Manual s/n prefix 037
Contents
1. VITA BIAS S9 ___ inte I2AX7 12AU7 Q Ba re m 84VN o NEAR is zt GRID Im Y sty TM 14 5K 405K 405K B B TT 3 s 50v t x NOTE THIS VOLTAGE VARIES WIDELY DUE TO TUBE VARIATION 375V Sec Wt Seb O C1 1 lt O CI5 ALF O s 5 E 5v y SYNC AMPLIFIER Oi ie x 1000 IV OI ne Le S2A D Rance t R26A R266 O xo O Ra oem Te G x 10 x co pers Se AMPLIFIER Y 375 V S3D p i ren Q R99 15 8K 2 6 COPYRIGHT 1959 BY HEWLETT PACKARD COMPANY This drawing is intended for the operation R92 and maintenance of Hewleit Packard equip t S3A D SINE 3000 ment and is not lo be used otherwise or 4 75V reproduced without written consent of the O FUNCTION 2 TRIANGULAR Hewlett Packard Company Bue 2024 FUNC GEN TOSTAE Figure 4 10 Model 202A Function Generator and Amplifier amp II000 GI 9Seq AI 199S Sect V Page 1 SECTION V TABLE OF REPLACEABLE PARTS NOTE Standard components have been used in this instrument whenever possible Special components may be obtained from your local Hewlett Packard representative or from the factory When ordering parts always include 1 Stock Number 2 Complete description of part including circuit reference 3 Model number and serial number of instrument 4 If part is not listed give complete2. of the sync pulse amplifier V17 through an RC coupling which lowers the average voltage on the grid to B In the absence of pulses V17 is biased to cut off by the bleeder to B When a positive pulse appears at the grid it momentarily turns VI7 on thus inducing a large voltage swing in the pulse transformer primary The resistor and diode in the secondary remove the positive excursion resulting in a negative pulse at the SYNC OUT ter minals 3 7 POWER SUPPLY The Power Supply is a full wave rectifier and regula tor which supplies 375 volts The 75 volt and 225 volt regulated outputs are taken from a voltage divider across the 375 volt supply The main requirement on the three regulated voltages is very low impedance at low frequencies Reasonable vari ations in the actual voltages do not affect the output frequency or waveform 4 1 GENERAL Most of the following analyzing and adjustment pro cedures require the measurement of dc voltages or the observation of waveforms To obtain accurate results use a voltmeter with an input resistance of 100 megohms or more The Model 410B Vacuum Tube Voltmeter is recommended All dc voltages are measured with respect to B and not with respect to the chassis The B points in the instrument are connected with black hook up wire CAUTION Isolate all test equipment from the main chassis or ground Otherwise both B and one side of the output may be connected to the main cha
3. 4 12 ADJUST SQUAREWAVE AMPLITUDE Adjust control R63 to produce an output squarewave with the same peak to peak amplitude as the sine and triangular output waveforms 4 13 FREQUENCY RATIO AND CALIBRATION PROCEDURE The following procedure is intended for use after replacement of the Range Switch or any of the fre quency determining components on the Range Switch This procedure is also required following replace ment of frequency determining potentiometer R58 1 Remove the cabinet or top and bottom instru ment covers 2 Check that the upper and lower dial stops fall about an equal distance outside the upper and lower dial calibration marks Correct the dial setting if necessary by rotating the dial on the dial mounting hub The dial stops and not the potentiometer me chanical stops should be limiting dial travel 3 Turn the 202A on set the line voltage to 115 volts turn the FUNCTION switch to SQUARE and allow at least a 1 hour warm up period 4 Adjust power supply then adjust DC Balance and Distortion 5 Determine the ratio between the two frequencies obtained with the frequency dial at 0 8 and 12 with the RANGE switch at Xl Frequency determination is most easily accomplished by measuring the period of the unknown frequency An electronic counter such as p Model 522B 523B 524B will be needed A frequency of 0 8 cps has a period of 1250 milliseconds while 12 cps has a period of 83 3 millise
4. POWER 115 or 230 volts 410 50 to 1000 eps 150 watt DIMENSIONS Cabinet Mount 20 3 4 in wide 12 3 4 in Rack Mount 2 1 INSPECTION After the instrument is unpacked the instrument should be carefully inspected for damage received in transit If any shipping damage is found follow the procedure outlined in the Claim for Damage in Shipment page at the back of the instruction book 2 2 CONTROLS AND TERMINALS RANGE This switch is used to select the desired frequency range to be covered by the frequency dial FUNCTION This switch is used to select any one of the three types of output waveform FREQUENCY This dial is calibrated directly in cycles per second for the X1 frequency range of the oscillator The knob just below the dial escutcheon is directly con nected to the frequency varying element The lower knob is a mechanical vernier for fine adjustment of the frequency AMPLITUDE This control adjusts the amplitude of the oscillator voltage admitted to the amplifier and therefore the output of the instrument This control is calibrated from 0 to 100 in arbitrary units POWER This toggle switch controls the power supplied to the instrument from the power line FUSE The fuseholder which is located on the panel con tains the power line fuse Refer to the Table of Replaceable Parts for the correct fuse rating Sect II Page 1 SECTION I OPERATING INSTRUCTIONS OUTPUT This group consists of three
5. the voltage across C will be triangular Since there Figure 3 3 Sect III Page 3 is virtually no signal at the junction of R and C the output voltage must also be triangular In this case the frequency of the applied signal is so low that the amplifier used must be direct coupled There is a net voltage rise between input level and Output level in a dc amplifier In this particular application the average output level is determined as the average of the plus reference and minus reference levels since the output excursion is limited to these levels If this level does not coincide with the average level of the applied squarewave then the positive and negative excursions of the sguarewave will not be equal resulting in unequal rise and fall rates of the output triangle Because the squarewave input is generated from the triangular output by the bi stable circuit the net result is that under such conditions the squarewave is really a rectangular wave The resulting rectangular wave has an average value just equal to that demanded of the amplifier input by virtue of the pre set output level The average levels of the input and output are stabilized by the use of a differential amplifier that has high gain to the difference between the volt age applied to its inputs but little or no gain to any voltage change common to both inputs Figure 3 4 shows how this is done The right hand grid of the differential amplifier Vl5 is the si
6. then be connected to the chassis of the equipment being driven Under these conditions the internal impedance of the Model 202A from either OUTPUT terminal to ground is 7900 ohms in series with a 1 yf capacitor C29 A maximum dc voltage of 400 volts may be applied between either OUTPUT terminal and the G terminal without damaging the 1 pf capacitor C29 The 40 ohms internal impedance resistive will shunt the impedance existing between the two signal inputs of the system being driven Under circumstances where the connection places the Model 202A in series with a path carrying cur rent distortion of the Model 202A output will occur if greater than 10 ma peak current is caused to flow through the Model 202A output system EQUIPMENT BEING SUPPLIED G O OUTPUT groundor no izi signal point RO Figure 2 2 Balanced Output Connections 2 7 SYNC OUT The SYNC OUT is a negative pulse of less than 5 microseconds duration and at least 10 volts peak amplitude It occurs on one of the sine and tri angular crests and at the rise or fall of the square wave It occurs at the positive crests with respect to one of the OUTPUT terminals and at the nega tive crest of the other Therefore it can be changed by 180 with respect to the output system by re versing connections to the two OUTPUT terminals which are otherwise completely interchangeable The SYNC OUT terminal marked G is directly connected to the chassis 000
7. Changes CHANGE dl Table of Replaceable Parts 681 Change Stock No to 1910 0009 Under MISCELLANEOUS Fuseholder Change Stock No to 1400 0084 Figure 4 7 Power Supply schematic diagram The wire color code of Tl primary is as follows 230V 0 1000 u GRN BLK 0 1000 u REO BLK RED BLK Table of Replaceable Parts CR2 thru CR13 Change to diode 1N459A fP Stock No 1901 0033 ERRATA of Replaceable Parts Change description to Capacitor fixed ceramic 0 01 uf 20 1000 vdcw C15 Change description to Capacitor fixed polystyrene 0 1 uf 5 400 vdew R48 Change value to 10 31K ohms 3 15 62 1 8 62 PRINTED IN U S A
8. R54 and R60 are adjusted properly there is no dc component across either section of the AMPLITUDE control When the FUNCTION switch is in the squarewave position there is no signal input to one section of the AMPLITUDE control hence the tap on that section merely carries the constant bias level set by the cathode of V4 The other section is connected through a network to the clamp section of the bi stable circuit R22 of this network adjusts the aver age level of the squarewave applied to the amplitude control to the same value as the cathode of V4 The dc levels at the input to the amplifier are inde pendent of AMPLITUDE control setting The dc levels of the two output terminals may be adjusted to be equal by R65 Control R65 varies the dc level of the signal on one grid of the second stage of the amplifier When these adjustments are made the dc component between the output terminals will remain at a very low value independent of amplitude Setting or waveform selected Sect IV Page 5 Control R49 varies the level to which the output of the integrator rises in a positive direction and Rol varies the level of the negative excursion The bias levels of the shaper diodes are not variable and therefore the triangle input to the shaper can have one and only one correct magnitude and average level Figure 4 2 shows the situation at the shaper when the two reference levels are properly adjusted Figure 4 2B shows the effect of hav
9. The Gudeman Co ADDRESS New Bedford Mass Milwaukee 4 Wis New York Y Hartford Conn St Louis Mo Niagara Falls N Y Milwaukee Wis Chicago 24 Ill Palo Alto Calif Dover N H South Plainfield N J Olean N Y Erie 6 Pa Clifton N J Schenectady 5 N Y San Francisco Calif Oakland Calif Danbury Conn Philadelphia 8 Pa Chicago 20 Ill Des Plaines Ill Greenwich Conn Brooklyn 37 N Y Chicago 10 Ill Indianapolis Ind Harrison N J Marion lll Bloomington Ind Brooklyn 37 Y North Adams Mass St Marys Pa Warren Pa New York 5 N Y Cleveland Ohio Chicago 50 Ill Brooklyn 37 N Y New York N Y Chicago 22 Ill Wakefield Mass Redwood City Calif Kansas City Mo Columbus 5 Ohio Alliance Ohio New York 13 N Y East Newark N J Long Island City N Y Chicago 44 Ill Cleveland 14 Ohio Rockford Ill Cleveland 3 Ohio Plainville Conn Burbank Calif Corning N Y Columbus Neb Chicago 22 Ill Philadelphia 24 Pa Philadelphia 44 Pa West Orange N J North Chicago Ill Keasbey N J Sunnyvale Calif CODE LETTER AK AL AM AN AO AP AQ AR AS AT AU AV AW AX AY AZ BA BC BD BE BF BG BH BI BK BL BM BN BO BP BQ BR BS BT BU BV BW BX BY BZ CA CB CD CE CF CG CH Cl CJ CK CL CM CN CO CP CQ CR CS CT CU CV CW MANUFACTURER Hammerlund Mfg Co Inc Indus
10. description function and location of part Corrections to the Table of Replaceable Parts are listed on an Instruction Manual Change sheet at the front of this manual RECOMMENDED SPARE PARTS LIST Column RS in the Table lists the recommended spare parts quantities to maintain one instrument for one year of iso lated service Order complete spare parts kits from the Factory Parts Sales Department ALWAYS MENTION THE MODEL AND SERIAL NUMBERS OF INSTRUMENTS INVOLVED 12 1 59 Sect V Page 2 TABLE OF REPLACEABLE PARTS 4 STOCK DESCRIPTION MFR amp MFR DESIGNATION NO TQ Capacitor fixed electrolytic 0180 0011 20 uf 450 vdcw Capacitor fixed paper 0160 0016 l uf 4 2095 400 vdcw Capacitor fixed paper 0160 0013 0 1 uf 410 400 vdew Capacitor fixed paper 0160 0018 22 uf 110 400 vdew Capacitor fixed paper 0160 0077 4 uf 10 600 vdcw Same as C4 Capacitor fixed mica 0140 0006 82 pf 41005 500 vdew Capacitor fixed mica 0140 0027 470 pf 41095 500 vdcw Capacitor fixed ceramic 0150 0012 01 uf tol 0 100 1000 vdcw Capacitor fixed mica 0140 0021 39 pf 10 500 vdew Same as C10 Capacitor fixed 0170 0059 l uf 45 400 vdew Capacitor fixed polystyrene 0170 0001 l pf 45 300 vdew Capacitor fixed polystyrene 0170 0023 01 uf 4595 600 vdew Capacitor fixed silver mica 0140 0079 001 uf 5 500 vdew Capacitor fixed ceramic 0150 0007 100 pf 45 500 vde
11. opposite end of R93A This is a slate wire connected to the AM PLITUDE control 4 Set the FUNCTION switch to TRIANGULAR and adjust R54 for a voltmeter indication of volts 5 Move the DC volts probe to the arm of R118 and adjust R118 for an indication of approximately 0 volts Sect IV Page 6 6 Set the AMPLITUDE control to minimum max imum CCW and move the voltmeter leads to the red OUTPUT terminals 7 Adjust R65 located behind a hole in the panel near the OUTPUT terminals for an indication of O volts 8 Set R119 located near Vl and T2 to the middle of its range 9 Disconnect the voltmeter and connect equipment as shown in Figure 4 1 10 Set the FREQUENCY dial to 10 the RANGE switch to X10 100 cps FUNCTION selector to SINE and the AMPLITUDE control for an output of approximately 10 volts rms ll Adjust R49 and R51 to eliminate the points or Spikes at the ends of the Oscilloscope pattern Ad justment of these controls will shift the output fre quency you should follow the frequency shift with the Distortion Analyzer Adjust the Distortion Analyzer sensitivity as necessary to obtain a useful pattern on the Oscilloscope see Figure 4 3 12 Adjust R60 for minimum distortion as indicated on the Distortion Analyzer Repeat steps Il and 12 until the distortion measured is at least 40 db below the output voltage 1 13 Connect the voltmeter COMMON lead to the common junction of AMPLITUDE
12. to or greater than 10 volts 4 18 SINE WAVE DISTORTION CHECK 1 Connect test setup as shown in figure 4 5 in cluding a 3 9K ohm shunt resistor across the OUT PUT terminals of Model 202A 2 Set Model 330B C D controls as follows INBUTD L yum yu TE TE TRE AF FREQUENCY RANGE Gruda ae wow es FREQUENCY DIAL sa 3 1 6 e Ee 100 cps PUNCTION kei TRES TITIO METER METER 30 RMS VOLTS 00011 3 MODEL MODEL 202A 530 B C D LOW FREQUENCY DISTORTION ANALYZER FUNCTION GENERATOR Figure 4 5 Sine Wave Distortion Test Setup 3 Set Model 202A controls as follows ERIN Cais vase Z Gis 2 g Bae St ee ei sS fa a A10 FREQUENCY DIAL 10 100 cps FUNCTION lt Sf eas a OL we Ae WS a en SINE AMPLITUDE adjusted for 10 6 volts output read on Model 330B C D 4 Disconnect cable from METER INPUT and re connect it to AF INPUT 5 Set FUNCTION to SET LEVEL and METER RANGE to 100 6 Adjust INPUT SENSITIVITY for 100 on the 10 scale full scale is 100 7 Set FUNCTION to DISTORTION 8 Tune Model 330B C D for null 9 Set METER RANGE to 3 and retune for null Reading should be less than 1 on the 3 scale full scale is 3 10 On Model 202A change RANGE to X100 and FREQUENCY toi 100 cps Repeat steps 1 through 9 at this frequency Reading should be less than 2 4 19 DIAL ACCURACY CHECK 1 Connect test setup as shown in figure 4 6 2 Allow 1 2 hour warmup perio
13. used in the instrument RS Recommended spares for one year isolated service for one instrument Sect V Page 7 TABLE OF REPLACEABLE PARTS CIRCUIT 6 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ Resistor variable composition linear taper 2100 0073 125 000 ohms 20 1 4 W BO Resistor fixed wirewound 0815 0001 30 000 ohms 5 10 W R Resistor variable composition linear taper 2100 0153 2000 ohms 20 1 3 W BO Resistor fixed composition 0690 3931 39 000 ohms 10 1W B Same as R43 Same as R66 Resistor fixed composition 0690 2741 270 000 ohms 410 1 W B Resistor fixed composition 0690 5641 560 000 ohms 41095 1 W B Same as R13 Resistor fixed composition 0690 1051 l megohm 41095 1 W B Resistor fixed composition 0690 2251 2 2 megohms 410 1 W B Resistor fixed composition 0693 2731 27 000 ohms 4109 2 W B Resistor fixed composition 0690 1841 180 000 ohms 41095 1 W B Resistor fixed composition 0690 2241 220 000 ohms 41095 1 W B Same as R74 Same as R75 This circuit reference not assigned See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument Sect V Page 8 00011 2 TABLE OF REPLACEABLE PARTS CIRCUIT 9 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ RS This circuit referen
14. 11 DC Balance and Distortion Adjustments 4 5 4 12 Adjust Sguarewave Amplitude 4 8 III PRINCIPLES OF OPERATION 3 1 4 13 Frequency Ratio and Calibration 3 lt l General 2 vw ouo dE HK 3 3 1 BPYOOOUUTS 4 8 3 2 Bi Stable Circuit uds 3 2 4 14 Replacement of R58 Potentiometer 4 8 3 3 Linear Integrator 3 3 4 15 Performance Check 4 8 3 4 Sine Synthesizer and Function 4 16 Output Voltage and Waveform Selector Switch 3 4 NE Ap ss 4 8 3 5 Output System 3 6 4 17 Sync Pulse Check 4 10 3 6 Sync Pulse Output 3 7 4 18 Sine Wave Distortion Check 4 10 3 7 Power Supply 3 8 4 19 Dial Accuracy Check 4 10 IV MAINTENANCE z 4 1 4 1 General 4 1 V TABLE OF REPLACEABLE PARTS 5 1 4 2 PowerSupply 4 5 1 Table of Replaceable Parts 5 2 LIST OF ILLUSTRATIONS Figure Page Figure Page 1 1 Model 202A Low Frequency Function 4 1 Minimum Distortion and Frequency Generator y S Z ee l o ZR Q a dee 1 0 Adjustment Instrumentation 4 6 2 1 Single Ended Output Connections 2 2 4 2 Effect of Triangle Maladjustment on 2 2 Balanced Output Connections 2 2 Distortion and Frequency 4 7 3 1 Model 202A Function Generator 3 1 4 3 Patterns Showing the Adjustments of R49 3 2 Details of Bi Stable Circuit and R51 R60 a
15. 11 2 3 1 GENERAL Figure 3 1 depicts the general scheme of the 2 Model 202A and indicates the waveforms produced The bi stable circuit consists of a flip flop circuit capable of producing a sguare wave output at point A pro vided it is triggered at the proper time This is done by including in the bi stable circuit a two way comparator circuit which produces the proper trig gers for the flip flop whenever the switching signal becomes equal to either the plus switching reference or the minus switching reference The triangular switching signal returned to the bi stable circuit SWITCHING REF BI STABLE CIRCUIT 4 INTEGRATOR SWITCHING SIGNAL Model Figure 3 1 202A Sect HI Page 1 SECTION PRINCIPLES OF OPERATION is that seen between points Band D The conversion of square wave to triangular wave takes place in the integrator unit which is carefully designed to produce an accurate integral of the applied square wave The bi stable circuit and linear integrator are loop coupled in such a manner that the resulting relaxation oscillator is suitable for very low fre quency Operation The sinewave output is taken from a point C between the triangular voltage at point B and the average level at point D The resistance between B and C is fixed and the network between C and D is a OUTPUT AMPLIFIER AVE VOLTAGE FROM ro VOLTAGE FROM 8 ro 0 AVE VOLTAGE FROM TO N THE
16. A R28A R24Bthru R28B R29 R30 thru R32 R33 34 R35 36 R37 R38 R39 R40 R41 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument 00011 2 TABLE OF REPLACEABLE PARTS een 4 STOCK DESCRIPTION MFR amp MFR DESIGNATION NO TQ Same as R14 Same as R5 Resistor variable composition linear taper l megohm 30 1 4 W BO Resistor fixed composition 3 3 megohms 4109 1W Optimum value adjusted at factory Average value shown B These circuit references not assigned Resistor fixed deposited carbon 900 000 ohms 41 Optimum value selected at factory Average value shown l I NN Resistor fixed deposited carbon 800 000 ohms x 1 Optimum value selected at factory Average value shown NN Same as R22 Resistor fixed deposited carbon 5 16 megohms 41 1W Resistor fixed deposited carbon 405 000 ohms 419 1W Resistor fixed deposited carbon 2 163 megohms 419 1W Resistor fixed composition 1 5 megohm 10 1 W Resistor fixed deposited carbon 1 031 megohm 419 1 W Same as R3l Same as R37 Resistor fixed composition 33 000 ohms 41095 2 W Resistor fixed composition 12 000 ohms 410 56 1 2W Optimum value selected at factory Average value shown B Resistor fixed composition 150 000 ohms 41095 2 W B R
17. EQUENCY controls for the desired frequency The frequency dial scale must be multiplied by the multiplying factor indicated by the RANGE switch setting to obtain the oscillator frequency Example 4 on dial scale x 1 multi plying factor indicated by RANGE switch setting 4cycles sec 3 Set the FUNCTION switch for the desired output waveform 4 Connect the equipment under test to the OUTPUT terminals 5 Adjust the AMPLITUDE Control for the desired output voltage Because the frequency response is rated 40 2 db the output amplitude may be mea sured at any convenient frequency and the output level will be correct within these limits for any other frequency NOTES When small output voltages are required it may be desirable to use an external attenuator This is because the hum and noise in the output is nearly constant with output amplitude To minimize distortion in the output waveform always use the lowest RANGE when the overlap of the FREQUENCY dial permits a choice 2 5 SINGLE ENDED OUTPUT The terminal marked G is isolated from the actual OUTPUT terminals For single ended operation G EQUIPMENT BEING SUPPLIED RO Figure 2 1 Single Ended Output Connections must be connected to one of the OUTPUT terminals and the strapped pair will then be the ground side of the output 2 6 BALANCED OUTPUT Connect the two OUTPUT binding posts to the eguip ment being supplied The G binding post may
18. HP Archive This vintage Hewlett Packard document was preserved and distributed by www hparchive com Please visit us on the web ocanned by on line curator Tony Gerbic For FREE Distribution Only 202A HEWLETT PACKARD COMPANY 202 A LOW FREQUENCY FUNCTION GENERATOR vzoz OPERATING AND SERVICE MANUAL MODEL 202A SERIALS PREFIXED 037 LOW FREQUENCY FUNCTION GENERATOR Copyright HEWLETT PACKARD COMPANY 1959 1501 PAGE MILL ROAD PALO ALTO CALIFORNIA U S A 00011 3 Printed MAR 1962 Table of Contents List of Illustrations TABLE OF CONTENTS Section Page Section Page I GENERAL INFORMATION 1 1 IV MAINTENANCE cont g 1 1 General ae e ko 4E kup us Q amp xe 3 1 1 4 3 Function Generator bi stable cir cuit and integrator 4 2 4 4 Sine Synthesizer and Function SELECTOP oo id S 4 2 II INSTRUCTIONS 2 1 435 Output Amplifier rn 4 3 sl Inspection 9339 43639 x9 2 1 4 6 Ou 2 2 Controls and Terminals 2 1 smelui 4 3 4 7 Tube Replacement 4 3 2 3 230 Volt Operation 2 1 S pU EE 4 8 Tube Replacement Chart 4 4 2 4 Operation Z eu we 2 1 p 2 5 Single Ended Output 9 2 4 9 Power Supply Regulator Adjustment 4 4 4 10 Theory of DC Balance and Dist 2 6 Balanced Output o6 9 93 9 3 2 2 2 be 2 7 Syne DI 2 2 Adjustments ss ui 4
19. OR 130 OSCILLOSCOPE AD MODEL 330 DISTORTION ANALYZER AD MODEL 202A LOW FREQUENCY FUNCTION GENERATOR Figure 4 1 Minimum Distortion and Frequency Adjustment Instrumentation Sect IV Page 7 Ref A Correct setting of Triangle amp Sine AveN reference levels B Both Ref levels too large Causes decrease in frequency and high 3rd harmonic distor Triangle amp Sine Ave tion i e flattened peaks Proper Ave C Ref too high and Ref too low Frequency correct but large 2nd harmonic as seen by peak flattening on one side and sharpening on other Also sine average not same as triangle Ref Ref D References are correct but tri angle unbalanced Frequency correct but high second harmonic component in phase with funda Triangle amp Sine Ave L Ref no Figure 4 2 Effect of Triangle Maladjustment on Distortion and Freguency Ten Segment Approximations Used for Clarity Sect IV Page 8 00011 3 A R60 and R119 misadjusted B R51 misadjusted C R49 misadjusted D R49 and R51 misadjusted in same direction E R49 and R51 misadjusted F R49 and R51 misadjusted in opposite direction of pattern D above Typical adjusted pattern for mini mum distortion and correct fre quency Figure 4 3 Patterns Showing the Adjustments of R49 R51 R60 and R119 to Obtain Minimum Distortion and Correct Frequency 00011 2
20. R63 v20 v25 V24 V22 RII9 LI vel v5 V6 VI V 3 v2 R5I R49 T4 JE y MP S 518 R65 R93 VI VI8 VIT VI6 VIS Figure 4 8 Model 202A Bottom View Bottom Plate Removed 1 T000 ET eseq AI 9 9 100 F545 RED R123 L C358 8t 375 REG 150K T 20UF R78 IBOK 210 SS R79 C3 220K pf YELLOW 225 BLUE 75 REG ce dpf BLACK x NOTES APPLY TO FUNCTION GENERATOR 8 AMPLIFIER SECTION AS WELL AS TO POWER SUPPLY SECTION CONDITIONS OF DC VOLTAGE MEASUREMENT K 1000 OHMS PRI M MEGOHM GRN BLK I H5 230V 50 1000 POWER SUPPLY b MAIN EXTERNAL CHASSIS ISOLATED FROM POWER SUPPLY 2 MEASURED BETWEEN THE INDICATED POINTS AND B VOLTAGES WITH A VOLTMETER OF I22MEGOHMS INPUT RESISTANCE rh INTERNAL CHASSIS ONE POINT GONNEGTION TO DIVIDER B 19 ANY BLACK LEAD IN POWER SUPPLY EXCEPT T R78 amp R79 PRIMARY START POWER SUPPLY RETURN IS NOT CONNECTED TO CHASSIS 3 PANEL GONTROLS SET AS FOLLOWS RANGE AT FREQUENCY AT 5 FUNCTION AT SINE BLACK TI AMPLITUDE AT MAX CAPACITY IN PUF UNLESS OTHERWISE NOTED 202A PS TOJ7AB O SCREWDRIVER ADJ ELECTRICAL VALUE ADJUSTED AT THE FAGTORY AVERAGE VALUE SHOWN PART MAY BE OMITTED TRANSFORMER DETAIL Figure 4 9 Power Supply pI 99ed IT000 375V n 4 375V RIOS 5 120K 120K R 2 R36 1 5M VI5 sisovf d RIOA 1 hee o
21. RESS New York N Y Chicago 18 IIl Manchester N H San Jose Calif Waseca Minn Chicago 47 Ill Freeport Ill Akron 8 Ohio Huntington Ind Chicago 5 Ill Skokie Ill Harrisburg Pa Camden 3 N J Collingdale Pa Los Angeles 58 Calif New Rochelle N Y Attleboro Mass Mansfield Ohio Van Nuys Calif Los Angeles 65 Calif Newark 5 N J Burbank Calif San Francisco Calif Philadelphia 18 Pa Boonton N J New York 21 N Y AHleboro Mass Chicago Ill Danvers Mass Elkhart Ind West Orange N J Carlstadt N J Clifton N J Oakland Calif Combridge 39 Mass Culver City Calif El Segundo Calif Sandwich IIl Cleveland Ohio Philadelphia 30 Pa Mt Vernon N Y Newton Mass Newark 4 N J Palo Alto Calif Union N J Chicago 30 Ill Indianapolis Ind Santa Monica Calif Los Angeles 42 Calif Chicago 15 Ill Paramus N J Philadelph a 34 Pa Swissvale Pa New York ll N Y Yonkers N Y Bridgeport 2 Conn New York 13 N Y Cincinnati 6 Ohio New York N Y Princeton Ind Los Angeles Calif Palo Alto Calif Ogallala Nebr MANUAL CHANGES MODEL 202A LOW FREQUENCY FUNCTION GENERATOR Manual Serial Prefixed O37 Manual Printed 1 61 To adapt this manual to instruments with other serial prefixes check for errata below and make changes shown in tables Instrument Serial Prefix Make Manual Changes Instrument Serial Prefix Make Manual
22. SYNTHESIZED FUNCTION f BD m 36 Function Generator Sect II Page 2 non linear system which synthesizes a sinewave from the triangular wave This network consists of a group of biased diodes arranged in such a man ner that at certain predetermined voltage levels they begin to conduct therefore providing shunt paths from C to D Each additional shunt path reduces the slope of the triangle in the proper amount so that the wave is shaped to approximate a sinewave This approximation is as shown and the degree to which a sinewave may be approached depends on the number of diodes Thus there are available the sinewave C triangular wave B and square wave functions with respect to D to be selected and brought to the OUTPUT terminals through the output amplifier The output amplifier has a differ ential input and push pull output 3 2 BI STABLE CIRCUIT Figure 3 2 shows the details of the bi stable circuit and includes the integrator in block form in order to indicate the bilateral connection from integrator output to comparator input The portion of the diagram composed of V1 V2 and V3 is the bi stable circuit Actually this circuit is a combination of two circuits If capa citors C10 and C13 are disconnected so that there is no possibility of inductive coupling from grids to cathode of Vl and V2 the remaining circuit is the well known flip flop or Eccles Jordan trigger circuit The other circuit which
23. Sinewave badly distorted DC component at OUT PUT terminals inde pendent of AMPLITUDE control setting or varied by AMPLITUDE control Maladjustment of R65 R54 and R118 or defective tubes V4 V18 V19 V20 See DC Balance Adjustment 4 5 OUTPUT AMPLIFIER TABLE 4 4 CAUSE AND OR SYMPTOMS REMEDY Replace V18 V19 V20 If distortion remains turn off the power and mea sure resistance be tween internal chassis and main chassis See para graph 4 9 Increased distortion when amplifier is loaded with 4000 ohms DC voltage component See paragraph 4 4 exists across the OUT PUT terminals Distortion increases appreciably with re duced AMPLITUDE control setting Replace variable resistor R93A R93B Failure to deliver 10 volts rms sinewave output Adjust regulated B voltage See para graph 4 9 Replace V18 V19 V20 Hum in output voltage Excessive hum from power supply See paragraph 4 9 Sect IV Page 3 After adjustment or tube replacement the amplifier should meet the following specifications The output voltage should not drop more than 2 when a 4000 ohm load is connected to the output The distortion should remain within specifi cations when the output is loaded with 4000 ohms or higher The peak to peak output voltage should be at least 30 volts 10 6 volts rms
24. TERS USED IN TABLE OF REPLACEABLE PARTS TO DESIGNATE THE MANUFACTURERS MANUFACTURER Aerovox Corp Allen Bradley Co Amperite Co Arrow Hart amp Hegeman Bussman Manufacturing Co Carborundum Co Centralab Cinch Jones Mfg Co Hewlett Packard Co Clarostat Mfg Co Cornell Dubilier Elec Co Hi Q Division of Aerovox Erie Resistor Corp Fed Telephone amp Radio Corp General Electric Co General Electric Supply Corp Girard Hopkins Industrial Products Co International Resistance Co Lectrohm Inc Littlefuse Inc Maguire Industries Inc Micamold Radio Corp Oak Manufacturing Co P R Mallory Co Inc Radio Corp of America Sangamo Electric Co Sarkes Tarzian Signal Indicator Co Sprague Electric Co Stackpole Carbon Co Sylvania Electric Products Co Western Electric Co Wilkor Products Inc Amphenol Dial Light Co of America Leecraft Manufacturing Co Switchcraft Inc Gremar Manufacturing Co Carad Corp Electra Manufacturing Co Acro Manufacturing Co Alliance Manufacturing Co Arco Electronics Inc Astron Corp Axel Brothers Inc Belden Manufacturing Co Bird Electronics Corp Barber Colman Co Bud Radio Inc Allen D Cardwell Mfg Co Cinema Engineering Co Any brand tube meeting RETMA standards Corning Glass Works Dale Products Inc The Drake Mfg Co Elco Corp Hugh H Eby Co Thomas A Edison Inc Fansteel Metallurgical Corp General Ceramics amp Steatite Corp
25. appears in the bi stable circuit is a voltage comparator known as the Multiar The multiar is a circuit which employs a regenerative loop to produce a pulse when the two input voltages are equal There are two of these in the bi stable unit One multiar is composed of Vl V3A and and the other of V2 3B and TI The cathode of V3A and the plate of V3B are con nected to reference voltages derived from the volt age regulator tubes V5 and V6 The triangular wave is applied to the plate of V3A and the cathode of V3B As the voltage on the plate of V3A rises towards the plus switching reference Vl is con ducting but when V3A conducts a negative pulse is formed on the grid of Vl which flips the Bi Stable Unit to its other stable state and starts the voltage on the cathode of V3B towards the minus switching Figure 3 2 Details of Bi Stable Circuit and Switching System reference When V3B conducts the Bi Stable Unit is flipped back to its original state completing one cycle of operation Voltage regulator tubes V5 and V6 are connected by a voltage divider from which the switching refer ence voltages are taken They also provide the limiting voltages applied to tubes V7 and V8 which are seen to be a push pull clamping system In asmuch as the integrator output is directly related to the input it is seen that the magnitude of square wave applied must be carefully controlled Al though only the squarewave appearing at the p
26. as 393 5 Measure the voltage between pin 5 of tube V6 and B This voltage should be about 4 75 volts Variations in OA3 tubes can cause this voltage to fallat any point between 68 and 85 volts 6 Repeat step 3 if you replace either V5 or V6 The characteristics of cold cathode regulator tubes drift during about the first 72 hours of operation This drift can affect the 202A output A 72 hour aging is recommended for a new tube for either V5 or V6 7 Test the regulated output voltage at pin 5 of tube V5 while varying line voltage between 103 and 127 volts The regulated voltage will normally not change by more than 41 Check power supply tubes and components if the change is excessive 4 10 THEORY OF DC BALANCE AND DISTORTION ADJUSTMENTS The output AMPLITUDE control is located at the input to the output amplifier If the dc component at the output terminals is to be zero for all settings of the AMPLITUDE control the dc levels at the ends of the AMPLITUDE control must be the same and also equal to the average level of the input wave From the schematic wiring diagram it is seen that the common connection between the two sections of the control is connected to the cathode of V4 The level of this point can be adjusted to the desired value by R54 The signal impedance of this point is very low compared with the magnitude of the AMPLITUDE control impedance and therefore the cathode of V4 has virtually zero signal When R49 R51
27. ave is approximated by varying the shunt resistance across R93B is steps determined by the diode synthesizing network The waveform slope at first is just that determined by R94 R93B and the input waveform When the first diode conducts R93 is shunted by a predetermined amount decreas ing the slope Each diode in turn decreases the slope until all the diodes are conducting and the triangular wave has reached its crest The triangular wave starts down the diodes stop conducting in turn until the triangular wave has reached its crest The triangular wave starts down the diodes stop conduct ing in turn until the triangular wave reaches the average level The other half cycle is formed in the same manner but by the diodes that are biased to shape the negative excursion It can be shown that using seven segments to approx imate one quarter cycle of the sinewave results in ap proximately 1 6 rms distortion However variations in the diodes limit the practical result to about 1 rms distortion In the triangular wave position of the FUNCTION selector switch the non linear load consisting of the diode network is replaced by R95 so that the combination R94 and R95 is a simple linear divider for all voltage levels It is adjusted to give equal 2375 VIS v19 375 Figure 3 7 sine and triangular wave peak magnitude The Squarewave is connected to the FUNCTION selector switch through the divider R59 and R22 which adjusts the av
28. ce not assigned Resistor fixed wirewound HP 02A 26C These circuit references not assigned Resistor fixed wirewound 0816 0005 2500 ohms 41095 10 W S Same as R62 Resistor variable composition dual tandem 2100 0258 linear taper 1 megohm sect 20 BO Same as R53 Resistor fixed deposited carbon 0727 0199 67 500 ohms 1 1 2 W NN Same as R6 Resistor fixed deposited carbon 0730 0036 15 800 ohms 41 1 W NN R100 101 These circuit references not assigned Resistor fixed composition 0690 1821 1800 ohms 109 1 W p Resistor fixed wirewound 0811 0038 14 500 ohms 11 3 W AC Same as R15 Same as R16 Same as R15 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument 00011 2 Sect V Page 9 TABLE OF REPLACEABLE PARTS CIRCUIT STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ R109 Same as R65 R110 Resistor fixed deposited carbon 0727 0096 920 ohms 1 1 2 W R111 Resistor fixed deposited carbon 0727 0165 13 200 ohms 11 1 2 W R112 Resistor fixed deposited carbon 0727 0187 37 400 ohms 1 1 2 W R113 Resistor fixed deposited carbon 0727 0201 71 560 ohms 1 1 2 W R114 Resistor fixed deposited carbon 0727 0213 115 000 ohms 1 1 2 W R115 This circuit reference not assigned R116 Resistor fixed deposited carb
29. conds 6 The ratio obtained in step 5 must be 15 to 1 Adjust by loosening the coupler between the dial and poten tiometer R58 shafts See Figure 4 4 for coupler access hole location Rotate one shaft with respect to the other to obtain a period of 83 3 milliseconds with a dial reading of 12 Tighten both set screws in the coupler Sect IV Page 9 7 Set the frequency dial to 0 8 and adjust control R109 to obtain a period of 1250 milliseconds Check the setting made in step 6 and if necessary repeat step 6 If R109 has insufficient range center the control me chanically and repeat steps 6 and 7 This will elec trically center the adjustment range of R109 which can then be used to make any final adjustments 8 Check calibration of the Xl range The out put frequency should be within 2 of the dial read ing over the entire range Adjust R26B if neces sary 9 Check the calibration of the other ranges Ad just R24B for the X 01 range R25B for the X 1 range R27B for the X10 range and R28B for the X100 range On the X100 range only adjust C33 to calibrate the high end of the band 10 Replace the cabinet or the top and bottom cover 4 14 REPLACEMENT OF R58 POTENTIOMETER Replacement of the frequency control potentiometer involves two basic operations 1 The mechanical procedure for replacing a de fective potentiometer with a new one 2 The necessary electrical adjustments described in pa
30. controls R93A and R93B violet wire 14 Connect the DC volts probe to the opposite end of R93B This is a green wire connected to the AM PLITUDE control 00011 2 15 Switch the FUNCTION selector to TRIANGULAR and note the voltmeter indication 0 5 on 0 l scale is O volts Adjust R49 to reduce the dc voltage to one half of its initial value then adjust R51 to remove the remaining dc voltage The voltmeter should now indicate O volts 16 Set the FUNCTION selector to SINE and adjust R118 for a voltmeter indication of volts 17 Verify the distortion in the output sine wave at 100 cps first on the X10 RANGE with the FRE QUENCY dial at 10 then on the X100 RANGE with the FREQUENCY dialatl the distortion indi cations are not approximately identical careful adjustment of R119 will lower the 100 cps distortion on the X100 RANGE 18 Connect the voltmeter COMMON lead to the common junction of AMPLITUDE controls R93A and R93B violet wire Connect the DC volts probe to the green wire on the opposite end of R93B 19 Set the FUNCT ION selector to SQUARE and the RANGE switch to Adjust R22 for a volt meter indication of volts 20 Any dc between the red OUTPUT terminals with the AMPLITUDE control at minimum may be elim inated by adjusting R65 behind the hole in the panel This voltage should vary less than 40 5 volts when the AMPLITUDE control is rotated through its full range AD MODEL 120
31. d 3 Set Model 202A controls as follows RANGE Z Z S S 223 Gas huge d RID S N a X100 FREQUENCY seu am kroketi 12 1200 cps FUNC TION as zija dirt Rare a E SQUARE 4 Set Model 523C D for period measurement as follows FUNCTION SELECTOR PERIOD PIME UNDLS 15 s Su b S Q Be dhe oe he 5 Model 523C D should read between 816 and 850 MODEL 202A LOW FREQUENCY FUNCTION GENERATOR MODEL 523 C D ELECTRONIC COUNTER GECCEG O un Figure 4 6 Dial Accuracy Test Setup 6 Set Model 202A RANGE to 120 cps and Model 523C D TIME UNIT to MILLISEC 00011 3 Sect IV Page 11 7 Counter should read between 8 16 and 8 50 8 Set Model 202A RANGE to X1 and FREQUENCY dial to 1 4 1 4 eps 9 Counter should read between 699 9 and 728 5 10 Set Model 202A RANGE to X1 14 cps 11 Counter should read between 6999 9 and 7284 7 12 Set Model 202A RANGE to X 01 FREQUENCY dial to 8 008 cps and Model 523C D TIME UNIT to SEC 13 Counter should read between 121 25 and 128 75 Due to such a low frequency the counter may not start its count for approximately 2 min and 5 sec SEE PARA 4 13 T2 T3 CI4 v2 R28B R27B R26B R25B R24B R49 RSI V6 V5 V2Il V3 VI RIS R58 TI RIO9 Figure 4 7 Model 202A Top View Cover Removed v22 C6 V24 v25 gI 95864 Al 3o9S 11000 V23 R22 R60 R54 V8 V4 V7
32. erage voltage of the squarewave to the voltage at the cathode of V4 In the squarewave position of the selector switch R63 parallels R93B to adjust the amplitude of the squarewave to be equal to the amplitude of the sinewave and the triangular wave 3 5 OUTPUT SYSTEM The output system consists of three stages as shown in Figure 3 7 The first stage V18 is a dual triode acting as a pair of separate cathode followers These cathode followers isolate the signal input from the output stage Any dc unbalance at the output ter minals can be corrected by varying R65 The second stage V19 is a differential amplifier The difference between the two signals at its grids appears dt both plates in nearly equal magnitudes and 180 out of phase This effect is due to the large common cathode resistance In this stage ampli fication takes place and also the signal difference E minus F is converted to push pull voltages The third stage V20 is another pair of cathode followers The signals appearing at the plates of V19 are H36 v20 R99 R97 50 M 51 Output Amplifier System of Model 202A Figure 3 8 attenuated before being applied to the cathode follower grids The small shunt capacitors on the upper sides of the dividers improve the high frequency response of the amplifier The voltages appearing at the cathode follower output terminals are equal in mag nitude and 180 out of phase Negative feedback is used to reduce distortion
33. esistor fixed composition 1200 ohms 4109 1W 2100 0074 0690 3351 0730 0103 0730 0100 0730 0126 0730 0088 0730 0113 0690 1551 0730 0106 0693 3331 0687 1231 0693 1541 0690 1221 Sect V Page 5 Sect V Page 6 00011 2 TABLE OF REPLACEABLE PARTS CIRCUIT 4 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ Resistor fixed composition 0690 3351 3 3 megohms 410 1W B Same as R43 Resistor fixed composition 0690 1231 12 000 ohms 41095 1 W B Resistor fixed deposited carbon 0730 0031 10 310 ohms 1 1 W NN Resistor variable wirewound linear taper 2100 0006 5000 ohms 410 2 W BO Resistor fixed deposited carbon 0730 0034 14 400 ohms 4195 1 W NN Same as R49 Resistor fixed deposited carbon 0730 0044 27 500 ohms 41975 1 W NN Resistor fixed deposited carbon 0730 0048 33 000 ohms 4196 1 W NN Same as R49 Resistor fixed deposited carbon 0730 0049 37 000 ohms 195 1W NN This circuit reference not assigned Resistor fixed deposited carbon 0730 0070 103 500 ohms 41 1 W NN Resistor variable wirewound 2100 0244 100 000 ohms 1 8 W Same as R13 Optimum value selected at factory Average value shown Same as R49 This circuit reference not assigned Resistor fixed wirewound 0816 0002 3000 ohms 10975 10 W S See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity
34. gnal input and is driven through R by the rectangular wave appearing on the FREQUENCY control The average voltage of this rectangular wave is depen dent on the clamping levels and the ratio of on to Off time When the system is adjusted for equal on off times squarewave the average is just the average of the clamping levels The left hand grid has no signal because the voltage divider which in cludes the balance control is connected to the no signal sides of the clamping tubes However any change in the clamping level changes the average level appearing on both input grids in the same amount Due to the large common cathode resistors of V15 and V16 a common mode change has very little effect The input to the left hand grid has another function If the balance control R60 is varied slightly the output of the amplifier will show a considerable change in average level and therefore Generalized Miller or Feedback Integrator Sect IH Page 4 E TRIANGLE BI STABLE CIRCUIT Figure 3 4 the average level of the output can be adjusted to exactly the voltage midway between the reference levels This control then serves adequately to adjust the triangular wave balance which in turn equalizes the on off time of the squarewave The signals appearing at the plates of the first tube V15 are 180 out of phase and nearly equal in magnitude These signals are also very nearly the difference between the inputs on the two grids S
35. in Distortion and Correct Freq Adj DC Bal Adj Power Supply DC Bal Adjust Minimum Distortion and Correct Freq Adjust Min Distortion and Correct Freq Adj Min Distortion and Correct Freq Adj Set dc output component to zero by R65 with amplitude control setting V2l No effect V22 V23 V24 V 25 4 9 POWER SUPPLY REGULATOR ADJUSTMENT Resistance measured between inner and outer chassis should be at least two megohms with OUTPUT ter minals disconnected from panel ground or a load This resistance check should be made before starting the following adjustment procedure Connect the shorting strap between the lower output terminal and chassis ground Connect the dc voltmeter between B and the inner chassis The voltmeter must not be grounded and the common terminal should be connected to B Possible change in 4 375 and 4 225 regulated voltages control min None Carry out procedure under Power Supply Regulator Adjustment Paragraph 4 9 2 Connect the 202A to the power line and turn on The voltmeter indication should be between 190 and 230 volts with line voltage set to 115 volts 3 Measure the regulated output voltage between B and pin 2 of tube V5 Adjust control Rll to give a voltage of 225 volts 4 Measure the voltage between pin 5 of tube V5 and B This voltage should be about 375 volts Var iations in OA3 tubes can cause this voltage to be as low as 365 or as high
36. ince there is no signal on the left grid the only signal into the amplifier is that at the junction of R and C which is the condition originally required The second stage is a push pull amplifier employing the signals from the plates of the previous stage Again the common cathode resistance is very high but there is very little degeneration of the push pull input The gain of the system to changes common to both grids is about one half while the gain to voltages appearing between the input grids is something over 290 Finally C is fed back to the signal grid from the cathode of VITA which is 180 out of phase with the signal input The cathode follower is used as an isolation stage between the integrator and the bi stable circuit This completes the oscillating loop with its inherent production of both square and triangular functions B0 M S 8B Simplified Linear Integrator 3 4 SINE SYNTHESIZER AND FUNCTION SELECTOR SWITCH The triangular wave from the linear integrator is connected to R94 In the SINE position of the FUNC TION selector switch S3 the other end of R94 is connected to the sine synthesizing diodes and to R93B one half of the dual AMPLITUDE potentio meter The synthesized sinewave signal appears as the difference signal between points C and D but an error signal which appears at D with respect to B also appears at C with respect to B This composite signal is applied to a differential amplifier in the outpu
37. ing the reference levels adjusted for too large a magnitude but with the proper average value Figure 4 2C shows the effect of having reference levels adjusted for a triangle of the proper magnitude but incorrect average level This indicates a close relationship between correct frequency calibration and minimum distortion In fact the two conditions are simul taneously satisfied by optimum settings of the same adjustments 4 11 DC BALANCE AND DISTORTION ADJUSTMENTS The following test procedure requires a dc voltmeter with an input resistance of at least 100 megohms such as an p Model 410B In addition the volt meter must not be grounded as the common side of the meter must be connected to points within the 202A that are not at ground potential A Distortion Analyzer and an Oscilloscope will also be required A 20 minute warm up is recommended before you start this procedure You should also adjust the power supply as outlined in paragraph 4 9 1 Adjust the insulated 410B voltmeter to indicate 0 5 on the 1 volt range with the dc leads shorted Use either the or the position of the SEL ECTOR switch whichever one will permit the 0 5 setting with the ZERO ADJ control This meter indication will be called O volts in the remaining portion of this procedure 2 Connect the COMMON lead from the voltmeter to the common junction of AMPLITUDE controls R93A and R93B violet wire 3 Connect the DC volts probe to the
38. late of Vl is needed to drive the integrator the clamp is made push pull to prevent excessive current variations in the regulator tubes The action of V7B and V8B is such that if the applied waveform has peak excursions in excess of the potentials on the remaining cathode and plate these being deter mined by regulator tubes V5 and V6 a current will flow through R20 which drops the voltage to very nearly the potential of the regulated element of the conducting section of the diode The action of the other diodes is the same but 180 out of phase inasmuch as they are coupled to the plate of V2 In this way waveforms appearing on the clamped sides of R21 and R20 are assured to be of equal magnitude as well as 180 out of phase and further the average of dc level of the squarewave is ac curately controlled 3 3 LINEAR INTEGRATOR Consider the block diagram of the linear of feed back integrator as shown in Figure 3 3 Starting with the output voltage E it is seen that if the gain of the amplifier is high then the signal appearing at the junction of R and C the amplifier input must be small For a fixed output E as the gain is in creased the resultant signal at the input of the am plifier becomes arbitrarily small Since the voltage at the junction at R and C is arbitrarily small a squarewave applied to the input will cause a constant current in R Because the current charging and dis charging C is constant except for direction
39. lower the output impedance and improve stability This improved stability applies not only to the signal output but to the dc level at the output terminals The symbol for chassis or ground is used for the first time in the output terminal network R98 R99 and C29 In all other description the reference level for operation has been B and in the Model 202A the B line is completely isolated from the chassis Thus the chassis ground is available for whatever FULL WAVE RECTIFIER STOR Figure 3 9 Sect NI Page 7 B Q SYNC OUT Q P M a LI B0 M 60 VIT Sync Output Circuit of Model 202A connection is desired It is possible to consider the two output terminals as a transformer output and further to balance this apparent transformer to chassis by making R98 equal to R99 The capacitor C29 insulates the apparent transformer secondary from ground If single ended operation is desired the ground connection can be tied to either output terminal without affecting the amplifier 3 6 SYNC PULSE OUTPUT The output sync pulse is obtained from the bi stable circuit Vl and V2 On the minus switching reference at the plate of multiar diode V3 one positive pulse and one negative pulse appear for every cycle of operation These pulses are coupled to the grid 0 375 VOLTS REG 225 VOLTS REG C 75 VOLTS REG 8D M 6I Model 202A Power Supply Sect III Page 8
40. m V5 and return it to the original connection on R58 5 If the instrument meets the above voltage re quirements then the integrator section is functioning normally and the fault is confined to the bi stable circuit If the instrument does not pass the test then the trouble is in the integrator After all defective parts have been replaced and the necessary adjustments made an oscilloscope should be connected between pin 3 tube V17 and B to see if a good triangular waveform is obtained on all ranges TABLE 4 2 CAUSE AND OR SYMPTOM REMEDY No output voltage Power Replace Vl V2 Supply Section normal V3 Vl106 no triangle voltage be or VI7 If tube tween V17 pin 3 and B replacement fails on any range to cure the trouble See analysis pro cedure following this chart Check RANGE switch contacts components and connections Check Cl4 Cl18 for excessive leakage Same symptoms as above on one or more ranges TABLE 4 2 CONT D CAUSE AND OR SYMPTOM REMEDY Same symptoms as above when frequency dial is set near low frequency end Try replacement tubes for V15 V16 and or V17 Replace tubes V15 V16 V17 Check DC Balance Triangle not linear 4 4 SINE SYNTHESIZER AND FUNCTION SELECTOR When the trouble has been corrected in the Sine Synthesizer and Function Selector the following checks should be made to determine if
41. ms 10 6 volts rms for sine wave FREQUENCY RESPONSE Constant within 40 2 db over entire frequency range at rated output and load INTERNAL IMPEDANCE Approximately 40 ohms over the entire range SINE WAVE DISTORTION Less than 1 on all ranges except X100 Less than 2 rms on X100 00011 2 1 1 GENERAL The Model 202A Low Frequency Function Generator is a compact convenient and versatile source of transient free test voltages between 008 and 1200 cycles per second It is useful for any general purpose low frequency testing application and is particularly valuable in the testing of servo systems geophysical equipment vibration and stability char acteristics of mechanical systems electro medical equipment and for tne electrical simulation of mechanical phenomena Three types of output wave form are available sine square andtriangular Also a sync output pulse is available for external use The Model 202A Low Frequency Function Generator contains a type of relaxation oscillator that is par ticularly advantageous for the generation of very low frequencies Botha triangular and a sguarewave voltage function of time are inherent in the oscillating system Also a Sinewave function is produced by synthesis from the triangular wave Output amplitude and distortion are virtually in dependent of the frequency of operation This type Sect I Pagel SECTION GENERAL INFORMATION of oscillating system in inherently a c
42. nd R119 to Obtain Minimum Switching System 3 2 Distortion and Correct Frequency 4 9 3 3 Generalized Miller or Feedback 4 4 Output Voltage and Sync Pulse Test Setup 4 10 Integrator nou uoce a 3 3 4 5 Sine Wave Distortion Test Setup 4 10 3 4 Simplified Linear Integrator 3 4 4 6 Dial Accuracy Test Setup 4 10 3 5 Sine Synthesizer and Function Selector 3 5 4 7 Model 202A Top View Cover Removed 4 12 3 6 50 Waveforms 3 5 4 8 Model 202A Bottom View 3 7 Output Amplifier System of Model 202A 3 6 Bottom Plate Removed 4 13 3 8 Sync Output Circuit of Model 202A 3 7 4 9 Function Generator and Amplifier 4 14 3 9 Model 202A Power Supply 3 7 4 10 Power Supply 4 15 b 00011 2 iii Sect I Page 0 ENCY Low PREQUEL rom TION GENE x wo ac pacs 20 cag onm Figure 1 1 00011 2 Model 202A Low Frequency Function Generator Table 1 1 Specifications FREQUENCY RANGE 0 008 to 1200 cps in five decade ranges with wide overlap at each dial extreme DIAL ACCURACY Within 42 from 1 2 to 12 on dial 3 from 8 to 1 2 FREQUENCY STABILITY Within 41 including warm up drift and line voltage variations of 10 OUTPUT WAVEFORMS Sinusoidal square and triangular Selected by panel switch MAXIMUM OUTPUT VOLTAGE At least 30 volts peak to peak across rated load 4000 ohms for all three wavefor
43. nt Sect V Page 4 TABLE OF REPLACEABLE PARTS CIRCUIT 4 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ Rl This circuit reference not assigned R2 3 Resistor fixed composition 100 ohms 410 1 2 W R4 Resistor fixed composition 220 000 ohms 104 2 W R5 Resistor fixed composition 27 000 ohms 41095 1W R6 Resistor fixed composition 390 000 ohms 41095 1 W RT Same as R2 R8 Resistor fixed wirewound 25 000 ohms 10 10 W R9 Same as R2 R10 Resistor fixed deposited carbon 284 000 ohms 1 1 W Rll Resistor variable composition linear taper 25 000 ohms 420 1 3 W R12 Resistor fixed deposited carbon 181 000 ohms 196 1 W R13 Resistor fixed composition 330 000 ohms 41095 1 W R14 Resistor fixed composition 22 000 ohms 410 1 W R15 Resistor fixed composition 120 000 ohms 10 2 W R16 Resistor fixed composition 82 000 ohms 10 2 W R17 Same as R15 R18 Same as R13 NN BO NN 0687 1011 B 0693 2241 B 0690 2731 B 0690 3941 B 0816 0009 S 0730 0083 2100 0009 0730 0077 0690 3341 B 0690 2231 B 0693 1241 B 0693 8231 B See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument R24 thru R28 R24A thru R27
44. on 0727 0222 214 000 ohms 1 1 2 W R117 Resistor fixed composition 0687 4751 4 7 megohms 104 1 2 W R118 Resistor variable composition linear taper 2100 0015 500 000 ohms 20 1 4 W R119 Resistor variable wirewound linear taper 2100 0054 500 ohms 10 2 W BO R120 thru Same as R42 R123 S1 Switch toggle SPST 3101 0001 S2 Range Switch Assy includes C15 thru C18 202A 19W C33 R24A thru R28A R29 Function Switch Assy includes C34 R94 202A 19B R95 R117 Transformer power 9100 0026 Transformer pulse 9130 0002 Transformer pulse 402A 60B Tube electron 6AU6 1923 0021 Tube electron 6AL5 Tube electron 6C4 1921 0005 Tube electron OA2 1940 0004 Tube electron OA3 1940 0006 Same as V3 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument Sect V Page 10 00011 3 TABLE OF REPLACEABLE PARTS CIRCUIT 4 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ These circuit references not assigned Tube electron 12AX7 Z7 1932 0030 Tube electron 12AU7 ZZ 1932 0029 Same as V15 Same as VIT Tube electron 9U4GA B ZZ 1930 0008 Tube electron 6AV5GA or ZZ 1923 0023 6AU5GT ZZ 1923 0020 Same as V Same as V5 MISCELLANEOUS Binding Post Assembly red HP AC 10D Binding Post Assembly black HP AC 10C Binding Post In
45. onstant am plitude device so that no A V C system with as sociated delay in stabilization after freguency changes is required The frequency range from 008 to 1200 cycles per second is covered in 5 bands The frequency dial is linear The output system is a direct coupled amplifier System designed for either single ended or balanced output It has good stability with respect to direct current in the output and very low hum level Both the FUNCTION selectro switch and the AMPLITUDE control are so arranged that the characteristics of the amplifier are independent of their position The internal impedance of the output amplifier is approx imately 40 ohms and the unit is rated to deliver at least 30 volts peak to peak to a 4000 ohm load negative peak sync pulse of 10 volts into a 2500 ohm load is also provided It has a duration of less than 5 microseconds and occurs at the crest of the sinewave and at corresponding positions with the other functions Table 1 1 Specifications Cont d OUTPUT SYSTEM Can be operated either balanced or single ended Output system is direct coupled dc level of output voltage remains stable over long periods of time HUM LEVEL Less than 0 5 at rated output SYNC PULSE 10 volts peak negative less than 5 microseconds duration Sync pulse occurs at crest of sine wave and with corresponding positions on other waveforms WEIGHT Cabinet Mount Net 42 lbs Rack Mount Net 37 lbs
46. ragraph 4 13 All necessary specialized instructions are included with the replacement potentiometer 4 15 PERFORMANCE CHECK 4 16 OUTPUT VOLTAGE AND WAVEFORM CHECK 1 Connect test setup as shown in figure 4 4 in cluding a 3 9K ohm shunt resistor across the OUT PUT terminals of Model 202A 2 Set Model 202A controls as follows RANGE oue 5 Re e AL S xe xf ui X10 FREQUENCY DIAL 4 i59 93 xs 10 100 cps AMPLITUDE ded uM s s s full cw FUNCTION 5x x En SINE 3 Set oscilloscope VERTICAL SENSITIVITY to 5 volts cm Sect IV Page 10 4 Sinewave observed should be sinusoidaland have an amplitude of at least 30 volts peak to peak 5 Set FUNCTION to TRIANGULAR 6 Wave observed should betriangular and have an amplitude of at least 30 volts peak to peak 7 Set FUNCTION to SQUARE 8 Sguare wave observed should have an amplitude of at least 30 volts peak to peak 4 17 SYNC PULSE CHECK 1 Connect test setup as shown in figure 4 4 except oscilloscope is to be connected to SYNC OUT on Model 202A and not to OUTPUT MODEL 3OB OSCILLOSCOPE MODEL 202A LOW FREQUENCY FUNCTION GENERATOR Figure 4 4 Output Voltage and Sync Pulse Test Setup 2 Set RANGE to X100 and FREQUENCY DIAL to 10 1000 cps 3 Set oscilloscope VERTICAL SENSITIVITY to 5 volts cm and SWEEP TIME to 1 sec cm 4 The negative pulse observed should be less than 5 sec duration and have an amplitude equal
47. ssis through the test equipment If this happens one cathode resistor in output stage V20 will be shorted and the tube will be severely damaged Whenever possible the instrument frequency should be set to approximately 50 cycles sec to permit the use of a capacitor in series with the ac voltmeter or oscilloscope to eliminate the dc component Interaction between most of the circuits of the Model 202A makes a fairly definite procedure for trouble shooting necessary For example a fault in the oscillator section may easily cause considerable voltage deviations in the output system Therefore it is more desirable to divide the instrument into five sections as follows and consider each in turn Power Supply Function Generator Sine Synthesizer and Function Selector Output Amplifier Sync Out ob ow bo Sect IV Page l SECTION IV MAINTENANCE 4 2 POWER SUPPLY After power supply parts replacements or adjust ments a final check of regulated voltages should be made See Power Supply Regulator Adjustments in paragraph 4 9 TABLE 4 1 CAUSE AND OR SYMPTOM REMEDY Blown fuse Fl Instrument inoperative Indicator lamp won t no output volt Measure resistance from V2l socket pins 2 or 8 to B 99 000 ohms or more replace Val If less than 55 000 ohms clear short circuit in filter or regulator circuits then replace V2l Instrument inoperative Indicator lamp lights no outp
48. sulator 2 holes HP AC 54A Binding Post Insulator 3 holes HP AC 54B Connector Assembly binding post with G 76K ground link HP Coupler flexible 1 4 to 1 4 shaft HP AC 32A Coupler metal bellows type HP 417A 32 Dial frequency HP 202A 40A Escutcheon dial window HP G 99E Fuseholder T 1400 0084 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument TABLE OF REPLACEABLE PARTS CIRCUIT STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO Indicator dial HP 202A 40B Knob AMPLITUDE Knob FREQ Knob FUNCTION RANGE 6960 0003 Plug button R65 United Carr Fast Corp 1450 0020 1450 0022 Pilot Light Assembly jewel Pilot Light Assembly lampholder HP Socket tube 9 pin 1200 0008 Socket tube 7 pin AE 1200 0009 Socket tube octal AE 1200 0020 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrument Sect V Page ll CODE LETTER tN lt x lt C A m O Z O Z lt MO T Q T m U O gt N3X 2cHd 29382 r AC Wa AB AC AD AE AF AG AH AJ LIST OF CODE LET
49. t circuit The plus and minus switching references in the bi stable unit are adjusted so that the ratio of the triangular wave amplitude to the conduction voltages of the synthesizer diodes produces the least distortion of the sinewave This adjustment also fixes the average voltage at C and is equal to the average of the plus and minus switching references The dc voltages at D and the cathode of V4 are adjusted to be the average of the plus and minus Switching references Since these voltages are equal there is no change in DC level applied to the Output Amplifier as the AMPLITUDE control is varied Sect HI Page R59 R23 R22 BI STABLE LINEAR UNIT INTEGRATOR R94 Q s38 S3C RES 30 225 VOC PEG B 3 375 VOC REG e ab 225 VDC REG v4 P Ah M Ney 75VOC TO OUTPUT 75VDC 8 REG AMPLIFIER REG BD M 62B Figure 3 5 Sine Synthesizer and Function Selector A Waveform from integrator output to B Triangular regardless of function selector position B Waveform from Oto B with selector switch in sine position Note distortion especially at peaks C Waveform from D to B with selector switch in sine Mm position This is the distortion component present in waveform B above D Waveform from to i e difference between waveforms B and C above This is the approxi mated sinewave RO Figure 3 6 50 Waveforms Sect HI Page 6 The sinew
50. terminals The one marked G is connected directly to the instrument chassis The other two terminals vertically aligned are the OUTPUT terminals With respect to the ground terminal each of these outputs has equal magnitude of signal but they are 180 out of phase with each other The internal impedance between the two OUTPUT terminals is approximately 40 ohms SYNC OUT The Sync Out terminals are single ended and have an internal impedance of about 2 000 ohms Power Cable The three conductor power cable is supplied with a three prong plug The third prong is a round Off set pin which provides a chassis ground adapter may be obtained to permit use of this plug with two conductor receptacles 2 3 230 VOLT OPERATION This instrument is shipped from the factory with the power transformer primaries connected in parallel for 115 v operation unless otherwise spec ified on the order 1f 230 v operation is desired the primaries will have to be connected in series as shown in Transformer Details on the schematic wiring diagram of the Power Supply Section 2 4 OPERATION The following step by step procedure should be used as a guide when operating this instrument 1 Turn the POWER switch to ON Allow thirty seconds for oscillations to start The instrument will operate nearly within specifications after a few minutes warm up It will be within specifi cations after 30 minutes Sect II Page 2 2 Set the RANGE and FR
51. the instru ment is again functioning correctly l Sine Wave Observe the waveform between pin 2 V18 and B with oscillator set to 50 cycles sec and the AMPLITUDE control at maximum Set the FUNCTION switch in the SINE position The wave form should be substantially sinusoidal and approx imately 30 volts peak to peak See Figure 3 6B Observe the waveform between pin 7 V18 and B with the same conditions as above The waveform should be similar to Figure 3 6C and approximately l volt peak to peak 2 Triangular Wave Observe the waveform be tween Pin 2 V18 and B with the oscillator set to 90 cycles sec and the AMPLITUDE control at max imum Set the FUNCTION switch in the TRIANGULAR position The waveform should be triangular and approximately 30 volts peak to peak Observe the waveform between pin 7 V18 and B with same conditions as above The waveform should be triangular and approximately 1 volt peak to peak 3 Square Wave Observe the waveform between pin 7 V18 and B with the oscillator set to 50 cycles sec and the AMPLITUDE control at maximum Set the FUNCTION switch to the SQUARE position The waveform should be square and approximately 30 volts peak to peak The dc voltage across the OUTPUT terminals should be adjustable to zero under any operating conditions by means of R65 TABLE 4 3 CAUSE AND OR SYMPTOMS REMEDY Maladjustment of R49 R51 and R60 or defective diodes CR2 through CRI3
52. trial Condenser Corp Insuline Corp of America Jennings Radio Mfq Corp E F Johnson Co Lenz Electric Mfg Co Micro Switch Mechanical Industries Prod Co Model Eng amp Mfg Inc The Muter Co Ohmite Mfg Co Resistance Products Co Radio Condenser Co Shalleross Manufacturing Co Solar Manufacturing Co Sealectro Corp Spencer Thermostat Stevens Manufacturing Co Torrington Manufacturing Co Vector Electronic Co Weston Electrical Inst Corp Advance Electric amp Relay Co E DuPont Electronics Tube Corp Aircraft Radio Corp Allied Control Co Inc Augat Brothers Inc Carter Radio Division CBS Hytron Radio amp Electric Chicago Telephone Supply Henry L Crowley Co Inc Curtiss Wright Corp Allen B DuMont Labs Excel Transformer Co General Radio Co Hughes Aircraft Co International Rectifier Corp James Knights Co Mueller Electric Co Precision Thermometer amp Inst Co Radio Essentials Inc Raytheon Manufacturing Co Tung Sol Lamp Works Inc Varian Associates Victory Engineering Corp Weckesser Co Wilco Corporation Winchester Electronics Inc Malco Tool amp Die Oxford Electric Corp Camloc Fastener Corp George K Garrett Union Switch amp Signal Radio Receptor Automatic amp Precision Mfg Co Bassick Co Birnbach Radio Co Fischer Specialties Telefunken c o MVM Inc Potter Brumfield Co Cannon Electric Co Dynac Inc Good All Electric Mfg Co ADD
53. ut voltage Defective 6AU5 tubes V22 V23 Instrument inoperative normal voltage at V 21 Extremely low or no voltage between V5 pin 5 and B Capacitor C6 short circuited Defective OA2 tube V5 Instrument inoperative normal 4375V reg ulated 4 225V reg off voltage Defective OA3 tube V6 75V regulated off voltage Opencircuit in R62 R84 R85 R9l or R92 Instrument inoperative No 4225 regulated 75 regulated voltages V5 and or V6 not ionized Sect IV Page 2 4 3 FUNCTION GENERATOR bi stable circuit and integrator A REPAIR ANALYSIS OF FUNCTION GENERATOR If replacing tubes does not restore the triangle voltage then a simple test should be made to deter mine whether the fault is in the integrator or the bi stable circuit This test is as follows Connect a high resistance dc voltmeter between B and pin 3 of tube V1 2 Set the RANGE switch to the X 01 position Dis connect the lead from the center lug of the variable resistor R58 Temporarily connect this lead to pin 5 V6 75 Reg 3 After this connection is made the voltage indi cated by the voltmeter should slowly climb until it is over 200 volts 4 Remove the lead from the 75 Reg supply and connect it to pin 2 V5 225 regulated The volt meter indication should now drop slowly to less than 140 volts Disconnect the lead fro
54. w This circuit reference not assigned See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recomne nded spares for one year isolated service for one instrument 00011 2 TABLE OF REPLACEABLE PARTS Sect V Page 3 CIRCUIT 6 STOCK REF DESCRIPTION MFR amp MFR DESIGNATION NO TQ Same as Cll C21 Capacitor fixed mica 0140 0010 820 pf 410906 500 vdcw C22 Same as Cll C23 Capacitor fixed ceramic 0150 0014 005 uf 500 vdcw C24 Same as C4 C25 This circuit reference not assigned C26 Same as C4 C27 28 Capacitor fixed mica 0140 0026 22 pf 41095 500 vdew C29 Same as C3 690 31 32 These circuit references not assigned C33 Capacitor variable ceramic 0130 0001 1 45 pf 500 vdcw Optimum value selected at factory Average value shown Same as C10 Capacitor fixed electrolytic 2 section 0180 0012 20 uf sect 450 vdcw CC Diode germanium BU 1910 0009 Diode silicon HP G 29M 45 Fuse cartridge 3 amp 115V T 2110 0003 Fuse cartridge 1 6 amp 230V E 2110 0005 Lamp incandescent 6 8V 2pin base GE 12 N 2140 0012 Inductor 6H at 125 MA 264 ohms HP 9110 0004 Power Cable Elec Cords Co 8120 0015 See List of Manufacturers Code Letters For Replaceable Parts Table TQ Total quantity used in the instrument RS Recommended spares for one year isolated service for one instrume
55. with a sinewave when the output is loaded with 4000 ohms or higher 4 6 SYNC OUT Specifications call for a negative sync pulse of 10 volts peak with a duration less than 5 microseconds The sync pulse occurs at the sinewave crest and at corresponding positions on other waveforms TABLE 4 5 CAUSE AND OR SYMPTOMS REMEDY No sync pulse Check for negative pulse with oscilloscope and with Model 202A set for highest frequency Replace V1 Large overshoot Replace CRI 4 7 TUBE REPLACEMENT Any tube with standard JETEC characteristics can be used for replacement purposes Whenever a tube is replaced that part of the in strument which might be affected by the change must be tested and if necessary adjusted to be within specifications See paragraph 4 8 Tube Replacement Chart Sect IV Page 4 4 8 TUBE REPLACEMENT CHART TABLE 4 6 TUBE EFFECT READJUSTMENT V7 V8 V15 V16 V17 V18 V19 V20 None Variations in bottoming voltage eliminated by clamps V7 and V8 Frequency shift and distortion increase due to contact potential variations DC output level shift probably as a function of amplitude con trol setting Possible change in frequency distortion or dc balance from change in regulated voltages Same effect as change in V3 possible but to much less degree Frequency change and unbalance of triangle Change in dc output component independent of AMPLITUDE M
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