HP-200A-Manual-1951 电路图.pdf

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1、HP Archive This vintage Hewlett Packard document was preserved and distributed by www. h parch Please visit us on the web ! Thanks to on-line curator: Kenneth Kuhn for supplying and scanning this vintage document. RadioFans.CN 收音机爱 好者资料库 I N S T R U C T I O N A N D O P E R A T I N G M A N U A L F O

2、R AUDIO OSCILLATOR 1 B Serial 30223 and Above HEWLETT-PACKARD COMPANY 395 PAGE MILL ROAD, PAL0 ALTO, CALIFORNIA, U. S . A. RadioFans.CN 收音机爱 好者资料库 1 1 G e n e r a1 D e s c r i p t i o n I The Model 200A Audio Oscillator is a general purpose oscillator which uses the resistance-tuned circuit to gener

3、ate alternating current voltages from 35 to 35,000 cycles/sec. This audio oscillator provides a source of voltage for amplifier testing, audio response 50 volts open circuit). Distortion - Less than 1% of rated output from 35 to 15, 000 cycles/sec. Hum - Less than of maximum output voltage Load impe

4、dance - 500 ohms (resistive) Approximate Internal Impedance - 75 ohms from 20to 15,000 cycles/ sec. Output ungrounded, not balanced to ground. -1- Power Supply Rating - .- P Voltage - 115 volts Frequency - 50 to 60 cycles/sec. Wattage - 75 watts Overall Dimensions - - Cabinet Model - 15-1/411 long x

5、 7-1/4 high x 10-5/811 deep Rack Model - 19 long x TI high x 10-3/4 deep ._ Panel - lqr1 long x 7 high Depth behind panel - 9-1/411 Weight - - Cabinet Model - 26-1/2 pounds Rack Model - 26-B/2 Pounds O p e r a t i n g I n s t r u c biens Inkpection - This instrument has been thoroughly tested and in

6、spected before being shipped and is ready for use when received. After the instrument is unpacked, it should be carefully inspected for any damage received in transit, outlined in the IIClaim for Damage in Shipment page at the back of this instruc- tion book. If any shipping damage is found, follow

7、the procedure _ Controls and Terminals - c . - AC Power - This toggle switch, which is located in the lower left corner of the control panel, controls the power supplied to the instrument from the power line. When the switch is in the On position, the red indicator will glow, Fuse - The fuseholder,

8、located on the underside of the chassis next to - the power cablep contains a one ampere cartridge fuse. RANGE - This rotary switch inserts various range resistors in the fre- quency determining circuit of the oscillator. cates the multiplying factor for the frequency dial calibration. The position

9、of this switch indi- Frequency Dial - The frequency dial is calibrated directly in.cycles per sec-nr,d FOP the lowest frequency range. -2 -, cr) N N 0 rF) 0 1% I .- AMPL. - This variable resistor controls the amplitude of the oscillator voltage admitted to the amplifier, and therefore the output vol

10、tage of the instru- ment. This control is calibrated frgm “Ott to ftlOOtt in arbitrary units. - Power Cable - The power cable consists of three conductors. Two of The third wire projects these conductors carry power to the instrument while the third conductor (green wire) is connected to the instrum

11、ent chassis. from the cable near the plug end of the cable and may be connected to a ground when it is desirable to have a grounded chassis. Operqtion - - Connect the power cable of the Model 200A into a 115 volts, 50/60 cycles poyer source and turn on the power switch. operate as soon as the tubes

12、have heated, but f o r maximum accuracy a warm- up period of about 30 minutes is necessary. The instrument will begin to Set the frequency dial and tlRANGE1l switch: so that their indications, when multiplied together, equals the desired frequency. For example, if it is desired to select an output f

13、requency of 800 cycles per second, set the frequency dial to f18011 and the flRANGE1l switch to r r l O f l . Connect the oscillator output binding posts to the equipment being driven and adjust the “AMPL.“ control for the desired output voltage. Although the rated load for the Model 200A is 500 ohm

14、s (resistive), higher or lower impedance loads may be used without damage to the instrument. higher impedance load will result in less power output and a lower impedance load will increase the percentage of distortion in the output voltage. A As the output voltage of the audio oscillator is reduced,

15、 the percentage of hum voltage will increase, large, relative to the sine wave output voltage. be remedied by operating the audio oscillator at or slightly below rated output and inserting a suitable attenuator between the oscillator and the equipment being driven by the oscillator. The voltagg divi

16、der circuit shown below is satisfactory for most applications. At the lower levels this hum voltage becomes quite This undesirable condition can MODEL 200A OSCILLATOR 400 ohms (9 100 ohms 0 - EQUIPMENT BEING SUPPLED * -3- Other values of resistance may be used to obtain different voltage divi- sions

17、. In all cases, the sum of the divider resistors must equal the rated load of 500 ohms. r - - c C i r c u i t D e s c r i p t i o n The Model 200A Audio Oscillator consists of an oscillator section, an amplifier section and a power supply. The oscillator section (tubes V1 and V2) is a resistance-tun

18、ed type cir- cuit. Basically, this oscillator is a two-stage resistance-coupled amplifier which is caused to oscillate by the use of a positive feedback network. work is a frequency-selective resistance-capacity combination which controls the frequency of oscillation, city of the network, it is poss

19、ible to tune the oscillator over a wide 1O:l range, and by using a switching arrangement to select different values of resistance for the network, several ranges are given to the oscillator. This net- By using a variable tuning capacitor for the capa- Negative feedback is used in the oscillator sect

20、ion in order to minimize distortion and to obtain a very high order of stability. The amount of negative feedback, is determined by a resistance network, one element of which is non- linear (the 3-watt lamp in the cathode of Vl). This element controls the amount of feedback in accordance with the am

21、plitude of oscillation and consequently maintains the amplitude of oscillation substantially constant over a wide fre- quency range. the linear portion of the tube characteristic. cient thermal inertia so that it operates well even at low frequencies. The negative feedback also keeps the operation o

22、f the system on It is notable that the lamp has suffi- Following the oscillator is the output amplifier section which includes tubes V3 and V4. mize distortion and to provide a good frequency response. Negative feedback is used in this amplifier in order to mini- The power supply section includes a

23、conventional full-wave rectifier with a low-pass pi filter for removing the ac components from the rectified wave. -4 M a i n t e n a n c e Cover and Bottom Plate Removal - The cover is removed by unscrewing the four screws which fasten the cover to the back of the instrument and sliding the cover t

24、oward the rear of the ins t rume n t The bcndorn plate is removed by unscrewing the four screws, one in each corner of the battam pta-t+-wkicgfasten -_ the plate to the chassis. -4- rube Replacement - . . d d When replacing any of the tubes except the power rectifier, it is desirable to measure the

25、dcstortion in the output if maximum performance from the instru- meatis desired, bacause a poor tube can cause excessive distortion without seemirigly affecting the operation. rated output with rated load. Replacement of Lamp R7 - The distortion should be less than 1% of the I 1 The 3-watt lamp R7 i

26、s operated at a very low level and should have an al- - most,infinite life. Therefore, the lamp should not be changed indiscriminately. Howfver, should the lamp require changing, it is necessary to check the ac voltage from the junction of R19 andC4 to ground with the new lamp in the circuit. As mea

27、sured with a high-impedance ac vacuum tube voltmeter, this voltage should be within the range of approximately 20 - 22 volts when the Model 200A is tuned to 400 cps. adjusting R11. If the voltage is not within this rangep it may be corrected by * If the voltage cannot be brought within the range fro

28、m 20 - 22 volts by means of R11, the new lamp should be rejected in favor of another, Inte%mittent Output - - W , tlJumpyll or intermitfent output accompanied by flashing of the 3-watt oscillator lamp (R7) is a reliable indication of a short in trimmer capacitor C1 or in the first two sections of th

29、e main tuning capacitor, occur, search out and clear the short with a weak air jet or other means. Do not bend the capacitor plates because bending capacitor plates will destroy the frequency calibration If these symptoms c r ) . N N 0 cr) A short in the back two sections of the main tuning dspacito

30、r or in krimmer C6 will prevent the circuit from oscillating. be cleared as explained above. Any such short should Distortion - Distortion may be caused by defective tubes, electrical leakage in the coupling capacitors, defective output transformer, defective electrolytic capacitors, low DC supply v

31、oltage, or excessive output voltage from the os- cillator section. b - Dial Coupler - 4 0 0 w An insulated coupler connects the main tuning dial to the shaft of the . main tuning capacitor. If this coupler should become loosened, rotate the capa- v cito -ompletely clockwise. To do this it will be ne

32、cessary to loosen the collar -5- of the stop on the rear of the panel bearing. When the capacitor is completely chsed, set the main tuning dial so that the dot to the Left of t135tt on the main tuning dial is exactly under the hairline. Tighten the coupler with the tuning dial and tuning capacitor i

33、n these relative positions, stop so that the tuning capacitor rotor cannot strike the frame or stator at either end of its arc. Then tighten the collar of the After the coupler has been tightenedand the dust cover replaced, it is desirable to check the calibration of the instrument. Frequency Calibr

34、ation - If a change occurs in the frequency calibration of this instrument after a long period of use, the cause of this change probably lies in the ageing of the resistors in the frequency-determining network. good stability, however, and the frequency calibration will remain accurate for a very lo

35、ng period of time These resistors have extremely , Each of the frequency-determining resistors consists of a precision one- watt resistor in series with a one-$half watt resistor. give the instrument a very accurate f-requency calibration. Therefore, adjusting the frequency calibration requires that

36、 the value of these small resistors be changed as necessary to obtain proper calibration. The latter is selected to An oscilloscope, an ac vacuum tube voltmeter, and a secondary fre- quency standard are needed to adjust the calibration of the Model 200A. secondary standard should have sinusoidal out

37、put and should provide frequencies of at least 1 kc and 10 kc. foi. thirty minutes or more, Then connect the Mo*del 200A to the vertical deflec- ting-plate input of the oscilloskope and the secondary frequency standard to the horizontal deflecting-plate input. The Before recalibrating, allow the Mod

38、el 200A to heat Next, check the calibration of the Model 200A by means of Lissajous figures on the oscilloscope, determining whether the frequencies generated by the M.odel 200A are in general higher or lower than the dial calibration. When making this check, it is necessary that the dust cover be t

39、ightly on the instru- ment as the frequency calibration will change when the dust cover is loose or off the instrument. If the instrument is in need of recalibration, the dial calibration will show a definite trend of error-either higher or lower. than the true output fre- quency for each range. cha

40、nge in the same directionI1. The various ranges of the instrument do not necessarily If the xl range requires readjusting, change the small resistors R1A and R4A. If the ouput frequency is higher than the dial calibration, increase the 4 I -6- value of the small resistors; if the. output frequency i

41、s lower than the dial cali- bration, decrease the value of the small resistor. ohms will change the calibration about 1/2%Q Do not change the value of Rl and R1A more than 50,000 ohms without making a corresponding change in R4 and R4A because it is necessary to keep the values of each set of range

42、resistors as equal as possible. be unstable. before checking the output frequency. A change of about 50,000 Unbalance in the-resistors will tend to cause the oscillator to After each change it is necessary to replace the dust cover securely The same procedure should be used if it is necessary to adj

43、ust the cali- bration of the other ranges. On the x10 range a change greater than 5,000 ohms should not be made in R2 and R%A without also changing R5 and R5A, range a change greater than 500 ohms should not be made in R3 and R3A without changing R6 and R6A. On the xl00 It is important that the dust

44、 cover be tightly in place after each adjustment, because the frequency calibration is affected by the position of the dust cover. If any considerable amount of change in the resistors is necessaryg it may be desirable to replace the entire range switch assembly. available from the Hewlett-Packard C

45、ompany. These assemblies are The vacuum tube voltmeter should be used to check the output from the instrument after the recalibration has been completed, . Set the main frequency dial of the Model 200A to ft10OT1 and the AMPL. control to about t18011 or more. Connect +he VTVM to the output terminals

46、 and measure the output of each range. If the range switch resistors have been properly adjusted, the difference between the obtput of the ranges with the dial set at tllOOtl should be within 1 db (approximately 12%)o), preferably less. cause is that the frequency determining re9istors for the range

47、 in question are not properly balanced, If the difference in output is greater than 1 db, the usual Trimmer Capacitors - Two trimmer capacitors are provided for the main tuning capacitor. These trimmers are adjusted at the factory and do not require further adjust- ment for the life of the equipment

48、. come misadjusted, directions for resekting should be requested of the Hewlett- Packard Company. If the trimmers inadvertently should be- -7- Trouble Shooting - The fallawing is a listing o f possible symptoms., causess and remedies. S yxn p t o m a Caas e s Remedies Instrument inoperative Blown fu

49、se Clear short circuit and (Indicator lamp wont light, no audio output) /si Instrument inoperative Defective tube Replace tube (see Tube (Indicator lamp lights, Check the 5V4 Replacement in Main- no audio output) tube first tenan ce section) replace fuse ? Xnt e rm i tt e nt Output Short circuit in DC power circuit capa- citor Replace capacitor Short circuit in C2 Clear the short circuit (two rear sections) a