HP-206A-Manual 电路图.pdf

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1、RadioFans.CN 收音机爱 好者资料库 RadioFans.CN 收音机爱 好者资料库 OPERATING AND SERVICING MANUAL MODEL 206A LOW DISTORTION AUDIO SIGNAL GENERATOR SERIALS PREFIXED: 010 - Copyright HEWLETT-PACKARD COMPANY 1959 275 PAGE MILL ROAD, PAL0 ALTO, CALIFORNIA, U. S. A. Printed 5/60 RadioFans.CN 收音机爱 好者资料库 SPECIFICATIONS FREQU

2、ENCYRANGE: CALIBRATION: CALIBRATION ACCURACY: FREQUENCY STABILITY: OUTPUT: FREQUENCY RESPONSE: DISTORTION: XUM LEVEL: OUTPUT METER: OUTPUT ATTENUATORS: POWER SUPPLY: DIMENS IONS : WEIGHT: ACCESSORIES AVAIUBLE: 20 cps to 20 kc in 3 ranges. Directly in cycles for the lowest range, from 20 to 200 cps.

3、X10 and XlOO multiplier provided for higher ranges. Each range covers approximately 270 degrees of. the 6 dial. f270 including warm-up drift. f15 dbm (0 dbm - 1 mw) into impedance of 50, 150 and 600 ohms. Approximately 10 volts open circuit. Output is center tapped and balanced to ground. Internal i

4、mpedance matches load impedance. Better than f0. 2 db, 30 cps to 15 kc, with output meter kept a t constant level (Ref: 1 kc). Less than 0. 170 a t frequencies above 50 cps and less than 0. 2570 from 20 cps to 50 cps. At least 75 db below the output signal or more than 100 db below zero level, which

5、ever is the larger. Calibrated in dbm (0 dbm = 1 mw) and also in volts at 600 ohm level. Readability a t least 0. 2 db at all points above 5070 scale reading. 111 db in 0. 1 db steps. Accuracy approximately 0. 1 db. 1151230 volts +1070, 501 1,000 cps, 140 watts. Cabinet Mount: 12-3/4 high, 20-3/4 wi

6、de, 14 deep. Rack Mount: 10-1 12 high, 19 wide, 13-318 deep behind panel. Cabinet Mount: Net 57 lbs. Shipping 78 lbs. Rack Mount: Net 50 lbs. Shipping 72 lbs. Model AC -16A Cable Assembly, two dual banana plugs. Model AC-16B Cable Assembly, dual banana plug to BNC. TABLE OF CONTENTS MODEL 206A LOW D

7、ISTORTION AUDIO SIGNAL GENERATOR Section I GENERAL DESCRIPTION Page 1-1 General . . . . . . . . . . . . . . . . 1-1 Section I1 OPERATING INSTRUCTIONS . . . . . . . . . . . . . . 2-1 Inspection 2-1 . . . . . . . . 2-2 Controls and Terminals 2-1 . . . . . . . . . . . . . . 2 -3 Operation 2-3 Section I

8、11 CIRCUIT DESCRIPTION General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator . . . . . . . . . . Selective Amplifier . . . . . . . . . . . Output Amplifier Voltmeter . . . . . . . . . . . . . . . . . . . . . . . . . . . . Attenuator . . . Impedance-Matching T ransforner . . .

9、. . . . . . . . . . Power Supply Section IV MAINTENANCE . . . . . . . . . . . Cover Removal . . . . . . . . . Tube Replacement Replacement of Lamp R13 . . . . . . Variable Resistors . . . . . . . . . . . . . . . . . . . Capacitor Drive Adjustment of Regulated Power Supply . . . . . . . . . Voltage L

10、eve 1 Adjustment of Oscillator Output . Adjustment of Selective Amplifier Gain Adjustment of Hum Balance . . . . . Calibration of Voltmeter . . . . . . . Adjustment of Output at 600G . . . . Adjustment for Centering Selective . . . . . Amplifier Output Level . . . . . . . . . . . Recalibration Lubri

11、cation of Tuning Capacitor Drive . . . . . . . . . . . Assembly Section V REPLACEABLE PARTS LET . . . . . . . . 5-1 SECTION I GENERAL DESCRIPTION 1-1 GENERAL The Model 206A Low Distortion Audio Signal Generator provides a precise source of continuously variable audio-frequency voltage suitable for u

12、se in making accurate gain or frequency response measurements of high-quality audio circuits. Any desired frequency within a range of 20 to 20,000 cycles /second is made available by an extremely low-distortion resistance-capacity oscillator within the instrument. A voltmeter, calibrated both in vol

13、ts and dbm, is provided to measure the output of the oscillator output amplifier. Following the voltmeter is an attenuator which permits the output level to be reduced in . 1 db steps to a maximum of 11 1 db. A line- matching transformer and associated switch permits the signal generator output to b

14、e coupled to a balanced line of 50, 150, or 600 ohms. An unbalanced 600-ohm output which bypasses the line -match - ing transformer also is provided. The Model 206A is suitable for FM transmitter maintenance, studio amplifier and console testing, as a low-distortion signal source for bridge measurem

15、ents, as a transmission-measuring set, and for any application requiring a low-distortion, accurately-known audio test signal. SECTION I1 OPERATING INSTRUCTIONS 2-1 INSPECTION This instrument was thoroughly tested and inspected before being shipped from the factory. After the instrument is unpacked,

16、 it should be carefully checked for any damage received in transit. If any shipping damage is found, follow the procedure outlined in the Claim for Damage in Shipment section on the last page of this instruction book. CONTROLS AND TERMINALS FUSE The fuseholder, located on the control panel, contains

17、 a cartridge fuse of the Slo-Blo type. For 115-volt operation, a 1.6-ampere fuse is used, and for 230-volt operation, an. 8 -ampere fuse of the same type is used. Characteristics of the Slo-Blo fuse used in the Model 206A are given in the Table of Replaceable Parts. POWER This rotary switch controls

18、 the power supplied to the instrument from the power l i m Illumination of the tuning dial window pro- vides indication that the power switch is turned on. IMPEDANCE The setting of this four -position rotary switch indicates the im- pedance at the output binding posts. In three positions (50, 150, a

19、nd 600) the switch connects windings of the impedance -matching transformer to the OUTPUT binding posts for balanced 50-ohm, 150-ohm, or 600-ohm operation. In the fourth position, 600G, the switch bypasses the impedance -matching transformer and arranges the output circuit for 600-ohm unbalanced ope

20、ration. CT OUTPUT G The Model 206A binding posts will accept either a banana plug or wire. The terminals are so arranged that any double banana plug with 314 inch spacing may be used to connect to any pair of adja- cent terminals. An additional set of binding posts, identical in type and arrange- me

21、nt with those on the control panel, is provided at the rear of the instrument. This set of four terminals is connected inparallel with the binding posts on the control panel. CT - This binding post is the impedance-matching transformer center -tap terminal. OUTPUT - These two binding posts are the o

22、utput terminals for the Model 206A Signal Generator. G - This binding post is connected to the chassis. By patching to terminal G any of the binding posts may be connected to the chassis. RANGE This rotary switch controls the magnitude of the resistance in the frequency-determining circuits. The pos

23、ition of the RANGE switch indicates the multiplying factor for the tuning dial indication. FREQUENCY This knob is the fine control for adjusting the capacity in the fre- quency-determining circuits of the Model 206A. The coarse control for the frequency-determining capacity adjustment is directly co

24、nnected to the tuning dial and capaci- tor drive mechanism. The coarse control is the knob imme- diately below the tuning dial. The tuning dial is calibrated in cycles per second for the lowest range, and its indication multiplied by the factor indicated by the RANGE switch will give the actual outp

25、ut frequency of the oscillator. AMPLITUDE This knob varies the setting of the variable resistor which controls the level of the input to the output amplifier. The voltage level of the amplifier output is indicated by the meter on the control panel. 0-1 DB, 0-10 DB, 0-100 DB These three dials are the

26、 controls for the three-section attenuator, which is inserted in the output path between the output meter and the line -matching transformer. The attenuation in db inserted in the circuit is equal to the sum of the three control knob settings, and the reading of the output meter minus the inserted a

27、ttenuation is the level of the signal at the generator OUTPUT binding posts. The attenuator provides a means for reducing the output voltage, in . 1 db steps, to a maximum of 111 db below the level indicated by the meter. POWER CABLE The three-conductor power cable is terminated in a polarized three

28、- prong male connector recommended by the National Electrical Manufacturers1 Association. The third contact is an offset round pin, added to a standard two-blade a-c plug, which grounds the in- strument chassis when used with the appropriate receptacle. To use this NEMA plug in a standard two-contac

29、t outlet, it is recommended that instead of breaking off the ground terminal, a 2-prong to 3-prong adapter be used. The ground connection emerges from the adapter as a short lead which should be connected to ground for the protec- tion of operating personnel. 2-3 OPERATION The procedure for operatin

30、g the Model 206A Low Distortion Audio Signal Generator is as follows. 1. General With the instrument plugged into a power source of specified voltage and frequency, and the power switch at ON allow a warm-up period of a few minutes. Specified accuracy of +2% will be obtained after a few minutes warm

31、up. For maximum accuracy, however, allow a 20-30 minute warmup. NOTE If a 230-volt power source is used, check (1) that power transformer Tl is strappedfor 230- volt operation (strapping options are shown on the schematic diagram), and (2) that fuse F 1 is an. 8-ampere Slo-Blo fuse. 2. Selecting Fre

32、quency The desired output frequencies are obtained by the combined use of the FREQUENCY controls and the RANGE switch. The frequencies from 20 cps to 20,000 cps are covered in three ranges as follows: X1 Range: 20 cps to 200 cps X10 Range: 200 cps to 2,000 cps XlOO Range: 2,000 cps to 20,000 cps The

33、 FREQUENCY tuning dial is calibrated in cycles per second for the lowest or XI range. The higher ranges multiply the calibration of the tuning dial by the indicated factors of 10 or 100. For example, to select a frequency of 400 cps, set the tuning dial to 40 and the RANGE switch to X10. A frequency

34、of 10,000 cps is selected by setting the tuning dial to 100 and the RANGE switch to X100. 3. Connecting the Load Connect the load to the OUTPUT binding posts. If the impedance of the load is 50, 150, or 600 ohms, the instrument can be set (see par. 5 below) to match the load impedance. 4. Setting th

35、e Output Voltage Level To keep hum at a satisfactory level below that of the output volt- age, the output from the amplifier should be maintained at a rel- atively high level and then reduced to the desired level by means of the attenuator. In following the procedure for setting the output voltage l

36、evel, it is important to understand the position of the meter in the output circuit and also the calibration of the meter. The me- ter is across the output of the output amplifier, ahead of the attenuator, but is so calibrated that when the attenuator is set for zero attenuation and the instrument i

37、s working into a matched resistive load, the level of the signal at the 0 UTPUT binding posts may be read on the meter in dbm. To convert the dbm read- ing to volts, quick-reference graphs have been provided at the end of this section. (When working into a matched 600-ohm load with the attenuator at

38、 zero attenuation, the voltage at the OUT- PUT binding posts may be read directly on the meter. ) The following procedure should be used for setting the output voltage level: a. Set the level of the output amplifier. Use the output meter reading as an indication of the amplifier output, and adjust t

39、he level by means of the AMPLITUDE control (on the con- trol panel). Unless the noise level in the output signal is non-critical, the output amplifier always should be adjusted for a meter indication of t15 dbm. b. Determine the level in dbrn for the output voltage desired. The quick-reference graph

40、s referred to above are arranged to show the relationship between db referred to 1 milliwatt into a matched load and the voltage across a corresponding matched load. To determine the level in dbrn for an output voltage of . 23 volts into 600 ohms, for example, refer to the graph and find the level i

41、n dbrn for .23 volts into 600 ohms. The level will be found to be -10.5 dbm. c. Compute the amount of attenuation required to bring the out- put down to the desired level. With the output from the am- plifier at t15 dbm, attenuation of 25. 5 db will be required to bring the output to - 10. 5 dbrn at

42、 the OUTPUT binding posts (t15 dbrn minus 25. 5 db equals -10. 5 dbrn). d. Set the attenuator for the loss requied. The loss inserted by the attenuator is the sum of the settings of the dials. Using as an example the condition described above where a loss of 25. 5 db is required, all three dials wil

43、l be set for loss (20 db t 5 db t . 5 db equals 25. 5 db). NOTE A method for determing the voltage across a non-matching load is described below in para- graph 5. Setting Output Impedance. 5. Setting Output Impedance The output impedance of the generator is determined by the set- ting of the IMPEDAN

44、CE switch. For balanced 50-, 150-, or 600-ohm operation, set the IMPEDANCE switch to 50, 150, or 600. For balanced-to-ground operation, patch binding post CT to binding post G. For 50- or 150-ohm unbalanced operation, set the IMPEDANCE switch to the 50 or 150 position, and connect the lower OUTPUT b

45、inding post to ground at terminal G. For 600-ohm unbalanced operation, set the IMPEDANCE switch to 600G. At the 600G position, the IMPEDANCE switch connects the lower OUTPUT binding post to the G binding post. (In the 600G position, the matching transformer is bypassed, and an advantage in distortio

46、n and frequency-response characteristics is obtained. ) The calibration of the voltmeter and attenuator is correct only when the instrument is working into a matched resistive load. The VOLTS calibration of the meter is correct onlv when work - ing into a 600 ohm load; the DBM calibration is correct

47、 when working into a 50-. 150-. or 600-ohm load provided the IMPED- ANCE witch is in the which matches the output imped- ance to the load. If it is desired to work the generator into resistive loads other than 50, 150, or 500 ohms, the following method may be used to compute the voltage across the e

48、xternal load. a. With the RANGE switch and FREQUENCY controls set for the desired output frequency, set the IMPEDANCE switch for the impedance nearest that of the load into which the generator will be working. b. Choose the output level in dbm and add 15 (the reading of the output meter) to it. Set

49、the attenuator dials for the sum. c. Refer to the voltage graph, and obtain the voltage across the generator output impedance at the chosen output level. (The generator output impedance is the setting of the IM- PEDANCE switch; the output level is t15 dbm minus the setting of the attenuator dials. ) For example, if the IM- PEDANCE switch is set for 150 and the output level is -10 dbm (attenuator dials set for 25 db), the graph shows the voltage across