RCA 77 DX Mike manual - American Radio History
Contents
1. Hum may originate in any part of the audio system In the microphone circuit it may result from ground loops or unbalance caused by improper cable connections to the pre amplifier terminal board or microphone plug Hum may also be induced into the microphone transformer or ribbon by magnetic fields emanating from power transformers or electri cal machinery In the 77 0 Microphone the design of the ribbon circuit and the transformer and the thorough shielding of the transformer have reduced hum pickup from these sources to a minimum In the event that exceptionally strong fields are encountered the induced hum may be minimized vy turning or tilting the microphone or changing its location Turning the frequency response selector to the Vi or Vo positions will also reduce the hum together with the overall low frequency response MAINTENANCE It is recomnended that no attempt be made to make repairs other than replacement of Screens transformers mounting parts and cables For microphone mechanism repairs return the unit to the factory Secure a Repair Order and Returned Apparatus Tag from the ACA Field Office or write to RCA Service Company Returned Apparatus Control Camden N J Attach the tag properly filled out to the damaged equipment and send the equipment and the repair order to the manufacturer CAUTION To prevent permanent damage to the ribbon do not test continuity of the microphone with circuit che2. 97503 t HM TX a i i _ SWITCH THUMBNUT 1 50915 50907 Ms 7 EE Lu E m STUD CUSHION E E 44677 C enO i CAP NUT p 95216 CUSHION 4 MOUNTING ASSEMBLY 50925 with the checker microphone lines PLATE 50909 __ INDICATOR 56702 7 SHUTTER i 50910 i 2 nc ist MOTOR ASSEMBLY REAR VIEW GASKET 4467 SPRING i NUT 44440 27450908 i ABLE MI 43C SPECIFY LENGTH J 4 ot CLAMP i 19828 4 1 4 STRAIN RELIEF 58878 174350 E Figure 6 Parts Location Diagram of 5 When testing the observe the same precautions or make certain that the microphones are disconnected Although the screens provide ex cellent protection minute iron particles commonly found on work benches and in maintenance shops may be drawn through the screen by the powerful magnet If allowed to accumulate these particles may mar the quality of reproduction To remove the top screen assembly for re placement first remove the side thumbscrews and mounting hardware at the top of the microphone fork Then unscrew the two machine screws on the side bands near the top and lift the screen assembly off the microphone REPLACEMENT PART
3. Fork microphone fork casting only 18393 Screen Assy comprising front 50906 with 1 8 pipe threaded hole in base and 1 2 8 hole in ends of prongs screw washer hd 2 56 x 3 16 14 52469 Gasket cable rubber 7 16 0 0 44671 cover 9 32 1 0 7 32 thick spring cable guarda thumb 1 dia x 3 16 thick 50907 Stud cushion mtg 2 3 32 19 93817 with 1 8 pipe threaded hole in with 1 8 pipe thread one end center fork base locking 1 4 20 x 3 8 1g thread other end SCREEN ASSEMBLY RIBBON CLAMP S9SCREw 93618 E 1944446 97472 RIBBON CLAMP SCREW 50909 7 RAIT _ _ 54327 SCREW ys INDICATOR FE id SCREW RIBBON CLAMP metre SHUTTERS E4329 STOP 50910 _ WASHER 95225 RIBBON CLAMP cod ie BUSHING 1 E5223 1995224 THRUST MOTOR ASSEMBLY 2 REAR 733975 5 i ACOUSTIC LINE S ASSEMBLY 9398 REACTOR 621395 TRANSFORMER 7744440 w9T503 THUMBNUT 350915 93974 E gt CUSHION Uus i CABLE 4467 m T DIT Mt 43 _ ur CAP NUT Fees 9522 CUSHION 93973 ku CABLE CLAMP 93972 STRAIN 179946 LIST OF PARTS 758878 Figure 7 Parts Location Diagram of MI 11006 C WWW americanradiohistorv com Description MI 4045 F Continued Strain relief black ne
4. the MI 4045 F microphone is primarily intended for broad cast use it is finished in satin chrome and a low gloss umber gray enamel The MI 11006 C microphone is intended for television use and is therefore completely finished in a low gloss umber gray enamel which eliminates glaring reflections usually seen on highly polished microphones WWW _ americanradiohistorv com 1 Instead of being open on both sides as in the conventional velocity microphone the ribbon element in this microphone is coupled to an acoustic labyrinth which forms the body portion of the microphone The tube connect ing the back of the ribbon to the labyrinth is slotted directly behind the ribbon and fitted with an adjustable shutter to secure various areas of opening When the opening is completely closed the microphone operates as a non directional pressure microphone at the wide open position the microphone becomes bi directional With the proper size opening the pattern becomes a cardioid by virtue of the phase shift which occurs Openings smaller or larger than this critical size produce directional patterns with various sized rear lobes Different amounts of low frequency attenu ation are obtained by a reactor shunting the output APPLICATION The microphones are intended primarily for indoor use and if used outdoors may require some additional protection against the wind The choice of directional patterns makes possible a considerable degre
5. BROADCAST AUDIO EQUIPMENT Type 77 DX Polydirectional Microphone RADIO CORPORATION OF AMERICA ENGINEERING PRODUCTS DIVISION CAMDEN N J 1B 24884 2 EQUIPMENT LOST OR DAMACED IN TRANSIT When delivering the equipment to you the truck driver or carrier s agent will present a receipt for your signature Do not sign it until you have a inspected the containers for visible signs of damage and b counted the containers and compared with the amount shown on the shipping papers If a shortage or if evidence of damage is noted insist that notation to that effect be made on the shipping papers before you sign them Further after receiving the equipment unpack it and inspect thoroughly for concealed damage This should be done within 15 days if possible If concealed damage is discovered immediately notify the carrier confirmed in writing and insist upon an inspection and report In addition to the above the shortages or damages should also be reported to RCA but do not return any damaged equipment unless we have furnished complete return shipping instructions Transportation companies are required to adjust for damage resulting from their negligence and RCA will assist vou if necessary in obtaining settlement Accordingly you should save all shipping papers letters or invoices concerning the shipment until it is certain that the equipment was delivered in good condition or until any damage has been adjusted REPLACEM
6. ENT PARTS When ordering replacement parts please give symbol description and stock number of each item ordered The part which will be supplied against an order for a replacement item may not be an exact duplicate of the original part However it will be a satisfactory replacement differing only in minor mechanical or electrical characteristics Such differences will in no way impair the operation of the equipment The following tabulations list service parts and electron tube ordering instructions according to your geographical location SERVICE PARTS LOCATION ORDER SERVICE PARTS FROM Continental United States Alaska and Hawaii Service Parts Order Service Bldg 60 19th amp Federal Sts Camden 5 New Jersey or through your nearest RCA Regional Office Emergency orders may be telephoned telegraphed or teletyped to RCA Emergency Service Bldg 60 Camden N J Telephone WO 3 8000 Dominion of Canada RCA Victor Company Limited 1001 Lenoir Street Montreal Quebec or through your local Sales Representative or his office Outside of Continental United States Alaska RCA International Division Clark N J U S A or through your Hawaii and the Dominion of Canada local Sales Representative ELECTRON TUBES LOCATION ORDER ELECTRON TUBES FROM Conunental United States Alaska and Hawaii Local Tube Distributor Dominion of Canada RCA Victor Company Limited 1001 Lenoir Street Montreal Que bec or through your loc
7. R Polydirectional Microphone Type 77 DX 4045 and MI 11006 C RADIO CORPORATION OF AMERICA ENGINEERING PRODUCTS DEPARTMENT CAMDEN N J Printed in U S A 5105 576 WWW americanradiohistorv com Figure Type 77 DX Microphone 4045 gt SE fag ee PTT zs Figure 2 Type 77 DX Microphone MI 11006 C WWW americanracdiohistorv com TECHNICAL DATA Output Impedance 250 ohms may be changed to 30 or 150 ohms Load impedance Unloaded input transformer Effective Output Level all output connections Bi directional 50 dbm 144 db Uni directional U 53 dbm 6 2 147 db Non directional 56 6 150 db L 1 L 2 L 3 between 50 and 53 dbm Gq rating Hum Pick up Level 128 dbm Dimensions and Weight Length 11 1 2 inches Width 3 3 inches Depth 2 1 2 inches weight Total 4 1 2 pounds Less cable 3 pounds Cab le 83 3 conductor shielded 30 feet long no plug Finish Tv Gray and Satin Chrome 1 4045 Gray MI 11006 cC Stand Fitting 1 2 inch pipe thread Sound Pressure 10 dynes cm2 Referred to a hum field of 1 x 10 3 gauss DESCRIPTION The RCA Type 77 DX Polydirectional Micro phones MI 4045 F and MI 11006 C are high fidelity microphones of the ribbon type which may easily be adjusted to obtain a variety of directional patterns Since
8. S The following parts list is included to provide identification when ordering replace ment parts Order from ACA Replacement Parts Department Camden New Jersey giving the Stock Number and Description of the parts wanted Replacement parts supplied may be slightly different in form or size from the original parts but will be completely inter changeable with them To remove a transformer reactor or cable for replacement purposes first lower the bottom cover as described under Connections Before removing the cable be sure to loosen the cord guard and cable clamp CAUTION Keep the microphone away from iron filings or magnetic dust WWW americanracdiohistorv com Stock Description Description Jo 1 nut with 1 1 8 32 insi Acoustic line assy less band 93981 transformer amp switch assy 50908 n guum brass microphone fork 95218 retaining 5 a 9 Swivel 0 296 1g x 0 373 0 0 with 9 16 18 thread x 0 261 1 0 with 9 16 dia 0 030 thick shoulder e fork Swivel 95219 5 3 4 0 0 x 7 32 thick with Clamp cable incl bushings 19828 hex nut 1 4 28 tapped hole in center Cushion mounting assy complete 50925 Plate 1 for poly 205158 directional char diamond Cushion rubber 1 dia x 9 16 44677 shape with 1 4 dia hole thick with 1 4 dia hole in in center amp 2 mtq holes center 104 dia
9. al Sales Representative or his office Outside of Continental United States Alaska Local Tube Distributor or from Hawaii and the Dominion of Canada Tuhe Department RCA International Division 30 Rockefeller Plaza New York 20 New York U S A If for any reason it is desired to return tubes please return them to the place of purchase PLEASE DO NOT RETURN TUBES DIRECTLY TO RCA WITHOUT AUTHORIZATION AND SHIPPING INSTRUCTIONS It is important that complete information regarding each tube including type serial number hours of service and reason for its return be given When tuhes are returned they should be shipped to the address specified on the Return Authorization form A copy of the Return Authorization and also a Service Report for each tuhe should be packed with the tubes LIST OF RCA REGIONAL OFFICES Atlanta 3 Georgia Boston 16 Mass Chicago 54 Cleveland 15 Ohio 522 Forsyth Bldg Room 2301 John Hancock Bldg 1186 Merchandise Mart Plaza 1600 Keith Bldg Lamar 7703 200 Berkley St Delaware 7 0700 Cherry 1 3450 Hubbard 2 1700 Dallas 1 Texas Holly wood 28 Calif Kansas City 6 Missouri New York 20 New York 1907 11 McKinney Ave RCA Bldg 1560 N Vine St 340 Dierks Bidg 36 W 49th St Riverside 1371 Hollywood 9 2154 Harrison 6480 Judson 6 3800 Branch San Francisco 2 Calif 420 Taylor St Ordway 3 3027 WWW americanradiohistorv com p BROADCAST AUDIO EQUIPMENT INSTRUCTIONS FO
10. cker without connecting resistor of at least 50 000 ohms in series Www americanradiohistorv com gt 944 n pe SS ily qu 4 UIT LL n SS Imm 270 ES FA 1 S L 3 POSITION NON DIRECTIONAL POSITION Figure 4 Directional Patterns www americanracdiohistorv com OPEN CIRCUIT RESPONSE OF A TYPICAL TYPE 77DX MICROPHONE CEI L O DECIBELS HT UNIDIRECTIONAL POSITION Io 1 000 9993 15 000 5 DECIBELS 60 100 1000 10 000 15 000 FREQUENCY IN CYCLES PER SECOND 472178 0 Figure 5 Frequency Response Curves Www americanradiohistorv com SCREEN ASSEMBLY _ RIBBON CLAMP SCREW 50906 ie 44446 97472 i RIBBON CLAMP T SCREW 654127 F _ 54327 _ _ SCREW E 84327 RIBBON RE 7 SCREW 52469 E i RIBBON CLAMP 54329 d STOP WASHER 95220 RIBBON CLAMP a S a 42920 eras a _ GARE wan Ny BUSHING e 95218 THUMBNUT 7 T 95219 sl jia AO THRUST c FORK F 16395 ACOUSTIC LINE ASSEMBLY 4 993981 L d gei RE ACTOR AM _ TRANSFORMER 97504 E se eg cer bt
11. e of control of the ratio of direct sound to reverberant sound aS well as the possible reduction of unwanted sound such as audience noise in a studio The wide angle of pick up provided by the cardioid pattern is useful in covering large groups with a single microphone For close talking applications the non directional characteristic is of considerable value since the low frequency response is not accentuated as in the case of a velocity microphone Numerous other applications of the various directional patterns as well as the different response curves will no doubt suggest themselves to the user OPERAT ION Mounting The microphone will mount on any stand having a 1 2 inch pipe thread Other stands will require a suitable adaptor The micro phone is cushion mounted and a fork mounting is provided so that the microphone may be fitted to the desired position 2 Connections As shipped the microphone is connected for an output impedance of 250 chms To connect the microphone for an output impedance of 30 or 150 ohms first lower the bottom cover by removing the four machine screws around the rim of the cover Pull the cover down until the transformer terminal board connections are accessible For the proper cable con nections refer to figure 3 Directional Characteristics The adjustable shutter over the slot in the tube leading to the acoustic labyrinth may be rotated by means of a screwdriver ad justment extending thro
12. hole in base and 1 3 8 hole in ends of prongs Gasket cable rubber 7 16 0 D x 9 32 1 0 x 7 32 thick Nut cushion retaining knurled cap nut with 1 1 8 32 inside thread LIST OF PARTS 54127 54329 44446 52920 56702 50909 45385 97472 54327 50910 93981 95223 93972 93973 44677 93975 44671 95221 WWW americanracdiohistorv com Continued Stock Description Fo Nut thumb 1 dia x 3 16 thick with 1 8 pipe threaded hole in center fork base locking Nut thumb knurled fork swivel 3 u 0 D x 7 32 thick with 1 28 tapped hole in center Nut knurled cable guard spring retaining 5 8 0 0 x 7 16 1g with 9 16 18 thread Plate designation for poly directional char diamond shape with 1 4 dia hole in center and 2 mtg holes 104 dia Reactor iron core impedance at 50 CPS 0 5 v 91 ohms 7 5 D C res 28 ohms round can Screen assy comprising front 4 rear screen and band Screw for screen amp cover 2 56 x 3 16 1g Spring cable guard Stud cushion mtg 2 3 32 1g with 1 8 pipe thread one end 1 4 20 x 3 8 lg thread other end Strain relief neoprene black 2 5 16 1g with 0 308 dia hole Switch rotary single circuit 3 pos screw driver slotted shaft music voice washer aluminum alloy fork swivel thrust 9 16 0 0 x 0 260 I D 0 190 thick Washer stop microphone fork swivel stop washer 9 16 0 D x 0598
13. oprene 2 5 16 10 with 0 308 dia hole Switch rotary single circuit 3 pos screw driver slotted Shaft music voice Reactor iron core impedance at 50 CPS 0 5 v 91 ohms 73 5 D C res 28 ohms round can Transformer microphone tapped for 30 150 250 ohms output Impedances turns ratio 1 23 5 24 round can washer aluminum alloy fork swivel thrust 9 16 0 D x 0 260 1 0 x 0 190 thick washer stop microphone fork Swivel stop washer 9 16 0 0 x 0598 thick with 1 u x 11 64 elongated hole in center ASSEMBLY Clamp ribbon top large Clamp ribbon bottom large Clamp ribbon top small Clamp ribbon bottom small Indicator shutter position indicator and adjuster Fiate shutter pressure 012 thick phos bronze 2 1 16 lg x 7 16 wide Ribbon microphone corrigated aluminum foil 2 lg x 054 wide Screw fil hd 1 72 x 5 16 1g large ribbon clamps Screw fil hd 0 80 x 1 8 1g small ribbon clamps shutter acoustic tube 005 thick phos bronze cam shaped MI 11006 C Acoustic line assy less band transformer amp switch Bushing brass microphone fork Swivel 0 296 1g x 0 373 0 D x 0 261 1 0 with 9 16 dia x 0 030 thick shoulder Clamp cable clamp including bushing amp hardware Cushion mtg assy complete Cushion rubber 1 dia x 9 16 thick with 1 u dia hole in center Fork microphone fork casting only with 1 8 pipe threaded
14. or depends upon the particular instal lation The same holds true for the placement of the microphone Consult figure 4 for the directional patterns of the six reference positions WWW ENAMEL elo SLEEV ING i SOLDERED TO GEEN LEAD YELLOW MX 2 SLE E VIM PA GREEN T BLACK 2 77D 77 MICROPHONE Bik PLK esto e 1 i BiK e sn 1504 CABLE CONNECTIONS MI 4045 1x4 MI 4065F 11306 B and M 006C 14977 Figure 3 Schematic and Connection Diagram Frequency Response Settings For sound sources greater than three feet from the microphone the frequency response selector can be used in the M position for any of the directional response patterns If the non directional characteristic is used no low frequency attenuation should be re quired even for very small distances If the bi directional or uni directional patterns are used low frequency attenuation will be required when the sound source is less than 3 feet from the microphone unless special effects are desired It is suggested that the V position be used for distances down to 1 foot and the Vo position for still shorter distances Refer to figure 5 for frequency response curves of the M Vo settings Hum
15. thick with 1 4 x 11 64 elongated hole in center Transformer microphone tapped for 30 150 250 ohms output impedance turns ratio 23 5 2 round can Clamp ribbon top large Clamp ribbon bottom large Clamp ribbon top small Clamp ribbon bottom small Indicator shutter position indicator and adjuster Plate shutter pressure 012 thick phos bronze 2 1 16 1g x 7 16 wide Ribbon microphone corrigated aluminum foil 2 19 0 05u wide Screw fil hd 1 72 x 5 16 1g for large ribbon clamps Screw fil hd 0 80 x 1 8 1g Small ribbon clamps shutter acoustic tube 005 thick phos bronze cam shaped 93974 95224 50908 205159 97504 93818 52469 93817 58878 50915 97505 95225 97503 MOTOR ASSEMBLY 54127 54329 uuu 6 52920 56702 50909 45385 97472 54327 50910 RADIO CORPORATION OF AMERICA ENGINEERING PRODUCTS DIVISION CAMDEN N J
16. ugh the rear screen flush with a designation plate The plate is marked U N and B as symbols for the uni directional non directional and bi directional patterns Three additional markings L 1 L 2 and L 3 are used as reference points for other directional patterns which may be obtained Refer to figure 4 for the patterns associated with each of the Six symbols Stops are provided on the continuously variable pattern selector at the six marked positions although the shutter may be set at any intermediate position Frequency Response At the bottom of the lower shell is a screwdriver operated selector marked M music V1 and Vo voice The voice positions connect a reactor across the entire secondary or part of the secondary of the output trans former depending on the switch position see diagram figure 3 Refer to figure 5 for the frequency response characteristics of each setting AS can be seen from the curves the reactor attenuates the low frequency response This is eSpecially desirable when the micro phone is less than three feet from the source of sound and the low frequency response would otherwise be exaggerated Phasing The Type 77 DX Microphone is phased so that the red cable lead is electrically positive when the sound pressure on the front of the microphone is in the positive half of the cycle When the outputs of two or more microphones are connected into a mixing circuit it is necessary that the o
17. utputs of all such micro phones have the same phase relation Other wise the output of one microphone will oppose the output of another resulting a reduction in output and introducing varying degrees of distortion To check the phasing of two or more micro phones connect one microphone to the associ ated amplifier input and set the volume control to obtain the desired output while talking into the microphone Then connect the second microphone in parallel with the first and without changing the volume control setting hold both microphones close together and talk into them If the volume decreases from the previous level reverse the connections of one of the microphone cables at the microphone plug Check each additional microphone for phasing in this manner and if necessary reverse the cable connections to correct the phasing to agree with that of the microphone already connected When the sound source is directed toward the back of the microphone there will be a large phase shift when changing the pattern selector from bi directional to non direction al or the reverse The safest way to avoid undesirable directional effects resulting from the above is to set microphones operating close to one another on the same directional response position or at least avoid having some on the non directional pattern and the others on the bi directional pattern Directional Setting The proper position of the pattern se lect
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