HP 205AG User's Manual
Contents
1. 000001 00001 001 1 OUTPUT METER VOLTAGE MULTIPLYING FACTOR 6 M 62 FOR 600 OHM LOAD Figure 2 1 Output Voltage Correction Factors When i Using Output Attenuators 00090 2 Ji Model 205AG 2 1 CONTROLS AND TERMINALS POWER ON This switch controls the power supplied to the instru ment from the power line LOAD ON This switch is used to connect an internal load across the OUTPUT terminals INPUT These terminals are the input for the audio fre quency INPUT LEVEL vacuum tube voltmeter in the instrument INPUT ATTENUATOR DB This switch is the range switch for the INPUT LEVEL meter and is calibrated in steps of 5 db from 0 to 40 db FREQUENCY RANGE The position of this switch indicates the multiplying factor to be used with the frequency dial indication FREQUENCY Dial This dialis calibrated in cycles per second The out put frequency is the frequency dial indication multi plied by the FREQUENCY RANGE switch position AMPLITUDE This control adjusts the amplitude of oscillator voltage applied to the output amplifier The cali bration is in arbitrary units IMPEDANCE This switch selects the instrument output impedance The available impedances are 50 200 600 and 5000 ohms OUTPUT The instrument output appears at four terminals The terminal marked CT is the center tap of the lin2. ENES T Ayyy GERM TYPE SPY CRE BANNED COL E BALA OPE NN RZ IAC UD STI H e EAL SEN NE id lt lt lt ef 5 c gt 5 e lt lt a es C c c a gt ure N Sa M S uS V V N Woo D CE SUSAN aS VARS VS N Wd V dt OPERATING AND SERVICING MANUAL MODEL 205AG AGR SERIALS PREFIXED 012 AUDIO SIGNAL GENERATOR Copyright HEWLETT PACKARD COMPANY 1955 1501 PAGE MILL ROAD PALO ALTO CALIFORNIA U 8 A dp 00090 2 Printed MAY 1961 Model 205AG Specifications SPECIFICATIONS FREQUENCY RANGE 20 cps to 20 kc in three decade bands 20 cps to 200 cps X10 200 cps to 2 kc X100 2 kc to 20 kc Calibration covers approximately 270 degrees on 6 inch diameter main dial CALIBRATION ACCURACY Within 2 at normal ambient temperatures Includes warm up and changes due to aging of tubes and components OUTPUT 5 watts maximum into resistive loads of 50 200 600 and 5000 ohms Output circuit is balanced and center tapped any terminal may be grounded FREQUENCY RESPONSE 1 db 20 cps to 20 kc at output levels up to 30 dbm with output meter reading held at 37db x1 5db 20cps to 20 kc at output levels above 30 dbm with output meter reading held at 37 d
3. 2 4 INPUT LEVEL METER OPERATION The Input Level meter is an independent audio tre quency vacuum tube voltmeter suitable for monitor ing the output voltage of a device under test The meter is calibrated voltsand dbabove 1 milliwatt in 600 ohms when the INPUT ATTENUATOR DB Switch is on zero When making comparative measurements across a constant impedance the meter and INPUT ATTENU ATOR DB switch will indicate directly the change jn db in the circuit under test When using the Input Level meter to monitor a 600 ohm circuit the power level in db above 1 milli watt is equal to the meter indication plus the indi cation of the INPUT ATTENUATOR DB switch When making power measurements in circuits with impedances below 600 ohms the absolute level in db above or below 1 milliwatt is equal to the level indicated on the meter plus the INPUT ATTENU ATOR DB switch indication plus a correction factor for the circuit impedance Figure 2 2 gives correction factors for impedances between 1 and 600 ohms The input voltage level for any range of the INPUT ATTENUATOR DB switch is the voltage indicated by the Input Level meter multiplied by the factor indicated below for the particular range of the IN PUT ATTENUATOR DB switch in use INPUT ATTENUATOR DB Position Meter Voltage Multiplying Factor 0 1 5 1 78 10 3 16 15 5 62 20 10 25 11 18 30 31 62 35 56 23 40 100 00090 2 Model 205AG Sect
4. 2AG 34 10 10 steps 1db step Stock No 2AG 34A 10 10 steps 10db step Stock No 2AG 34 100 10 steps 10db step Stock No 2AG 34A 100
5. II Page 3 30 20 NPUT METER CORRECTION DBM io i 10 100 1000 IMPEDANCE OHMS M 63 LN Figure 2 2 Input Level Meter Correction Curve 00090 2 Model 205AG 3 1 GENERAL The Model 205AG Audio Signal Generator consists of an oscillator an amplifier output meter and atten uator line matching transformer and a conventional power supply see Figure 3 1 The oscillator section tubes V1 and V2 is a re sistance tuned type circuit Basically this oscil lator is a two stage resistance coupled amplifier which is caused to oscillate by the use of a positive feedback network This network is a frequency Selective resistance capacity combination which controls the frequency of oscillation By using a variable tuning capacitor for the Capacity of the network it is possible to tune the oscillator over a wide 10 1 range and by using a switching arrange ment to select different values of resistance for the network several ranges are given to the oscillator Negative feedback is used in the oscillator section in order to minimize distortion and to obtain a very high order of stability The amount of negative feed back is determined by a resistance network one element of which is non linear the 3 watt lamp in the catho
6. amplifierwith negative feed back a full wave rectifier and a dc milliammeter calibrated in volts and decibels 0 10008 ATTEN POWER Ro 15 230 v Block Diagram Model 205AG Model 205AG 4 1 CABINET REMOVAL Remove four screws from the rear of the cabinet and remove the rear cover Place instrument on its back and loosen the two screws located on the under Side of the front panel bezel Free cabinet and lift from instrument 4 2 TUBE REPLACEMENT The tubes in this instrument may be replaced with any tube having EIA standard characteristics When ever a tube is replaced with the exception of V7 or V8 the distortion should be measured to see that it does not exceed the specifications When tubes V7 or V8 are replaced it may be necessary to adjust the zero setting of their respective meters 4 3 DISTORTION Excessive distortion may be caused by defective tubes open by pass capacitors and low voltages 4 4 CAPACITOR DRIVE LUBRICATION The capacitor drive should be lubricated once a year Remove the cover plate from the top of the capacitor Shield Put one drop of light oil on each of the bear ings on the small gear shaft at the top of the drive The capacitor ball bearings do not need lubrication 4 5 FREQUENCY CALIBRATION ADJUSTMENT The range switch resistors to R6 inclusive in conjunction with the tuning capacitor assembly Cl and C2 determine the frequency of the oscillation o
7. I9 is mounted on the shield Surrounding the Freq Range Switch If the voltage cannot be brought within the 21 to 25 volts range by means of RI9 the new lamp should be rejected in favor of another 4 9 INTERMITTENT OUTPUT Jumpy or intermittent output accompanied by flash Sect IV Page 3 ing of the 3 watt oscillator lamp RII is a reliable indication of a short in trimmer capacitor or in the first two sections of the main tuning capacitor 1 these symptoms 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 short in the back two sections of the main tuning capacitor will prevent the circuit from oscillating Any such short should be cleared as explained above TABLE 4 1 TROUBLESHOOTING CHART The following is a listing of possible Symptoms causes and remedies Instrument inoperative Indicator lamp won t light no audio output Instrument inoperative Indicator lamp lights no audio output Intermittent output Output Level Meter inoperative Excessive distortion 00090 2 CAUSES REMEDIES Blown fuse Defective tube Check the 5U4GA B tube first Short circuit in DC power circuit capacitor Short circuit in C2 two rear sections Capacitors C3 C4 C C8 or C9 intermittently open Short circuit in C2 two front sections or Cl 6H6 tu
8. Model 205AG Sect V Page 7 Table 5 1 Replaceable Parts Sheet 7 of 7 Ckt Ref Description Mfr Stock No TQ RS MISCELLANEOUS Binding Post Assembly black 28480 AC 10C Binding Post Assembly red 28480 AC 10D Conversion kit conversion of cabinet 28480 35F 95A mount to rack mount in the field Jewel pilot light Knob AMPL Lampholder for R11 Vernier drive disc Window dial 75915 1400 0084 72765 1450 0020 Knob INPUT DB FREQ RANGE 28480 G 74N IMPEDANCE 0 10 DB lower attenuator 0 100 DB upper attenuator 28480 G 74F 28480 G T4K Lampholder 2 pin base 12165 1450 0022 72765 1450 0013 Spring vernier drive disc 28480 1460 0019 Vernier drive disc on shaft 28480 G 14A 28480 G 14B 28480 G 99K 00090 2 See introduction to this section MANUAL CHANGES MODEL 205AG AUDIO SIGNAL GENERATOR Manual Serial Prefixed 012 Manual Printed 5 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 Changes 6 CHANGE 1 Paragraph 4 1 step b Change the setting of LOAD switch to OFF Paragraph 4 7 line 5 of step c I Change to read diodes CR1 CR2 CR3 and CR4 should be replaced and the above adjustments repeated CHANGE 2 The 205AG contains
9. NGE FREQUENCY dial 40 LOAD ON IMPEDANCE 5000 OUTPUT ATTENUATOR DB 40 OUTPUT ATTENUATOR DB 6 to obtain 53 v on AMPLITUDE OUTPUT LEVEL METER The Input Level meter should indicate zero db with the controls set as above If the meter indication is incorrect adjust the variable resistor R47 to correct the meter indication The variable resistor R47 is reached through a hole in the left side of the chassis Instrument removed from cabinet After the zero db level is in adjustment change the attenuators to 41 db and 51 db which will in dicate 5 db and 5 db respectively If the meter tracking at these points is not satisfactory then the 6H6 tube V9 should be replaced and the above adjust ments repeated 4 8 REPLACEMENT OF LAMP RII The 3 watt lamp RH is operated at a very low level and should have an almost infinite life Therefore the lamp should not be changed indiscriminately However should the lamp require changing it is necessary to measure the ac voltage from the junction of R58 and C4 to the chassis with the new lamp in the circuit This voltage should be measured with high impedance vacuum tube voltmeter such as Hewlett Packard Models 4006 400D or 410B To make this measurement and adjustment the in strument must be removed from the cabinet Set 00090 2 Model 205AG the oscillator frequency to 1000 Cycles sec and vary the resistor RI9 so that 21 to 25 volts is obtained The resistor R
10. O3H 40 M3LSNITOK Y SisSVH3 ONY SINIOJ 03 VD 0NI BHi N334138 NJNVI IN3W3NASY3W Z 10001 06 AOE 1 39v170 0 40 SNO 00090 2 o T o 90001 0 90 0 0 zv v G E ot O ior wouvewauuy LAJENG A000 1v Ag2 iz 6 os 30vr0 OSO 98 X098 99 t 1035 69 SNOI03S x m E MOIIOVdYO 9NINDI Z9 8 5 002 08 O Model 205AG 5 1 INTRODUCTION This section contains information for ordering re placement parts for the Model 205AG Audio Signal Generator Table 5 1 lists replaceable partsinalpha numerical order of their reference designators Detailed in formation on a part used more than once in the in strument is listed opposite the first reference desig nator applying to the part Other reference desig nators applying tothe same part refer to the initial designator Miscellaneous parts are included at the end of the list Detailed information includes the following a Reference designator b Full description of the part c Manufacturer of the part in a five digit code see list of manufacturers in appendix d Hewlett Packard stock number Total quantity used in the instrument TQ col
11. TQ ns C23 Capacitor fixed mica 76433 0140 0055 1 1 150 pf 500 vdew Optimum value selected at factory Average value shown C24 Capacitor fixed ceramic 00853 0150 0008 1 1 5 pf 500 Optimum value selected at factory Average value shown CR1 Diode germanium IN90 73293 1910 0004 6 6 thru CR6 1 Fuse cartridge 1 6 amp 71400 2110 0005 1 10 for 118 volts operation Fuse cartridge 0 8 amp 75915 2110 0020 for 230 volts operation 11 Lamp incandescent 6 8v 2 pin base 24455 2140 0012 1 1 GE 12 L1 2 Reactor 6h 0125 MA 240 ohms 28480 9110 0004 2 1 Meter OUTPUT LEVEL 28480 1120 0003 1 1 M2 Meter INPUT LEVEL 28480 1120 0002 1 1 Pi Cable power 70903 8120 0015 1 1 R1 Resistor fixed deposited carbon 19701 0730 0136 2 1 8 3 megohms 1 1 W part of S1 R2 Resistor fixed deposited carbon 19701 0730 0102 2 1 830 000 ohms 105 1 W part of S1 R3 4 Resistor fixed deposited carbon 19701 0730 0063 2 1 830 000 ohms 1 1 W part of S1 R5 Same as R2 part of S1 R6 Same as R1 part of 81 RT thru Not assigned R9 R10 Resistor fixed wirewound 75042 0812 0010 1 1 3000 ohms 595 5 W See introduction to this section 00090 2 Sect Page 4 Table 5 1 Replaceable Parts Sheet 4 of 7 Model 205AG linear taper 20 000 ohms Ckt Ref Description Mfr Stock No TQ RS R11 Lamp incan
12. b reference 1000 cps DISTORTION Less than 1 at frequencies above 30 cps INTERNAL IMPEDANCE Approximately 1 6 load impedance with zero attenuator Setting Approaches loadimpedance with attenuator settings of 20 db or more HUM LEVEL More than 60 db below the output voltage or 90 db below zero level 1 mw 600 ohms whichever is the larger OUTPUT METER Calibrated in volts and dbm 0 dbm 1 mw 600 ohms Full scale values 65 volts 37 dbm Reads on 600 ohm basis regardless of output impedance selected OUTPUT ATTENUATOR Provides 110 db in 1 db steps INPUT METER Calibrated in dbm 0 db 1 mw 600 ohms from 5 to 8 dbm and in volts from 0 to 2 v rms Voltage accuracy is 5 of full scale INPUT ATTENUATOR Extends meter range to 48 dbm and to 200 v rms in 5 db steps Accuracy 0 1 db POWER SUPPLY 115 230 volts 10 50 1000 cps 150 watts DIMENSIONS Cabinet Mount 20 3 4 in wide 12 3 4 in high 15 1 2 in deep Rack Mount cup fm TOP TLLA d H 72 NIN d x End T T3 SIOE I peer 205AGR WEIGHT Cabinet Mount 56 lbs shipping weight 78 lbs Rack Mount 49 lbs shipping weight 71 lbs 00090 2 Table of Contents List of Illustrations and Tables Section I GENERAL DESCRIPTION 1 1 General 1 2 Inspection TABLE OF CONTENTS OPERATING INSTRUCTIONS 2 1 Control
13. be V7 defective Defective tube Open circuit in capacitor 10 abc C15 C16 C17 or Defective output or line matching trans former Clear short circuit and replace fuse Replace tube Replace capacitor Clear the short circuit as outlined in Paragraph 4 9 Replace capacitor Clear the short circuit asoutlined in Paragraph 4 g Replace tube Replace tube Replace capacitor Replace transformer Model 205AG Sect Page 4 A IA dol DVS0Z PON 00090 2 ev cA ei 222 21 212 v 9 SA 519 912 812 j IL Sect IV Page 5 Model 205AG BA 212 21 peaoureH joutqe META DVS08 TOPON 6 9 ant 62H S 9 918 tA 868 00090 2 Model 205AG e amp a d o o Uu euSig ISPON veo n g p 03111WD 38 AVW Lave NMOHS MIVA 39VU3AY ANOLOVS AV 031sDfOv INWA 1v9n410373 X f eW SWHO OOO x 03108 31 dd ALIOVdYD auos v obor os z SISSY AF 13873 O AY BO INAN NO OVO iv 80 17009 10 BONVOSdWI OU3Z JV 10 OO iv WIG AON30538j LY 39NYH XON3QD3H4 135 AONVLSIST GWHO
14. ck tracking of the rest of the frequency dial if there is no constant error in tracking pro ceed with the next step If there is a constant error proceed with one of the following methods which ever is the easiest 1 Loosen set screws and reset the dial to take the error into account then repeat steps b and c This method is best if the other ranges also have a con Stant error in the same direction Sect IV Page 2 2 Change the small padding resistors in series with the precision resistor on the range switch Increas ing the value of the resistor by 10 000 ohms will lower the frequency of the range approximately 1 decreasing the value of this resistor will raise the frequency of the range Retrace steps a through d When the range has been properly adjusted the other ranges may be adjusted as follows 1 X100 range Change the padding resistor in series with the pre cision resistor change of 1000 ohms will change the frequency approximately 1 on this range Then 20 000 cycles on the dial is corrected by varying C 7 A change of 50 to 200 pf is usually adequate 2 Xlrange An increase of 100K ohms in the padding resistor will decrease frequency approximately 1 on this range There may be a small tracking error less than 2 at the top or the bottom of the range This is normal to the instrument and cannot be eliminated f If satisfactory calibration cannot be obtained in the above ma
15. de of VI This element controls the amount of feedback in accordance with the amplitude of os cillation and consequently maintains the amplitude of VOLUME CONTROL OSCILLATOR SECTION AMPLIFIER TUBES V3 v4 TUBES v2 v5 v INPUT LEVEL METER TUBE V8 V9 8 METER M2 Figure 3 1 00090 2 OUTPUT LEVEL METER Sect Page 1 SECTION III CIRCUIT DESCRIPTION oscillation substantially constant over a wide fre quency range The negative feedback also keeps the Operation of the system on the linear portion of the tube characteristic The amplifier section consists of a voltage amplifier tube directly coupled to a phase inverter which drives the push pull output tubes The tertiary winding on the output transformer provides negative feedback for the amplifier The output meter and attenuator section is made up of an average reading type voltmeter and two bridged T type attenuators The attenuators and voltmeter connected between the output transformer sec ondary and the primary of the line matching trans former A full wave rectifier and a dc milliammeter cali brated in volts and decibels make up the Output Level meter The line matching transformer is used to change the 500 ohms line impedance to 50 200 600 or 5 000 ohms output impedance The Model 205AG also includesanInput Level meter which is of the average respondingtype The meter consists of a two stage
16. descent 120 V 3 W 24455 2140 0001 1 1 candelabra screw base R12 Resistor fixed composition 01121 0690 3331 1 1 33 000 ohms 10 1 W R13 14 Resistor fixed composition 01121 0690 1041 2 1 100 000 ohms 1075 1 W R15 Resistor fixed composition 01121 0690 5641 3 1 560 000 ohms 1095 1 W R16 Resistor fixed wirewound 35434 0816 0004 1 1 800 ohms 109 10 W R17 Resistor fixed wirewound 35434 0816 0009 1 1 25 000 ohms 1095 10 W R18 Resistor fixed wirewound 35434 0816 0008 1 1 10 000 ohms 10 10 W R19 Resistor variable wirewound 71450 2100 0004 1 1 linear taper 1000 ohms 10 2 W R20 Resistor fixed wirewound 35434 0819 0004 1 1 10 000 ohms 1095 20 W R21 Resistor variable composition 71450 2100 0009 1 1 25 000 ohms 2045 1 3 W R22 Resistor fixed composition 01121 0690 1051 1 1 1 megohm 100 1 W R23 Resistor fixed composition 01121 0690 8221 1 1 8200 ohms 10 1 W R24 Resistor fixed composition 01121 0690 1251 1 1 1 2 megohms 10 1 W Optimum value selected at factory Average value shown R25 Resistor fixed composition 01121 0689 2235 2 1 22 000 ohms 595 1W R26 27 Same as R15 R28 Resistor fixed wirewound 35434 0819 0005 1 1 500 ohms 10 20 W R29 Resistor variable composition 71590 2100 0161 1 1 See introduction to this section 00090 2 Model 205AG Table 5 1 Rep
17. e matching transformer terminal is con nected to the chassis The two vertically spaced terminals are connected to the line matching trans former through the IMPEDANCE switch A balanced output is obtained from the vertically spaced terminals 00090 2 Sect Page 1 SECTION IH OPERATING INSTRUCTIONS and an unbalanced output may be obtained by con necting the terminal to one of the output terminals with the captive link provided OUTPUT LEVEL This meter indicates the voltage at the output ter minals when the IMPEDANCE switch is set at 600 output attenuators both at zero and the instrument is loaded with the internal or an external 600 ohm load Under other operating conditions the meter may be used as a monitor to insure constant output voltage INPUT LEVEL This meter measures the voltage applied to the input terminals and the range of the meter is controlled by the INPUT ATTENUATOR DB range switch FUSE The fuseholder located on the back of the chassis contains the power line fuse Refer to the Table of Replaceable Parts for the correct fuse rating Power Cable The three conductor power cable is supplied with NEMA approved three prong plug The third con ductor provides a chassis ground An adapter may be obtained to permit use of this plug with two conductor receptacles OUTPUT ATTENUATORS These two attenuators are used to reduce the output level in one db steps to a maximum of 110 db belo
18. eet 6 of 7 Model 205AG Ckt Ref Description Mir Stock No TQ RS R58 Resistor fixed composition 01121 0690 2731 1 1 27 000 ohms 1095 1 W Optimum value selected at factory Average value shown R59 Resistor fixed wirewound 12697 0813 0002 1 1 7 ohms 10 2 W R60 Resistor fixed composition 01121 0693 4721 1 1 4700 ohms 10 2 W R61 Resistor fixed composition 01121 0693 1801 1 1 18 ohms 10 w W Optimum value selected at factory Average value shown R62 63 Resistor fixed composition 01121 0687 6811 2 1 680 ohms 10 1 2 W 51 Range switch assembly 28480 2AG 19WB 1 1 S2 Impedance switch assembly includes S3 28480 24 59 lil S3 Switch toggle SPST 04009 3101 0001 2 1 54 Input attenuator assembly 28480 20 53 111 include R36 thru R44 55 Same as 83 Transformer power 28480 9100 0041 Lit T2 Transformer audio output 28480 9120 0009 111 T3 Transformer impedance matching 28480 9120 0020 1 1 Vi Tube electron 6J7 80131 1923 0032 1 1 v2 Tube electron 6F6 80131 1923 0031 1 1 v3 Tube electron 6597 80131 1939 0005 1 1 V4 Tube electron 6J5 80131 1921 0008 1 1 V5 6 Tube electron 6L6 80131 1923 0034 2 2 V7 Not assigned V8 Tube electron 6SNTGT 80131 1932 0025 1 1 v9 Not assigned V10 Tube electron 5U4GA B 80131 1930 0008 1 1 See introduction to this section 00090 2 gt
19. f Recommended spare quantity for complete maintenance during one year of isolated service RS col Sect V Page 1 SECTION V REPLACEABLE PARTS 5 2 ORDERING INFORMATION To order a replacement part address order or in quiry either to your authorized Hewlett Packard Sales office or to CUSTOMER SERVICE Hewlett Packard Company 395 Page Mill Road Palo Alto California or in Western Europe to Hewlett Packard S A Rue du Vieux Billard 1 Geneva Switzerland Specify the following information for each part a Model and complete serial number of instru ment b Hewlett Packard stock number Circuit reference designator d Description Toordera part not listed in Table 5 1 give a com plete description ofthe part and include its function and location Table 5 1 Replaceable Parts Sheet 1 of 7 Ckt Ref Description Mfr Stock No TQ RS Attenuator output complete Al Assembly attenuator 10 steps 1 db step 2 Assembly attenuator 10 steps 10 db step C1 Capacitor variable ceramic 7 45 pf 500 vdew 28480 2AG 34 1 1 28480 2AG 34 10 28480 2AG 34 100 72982 0130 0001 1 1 See introduction to this section 00090 2 Sect V Page2 Model 205AG Table 5 1 Replaceable Parts Sheet 2 of 7 Ckt Ref Description Mfr Stock No RS c2 Capacitor variable air 76854 0121 0004 1 1 12 4 535 pf tuning capac
20. f the unit and also affect the amplitude I the Output fre quency is not within 2 of that indicated by the dial or if the amplitude varies more than 41 2 db from 200 to 2000 cps the following procedure is recom mended 00090 2 Sect IV Page 1 SECTION IV MAINTENANCE NOTE For all adjustments the output must be loaded with the internal load Tura the LOAD switch ON The frequency calibration will be correct only when the shields around and above the main tuning capa citor are firmly in place Using a gentle airstream blow out any dust that may be present on the tuning capacitor a Check for proper setting of dial on shaft At one end of the frequency dial will be either a small dot or an extra line This should be under the in dicator hairline when the tuning capacitor is at that end of its travel This may be adjusted by loosening Set screws on one side of the coupler behind the panel then rotating the dial until correctly lined up Check and tighten all set screws in the dial drive mechanism b Turn on the instrument and allow at least 30 minutes for it to warm up c Set to X10 range and dial to 20 Set the output meter to 50 volts Change dial setting to 200 The panel output meter should then read 50 volts 2 volts and the frequency should be 2000 cps 4 290 If both frequency and amplitude are in error adjust C1 and C22 for the best compromise between correct frequency and correct amplitude d Che
21. itor C3 Capacitor fixed paper 14655 0160 0024 2 1 0 5 uf 10 400 vdew C4 Capacitor fixed electrolytic 37942 0180 0005 1 1 10 pf 50 450 C5 Capacitor fixed paper 56289 0160 0018 1 1 0 25 pf 10 400 vdew C6 Not assigned CT Capacitor fixed mica 76433 0140 0031 1 1 220 pf 10 500 vdew i Optimum value selected at factory Average value shown C8 9 Capacitor fixed paper 56289 0160 0001 2 1 0 1 10 600 vdew i Optimum value selected at factory E Average value shown C10 Capacitor fixed electrolytic 37942 0180 0016 1 1 ABC 3 sections 10 pi sect 450 C11 Not assigned C12 13 Capacitor fixed paper 56289 0160 0005 2 1 0 047 uf 1095 600 C14 Same as C3 ii C15 Capacitor fixed paper 72758 0160 0077 4 1 thru 4 uf 10 600 vdew 18 C19 Capacitor fixed electrolytic 37942 0180 0026 1 1 20 uf 50 vdew C20 Capacitor fixed titanium dioxide 78488 0150 0011 111 1 5 pf 420 500 Part of S1 C21 Capacitor fixed ceramic 96095 0150 0002 1 1 39 pf 5 500 vdew C22 Capacitor fixed ceramic 72982 0130 0003 111 1 5 7 pf 500 vdcw See introduction to this section 00090 2 Model 205AG Table 5 1 Replaceable Parts Sheet 3 of 7 Sect V Page 3 Ckt Ref Description Mtr Stock No
22. laceable Parts Sheet 5 of 7 Sect V Page 5 Ckt Ref Description Mfr amp Stock RS t R30 Resistor fixed deposited carbon 19701 0727 0170 1 1 18 000 ohms 1 1 2 W R31 32 Resistor fixed composition 01121 0690 1031 2 1 10 000 ohms 1095 1 W R33 Resistor fixed wirewound 35434 0819 0002 111 2500 ohms 1042 20 W R34 Not assigned R35 Resistor fixed wirewound 83777 0817 0001 1 1 600 ohms 195 20 W R36 Resistors part of Input Attenuator thru Assembly not separately replaceable R44 R45 Resistor fixed composition 01121 0687 1051 2 1 1 megohm 10 1 2 W R46 Resistor fixed wirewound 75042 0813 0001 1 1 1000 ohms 1095 1 W R47 Resistor variable wirewound 42190 2100 0022 1 1 500 ohms R48 Resistor fixed composition 01121 0690 1021 1 1 1000 ohms 1095 1 W R49 Same as R45 R50 Resistor fixed composition 01121 0690 1541 1 1 150 000 ohms 1095 1 W R51 Resistor fixed composition 01121 0690 2741 1 11 270 000 ohms 10 1 W R52 Resistor fixed composition 01121 0690 3331 1 1 33 000 ohms 10 1 W R53 Resistor fixed composition 01121 0690 1831 1 1 18 000 ohms 10 1 W R54 Not assigned R55 Same as R25 R56 Not assigned R57 Resistor Optimum value selected at factory 00090 2 See introduction to this section Sect V Page 6 Table 5 1 Replaceable Parts Sh
23. nner it may be necessary to return the instrument to an authorized repair station or the factory 4 6 OUTPUT LEVEL METER ADJUSTMENT The procedure for adjusting the Output Level meter is as follows a With the instrument operating and Vol control at zero adjust the meter pointer to zero with zero adjustment screw on the meter b Connect an accurate vacuum tube voltmeter across the 600 ohms output terminals with the 600 ohms internal load switched on Set the in strument for 100 cycles sec output zero atten uation and adjust the Vol control until the external voltmeter indicates 55 volts Adjust the variable resistor R29 until the Output Level meter indicates exactly 55 volts The resistor R29 which is reached through a hole in the back of the chassis can be turned with a screwdriver Up to 1 change in frequency on any range may be made by adjusting only one of the two range resistor padders on that range Ifa greater fre quency change is needed adjust both padders Ifthisis not done the relative amplitude between ranges will be affected Model 205AG 4 7 INPUT LEVEL METER ADJUSTMENT This meter is adjusted as follows a With the instrument operating short circuit the Input Terminals Adjust the meter pointer to zero with zero adjustment screw on the meter b Connect the nput terminals to the Output ter minals and set the instrument controls as follows Setting INPUT ATTENUATOR DB FREQUENCY RA
24. ny desired frequency range within the range of 20 to 20 000 Cycle sec is made available by the resistance tuned audio oscillator within the instrument In addition to the audio oscillator two voltmeters are provided One voltmeter measures input to and the second measures output from the device under test An attenuator is provided to set the output voltage at any desired level The output impedance can be changed by means of a selector switch to 50 200 600 or 5000 ohms T ANS PANS Sect I Pagel SECTION GENERAL DESCRIPTION This audio signal generator is typically used for amplifier gain measurements network frequency response source of voltage for distortion measure ments broadcast transmitter audio response loud Speaker response general laboratory application and production testing 1 2 INSPECTION After the instrument is unpacked it should be care fully inspected for damage received in transit If any shipping damage is found follow the procedure outlined in the Claim for Damage in Shipment page in this instruction manual Figure 1 1 Audio Signal Generator 00090 2 Sect Page 0 Model 205AG OUTPUT ATTENUATION DB
25. s and Terminals 2 2 Oscillator Operation 2 3 Output Level Meter Operation 2 4 Input Level Meter Operation IH CIRCUIT DESCRIPTION 3 1 General Number Title PPP Page Section 2 1 1 IV 1 1 1 1 H 1 H 1 1 1 2 1 2 PPP m i 1 MAINTENANCE 4 1 Cabinet Removal r 4 2 Tube Replacement IV 1 4 3 Distortion 4 4 Capacitor Drive Lubrication 4 5 Frequency Calibration Adjustment IV 1 4 6 Output Level Meter Adjustment IV 2 4 7 4 8 4 9 5 1 Introduction LIST OF ILLUSTRATIONS Page Number 1 1 Model 205AG Audio Signal Generator 1 1 3 1 2 1 Output Voltage Correction Factors when using Output Attenuators 2 2 Input Level Meter Correction Curve Number 4 1 5 1 iv H 0 n 3 d od Hf 1 Block Diagram Schematic Diagram LIST OF TABLES Title Troubleshooting Chart Replaceable Parts Model 205AG Page e anes Iv 1 IV 1 IV 1 IV 1 Input Level Meter Adjustment IV 2 Replacement of Lamp R11 IV 2 Intermittent Output 1V 3 REPLACEABLE PARTS V 1 s G d sto V 1 5 2 Ordering Information V 1 Title Page ziv 1 Top View Cabinet Removed IV 4 Bottom View Cabinet Removed 1V 5 HER IC IV 6 Page IV 3 v 1 00090 2 Model 205AG 1 1 GENERAL The Model 205AG Audio Signal Generator contains all the necessary instruments for accurate gain or frequency response measurements A
26. two terminal boards on which are mounted a variety of small parts The boards used in earlier instruments 24 terminal board Stock 2G 75A 14 terminal board Stock 2G 75B utilized solder lugs to mount parts The boards used in later issue instruments having serial prefix number 151 large board Stock No 2G 75C smali board Stock 20 750 are directly interchangeable and the etched circuit board will be supplied as a replacement part for both types CHANGE 3 Figure 4 3 Change to read 6807 CHANGE 4 Table of Replaceable Parts Was C19 Capacitor fixed 20 ufa 50 vde Mfr 37942 P Stock No 0180 0026 TQ 1 RS l Now C19 Capacitor fixed 20 pfd 50 vde Mir 56289 dp Stock 0180 0049 TQ 1 8 1 CHANGE 5 Table of Replaceable Parts Delete the following Spring Compression Stock No 1460 0019 1 ea Vernier Disc Stock No G 14A 1 Vernier Disc Stock No G 14B 1 ea Add the following Disc Ass y Vernier Drive Stock No G 14J Mfr 28480 TQ 1 Bearing Capacitor Drive Stock No G 36J Mfr 28480 TQ 1 Spring Thrust Stock No G 91A Mfr 28480 TQ 1 CHANGE 6 Table of Replaceable Parts Attenuator output complete Stock No 2AG 34 Attenuator output complete Stock No 2AG 34A 12 14 62 9 1117 Rev A Was Now Was Now Was Now Assembly attenuator Assembly attenuator Assembly attenuator Assembly attenuator 10 steps 1db step 4 Stock No
27. uators are set at zero With any matched load 50 200 600 or 5000 ohms the output power in db above or below 1 milliwatt is equal to the Output Level Meter indication less the output attenuator settings For example an Output Level meter indication of 35 db and a total output attenuation of 45 db will produce an output level of 10 dbm into a matched load Figure 2 1 is a chart of meter voltage multiplying factors for any value of output attenuation With the IMPEDANCE switch set at 600 ohms and an in ternal or external 600 ohm load the output voltage will be the Output Level meter voltage indication multiplied by a factor obtained from Figure 2 1 opposite the total output attenuation For example with the output attenuators set for 40 db all Output Level meter indications should be multiplied by 01 to obtain the true output voltage into a 600 ohm load To obtain the true output voltage into a 50 200 or 5000 ohm load the following factors must be applied to the true voltage across a 600 ohm matched load 600 Ohm Voltage Multiplying Factor Load Impedance 50 0 289 0 577 2 89 Model 205AG For example with an Output Level Meter indication of 40 volts and the output attenuators set at 40 db we find from Figure 2 1 that the true output voltage into 600 ohms would be 40 volts multiplied by 0 01 or0 4 volts To convert this to a voltage across a 200 ohm matched load multiply by 0 577 or 0 4 x 0 577 0 2308 volts
28. w the output level indicated on the OUTPUT LEVEL meter 2 2 OSCILLATOR OPERATION The procedure for operating the Model 205AG Audio Sigoal Generator is as follows a Connect the instrument power cable to a 115 230 V alternating current power line and the output terminals to the equipment being tested Set the IMPEDANCE switch to match the load When the Signal Generator is operated into a high impedance Sect Page 2 load the Load Switch must be turned on otherwise the Output Level Meter and the Attenuator indications willnot be correct The Load Switch should be off when the instrument is connected to loads within the range of the line matching impedances b Turn the power switch to ON and allow approxi mately five minutes for the instrument to stabi lize Setthe Freq Range control and the frequency dial so that their indications when multiplied together equalthe desired frequency For example Fre quency dial indication 20 FREQUENCY RANGE X100 20 x 100 2000 cycles second c Set the output attenuators and the AMPLITUDE control to obtain the desired output level Dis tortion in the output will be minimized by keeping the Output Level meter indication near maximum and reducing the output with the output attenuators 2 3 OUTPUT LEVEL METER OPERATION The Output Level meter is calibrated directly in output voltage and db above 1 milliwatt when the instrument is operating into a 600 ohm load and both output atten
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