HP Archive
Contents
1. The above switches and pots must be used together as designated although the current attenuator assembly may be used on any serial numbered instrument CHANGE NO 13 Figure 5 7 Change primary power input to T2 as shown below Table 6 1 Change hp part no WI to 8120 0050 Change hp part no of Shield bottom in miscellaneous to 200 AB 6B Change hp part no of Bracket pot in miscellaneous to 618B 12B Delete J1 and S4 CHANGE NO 14 Table 6 1 Change the hp part no of MP1 to 1500 0002 Change the hp part no of MP2 to 5040 02122. 3 1 Section IV Model 201C ATTENUATOR di RANGE O ATTENUATION O ATTENUATION 1 I VERNIER l EREQUENCY OSCILLATOR AMPLIFIER 0 40db via V2 V3 V4 V5 ATTENUATOR O 600n O lOdb Y 6000 20 40db POWER SUPPLY 201C 8 1988 Figure 4 1 Block Diagram of Model 201C 4 0 Model 201C Section IV SECTION IV THEORY OF OPERATION 4 1 GENERAL 4 2 The Model 201C consists of an oscillator section an amplifier section an output attenuator and a power supply as shown in the block diagram Figure 4 1 4 3 OSCILLATOR SECTION 4 4 The oscillator section consists of V1 and V2 as a resistance coupled amplifier containing two feedback loops The positive feedback loop sets up oscillation while the negative feedback loop reduces distortion and maintains a constant amplitude of oscillation The positive feedback network contains fixed resistances established by the RANGE switch and a variable capacitance A simplified schematic diagram is shown in Figure 4 2 The network is designed so that RI C1A and B R8 CIC and D Figure 4 2 Simplified Schematic Diagram of Oscillator Section 4 5 The oscillator output is coupled to the input stage through C8 and the input voltage is derived from this signal Oscillation will occur when there is zero phase shift between the voltage applied to the network and the voltage applied to the grid of V1 The zero phase shift point is also the point of minimum loss through
3. Excessive Distortion II OPERATING INSTRUCTIONS 3 1 5 32 Repair L spes 3 1 Controls and Terminals 3 1 5 33 Cabinet Removal 3 7 Operating Instructions 3 1 5 35 Tube Replacement 3 8 Low Level Applications 3 1 5 37 Replacement of Lamp 5 39 Replacing Range Switch Section Page 5 40 Adjustment of Factory Selected IV THEORY OF OPERATION o o 000 4 1 e ACCU D ELE 4 l General 2 25 RANIA sae ita 4 1 Rate 4 3 Oscillator Section AAA e E 4 1 VI REPLACEABLE PARTS 4 8 Amplifier Section o oooo o o 4 1 ER RIA es e a aa 64 Ordering Information Section Page 6 6 Non Listed Parts V MAINTENANCE ji oss SR TGT rra ie 5 St luid el n 1 22 ceu os 5 1 APPENDICES S3 T stEq ipin tit 2r swe cana vars we 5 1 A CODE LIST OF MANUFACTURERS 5 5 Periodic Maintenance 5 1 B SALES AND SERVICE OFFICES 5 8 Performance Checks 5 1 C MANUAL BACKDATING CHANGES LIST OF TABLES Number Page Number bi Specifications cs aa rra eier 10 54 Frequency Response Check 5 1 Required Test Equipment 50 5 5 Troubleshooting Chart 5 2 Tube Replacement List eee 5 0 5 6 Factory Selected Components 5 3 Calibration Accuracy Check 5 1 6 1 Replaceable Parts ESTE LIST O
4. R43 CI2C R3 sl 800 350V Ci2B 40 4 2 8 V6 A SARAGT R29 4 4 8 7 7 18 RARI i E 3 3 7 2 2 201C D 19694 Section V R34 R35 R36 R37 59480218370 5400 31297 o 6 B S3A f ii R44 3 600 CAR H y 538 O Ku O D R38 R39 R40 Ana R46 jee 19 6 66 7 277 4 26200 908 Lio DB B 20 DB 36 08 4958 Figure 5 7 Schematic Diagram Page 5 9 5 10 Appendix C Model 201C amp MANUAL BACKDATING CHANGES MODEL 201C AUDIO OSCILLATOR Manual Serial Prefixed 351 hp Part No 201 C 906 This manual backdating sheet makes this manual applicable to earlier instruments Instrument component values that differ from those in the manual yet are not listed in the backdating sheet should be replaced using the part number given in the manual Instrument Serial Number Make Manual Changes Instrument Serial Number Make Manual Changes 4 through 9 11 12 13 351 06158 to 06108 All Attenuator switches 006 and 133 5 through 9 11 13 14 308 7 through 9 11 12 13 CHANGE NO 1 Table of Replaceable Parts Coupler flexible Change to hp Part No 5060 0210 C12A is single capacitor 10 uF hp Part No 0180 0002 Change C12B to C12A B CHANGE NO 2 Table of Replaceable Parts and Figure 5 8 Schematic Delete R42 45 Change T1 to hp Part No 9120 0037 If T1 is replaced by current Part No add R42 and R45 CHANGE NO 3 Frequency drive gears are changed separate pa
5. Model 201C with vernier to obtain 42 5 volts on Model 331A On Model 331A set FUNCTION to SET LEVEL METER RANGE to 100 and adjust INPUT SENSITIVITY for 100 full scale is 100 Set FUNCTION to DISTORTION and tune Model 331A for null Set METER RANGE to 1 and retune for null Reading should be less than 1 full scale is 1 Repeat steps a through g except set Model 201C RANGE to X100 and frequency dial to 200 0 L Model 201C 20 kHz and Model 331A FREQUENCY RANGE to X1K and FREQUENCY dial to 20 NOTE H the Model 201C is slightly out of specification refer to Adjustments Paragraph 5 16 and Factory Selected Components Table 5 6 If a malfunction exists refer to Troubleshooting Para graph 5 24 5 18 ADJUSTMENTS 5 17 POWER SUPPLY 5 18 Proper operation of the power supply is vital to proper operation of the instrument Excessive ripple in the output or a low output voltage can cause the instrument to have excessive distortion or otherwise operate out of specification To check the power supply measure the power supply ripple and check the B voltage as described in Table 5 5 1 For cabinet removal refer to Paragraph 5 33 5 19 OUTPUT VOLTAGE a Connect Model 201C as shown in Figure 5 2 and proceed as follows b Rotate RANGE switch to X10 position c Rotate frequency dial to 20 d Rotate amplitude control to 100 fully clockwise e Set ATTENUATIO
6. d CHECK OR SYMPTOM POSSIBLE CAUSE REMEDY 3 AMPLIFIER Load instrument with 600 ohms Measure low frequency distortion at output terminals Excessive 2nd Harmonic distortion Defective V4 or V5 Replace Load instrument with 600 ohms Measure signal voltage on V3A grid pin 5 for approximately 13 V rms when instrument delivers 1 watt Signal voltage on grids pin 5 of V4 and V5 should be approximately 5 V rms Weak signals driving V4 and V5 Defective V3 Replace Amplitudes of signals driving V4 and V5 Defective R21 Investigate and replace not equal or R22 Rotation of amplitude control causes erratic amplitude variation in output Measure dc voltage for approximately 0 2 volts Defective C9 Replace See Paragraph 5 31 Voltage high Voltage above satisfactory Control still pro Defective R17 Replace duces unstable output variation Re m Figure 5 4 Left Side View 5 6 Model 201C CoNo R30 R32 R42 R20 R23 cic CIB C2 C3 CIA DSI Figure 5 5 Bottom and Right Side Views ol I l ee bel Kl E d gt Section V 5 7 Section V 5 33 CABINET REMOVAL 5 34 To remove instrument from the cabinet unscrew the two machine screws on the rear of cabinet and pull front panel forward The bezel remains attached to front panel 5 35 TUBE REPLACEMENT 5 36 Tubes used in the Model 201C are listed in the Tube Replacement List Table 5 2 A tube may be replaced wi
7. the network as shown in Figure 4 3 The frequency of oscillation relative frequency in Figure 4 3 is given by the expression 1 Fr 27 y R1 C1A B R8 CIC D KA VA VA 1 2 4 8 RELATIVE _ FREQUENCY Ratio 6 5 1 9 Phase Figure 4 3 Oscillator Network Characteristics 4 6 The cathode by pass capacitors in the oscillator section C5 C7 correct phase shift at higher frequencies 4 7 The negative feedback network minimizes change of output amplitude with change in frequency The incandescent lamp used as a cathode bias resistor for V1 is part of the negative feedback voltage divider It has a temperature resistance characteristic such that its resistance increases in direct proportion to the voltage applied to it Thus changes in its resistance will change the amount of negative feedback in the oscillator output The thermal inertia of the lamp is great enough to be unaffected by sine wave voltages at the lowest frequencies involved 4 8 AMPLIFIER SECTION 4 9 The amplifier section of the instrument consists of a voltage amplifier V3A direct coupled to a phase inverter V3B and a push pull output stage V4 and V5 The output transformer contains a tertiary winding for overall negative feedback around the amplifier As a result of negative feedback in excess of 30 dB very little distortion is introduced by the amplifier section of the instrument 4 1 Section V 5 0 Ta
8. the period or frequency for each frequency setting shown in Table 5 3 hp 201c AUDIO OSCILLATOR ELECTRONIC COUNTER hp 5223L sof 10 gt a o a o Figure 5 1 Calibration Accuracy Check Table 5 3 Calibration Accuracy Check period 49 5 to 50 5 ms period 19 9 to 20 1 ms period 4 95 to 5 05 ms period 4 95 to 5 05 ms freq 495 to 505 Hz freg 1980 to 2020 Hz freq 1980 to 2020 Hz freq 4950 to 5050 Hz freg 19800 to 20200 Hz 5 11 FREQUENCY RESPONSE CRECK a Connect test setup as shown in Figure 5 2 including a 600 ohm load resistor across the output terminals of the Model 201C b Set the Model 201C frequency to 1 kHz and Attenuation Switch to O dB c Adjust the Model 201C amplitude vernier to obtain O dB reading on the voltmeter d Set the Model 201C to each of the frequency settings in Table 5 4 At each setting the voltmeter should read O dB 1 dB 5 1 Section V VOLTMETER Figure 5 2 Frequency Response and Output Check Table 5 4 Frequency Response Check 1 dB to 1 dB dB to 1 dB 1 dB to 1 dB 1 dB to 1 dB 1 dB to 1 dB 1 dB to 1 dB 5 12 OUTPUT CHECK a Connect test setup as shown in Figure 5 2 using a 600 ohm 3 watt load resistor b Set the Model 201C Attenuation switch to 0 dB c Increase attenuation vernier in CW direction until the voltmeter reads 42 5 volts This is an output of 3 watts 5 13 DISTORTION CHECK 5 14 One Watt Output a Connect te
9. 07 V1 Change to 6837 hp Part No 1923 0037 V2 Change to 6K6 hp Part No 1923 0033 22 26 VAC AT 1000 CPS Figure 1 CHANGE NO 8 Table of Replaceable Parts C12 Change to 4 section 20 uF sect hp Part No 0180 0025 C12B Change to 20 uF R27 Change to 33 kohms hp Part No 0693 3331 NOTE Stock Nos in current manual may be used to improve hum and distortion CHANGE NO 9 Table of Replaceable Parts Rotary switch with pot change to hp Part No 3100 0371 pot only hp Part No 2100 0385 Knob change to hp Part No 0370 0024 CHANGE NO 10 For Serials Prefixed 311 331 and 351 06108 and below only Table of Replaceable Parts and Figure 5 8 Schematic Delete R46 Appendix C Model 201C CHANGE NO 11 Table of Replaceable Parts and Figure 5 8 Schematic Delete C13 and R30 CHANGE NO 12 Table of Replaceable Parts and Figure 5 8 Schematic Delete R47 169 ohm resistor hp Part No 0811 0041 and R48 potentiometer 100 ohms hp Part No 2100 0730 Add R24 Resistor fxd comp 470 ohms 10 2 W hp Part No 0693 4711 and R45 Resistor fxd comp 1 kohm 10 2 W hp Part No 0693 1021 Change schematic diagram as in Figure 2 V5 6V6GT 6K6GT va 6V6GT 6K6GT Figure 2 ATTENUATOR 3 Instrument Seria No Switch with pot Pot alone 0 to 236 03207 3100 0124 2100 0115 308 03208 to 331 03632 3100 0371 2100 0385 351 03633 and above 3100 0788 2100 0839 NOTE
10. F ILLUSTRATIONS Number Page Lt Model 2016 scx ia aaa IG aaa asa 1 1 4 1 Block Diagram of Model 201C 4 0 4 2 Simplified Schematic Diagram of Oscillator Section eum gw ens es mmis 4 1 4 3 Oscillator Network Characteristics 4 1 5 1 Calibration Accuracy Check 5 1 5 2 Frequency Response and Output Check ree ars 52 Number 5 3 Distortion Check 2 22 ovorum 24 CeftSide VIEW coin 5 5 Bottom and Right Side View 5 6 Tube Location Voltage and Resistance euer pase ied a 5 7 Schematic Diagram Section I Model 201C Table 1 1 Specifications Frequency Range 20 Hz io 20 kHz in three ranges 20 Hz to 200 Hz 200 Hz to 2 kHz 2 kHz to 20 kHz Calibration Accuracy 1 Calibration controls provided for standardizing bands Frequency Stability 2 under normal temperature conditions and including initial warmup aging of components etc Dial 6 inch diameter calibrated over 3009 of arc Total scale length 50 inches Frequency Response 1 dB over entire frequency range Reference 1 kHz Output 3 watts maximum or 42 5 volts into 600 ohm load One terminal at ground potential 50 volts maximum no load voltage Distortion Less than 1 2 50 Hz to 20 kHz at 1 watt output Less than 1 20 Hz to 20 kHz at 3 watts output Attenuator 0 to 40dB in IOdB steps concentric amplitude control varies output continuously zero to maximum at any at
11. HP Archive This vintage Hewlett Packard document was preserved and distributed by www hparchive com Please visit us on the web Thanks to on line curator Kenneth Kuhn for supplying and scanning this vintage document HP O a m AUDIO OSCILLATOR 201C i i 1 H l HEWLETT hp PACKARD Rs 9102 dH HEWLETT Ki PACKARD CERTIFICATION The Hewlett Packard Company certifies that this instrument was thoroughly tested and inspected and found to meet its published specifications when it was shipped from the factory The Hewlett Packard Company further certifies that its calibration measure ments are traceable to the U S National Bureau of Standards to the extent allowed by the Bureaw s calibration facility WARRANTY AND ASSISTANCE All Hewlett Packard products are warranted against defects in materials and workmanship This warranty applies for one year from the date of delivery or in the case of certain major compo nents listed in the operating manual for the specified period We will repair or replace products which prove to be defective during the warranty period provided they are returned to Hewlett Packard No other warranty is expressed or implied We are not liable for consequential damages Service contracts or customer assistance agreements are available for Hewlett Packard products that require maintenance and re pair on site For any assistance contact your nearest Hewlett Packard
12. N switch to O dB position f Adjust RIO for 45 volt indication on the volt meter 5 20 DISTORTION ADJUSTMENT a Connect the 201 output to the input of the 331A Distortion Analyzer as in Figure 5 3 b Set the 201C frequency dial to 50 and the Range to XI c Set the attenuation controls for a 42 5 volt output into a 600 ohm load d Adjust R48 for minimum distortion as indicated by the 331A 5 21 FREQUENCY CALIBRATION a Turn on the oscillator and allow 30 minutes for it to warm up Put 600 ohm resistive load on oscillator for all adjustments Section V b Set the RANGE switch to X10 and the dial to 20 Connect the instrument to the Frequency Counter If the output from the Model 201C is not 200 Hz adjust R7A so that the output is exactly 200 Hz when the dial rests on 20 X10 range NOTE It is necessary to remove the instrument from the cabinet for each adjustment and then replace it for check after each adjustment The instrument oscillates at a different frequency when removed from the cabinet Use non metallic bakelite etc aligning tools to adjust trimmer capacitors Set the Model 201C output to any convenient level for reference Change the dial setting to 200 and note the output The level should remain at the established reference and frequency should be within 1 2 percent of 2000 Hz If this is not the case adjust C2 and C4 alternately to obtain 2000 Hz at the established refe
13. Sales and Service Office Addresses are provided at the back of this manual m OPERATING AND SERVICE MANUAL hp Part No 201 C 906 MODEL 201C AUDIO OSCILLATOR Serials Prefixed 0961A Appendix C Manual Backdating Changes adapts this manual to Serials Prefixed 351 06357 and below 331 311 308 236 133 006 and serials 1358 to 557 and below Copyright Hewlett Packard Company 1959 P O Box 301 Loveland Colorado 80537 U S A Printed Aug 1971 D 9 Model 201C Table of Contents TABLE OF CONTENTS Section Page Section I GENERAL INFORMATION 1 1 5 10 Calibration Accuracy Check 1 D eseHpliom eere res rere ers 1 1 5 11 Frequency Response Check 1 4 Instrument Identification 1 1 5 12 Output E 1 7 Accessories Available 1 1 5 3 Distortion Check 5 16 Adjustmentsi RR Section Page 5 17 PowerSupply Zo EE E LIGNE EE 2 1 3 19 Output Voltage 1 euis 2 1 Inspections ii SE G 2 1 5 20 Distortion Adjustment 2 4 Power Requirements 2 1 5 21 Frequency Calibration 2 6 Power CABS Loi nc NGT aga kagak a an xc 24 5 22 Dial Retracking eere 29 230 VoltOper tion eaaa eee rnt 24 5 24 Troubleshooting 2 11 Repackaging for Shipment 2 1 5 25 Trouble Localization 5 28 Troubleshooting Chart Section Page 5 30
14. ations bend split rotor plates these plates are the outside plates of each section of C1 as described below to bring point on dial into calibration NOTE Outside rotor plates of each section are divided into segments The segment associated with specific dial points are those which engage the stator when the desired dial point is under the index To raise the frequency spread the plates To lower frequency squeeze plates c Start bending at highest frequency out of calibration and work toward the lowest frequency Bend the plates of the front two sections by the same amount as the rear two sections It should not be necessary to bend plates near the high end of the dial d If the above procedures do not result in correct calibration start over by adjusting C2 and C4 Then work toward the low end by setting the dial to the next numbered point and bending one of the outer rotor plates in each section 5f C1 at the point of mesh Continue this procedure to the low end of the dial to obtain approximately correct frequencies Repeat the bending procedure from the high end this time making fine adjustments of frequency with the other outer rotor plates In this way bending of any one plate is minimized e If bending process moves the dial out of calibration at 207 restore calibration at this point by bending the plates rather than by an adjustment of R7A NOTE If the X10 range is within specifications and the high end
15. aving similar characteristics can be substituted for the equipment listed 5 5 PERIODIC MAINTENANCE 5 6 The tuning capacitor drive bearing should be lubricated once or twice a year depending upon the amount of use One drop of light machine oil in each of the bearing holes is adequate The holes are located in the bearing projections of the vertical casting behind the front panel 5 7 The inside of the instrument should be cleaned occasionally to prevent accumulation of dust and dirt from shorting plates of the main tuning capacitor Clean tuning capacitor with extreme care DO NOT apply any force to it which could bend the plates and destroy calibration Compressed air under a pressure not to exceed 60 psi is recommended for cleaning 5 8 PERFORMANCE CHECKS 5 9 The Performance Checks are front panel procedures designed to compare the Model 201C with its published specifications These checks may be incorporated in periodic maintenance post repair and incoming inspection The Performance Checks should be conducted before any attempt is made to adjust or calibrate the instrument A Performance Check Test Card is provided at the end of this section for recording the performance of the instrument The card may be removed from the manual and used as a permanent record of the incoming inspection or of a routine Performance Check 5 10 CALIBRATION ACCURACY CHECK a Connect test setup as shown in Figure 5 1 b Check
16. ble 5 1 Recommended Test Equipment Instrument Type Required Characteristics DC Voltage Range 1 to 310 volts hp Model 427A Ohmmeter Range ohm to 500 megohms Accuracy 3 AC Voltage Range mV to 100 volts Multi Function Meter Distortion Measurement Range 20 Hz to 20 kHz Distortion Analyzer hp Model 331A Frequency Calibration Accuracy 2 Elimination Characteristics Fundamental frequency reduced by more than 60 dB Sensitivity Ability to measure distortion levels of 1 full scale Electronic Frequency Range 20 Hz to 20 kHz Counter hp Model 5223L Table 5 2 Tube Replacement List TUBE FUNCTION CHECK REQUIRED VI 6AU6 Oscillator Table 5 5 step 2 V2 6AQS Oscillator V3 6SN7GT Voltage Amp Table 5 5 step 3 phase inverter V4 6V6GT Output Tube Table 5 5 step 3 VS 6V6GT Output Tube Model 201C Model 201C Section V SECTION V MAINTENANCE 5 1 INTRODUCTION 5 2 This section provides maintenance and service information for the Model 201C Audio Oscillator The section includes recommended test equipment a tube replacement table performance checks adjustments repair procedures and a troubleshooting table The performance checks will verify proper instrument operation 5 3 TEST EQUIPMENT 5 4 Test equipment recommended for use in maintaining and checking performance of the Model 201C is listed in Table 5 1 Equipment h
17. d therefore it adjusts the output voltage of the instrument from zero to a maximum value established by the attenuator The outer control is a bridged T type attenuator providing 0 to 40 dB of attenuation in 10 dB steps 3 6 OUTPUT terminal Two binding posts on the lower center of the front panel are the output terminals for the oscillator Terminal marked G is connected to the chassis of the instrument 3 7 OPERATING INSTRUCTIONS a Connect the power cable to required power source b Turn the power switch ON and allow approximately five minutes for the instrument to reach its normal operating temperature c Set the FREQUENCY dial and RANGE switch for desired output frequency d Set ATTENUATION outer control to O dB then set inner control amplitude for desired output voltage e Set ATTENUATION outer control if desired to reduce output level in 10 dB steps NOTE When the attenuator is in the OdB position the amplifier output is delivered from less than 600 ohms at frequencies below 5000 Hz and it will produce its rated output 3 watts across a load of 600 ohms When the attenuator is positioned for 204B or more attenuation the internal impedance is 600 ohms 3 8 LOW LEVEL APPLICATIONS 3 9 To avoid excessive noise and hum at low output levels 40 dBm or less it it good practice to attenuate the oscillator output 30 or 40 dB and use the amplitude control as an output vernier to obtain desired level
18. eceptacle grounds the instrument The offset pin on the power cable three prong connector is the ground pin 2 8 To preserve the protection feature when operating the instrument from a two contact outlet use a three prong to two prong adapter and connect the pigtail on the adapter to ground 2 9 230 VOLT OPERATION 2 10 To operate the Model 201C from a 230 volt 10 source change the primary windings of T2 from a parallel to a series arrangement Refer to the schematic diagram and proceed as follows a Remove the two bare wire jumpers from the terminals on T2 These jumpers connect terminal 2 to 3 and 4 to 5 on the primary winding b Connect a new jumper between terminal 3 and 4 c Change the line fuse to a 0 8 A slo blo 2 11 REPACKAGING FOR SHIPMENT 2 12 The following is a general guide for repackaging for shipment If you have any question contact your local hp Sales and Service Office See Appendix at the back of this manual for office location NOTE If the instrument is to be shipped to Hewlett Packard for service or repair attach a tag to the instrument identifying the owner and indicating the service or repair to be accomplished include the model number and full serial number of the instrument In any correspondence identify the instrument by model number serial number and serial number prefix a Place instrument in original container if available If original container is not available a su
19. equencies above 50 Hz at 1 watt output and less than 1 per cent from 20 Hz to 20 kHz at 3 watts output 1 3 The output level of the Model 201C is adjustable An attenuator is also provided to adjust the output level over a O to 40 dB range in lO dB steps The attenuator is a bridged T type providing virtually a 600 ohm impedance looking back into the instrument at attenuation levels of 20 dB and above and keeps the hum level low relative to small signal levels With the attenuator in the O dB position output impedance becomes less than 600 ohms thus insuring good voltage regulation for varying load conditions providing maximum output power 1 4 INSTRUMENT IDENTIFICATION 1 5 Hewlett Packard uses a two section serial number The first section prefix identifies a series of instruments The last section suffix identifies a particular instrument within the series If a letter is included with the serial number it identifies the country in which the instrument was manu factured 1 6 If the serial prefix of your instrument differs from the one on the title page of this manual a change sheet will be supplied to make this manual compatable with newer instruments or the backdating information in Appendix C will adapt this manual to earlier instruments All correspon dence with Hewlett Packard should include the complete serial number 1 7 ACCESSORIES AVAILABLE 1 8 11000A Cable Assembly This cable assembly consists of two d
20. erenced but remember that components associated with reference tubes are also failure possibilities Perform the steps in the chart in the order given since the chart assumes that the section ahead of the one under investigation is operating satisfactorily For all testing of the Model 201C the use of a variable transformer to adjust the line voltage to 10 of the normal line voltage is recommended An instrument in good condition should operate over this range An instrument with marginal operation from weak tubes etc can be quickly identified at low line voltages and such weaknesses become easier to trace 5 30 EXCESSIVE DISTORTION 5 31 In general distortion in the Model 201C can come from the following a Leaky coupling capacitors C6 C8 C9 C10 C11 There should be no dc voltage on grids following these capacitors b Defective electrolytie filter and decoupling capa citors Make ripple measurements as described in Table 5 5 c Defective tubes When a tube is replaced in the instrument the distortion measurement should be rechecked d Low B Check the supply voltages against those shown in the Voltage and Resistance diagram with a line voltage of 115 volts 5 32 REPAIR Model 201C Section V Table 5 5 Troubleshooting Chart 9 CHECK OR SYMPTOM POSSIBLE CAUSE REMEDY 1 POWER SUPPLY Measure 310 VDC at 115 V line between pin 8 V6 and chassis Voltage low Defective V6 Replace Measure powe
21. esistance DI ta ta NOTES VOLTAGES MEASURED BETWEEN INDICATED POINTS AND CHASSIS WITH VOLTMETER OF 122 MEGOHM INPUT RESISTANCE CAPACITY VALUES IN pF RESISTANCE IN OBMS UNLESS OTHERWISE NOTED VALUE SELECTED DURING MANUFACTURE o b PANEL CONTROL Nu Tees A PANEL MARKING SCREWDRIVER ADJ d CHASSIS GROUND L EARTH GROUND RANGE 8 3M RBA 500K FREQ ADJ JA mga ma COPYRIGHT 1955 BY HEWLETT PACKARD COMPANY R2A R3A R2 R3 830K 83K O0 INT SIA i FREQUENCY DIAL H 1 1 d sig Pao R7 xioo R6 830K 83K RTA R6A 50K i 5K SI FREQ ADJ FREQ ADJ FREQ RESPONSE ADJ w n Q H CIA B CIC D R9 2000 RIO won Ri2 f AMPLITUDE 120K 27 ADJ C THOV Ra 5 Fas 39 6AUG pF j 2 De 6 96V_ C4 7 45 7 pF FREQ le7V RESPONSE ADJ 2 c5 E RTII LAMP Model 17 26VAC a5 AT IKHz ES 310V v Pei ME 22K VS 6V66TA v2 hc CIO R42 Del 56K 5 310V is cl T 47pF 220Y R30 R23 2 I2K 470K c9 cis 8 0 047 4 560 15V 25 pF R48 isov ATTENUATION Ris ite VERNIER 45V V3 95V GH add 6SN7GT 2 c7 s d p RI9 2 4700 4 bi R2I R25 22K 470K v4 i 6V6GTA Ne amp 4 RTII i 5 LAMP eg 3 CSC R3I EE 800 6 350V E Fl 1 Is6A SI 2 V6 5AR4GT Model 201C 310V v5 6V6GTA cio R42 bo 56K 8 5V 6SN7GT afi T 700 LM v4 i 6V6GTA We o LI A
22. he schematic and the typical value is shown Table 5 6 describes the function of the factory selected components and gives instructions for their selection Normally these components do not need to be changed unless another associated component is changed Table 5 6 Factory Selected Components COMPONENT FUNCTION AND SELECTION AVERAGE C5 Compensates for High Frequency response 56 pF Decrease C to increase amplitude X100 range C13 and R30 Minimizes distortion at 20 kHz 560 pF Change size of R30 first C13 has very little effect Value of R30 is function of oscillator tubes 12 kohm Adjusts frequency at high end of X10 range 0 Adjusts frequency at high end of X1 range l pF Decreases distortion caused by oscillations in the output amplifier Provides proper range for R10 Output Voltage 47 pF 1800 ohms 2200 ohms 2600 ohms Adjustment Increase R9 to increase amplitude Adjusts bias level of V2 Changes loop gain of amplifier 5 8 680 ohms 270 kohms NOTES 1 CONDITIONS OF MEASUREMENT ALL VOLTAGES AND RESISTANCES MEASURED FROM POINTS SHOWN TO CHASSIS WITH 122 MEGOHM INPUT IMPEDANCE VTVM LINE VOLTAGE 115V 60 Hz 2 CONTROL SETTINGS FREQ DIAL coca 100 RANGE ee petri tr ms X10 AMPLITUDE MAX v6 BAR4 NC 495 1 1 i 4700 14 1 4 1 1 1 l 1 I 1 1 A vi Soen 1970 6AU6 6AQ5 Figure 5 6 Tube Location Voltage and R
23. itable one can be purchased from your nearest hp Sales and Service Office If original container is not used b Wrap instrument in heavy paper or plastic before placing in an inner container c Use plenty of packing material around all sides of instrument and protect panel faces with cardboard strips d Place instrument and inner container in a heavy carton or wooden box and seal with strong tape or metal bands e Mark shipping container with DELICATE INSTRUMENT FRAGILE etc 2 1 Model 201C Section III SECTION Ill OPERATING INSTRUCTIONS 3 1 CONTROLS AND TERMINALS 3 2 ON Toggle switch controls line voltage to instrument 3 3 RANGE Three position rotary switch selects various values of resistance in the bridge circuit of the RC oscillator The position of this switch indicates the multiplying factor for the frequency dial calibration 3 4 FREQUENCY dial This control varies the capacitance in the bridge circuit of the RC oscillator to vary output frequency between range switch steps The dial is calibrated from 20 to 200 and its indication multiplied by the factor indicated by the RANGE switch will give the actual output frequency of the oscillator The small knob below the frequency dial is a vernier control for the dial 3 5 ATTENUATION This is a dual concentric control The inner control is a potentiometer which adjusts the amplitude of the oscillator voltage admitted to the amplifier an
24. of the X1 or X100 range is out of specifications refer to Factory Selected Components Table 5 6 5 24 TROUBLESHOOTING 5 25 TROUBLE LOCALIZATION 5 26 If the instrument fails to operate check the power source power cord and fuse before attempting more 54 Model 201C complicated troubleshooting If the instrument operates but not satisfactorily check the test setup for correct voltages connections terminations etc 5 27 The conservative design of the Model 201C indicates that most normal aging effects will be remedied by tube replacement and subsequent adjustments Electrical troubleshooting should always be preceded by a visual inspection A cold tube found simply by touch may save considerable time and effort in restoring the instrument to operation Look for signs of damage and overheated or burned out components associated with certain types of tube failure be alert for looseness of parts which if not trouble sources themselves suggest areas of future trouble The Troubleshooting Chart Table 5 5 lists checks to be performed starting with the power supply and proceeding through the instrument jn a manner which isolates circuit failures and also includes possible causes and remedies Isolation of a circuit failure is often possible by simply operating the front panel controls and observing their effect 5 28 TROUBLESHOOTING CHART 5 29 For simplification in the following chart tubes usually have been ref
25. r supply ripple at pin 4 of V4 or VS Ripple in excess of 25 vac Defective filter Replace capacitor C12B or C Defective V6 Replace Measure ripple at junction R28 and C124 Ripple in excess of 0 01 vac Defective C12A Replace OSCILLATOR Measure oscillator hum between negative terminal of C8 and chassis Remove lamp RT11 to eliminate oscillator signal Hum in excess of 0 02 vac Defective V1 or V2 Replace Replace lamp and measure oscillator voltage be tween negative terminal of C8 and chassis see Figure 5 5 Oscillator voltage not within range indicated on Defective lamp RTI 1 Replace lamp See Paragraph schematic 5 37 Excessively high OSC voltage Measure distortion between negative terminal of C8 and chassis If it exceeds 5 at 1 watt and 1000 Hz R10 out of adjustment Defective VI or V2 Dirty contacts on RANGE switch Shorted C1 C2 C3 or C4 Defective lamp RT11 Notch will appear in oscillator output waveform viewed on oscilloscope Defective V1 or V2 Defective lamp RTI1 Adjust R10 for proper oscillator voltage or replace V1 or V2 Check and clean RANGE switch Replace assembly when resistors are open or damaged See Para graph 5 39 Replace defective trim mers C2 C3 or C4 Foreign material may short Cl Replace lamp See Paragraph 5 37 Replace See Paragraph 5 35 Replace lamp 5 5 Section V Model 201C Table 5 5 Troubleshooting Chart Cont
26. rence level Check dial tracking across the X10 range In nearly all cases the dial tracking should be satisfactory If however the dial is out of calibration in the same direction across the band the dial may be adjusted slightly relative to the tuning unit as follows 1 Remove center knob on frequency dial 2 Loosen four screws which secure dial plate to drive shaft 3 Reset dial by desired amount 4 Tighten four securing screws Replace center knob 5 Repeat steps b through d of Paragraph 5 21 If the dial tracking cannot be brought into specifications in this manner or by compromising the calibration at the band extremes slightly within specifications to accommodate a larger error in the middle of the band then a retracking of the dial and the main tuning capacitor is indicated Retracking the dial involves bending the split rotor plates on the main tuning capacitor Cl Assuming dial retracking is unnecessary proceed with steps g and h Place RANGE switch in the X100 position and turn the frequency dial to 20 Adjust R6A so that the instrument oscillates at 2 kHz 5 3 Section V h Place RANGE switch in the XI position and set the frequency dial to 20 Adjust RSA so that instrument oscillates at 20 Hz 5 22 DIAL RETRACKING 5 23 Dial tracking is performed on the X10 range a Check frequencies at 200 150 100 70 50 30 and 20 on the dial b For each point outside specific
27. rts are available for replacement For entire gear assy replacement use current gear assy hp Part No 200AB 36B Gear 32 pitch 200AB 36C Gear 32 pitch 2AC 100Y shaft with gear 32 pitch Table of Replaceable Parts Add C16 560 pF factory adjusted hp Part No 0140 0028 average value Add R16 6800 ohms factory adjusted hp Part No 0690 6821 average value Parallel combination R16 and C16 is connected in series with signal lead to top AMPLITUDE control R17 Delete R46 CHANGE NO 4 Delete C17 This capacitor may be added to improve distortion CHANGE NO 5 Table of Replaceable Parts Miscellaneous Add the following 1 Disc vernier 5020 0236 Disc vernier drive 5040 0211 Spring compression 1460 0019 Model 201C Appendix C Delete the following Disc assy vernier drive hp Part No 5040 0607 Mfr 28480 TQ 1 9 Spring thrust hp Part No 5000 0637 Mfr 28480 TO 1 It is advisable to replace with current vernier drive assy CHANGE NO 6 Table of Replaceable Parts S3 Attenuator switch assy w pot change to 201C 19A pot only hp Part No 2100 0115 switch w pot hp Part No 3100 0124 CHANGE NO 7 Table of Replaceable Parts see Figure 1 Add R46 390 kohms hp Part No 0687 3941 R9 Change to 2 4 kohms hp Part No 0689 2425 R12 Change to 82 kohms hp Part No 0690 8231 R14 Change to 1 kohm hp Part No 0693 1021 R15 Change to 7 5 kohms hp Part No 0816 00
28. st setup as shown in Figure 5 3 including a 600 0hm load resistor across the output terminals of Model 201C DISTORTION ANALYZER hp331A Figure 5 3 Distortion Check 5 15 Model 201C Set Model 331A controls as follows NEUT non euism sau A jer een A an aa AF FREQUENCY RANGE eee XI FREQUENCY dial e iu vium xn 50 FUNCTION 8 nea cure as VOLTMETER On Model 201C set RANGE to Kl and frequency dial to 50 50 Hz Adjust output voltage level of Model 201C with vernier to obtain 24 5 volts on Model 331A On Model 331A set FUNCTION to SET LEVEL METER RANGE to 100 and adjust INPUT SENSITIVITY for 100 full scale is 100 Set FUNCTION to DISTORTION and tune Model 331A for null Set METER RANGE to 1 and retune for null Reading should be less than 1 245 full scale is 1 Repeat steps a through g except set Model 201C RANGE to X100 and frequency dial to 200 20 kHz and Model 331A FREQUENCY RANGE to X1K and FREQUENCY dial to 20 Three Watt Output a Connect test setup as shown in Figure 5 3 including a 600 ohm 3 watt load resistor across the output terminals of Model 201C Set Model 331A controls as follows INPUT 4225 ES a Hien e 8 gue 8 Om gen AF FREQUENCY RANGE sive o cm rk RR XI FREQUENCY did seh esters Cedo 20 FUNCTION an andi e loas xs METER On Model 201C set RANGE to Kl and frequency dial to 20 20 Hz Adjust output voltage level of
29. tenuator setting Output Impedance 600 ohms 10 20 dB 30 dB and 40 dB settings Less than 600 ohms 0 dB and 10 dB settings Hum Voltage Less than 0 03 of rated or attenuated output Amplitude control at maximum Power 115 230 volts 1075 nominal 120 W maximum 48 440Hz 85W Accessories Available HP 11000A Cable Assembly 4 feet of RG 58 U 50 ohm coaxial cable terminated at each end with a dual banana plug HP 11001A Cable Assembly 45 inches of RG 58 U 50 ohm coaxial cable terminated at one end with a dual banana plug and with a UG 88 U Type BNC male connector at the other Dimensions Cabinet Mount 7 1 2 inches wide 11 1 2 inches high 12 1 2 inches deep 191 X 292 X 318 mm Rack Mount 19 inches wide 6 31 32 inches high 10 5 16 inches deep 482 6 X 177 0 X 261 9 mm Weight Cabinet Mount Net 16 Ibs 7 2 kg Shipping 19 Ibs 8 6 kg Rack Mount Net 20 lbs 9 kg Shipping 30 lbs 13 5 kg 9 Model 201C Section I SECTION GENERAL INFORMATION 1 1 DESCRIPTION 1 2 The Model 201C Audio Oscillator Figure 1 1 has been designed for a general purpose audio testing and measurements such as amplifier testing transmission line measurements loud speaker testing frequency comparison and other high fidelity tests It contains a built in stabilized amplifier stage delivering 3 watts of power into a 600 ohm resistive load with distortion held to 1 2 per cent at fr
30. th any tube of its type having standard characteristics but distortion measurements should be made after replacing any tube with the exception of the rectifier tube to insure that the instrument still meets the specifications set forth in the front of this manual 5 37 REPLACEMENT OF LAMP RT11 5 38 The lamp operates well below its rating and should have a long life unless it is damaged by severe mechanical vibration A damaged lamp may be detected by the presence of a notch in the output waveform and by the presence of excessive oscillator voltage If the lamp opens the circuit will not oscillate When the lamp is replaced check the oscillator voltage between the negative terminal of C8 and the chassis If the voltage does not fall within the Model 201C limits specified on the schematic adjust R10 to obtain proper oscillator voltage 5 39 REPLACING RANGE SWITCH a Remove instrument case see Paragraph 5 33 b Remove defective RANGE switch Note routing of leads c Install replacement switch with black wire toward the center shield of the chassis and the wiper lugs on the ceramic wafer horizontal d Carry out frequency calibration procedure as described in Paragraph 5 21 5 40 ADJUSTMENT OF FACTORY SELECTED COMPONENTS 5 41 Certain components within the Model 201C are individually selected in order to compensate for slightly varying circuit parameters These components are denoted by an asterisk on t
31. ual banana plugs and a section of RG 58C U 50 ohm coaxial cable 44 inches overall Plugs are for binding posts spaced 3 4 inch between centers 1 9 11001A Cable Assembly This cable assembly consists of a dual banana plug a UG 88 U Type BNC male connector and a section of RG 58C U 50 ohm coaxial cable 45 inches overall The dual banana plug is for binding posts spaced 3 4 inch between centers Figure 1 1 Model 201C Model 201C Section Il SECTION INSTALLATION 2 1 INSPECTION 2 2 Unpack the instrument upon receipt and inspect it for signs of physical damage such as scratched panel surfaces broken knobs etc If there is any apparent damage file a claim with the carrier and refer to the warranty page in this manual 2 3 An electrical inspection should be performed as soon as possible after receipt To aid in electrical inspection a list of performance checks are in Section V Paragraph 5 8 These procedures make a good test as part of incoming quality control inspection 2 4 POWER REQUIREMENTS 2 5 The Model 201C requires a power source of 115 230 volts 10 48 to 440 Hz which can deliver up to 120 waits 2 6 POWER CABLE 2 7 For the protection of operating personnel the National Electrical Manufacturers Association NEMA recommends that the instrument panel and cabinet be grounded This instrument is equipped with a three prong conductor power cable which when plugged into an appropriate r
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