8 REFERENCE DESIGNATION 8 9 The unit system of reference designation used inthis manual is in accordance with the provisions of the American Standard Electrical and Electronics Reference Designations Minor variations due to de COMPLETE INSTRUMENT AI ASSEMBLY signand
49. leading edges of the square waves identi cal e Change Square Wave Generator FREQUENCY to 1 kHz and Time Base Plug in TIME DIV to 50 sec 02632 1 Model 1123 f Adjust A2R8 for same flatness and shape of both Square waves Section V Paragraph 5 31 c Make appropriate adjustments as listed in Table 5 2 to obtain optimum risetime and pulse re g Change Square Wave Generator frequency to sponse 20 kHz and Time Base Plug in TIME DIV to 5 usec h Adjust A2R10 for same flatness andshape of both square waves Note Because of adjustment interaction it may be necessary to repeat the proce i In each condition above amplitudes of both FRU square waves should differ by less than 1 4 4 minor divisions 5 31 PULSE RESPONSE ADJUSTMENT a Connectthe equipment as shown in Figure 5 6 Table 5 2 Pulse Response Adjustments Adjusts b Set controls as follows SAMPLING TIME BASE oo TIME DIV f d ook ow wo 10 nsec Level of top MAGNIFIER 8 c a X1 MODE 6 soos AUTO First peak SYNC PULSE SCANNING 9 s NORMAL Level of top SAMPLING VERTICAL AMPLIFIER VOLTS DIV e eee eee 50 mV VERNIER s Set for 10 cm display d Risetime should be less than 1 6 nsec PULSE GENERA TOR e Overshoot and ringing should be less than 3 TRIGGER 1 5 minor divisions OUTPUT n n e t g t n n 4
50. n and Zero Adjustment 3 2 9 2 DC Blocking Assembly Schematic 5 2 3 3 Remote Operation 4 4 4 4 3 3 9 3 Compression Test Set up r sr 5 2 3 4 High Impedance Loads 3 4 2 4 Pulse Compression Test Set up 9 2 3 5 100 1 Divider Compensation 3 5 5 5 Input Capacitance Test Set up 9 3 3 6 Model 1123 used as Buffer Amplifier 9 6 Pulse Response Test Set up 5 3 for Sync or Trigger Signals 5 7 3 6 5 7 Bandwidth Test Set up sa 5 4 3 7 Using DC Offset s e ss sssaaa 3 7 2 8 Noise Test Set up 9894 9954 5 4 5 9 Adjustment Location 257 5 5 5 6 4 1 Attenuator 100 1 4 1 8 1 Unit System Reference Designation 8 1 4 2 Impedance Converter s s s c s 7 4 1 8 2 Component Identification Assy A1 8 3 4 3 Constant Voltage Source 4 2 8 3 Model 1123A Waveforms 8 4 4 4 Constant Current Source 5559 4 2 8 4 Component Identification Assy A2 8 5 4 5 Miller Effect ee st tes 4 2 8 5 Model 1123A Schematic Diagram 8 5 LIST OF TABLES Table Title Page 1 1 Specifications f n ot g gt n nn 1 0 2 1 Shipping Carton Test Strength e saa 2 1 5 1 Required Test Equipment s s s s s s sea 5 0 9 4 Pulse Response Adjustments ss esa 5 5 6 1 Reference Designators and Abbreviations 6 1 6 2 Replaceable Parts 6 2 7 1 Manual Chang
51. nch ground lead 1 2 foot coax inch 3 conductor 6 3 Section VI Model 1123A Table 6 2 Table 6 2 Replaceable Parts Cont d Ref aes Description HP Part MISCELLANEOUS 1205 0010 01123 04101 1251 2229 01123 26101 01123 63201 1251 2088 Heat sink Cover Socket Pin Connector Assy output Plug Power a 5 OT 4 02632 1 4 1 1123 Section Paragraphs 7 1 to 7 10 SECTION VII MANUAL CHANGES AND OPTIONS 7 1 MANUAL CHANGES 7 2 This manual applies directly to standard Model 1123A Voltage Probe having a serial number prefixed by 842 referto Paragraph 1 9 The following para graphs provide instructions for modifying this manual to cover older lower serial prefix or newer higher serial prefix instruments Refer to the separate Manual Changes sheet supplied with this manual for Errata 7 3 OLDER INSTRUMENTS 7 4 Table 7 1 contains information on changes quired to adapt this manual to an older instrument lower serial prefix Check Table 7 1 for your in strument serial prefix and makethe changes indicat ed Notethatthese changes adapt the manual to cover a particular instrument as manufactured and there fore will not applytoaninstrument subsequently mod ified in the field 7 5 NEWER INSTRUMENTS 7 6 changes are made to the Model 1123A Volt age Probe newer instruments may have serial prefixes higher than 842 The manual fo
52. ncies and L2 peaking high frequencies 4 4 Model 1123A 4 41 INTERMEDIATE AMPLIFIER GAIN 4 42 determine Intermediate Amplifier gain the total emitter resistance inthe circuit of A2Q1 is equal to the sum of resistors R5 R6 and the internal re sistance of Q1 totaling approximately 90 ohms for all three Collector load resistance is equal to equivalent of A2R11 in parallel with A2R 15 approxi mately 200 ohms Therefore the low frequency gain of 201 is about 2 2 Potentiometer A2R5 provides low frequency gain adjustment Capacitor A2C9 is a temperature compensated capacitor with a large negative temperature coefficient which isusedto com pensate for the inherent negative temperature coef ficient of transistor high frequency response in all stages 4 43 CONSTANT VOLTAGE SOURCE 4 44 constant voltage source comprised of A2Q2 and A2Q3 furnishes a stable voltage level to the emitter network of 201 Zener regulator VR1 temperature compensated by CR1 produces a fixed voltage drop therefore the resulting level at the base of A2Q2 remains constant The majority of current through the diode network supplies probe circuitry Due to the differential amplifier A1Q3 Q4 used in the probe the current through CR1 and VR1 is relatively constant Transistor A2Q3 provides feedback around A2Q2 thus lowering the output im pedance of Q2 making it a more effective voltage source 4 45 TEMPERATURE COMPENSATION
53. nd low frequency gain By using this type of feedback amplifier dc drift in the probe tip assembly is almost completely eliminated 4 51 Tounderstand how the feedback system operates assume an input of 0 5 volts at the probe tip From previously established gain assume a 1 volt output at the emitter of A2Q4 The 0 5 volt input produces a10 microamp current flow through A1R2 to the base of A2Q11 Differential Feedback Amplifier A2Q10 Q11 provides gain of 0 5 which results in 0 25 volts at the emitter of A2Q10 The gain of this amp lifier is set by the ratio of the feedback resistor A2R28 to the input resistor AIR2 Input Balance Adjust A2R32 isadjusted during calibrationto insure zero volts at the base of A2Q11 and at the probe tip with no signal applied 4 52 With 0 25 volts at the bottom of A2R39 and 1 volt at the top of A2R44 the input to the Error Amplifier the base of A2Q8 should see a null zero volts at the summing point If no error is present at the base of A2Q8B the feedback signal does not change The Differential Input Amplifier A1Q3 Q4 is not affected and the output remains constant 4 53 If the output at the emitter of A2Q4 were slightly more positive than 1 volt the summing point would go slightly positive increasing the forward bias on A2Q8B The resulting small decrease in collector voltage on A2Q8B is coupled to the base of 206 After amplification and inversion by A2Q5 Q6 the 02632 1
54. nus position Observe the signal amplitude in each case 9 2 Model 1123A 6206A I80A EFFI T IO CABLE N DC BLOCKING ASSEMBLY __ 10 CABLE 1123A SPECIAL m 500 LOAD iN 11 41 5001 LOAD 15 GR TO 777 50A TEE 123A A 20 Figure 5 3 Compression Test Set up g Change Oscillator frequency to 200 kHz and Sweep Time to 2 usec div h Repeat steps d thru f i Ineachofthe above cases the signal compres sion should be less than 8 signal amplitude should be greater than 7 4 divisions 17 PULSE COMPRESSION CHECK a Connect the equipment as shown in Figure 5 4 b Set controls as follows SAMPLING VERTICAL AMPLIFIER VOLTS CM 10 mV VERNIER adjust for 10 cm display 140A BANANA TO BANANA II22A DC BLOCKING 1 POWER CABLE 5 a GR 2 10 a O CABLE EHE pe GR TO BNC 50 LOAD 50 TEE 500 TEE h 501 LOAD 4 3 TO BNC GR 2138 BNC 123534 19 Figure 5 4 Pulse Compression Test Set up 02632 1 Model 1123 SAMPLING TIME BASE SWEEP TIME 9 coc 10 ns LEVEL MODE FREE RUN SCANNING e se ees NORMAL SYNC PULSE ss s ee sees ON PULSE
55. o which the divider is connected Since the divider maintains a constant output impedance it can be used in point to point circuit probing without experiencing a base line shift or requiring response adjustments on the oscilloscope Specifications for the Model 10214 are listed in Table 1 3 CONNECTIONS 4 The Model 10214 is connectedtothe probe of the sampling system by sliding the probe into the body portion of the divider 5 USE WITH OTHER ACCESSORIES 6 If the circuit to be probed contains de potentials HP Model 10217A Blocking Capacitor must be used in conjunction with the Model 10214A Table 1 Specifications ATTENUATION 10 1 595 over bandpass of the sampling system INPUT IMPEDANCE 1megohm shunted by 2 5pF EFFECT ON RISETIME OF SYSTEM Negligible MAXIMUM INPUT VOLTAGE 350 20V pk to pk ac 7 CIRCUITS 8 The schematic of the Model 10214A is shown in Figure 2 The major components of the divider are resistor and a metal sleeve which is spring load to hold R1 in place The capacitance of is the capacitance between R1 and the metal sleeve C2 is the capacitance between the metal sleeve and the di vider body The capacitance of C1 determines the the high frequency division ratio of the divider At low frequencies the division ratio is accomplished between and the 100k ohm resistance of the sam pling system probe Resistor R2 and inductor L1 critically damp r
56. onstant current source must be available The source bias current in a FET must be held con stant to minimize parameter variations circuit shown in Figure 4 4 will provide this constant cur rent VARIABLE 2 RESISTANCE 2 4 Figure 4 4 Constant Current Source 4 16 Voltage divider R1 R2 establishes a voltage at the base of Q1 which provides forward bias to the transistor The inherent 0 6 volt drop across the 4 2 Model 1123A emitter base junction results in a constant voltage at the emitter of Ql As shown in Figure 4 4 the values used will produce a voltage drop of 4 4 volts across resistor R3 Simple calculations show that there is a constant current in the collector circuit ofapproximately 88 milliamps This current remains constant regardless of changes in the load resistance as long as Q1 does not become saturated 4 17 MILLER EFFECT 4 18 The Miller Effect in an amplifier results from the transistor interelement capacitance between base and collector Figure 4 5 is a simple common emitter amplifier with Miller Capacitance C1 shown in dotted lines Miller capacitance is detrimental in wide bandhigh frequency circuits having high voltage gain since its effects are amplified by the gain of the stage Amplificationof the effects of C1 is due to the out of phase and amplified signal at the collector of Ql This amplified signal causes more current to be drawn from the base
57. or Connector furnishes output signal from a 50 ohm source impedance Amplifier Provides current gain to drive 50 ohm loads e g the Model 1802A Dual Channel Vertical Amplifier Zero Adjustment Adjusts bias on probe cir cuitry to set dc offset at amplifier output Voltage Probe Performs highto low impedance conversion and supplies sufficient power gain to drive the Amplifier Designed to operate with inputs of 5 volts at the tip Ground Clip lead Used to connect signal com mon to amplifier common Figure 3 1 H23A VOLTAGE PROBE Ey 2 br 185 upt iatan 10 11 12 Model 1123A 123 7 Hook Tip Allows operator to connect probe to component leads or wires while leaving his hands free for making adjustments etc Model 10217A Blocking Capacitor Tip For use when examining a high frequency signal which has a large dc offset Model 10214A Divider Tip 10 1 Used to in crease dynamic range of probe system by pro ducing a 10 1 attenuation to the signal Model 10215A Divider Tip 100 1 Performs same function as 9 above except attenuates 100 1 Model 10228A Blocking Capacitor Tip For use when examining low frequency signals which have a large dc offset Model 1122A Power Supply optional Furnishes 15 volts and 12 6 volts to power four Model 1123A Voltage Probes Model 1123A Voltage Probe and Accessories 02632 1 Model
58. or is zero the dc output voltage at connector P1 is correct 4 28 DETAILED THEORY OF OPERATION 4 29 The overall function of the Probe having been discussedinthe preceeding paragraphs the following paragraphs now provide a stage by stage detailed description of the entire Probe circuit Refer to the schematic diagram Figure 8 1 in conjunction with the foliowing text 4 30 SOURCE FOLLOWER 4 31 To insure minimum loading to the circuit being tested source follower 101 is used immediately following the probe tip due to its input impedance characteristics Resistor 1 2 across the input per forms two functions 1 it establishes a fixed 100k ohm input resistance for the probe and 2 fixes the gate bias on 101 when no signal is present at the input Resistor 1 1 furnishes overload protection up to 50 volts by limiting the gate current of A1Q1 High frequency response is maintained by 1 1 Re sistor 1 is used as a damping resistor to mini mize the effects of lead inductance 4 32 CONSTANT CURRENT SOURCE 4 33 Source Follower A1Q1 is biased by Con stant Current Source A2Q9 Resistor values in the base andemitter circuits of A2Q9 establisha constant current of 5 milliamps to bias the source follower 4 3 Model 1123A low driftusinga FET source follower unless a matched pair is used or the drain bias current supply is vari able feedback amplifier is used to establish the dc output level a
59. or Probe 100 1 4 7 100 1 attenuation ratio of R1 to R2 in parallel with the load must be 100 1 Since R1 is 900K and equivalent to R2 and is approximately 9K the dc ratio is correct For high frequencies however the load impedance at the di vider output varies due to the load capacitance which is the input capacitance of the probe To min imize the effects of Cy which might be 2 to 3 pico farads a large capacitor C2 is added across the output This large capacitance performs two functions 1 it minimizes the effects of load capacitance and 2 with C1 it comprises a capacitive divider which providesa 100 1attenuationathigh frequencies Var iable capacitor C1 is added in parallel with R1 to 02632 1 provide compensation To keep the impedance ratio equal to 100 1 at high frequencies C1 and C2 should be adjusted to the same ratio as R1 R2 4 8 IMPEDANCE CONVERTER 4 9 Although there are several methods of accomp lishing impedance conversion the circuit shown in Figure 4 2 has been chosen due to its frequent usage in HP instruments reduce loading of cir cuits being tested high impedance inputs are used The field effect transistor FET provides this high input impedance similar to a vacuum tube HIGH Z INPUT LOW Z OUTPUT Figure 4 2 Impedance Converter 4 10 Source follower 01 coupled with emitter fol lower Q2 produces a high to low impedance
60. r these instruments Table 7 1 Manual Changes Instrument Serial Prefix Incorporate Change s Number Numbered 02632 1 willbe supplied with a Manual Changes sheet which contains the required updating information If the change sheet is missing contact the nearest HP Sales Service Office 7 7 OPTIONS 1 8 Optionsfor an HP instrument are standard mod ifications to standard instrument andare installed at the factory At the presnet time no options are offered for the Model 1123A Voltage Probe 7 9 SPECIAL INSTRUMENTS 7 10 Modifiedversions per customer specifications of any HP instrument are available on special order The manual for these special instruments having electrical modifications includes a separate insert sheet which describes the modifications and any changes requiredin addition to any Manual Changes sheet refer to Paragraph 7 6 Contact the nearest HP Sales Service Office if either of these sheets are missing from the manual for a special instrument being suretorefer to the instrument by its full speci fication number and name CHANGE 1 Table 6 2 Page 6 2 Al Change to HP Part No 01123 66501 Page 8 5 Figure 8 5 A1R 14 Delete 1 9 Delete 1 1 Section VIII Model 1123A Table 8 1 Table 8 1 Schematic Symbols and Conventions Refer to MIL STD 15 1A for schematic symbols not listed in this table Etched circuit board Field effect transistor
61. re 3 Test Set up Model 1123A b Make test set up as shown in Figure 3 c Adjust VERNIER for 8 division vertical display d InsertModel 10215 between probe and 50 ohm tee e Switch AMPLITUDE control on Square Wave Generator to 5 f Deflection should be within 0 4 divisions 5 of full 8 divisions 13 ADJUSTMENT PROCEDURE 14 Thefollowing procedure contains steps to adjust the divider compensation a Use test set up as shown in Figure 3 b Holdfrontportionof divider and loosen locking sleeve by turning ccw c Holdlocking sleeve and front portion while ad justing rear portion for optimum pulse response d Tightenlocking sleeve making sure pulse does not change 15 REPLACEABLE PARTS 16 Replaceable parts for the Model 10215A are listed in Table 3 When ordering parts be sure to include model number and HP Part Number Sales Service Office addressesare listedat the rear of this Operating Note Table 3 Replaceable Parts 10215 60701 Resistor amp Spring Assembly 10215 61501 Nut locking 10215 67701 10215 67702 5020 0457 Body Assembly Rear Body Assembly Front Probe Pin 02632 1 Model 1123 Appendix I MODEL 10217A BLOCKING CAPACITOR 1 DESCRIPTION 2 The HP Model 10217A Blocking Capacitor is a probing accessory for the HP Model 1425A 1410A oscilloscope sampling system The Model 10217A is ilustrated in Figure l The blocking capacitor is used to isolate t
62. robable in acircuit check dc voltages given schematics 8 17 WAVEFORMS 8 18 Typical waveform measurement points refer to Table 8 1 are located at strategic points along the main signal path Thenumbers inside the symbol re fer to a corresponding waveform photo Conditions for making the waveform measurements are given in Tabie 8 2 8 19 DC VOLTAGES 8 20 DC voltage levels are shown on schematic dia grams for all active components transistors mainly Conditions for making dc voltage measurements are given in Table 8 2 In locating points on printed cir cuit boards note a small dot on the board identifies the emitter lead of transistors the source lead of a field effect transistor FET the cathode lead of diodes and the positive side of electrolytic capacitors dual transistors only the tab denotes the collector leads 8 21 REPAIR AND REPLACEMENT 8 22 The following paragraphs provide procedures for replacing components and special considerations for removing components from printed circuit boards Section VI provides a detailed parts list to permit or dering of replacement parts If satisfactory repair or replacement cannot be accomplished notify the 8 2 Model 1123A nearest HP Sales Service Office addresses at rear of this manual immediately If shipment for repair is recommended see Section II of this manual for repack ing and shipping information 8 23 SERVICING PRINTED CIRC
63. s follows CHANNEL SELECTOR CHANNEL A MILLIVOLTS CM Um dE WS ES 10 SMOOTHING NORMAL POLARITY UP VERNIER For 10 cm display TIME CM 10 MAGNIFIER 1 SCANNING NORMAL SYNC PULSE ON TRIGGER w ow FREE RUN c Make connections as shown in Figure 3 d Adjust Channel A POSITION control to observe a 10 cm display e Overshoot should be less than 5 f Switch MAGNIFIER to X10 g Risetime from baseline to flat portion of pulse top should be less than 4 5 nsec 13 REPLACEABLE PARTS 14 There isonly one replaceable part for the Model 10228A whichis the probe pin HP Part No 5020 0457 For replacements contact the nearest HP Sales Service Office listed at the rear of this Operating Note Table 2 Test Equipment INSTRUMENT CHARACTERISTICS MODEL 100 psec risetime Pulse Gen HP 213B erator Sampling HP 140A 1GHz Bandwidth Oscilloscope w 1410A 1424A Test Oscilloscope HP 180A w 1801A 1821A 50 MHz Bandwidth Appendix I Model 1123A _ _ MODEL 10228 BLOCKING CAPACITOR RI CI Oel8UF 10228 1 Figure 2 Schematic Diagram 1424 TRIGGER 141 2138 PULSE OUT 1 I N BNC Ne 3 3 CABLE CABLE BNC TO N N TO GR
64. t can be ex tended by using divider tips T Loosen grooved locking nut on 100 1 adapter tip Holdback end of 100 1 attenuator and turn front 1 Perform installation and Zero adjustment as half direction necessary to produce a per shown in Figure 3 2 2 Slip the 100 1 attenuator tip on the end of the Voltage Probe 3 Connectthe ground clip lead to the Probe shank andattach to groundterminalat Calibrator output 4 Set VOL TS DIV selector to 02 9 Probe the 10 volt Calibrator output fect square wave Tighten locking nut making sure that compensa tion remains correct Note When corners contain peaks the probe tip is over compensated however if the corners are rounded off the tip is under compensated Figure 3 5 100 1 Divider Compensation 02632 1 3 5 Model 1123 Section Figure 3 7 Yl 123 8 13 Note 4 Positionhorizontaltrace center graticule line signals which are 1 volt in ampli Set INPUT switch to UP tude or small signals with 5 volts to 1 volt dc offset may be observed Mg 2 7 m without exceeding the 5 volt dy namic range of Model 1123A Signal should be 5 divisions in amplitude with its baseline 2 5 divisions below center screen 1 Toobserveasignal from 0 to 1 volt inamplitude make setup as shown in Figure 3 2 Note Output DC Level may be set from 5 2 Set INPUT switch to OFF to 5 voltsto shift
65. tentials AMPLITUDE 4 59 8 mos o on 05 an HP Model 10217A or 10228A Blocking Capacitor may be used in conjunction with the Model 10215A Whenused together however the Blocking Capacitor should be used in front of the Divider Tip 7 CIRCUITS MODEL 0215A DIVIDER 8 schematic of the Model 10215 is shown in Figure 2 The major components of the divider are resistor R1 which isused to damp lead inductance at thedivider input Resistor R1 and R2 with the 100k ohm parallelinputresistance inthe probe accomplish the divisionratioatlowfrequencies At high frequen cies the division is determined by C1 and C2 9 MAINTENANCE 10 The only maintenance recommended for the 10215A A 1 Model 10215A is to perform the performance check procedure ifa malfunction is suspected and compen sation adjustment of the divider tip Figure 2 Schematic Diagram 02632 1 JA ec Pale Rcx rr eerie rar FEE 27 m P n Appendix I Monitor Oscilloscope Vertical Amplifier DISPLAY gt gt 2 tee CHANNEL B VOLTS DIV om o9 9 o 0 4 005 COUPLING 4 3 s DC Monitor Oscilloscope Time Base TIME DIV 2 2 20 usec MODE AUTO Square Wave HP 211B Generator Monitor HP 180A w Oscilloscope 1801A 1820A OUTPUT Figu
66. the dynamic range Set VOLTS DIV to 2V at the input accordingly Figure 3 7 Using DC Offset 02632 1 3 7 1123 Section IV Paragraphs 4 1 to 4 13 SECTION IV PRINCIPLES OF OPERATION 4 1 INTRODUCTION 4 2 This sectioncontains theory of operation for the Model 1123A Voltage Probe The text is divided into three sub sections 1 Simplified Circuit Theory 2 Functional Description and 3 Detailed Theory of Operation Eachtypical circuit function is discussed once either inthe simplified theory or as it appears in the main signal path of the detailed theory The Functional Descriptionis discussed at block level for aquick overall understanding of instrument operation 4 3 SIMPLIFIED CIRCUIT THEORY 4 4 Severalcircuits inthe Model 1123A are common circuits and are discussed in their simplified forms By sodoing the detailed text is reserved for explain ingsignal flow special circuits and modifications to basic circuits Emitter followers inverting amplifi ers and other simple networks are not discussed 4 5 ATTENUATOR PROBE 4 6 Attenuator probes or probe tip adapters are used to extend the dynamic range of associated in struments Thisisaccomplished by a voltage divider in the probe or tip Figure 4 1 is an example of a typical 100 1 divider which includes compensating capacitors COMPENSATION ADJUSTMENT m whe oT 23 Figure 4 1 Attenuat
67. the response optimized during the adjust ment procedure 15 REPLACEABLE PARTS 16 There is only one replaceable part in the Model 102 14 the probe pin HP Part No 5020 0457 Con tact the nearest HP Sales Service Office for replace ments 02632 1 Model 1128 Appendix I MODEL 10215A 100 1 DIVIDER 1 DESCRIPTION 2 The HP Model 10215 100 1 Divider is signal probing accessory see Figure 1 which is designed for use with the Model 1123A Voltage Probe only The divider increases the dynamic range of the Model 1123A to 50 volts Specifications for the HP Model 10215A are listed in Table 1 Table 1 Specifications ATTENUATION 100 1 55 0 over bandpass of the HP Model 1123A Figure 1 Model 10215A INPUT IMPEDANCE 1 megohm shunted by 3 pF 11 PERFORMANCE CHECK EFFECT ON RISETIME OF 1123 Negligible MAXIMUM INPUT VOLTAGE 500 4 overload 12 Theperformance check procedure may beused 50 V peak signal with HP Model 1123 asanincoming quality assurance inspection or as an aid to troubleshooting Test equipment required to check and maintain the Model 10215A is listed in 3 CONNECTIONS 2 4 Model 10215 is connected to probe a Set controls as follows sliding the probe into the body portion of the divider Square Wave Generator 5 USE WITH OTHER ACCESSORIES FREQUENCY 55555555552 10 KHz SYMMETRY 6 If the circuittobe probed contains dc po
68. ument occurs during transit 2 3 INITIAL INSPECTION 2 4 MECHANICAL CHECK 2 5 Upon receipt of this instrument a complete visual inspectionof the shippingcarton should be per formed If there is evidence of rough handling or damage to the carton do not unpack the instrument until thecarriers agent is present Inspect the Model 1123A for damage such as bent or broken parts If damage is found refer to Paragraph 2 8 for recom mended claims procedure If no physical damage is apparent perform the electrical checks in Section V Retain all packaging material for possible future use 2 6 ELECTRICAL CHECK 2 7 This check will determine if the instrument is stilloperating within the specifications listed in Table 1 1 The performance and accuracy are certified as stated inthe warranty on the inside frontcover of this manual If the instrument does not operate as spec ified refer to Paragraph 2 8for recommended claim procedure 2 8 CLAIMS 2 9 If physical damage is found or the Model 1123A does not operate as specified notify the carrier and the nearest HP Sales Service Office immediately The Sales Service Office will arrange for repair or re placement without waiting for a claim to be settled with the carrier 2 10 REPACKAGING FOR SHIPMENT 2 11 If the instrument is to be shipped to a Sales Service Office for repairs attach a tag showing own 02632 1 er s name andaddress instrument model number and complete e
69. uses atwo section eight digit serial number to identify instruments The first 3 digits preceeding the dash are the serial prefix which identifies a series of instruments the last five digits identify a particular instrument within a series The serial number appears on a plate on the rear panel All correspondence with Hewlett Packard in regard toaninstrument should reference the complete eight digit serial number 1 11 SCOPE OF MANUAL 1 12 This manual provides operating and service information for the HP Model 1123A Voltage Probe Information in this manual applies directly to the in strument as manufactured with serial numbers pre fixed by the three digits indicated on title page If the serial prefix of the instrument is different from that on the title page a Manual Changes sheet is supplied Technicalcorrections 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 coverage of any HP instrument contact the nearest HP Sales Service Office addresses are listed at the rear of this manual Model 1123A Voltage Probe 1 1 ua Model 1123A Section II Paragraphs 2 1 to 2 14 SECTION INSTALLATION 2 1 GENERAL 2 2 This section contains preliminary inspection and installation procedures for the HP Model 1123A Voltage Probe In addition unpackingandclaims pro cedures are discussed in the event damage to the in str
70. ver slide special H M Ho H Hh H Hood tantalum time delay toggle titanium tolerance trimmer printed circuit picofarads 10712 farads peak inverse voltage part of porcelain position s potentiometer peak to peak micro 10 6 variabie watis with without working volts wirewound oH H W MH M n qd og rectifier 6 1 Section VI Table 6 2 Ret Desig Al 6 2 01123 66504 The Probe Board Assembly is not a field repairable item If trouble is evident the entire probe assembly 1 should Table 6 2 Replaceable Parts Probe Note be returned to HP for repair or replacement 01123 66502 0180 0230 0160 0127 0121 0060 0121 0060 0121 0114 0160 0161 0160 0154 0150 0121 0160 3285 0150 0121 0180 0116 0150 0093 0160 2246 0160 2249 0180 0230 0180 0230 0150 0093 1901 0049 1901 0040 9100 2598 9140 0146 9100 2276 9100 2258 9100 2258 9100 2258 1853 0061 1853 0036 1854 0071 1854 0372 1853 0020 1853 0020 1853 0020 1854 0374 1854 0071 1854 0071 1854 0374 0757 0401 0757 0924 0757 0924 0757 0900 2100 2060 Ex DJ CO pt OF H HR 99999 00000 00000 gt 600000 00900 PPPOE Probe Amplifier fxd ta 1 uf 50V fxd cer 1 uf 25V 20 var cer 2 8 pF var cer 2 8 pF var cer 7 25 pF fxd mylar 01 uf 200V 10 fxd mylar 0022 uf 200 1

Download Pdf Manuals

Related Search

Related Contents

LED Q9 DMX RG LED Q9 DMX RGB Spot - Flash  HT32F1655/HT32F1656 Development Board User Manual  マークが貼られた郵便受箱でお困りの場合  formation incoterms 2010    取扱説明書  Instruções de Operação e Segurança Instrucciones de Operación y  取扱説明書  PDF 748 ko  Alto-Shaam 4.10ESi Oven User Manual  

Copyright © All rights reserved. Failed to retrieve file