Figure 1-1. Major components of Radio Set AN/ARC-60 (less ARC type Relay K-15). 2 TAGO 269A - July

Transcription

1 TM HEADQUARTERS, Technical Manual DEPARTMENT OF THE ARMY No Washington 25, D. C., 9 July 1957 CHAPTER INTRODUCTION...3 Section I. GENERAL...3 Section II. DESCRIPTION AND DATA...3 CHAPTER OPERATING INSTRUCTIONS...8 Section I. INITIAL ADJUSTMENTS...8 Section II. OPERATING INSTRUCTIONS...9 CHAPTER ORGANIZATIONAL MAINTENANCE...10 Section I. OPERATORS MAINTENANCE...10 Section II. UNIT REPAIRMAN'S MAINTENANCE...12 Section III. TROUBLESHOOTING...14 CHAPTER THEORY...17 Section I. RADIO SET BLOCK DIAGRAM...17 Section II. RADIO RECEIVER R-508/ARC...17 Section III. FREQUENCY CONVERTER CV-431/ARC...21 Section IV. MINOR COMPONENTS...24 CHAPTER FIELD MAINTENANCE...29 Section I. GENERAL TROUBLESHOOTING TECHNIQUES...29 Section II. TROUBLESHOOTING RADIO SET AN/ARC Section III. REPAIRS AND ADJUSTMENTS...37 TAGO 269A - July 1

2 Figure 1-1. Major components of Radio Set AN/ARC-60 (less ARC type Relay K-15). 2 TAGO 269A - July

3 CHAPTER 1 INTRODUCTION Section I. GENERAL 1-1. Scope This manual covers operation, maintenance, and repair of Radio Set AN/ARC-60 (fig 1-1). This manual contains no installation instructions, however it does include typical connection data required to make this set operative. Installation instructions will vary with each type of aircraft that uses this radio set Forms and Records a. Unsatisfactory Equipment Reports. (1) Fill out and forward DA Form 468 (Unsatisfactory Equipment Report to Commanding Officer, Signal Equipment Support Agency, Fort Monmouth, N. J., as prescribed in AR (2) Fill out and forward AFTO Form 29 (Unsatisfactory Report) to Commander, Air Material Command, Wright-Patterson Air Force Base, Ohio, as prescribed in AF TO 00-35D-54. b. Damaged or Improper Shipment. Fill out and forward DD Form 6 (Report of Damaged or Improper Shipment) as prescribed in AR (Army); Navy Shipping Guide, Article (Navy); and AFR 71-4 (Air Force). c. Preventative Maintenance Forms. (1) Prepare DA Form , Operator First Echelon Maintenance Check List for Signal Corps Equipment (Radio Communication, Direction Finding, Carrier, Radar) (fig 3-1) in accordance with instructions on the back of the form. (2) Prepare DA Form , Second and Third Echelon Maintenance Check List for Signal Corps Equipment (Radio Communication, Direction Finding, Carrier, Radar), (fig 3-2) in accordance with instructions on the back of the form. Section II. DESCRIPTION AND DATA 1-3. Purpose and Use Radio Set AN/ARC-60 is a group of components installed in an aircraft to provide radio communications in the ultra-high frequency band. This radio set provides crystal-controlled amplitudemodulated voice transmission and continuously tunable reception in the frequency range between 228 and 258 megacycles Technical Characteristics Frequency Range mc Transmitting channels...16 Crystals required 16 each of ARC-type or equivalent Type of modulation Amplitude Type of transmission..voice Distance range: Transmitting miles at 5,000 feet altitude Receiving Line of sight distance Transmitting power output.1/2 watt Receiving sensitivity.. 7 microvolts for 10-mw output with 10-db signal-plus-noise to noise ratio Antenna..Quarter-wave, base fed inverted L whip Power input amperes at 28 volts TAGO 269A - July 3

4 1-5. Table of Components Quantity Item Height (in) Depth (in) Width (in) Unit weight (lb.) 2 Frequency Converter CV-431/AR 5 3/ /32 4 3/ Radio Receiver R-508/ARC 6 7/ / / Radio Set Control C-1917/AR 3 3/4 3 3/4 5 3/ Relay Frequency Oscillator O-423/AR 5 2 3/4 5 1/ Terminal Box J-503A/ARC 4 3/4 1 5/8 7 3/ Jack Box J-502/ARC 2 3/ Relay Switch RE-275/AR 1 3/4 3 3/ / Dynamotor DY-86/ARN-30 Included with Radio Receiver R- 508/ARC 3 Electrical Equipment Rack MT-1140/ARC Included with Radio Receiver R- 508/ARC and Frequency Converter CV-431/AR 1 Mount MT-1677/AR Included with Relay Frequency Oscillator O-423/AR 1 Relay K-15 (ARC type) 1 Antenna AT-701/AR 6 inches vertical 7 inches horizontal /4 inch diameter 10 Connector (ARC type) 1 Connector (ARC type) 2 Connector (ARC type) 1 Connector (ARC type) 1 Connector (ARC type) 2 Connector (ARC type) 2 Connector (ARC type) 2 Headset (ARC type) 2 Headset Bracket (ARC type) 2 Microphone (ARC type) 2 Microphone Bracket (ARC type) 1 Cap (ARC type for Radio Receiver R-508/ARC Coaxial Cable (ARC type) Mechanical Linkage Assembly (ARC type) 2 Technical Manual TM Length will vary with each installation Length will vary with each installation 1-6. Nomenclature and Common Name The following chart lists the AN nomenclature, the equivalent ARC type, and the common names of Radio Set AN/ARC-60. ARC type AN nomenclature Common name ARC-60 Radio Set AN/ARC-60 Radio Set UHF Transverter TV-10 Frequency Converter CV-431/AR Transverter Receiver R-19 Radio Receiver R-508/ARC Receiver Control Unit C-52 Radio Set Control C-1917/AR Control unit Oscillator-relay Unit K-13 Relay Frequency Oscillator O-423/AR Oscillator relay Junction Box J-13A Terminal Box J-506A/ARC Junction box Jack Box J-10 Jack Box J-502/ARC Jack Box Dynamotor D-10A Dynamotor DY-86/ARN-30 Dynamotor Relay Unit K-18 Relay switch RE-275/AR Antenna relay Mounting M-12A Electrical Equipment Rack MT-1140/ARC Equipment rack Mounting M-24 Mount MT-1677/AR Mount Relay K-15 Power relay Antenna A-16 Antenna AT-701/AR Antenna 4 TAGO 269A - July

5 Figure 1-2. Minor components of Radio Set AN/ARC-60 (less ARC type Connectors and 16744) Description of Radio Set AN/ARC-60 The radio set is a group of components installed in an aircraft. The major components are described in paragraphs 1-8 through 1-19 and are illustrated in figure 1-1. The minor components are shown in figure Description of Frequency Converter CV-431/AR a. This transverter is a combined transmitter and a receiver converter. The transmitter portion functions as an independent transmitter on a frequency range of 228 to 259 mc; it does not require the use of any VHF components for transmission. The converter section converts received signals in the range mc to mc, after mixing with a 110-mc crystal oscillator, and requires the use of a VHF receiver for reception. High voltage for all transverter circuits is supplied by the dynamotor mounted on the receiver. b. The transmitter is a five-tube, eight-channel, crystal-controlled, voice amplitude-modulated circuit designed for aircraft-to-ground transmission in the frequency range of 228 to 258 mc. Four type 5763 and one type 6201 electron tubes are used. One of the 5763 tubes is used as a crystal oscillator-doubler, two as amplifier-doublers, and the remaining one as a modulator. The triode sections of the 6201 function as a push-pull amplifier-tripler. The eight transmitting channels may all be located in one 4- megacycle band or they may be divided between two bands, each 4 megacycles wide with at least a 2- megacycle separation. The power output is rated at 0.5 watt. At an altitude of 5,000 feet, the transmitting TAGO 269A - July 5

6 distance range is approximately 60 miles. A type 1N82 crystal detector, with AF bypassing, is used to provide a means of checking the tuning and modulation with an external dc voltmeter. c. The converter section of the transverter comprises a mc uhf preselector, a 110-mc crystal oscillator using type 6201 electron tube, a crystal diode mixer, and a mc VHF matching network. Incoming signals between 228 and 258 megacycles, after being mixed with the 110- mc crystal oscillator frequency, are converted to 118- to 148-megacycle signals. The converted signal is fed to the receiver, which is tunable from 118 to 148 megacycles. The converter portion of the transverter contains a megacycle band-pass network between the UHF antenna connection and a 1N82 crystal mixer. The output from the crystal mixer feeds into the mc VHF matching network, whose output feeds into the receiver input. d. The transverter, as a component of the radio set, is controlled by the control unit Description of Radio Receiver R- 508/ARC a. The receiver is a nine-tube superhetrodyne, continuously tunable over the frequency range of megacycles. This receiver is used for the reception of voice amplitude-modulated signals. The receiver uses three type 9003 electron tubes as the first RF amplifier, the second RF amplifier, and the mixer, followed by a 9002 employed as the RF oscillator. A 14A7 is used as the first IF amplifier, a 14R7 as the second IF amplifier and avc, another 14R7 as the third IF amplifier and avc, and a 14F7 as the detector, noise limiter, and first AF amplifier. A 12A6 is used as the final amplifier. A four-section ganged capacitor is used to tune the RF oscillator and three RF tuned circuits. The RF oscillator frequency is 15 mc below the signal frequency. The IF section contains eight tuned circuits arranged in four pairs, each tuned to a frequency of 15 mc. b. Delayed avc is provided which allows the output to build up to approximately 170 milliwatts before taking hold. The receiver is designed for operation with the control unit. The avc circuit employs the diode sections of V106 and V107. c. One triode section of V108, a type 14F7, is incorporated in a series-diode noise-limiter circuit which provides for high attenuation of highfrequency pulses that may interfere with receiver operation. d. An input of 3 amperes at 14 volts dc, or 1.5 amperes at 28 volts dc is required for operation. High voltage is supplied by the dynamotor which mounts on the rear of the receiver chassis, and power connections are made through mating connectors on the base of the dynamotor and on the receiver chassis. The receiver mounts on the equipment rack. The receiver includes no operating controls and therefore may be located in any convenient site in the airplane; it is tuned remotely through the use of the control unit Description of Radio Set Control C- 1917/AR The control unit is an edge-lighted plastic panel, console-mounted unit, designed to control one receiver for the UHF reception only, one oscillatorrelay, and the two transverters. The frequency REC dial, marked MC, is calibrated for use in the UHF band or 228 to 258 mc. The controls comprise a combined VOL-OFF control to control the application of primary power and to adjust the audio level of the receiver output, and TRANS selector switch for interphone connection and selection of up to 16 UHF transmitting channels, and a combined receiver tuning control and "whistle-through" control to operate the oscillator relay. Edge-lighted panel illumination is provided by three midget flange-base lamps of the required rating (28 volts) installed in red-filter light assemblies, and is controlled by the aircraft's panel-lamp control. Electrical connections and mechanical linkage connections are made at the rear of the unit Description of Relay Frequency Oscillator O-423/AR Oscillator relay is designed for use with any control unit that includes a "whistle-through" control. It makes possible the precise tuning of the UHF receiver, to a crystal-controlled UHF transverter frequency. The oscillator relay is operated when the applicable receiver's tuning crank is pushed. The oscillator relay has the following functions: to connect high voltage to the receiver and transmitter simultaneously; to reduce the receiver sensitivity to a low value; to connect the transverter transmitter to a 50-ohm dummy load; to switch the microphone out of the circuit; to turn on a neon lamp relaxation-type oscillator, the AF output of which is injected into the microphone input circuit to provide about 20 percent tone modulation; and to connect the headset (TEL line) to the output of the receiver being 6 TAGO 269A - July

7 tuned. The oscillator relay includes a VHF WHISTLE LEVEL adjustment and an UHF WHISTLE LEVEL adjustment. These are preset and locked, and must not be disturbed by the operator. High voltage is obtained from the associated receiver and a low voltage from the existing primary power source. The oscillator relay requires Mount MT-1677/AR for installation. All connectors and controls are located on the front of the unit Description of Terminal Box J- 506A/ARC Junction box provides 33 terminals plus four grounded terminals, and a single-pole, double-throw relay. The terminals are arranged in pairs with wiresecuring nuts, except for those associated with the relay, which have one nut and one binding headscrew. Nine rubber-grommet openings are available for wire feed-through. The junction box is mounted by means of four holes in the base of the box. A hole in each corner of the base permits drainage of accumulated moisture Description of Jack Box J-502/ARC The jack box provides a microphone input jack and a headset input jack, and two collet-type openings for wiring connections into and out of the box. The jack box is mounted by means of two holes in its base Description of Dynamotor DY- 86/ARN-30 The dynamotor is completely enclosed and sealed. It is used to furnish high voltage to the receiver (on which it is mounted) and to the transverter. The dynamotor mounts by means of snapslides onto four shock mounts which are an integral part of the receiver chassis. Electrical connections are made through a connector on the receiver chassis. The dynamotor has a rated input of 1.7 amperes at 28 volts dc, and a rated output of ampere at 250 volts dc Description of Relay Switch RE- 275/AR The antenna relay is a single pole, double throw, coaxial relay assembly in a protected housing. Mounting provisions are part of the housing. The antenna relay is used for switching one antenna to either transverter Description of Electrical Equipment Rack MT-1140/ARC This equipment rack is a shock-proof vibration mount type and is used to mount each of the transverters and the receiver. Suitable holes are provided for fastening the equipment rack to a shelf or bulkhead. The component is secured to the equipment rack by snapslides engaging the grooved studs on the equipment rack. This equipment rack has flat, beryllium copper straps on the underside for ground connections Description of Mount MT-1677/AR This mount is a plate type and is used to hold the oscillator relay. Suitable holes are provided for fastening the mount to a shelf or bulkhead. The component is secured to the mount by snapslides engaging the grooved studs on the mount. This mount has disc-type springs on the top of the plate for mounting tension Description of Relay K-15 (ARC type) The power relay connects the 28-volt power source to the radio set. This relay is activated by the OFF- VOL switch in the control unit Description of Antenna AT-701/AR This antenna is a quarter-wave, base fed, inverted L-type designed to operate in the UHF band. It consists of a 1/4 inch diameter, stainless steel, L- shaped rod mounted on a small aluminum box containing a receptacle for coupling to a 52-ohm coaxial transmission line Additional Equipment Required A stable 28-volt dc primary power source is required for the operation of this equipment. A separate circuit to the aircraft's panel light control is required to provide control of the edge-lighted panel in the control unit. TAGO 269A - July 7

8 CHAPTER 2 OPERATING INSTRUCTIONS Section I. INITIAL ADJUSTMENTS Note: This section covers adjustments that should be performed by a unit repairman. Before making adjustments make certain that the radio set is connected as shown in figure Tuning Dial Alinement a. Turn OFF-VOL control fully clockwise and allow the radio set to warm up for two or three minutes. b. Set TRANS switch to desired frequency. c. Press the tuning crank and rotate. Tune for maximum whistle. d. If necessary, disengage the mechanical linkage at the control unit, and rotate the tuning control until the dial reads the exact frequency to which the TRANS switch has been set. e. Reconnect the mechanical linkage. Be careful not to change the relative position of the shafting and the tuning dial. f. Check alinement at several other crystal frequencies Whistle Level Adjustment Controls for whistle-level adjustment are on the front of the oscillator relay unit. To make this adjustment proceed as follows: a. Turn OFF-VOL control on the control unit to maximum. b. Connect a ME-30A vtvm or equivalent across a 300-ohm load to TEL on the jack box. c. Set TRANS switch on the transverter to any operable UHF position. d. Adjust UHF whistle-level on the oscillator relay for an indication of 1 volt output on the vtvm UHF Transverter Adjustments for Maximum RF Output a. Be sure that the antenna is properly connected. b. Be sure that the crystals are properly installed. c. Turn the OFF-VOL control on the control unit clockwise. Allow the radio set to warm up for 2 to 3 minutes. d. Set the TRANS switch on the transverter to the UHF frequency nearest to the center of the upper 4 mc spread being used. e. Connect a 1,000 ohm/volt or 20,000 ohm/volt meter (3 volt scale) between TEST jack on front panel of the transverter and ground. f. Press the microphone button and adjust the slotted screws located inside the transverter (fig 5-4) labeled HI 1, 2, 3, 4 for maximum output on the meter. g. Set TRANS switch on the control unit to the UHF frequency nearest to the center of the lower 4 mc spread being used. h. Press the microphone button and adjust the slotted screws located inside the transverter (fig 5-4) labeled LO 1, 2, 3, 4 for maximum output on the meter. 8 TAGO 269A - July

9 Section II. OPERATING INSTRUCTIONS Note: This section covers instructions on the controls and operation of the radio set Control Unit, Operating Controls (fig 2-2) Operating controls and their functions are listed below: Control Function OFF-VOL control Turns on the radio set and permits audio output adjustment. TRANS switch Selects UHF transmitting frequency, one position provides interphone communications. REC dial Tuning crank Indicates operating frequency. Tunes receiver to desired UHF frequency. When pressed, permits precise tuning of receiver to selected UHF frequency Operating Procedure a. Turn the OFF-VOL control on the control unit fully clockwise. Allow the radio set to warm up. b. Set the TRANS switch on the control unit to the desired UHF operating frequency. c. Press the tuning crank on the control unit and tune the receiver to maximum whistle. Adjust OFF- VOL control for comfortable listening level. Figure 2-2. Control unit, operating controls. d. To transmit, press the microphone button on the microphone and speak into the microphone. e. To receive, release the microphone button as soon as transmission is ended Stopping Procedure Turn the OFF-VOL switch maximum counterclockwise position or until a click is heard. TAGO 269A - July 9

10 CHAPTER 3 ORGANIZATIONAL MAINTENANCE Section I. OPERATORS MAINTENANCE 3-1. Scope of Operator's Maintenance a. The following is a list of maintenance duties normally performed by the operator of the radio set. These procedures do not require special tools or test equipment. b. Operator's maintenance for the radio set consists of the following: (1) Preventative maintenance (par. 3-2). (2) Operational check list (par. 3-4). (3) Checking cable connections Preventative Maintenance a. DA Form DA Form (fig. 3-1) is a preventative maintenance check list to be used by the operator. Items not applicable to the radio set are lined out in the figure. Reference in the ITEM block in the figure are to paragraphs that contain additional maintenance information pertinent to the particular item. Instructions for the use of the form appear on the back of the form. b. Items. The information in the chart below is supplementary to DA Form The item numbers correspond to the ITEM numbers on the form. Item Maintenance procedures 3 Use a clean cloth to remove dust, dirt, moisture, and grease from the antenna, microphone, headsets, and front panel controls on the control unit. If necessary, wet the cloth with Cleaning Compound and then wipe the parts with a dry clean cloth. 5 All control knobs should work smoothly, be tight on the shaft, and should not bind. Tighten all loose knobs and be sure that the knobs do not rub against the control unit panel. 8 Remove all rust from components and touch up bare spots with paint. 9 Repair and cuts in the insulation by covering them with rubber tape and then with friction tape. Replace or repair all broken cords and cables. Warning: Cleaning Compound is flammable and its fumes are toxic. Do not use near a flame and provide adequate ventilation Operator's Visual Inspection a. When the radio set fails to perform properly, turn off the power and check all the items in (1) through (6) below. Do not check any item with the power on. (1) Wrong settings of TRANS switch and tuning control. (2) Cables, headset cords, or antenna lead-in wire poorly connected. (3) Disconnected cables, plugs, or headset cord. (4) Grounded or broken antenna or antenna lead-in wire. (5) Tripped circuit breaker (usually indicates some other fault). (6) Low source voltage. b. If the above checks do not locate the trouble, proceed to the operational check list (par. 3-4) Operational Checklist a. General. The operational checklist will help the operator to locate the trouble quickly. The corrective measures are used to repair this trouble. If the measures suggested do not restore normal equipment performance, troubleshooting is required by a Field Radio Mechanic. Note on the repair tag what corrective measures were taken and how the equipment performed at the time of failure. b. Procedure. Place the set in operation (par. 2-5). After the radio set has had time to warm up, perform the steps in the order given in c below. Observe the equipment operation and perform any corrective measures necessary. 10 TAGO 269A - July

11 Figure 3-1. DA Form TAGO 269A - July 11

12 c. Operational Checklist. Action Normal indication Corrective measure 1. Turn OFF- VOL switch Dynamotor on receiver runs Check circuit breaker maximum clockwise Noise in headset Check power relay Check cable and plug connections at transverter, antenna, jack box, receiver and control unit. Action Normal indication Corrective measure 2. Set TRANS switch on control unit to desired frequency. 3. Press tuning crank and tune receiver for maximum whistle. Communication possible Same as 1. Higher echelon repair required. Section II. UNIT REPAIRMAN'S MAINTENANCE 3-5. Scope of Unit Repairman's Maintenance a. Following is a list of maintenance duties performed by the unit repairman. The scope of these instructions has been determined by the available tools, materials, test equipment, spare parts, and MOS of the unit repairman. b. Unit repairman's maintenance of the radio set consists of the following: (1) Preventative maintenance (par. 3-7). (2) Lubrication (par. 3-8). (3) Visual inspection (par. 3-9). (4) Troubleshooting (par. 3-9). (5) Sectionalization of trouble to a component (par. 3-11). (6) Replacement of defective tubes (par. 3-12). (7) Adjustment of tuning dial (par. 2-1). (8) Repair of defective cables (par. 5-26). (9) Transverter adjustment (par. 2-3). (10) Replacement of components Tools, Materials, and Test Equipment Required The tools, materials, and test equipment required for unit repairman's maintenance are listed below. a. Tools. (1) Tool Equipment TE-41. (2) Tube Puller (fig. 3-3). b. Materials. (1) Cleaning Compound (federal stock No ). (2) Cleaning cloth. (3) Grease, Aircraft and Instrument (GL). (4) Fine sandpaper. c. Test Equipment. (1) Multimeter TS-297/U. (2) Electron Tube Test Set TV-7/U Unit Repairman's Preventative Maintenance a. DA Form DA Form (fig. 3-2) is a preventative maintenance check list to be used by the unit repairman. Items not applicable to the equipment are lined out in the figure. References in the ITEM block in the figure are to paragraphs that contain additional maintenance information pertinent to the particular item. Instructions for the use of the form appear on the back of the form. b. Items. The information shown in the chart below is supplementary to DA Form The item numbers correspond to the ITEM numbers on the form. Item Maintenance procedures 22 Remove the dust cover on the transverter and check the two relays visible on the top of the chassis. Check for pitting and signs of wear. Clean contacts with Cleaning Compound. 29 Lubricate the radio set according to information in paragraphs 3-8, 5-11, and Inspect the dynamotor located on the receiver for signs of overheating. Remove the end covers at each end of the dynamotor and check to see that no oil or grease is present on the commutators or brushes. After 200 hours of operation, inspect the brushes at each end of the dynamotor for wear, spring tension, pitting, and correct fit to the commutator. Procedures for removal and replacement of the brushes is given in paragraph Do not tighten connectors too tightly. Threads on bolts may become stripped. Tightening terminal nuts in the junction box too tightly will result in twisting off entire terminal bolt. 12 TAGO 269A - July

13 Figure 3-2. DA Form TAGO 269A - July 13

14 3-8. Lubrication Remove the flexible mechanical coupling between the control unit and the receiver. Use a thin long Handled brush and apply a small amount of grease to the gears located on the control unit and the front of the receiver. Section III. TROUBLESHOOTING 3-9. Unit Repairman's Visual Inspection Before operating the equipment, inspect it. This will save repair time and may also avoid further damage to the radio set. Inspect the following for obvious defects. a. The proper seating and mounting of the transverter, receiver, control unit, antenna, antenna relay, oscillator relay, and power relay. b. That all plugs are securely connected to each component. c. The position of the circuit breaker. d. Proper connection to the source voltage. e. Junction box terminal connections. f. The condition of the dynamotor brushes Equipment Performance Check List a. General. The equipment performance check list is a procedure to systematically check equipment performance. All corrective measures which the unit repairman can perform are given in the Corrective measures column. When using the check list, start at the beginning and follow each step in order. If the corrective measures indicated do not fix the equipment, troubleshooting is required by higher echelon. Note on the repair tag how the equipment performed and what corrective measures were taken. b. Procedure. Place the radio set in operation as shown in c below: PREPARATORY c. Equipment Performance Check List. Step Unit Action Normal indication Corrective measures 1 Antenna and antenna relay Check for secure antenna lead-in connections to antenna and antenna relay. 2 Transverter Check for secure wire and plug connections. Tighten plug connector rings hand tight. Remove dust cover and check for proper seating of crystals and for correlation of crystal frequency and control unit frequency. 3 Receiver Check for secure plug and wire connections. Check and hand tighten plug connector rings and mechanical linkage nut. 4 Oscillator-relay and power relay Check for secure plug connections. Hand tighten plug connector rings. 5 Junction box Check that all wire connections and terminal nuts are secure 6 Control unit Check that all plugs are secure. Hand tighten plug connector rings and mechanical linkage nut. Set TRANS switch to desired operating channel. 7 Headset and microphone Check that headset cord and microphone cord are plugged in jack box. 14 TAGO 269A - July

15 EQUIPMENT PERFORMANCE 8 Control unit Turn OFF-VOL control maximum clockwise. 9 Receiver Press and rotate tuning crank. 10 Microphone Press button and speak into microphone. Dynamotor on receiver operates. Background noise in headset. Loud whistle heard in headset when approaching and on uhf channel. Sidetone heard in headset Carry on communication Check circuit breaker. Check source voltage. Check connections at power relay. Replace dynamotor. Check wiring from power relay to junction box. Replace receiver. Replace control unit. Check cable connections between receiver and junction box oscillatorrelay. Adjust oscillator relay for loud whistle (par. 2-2). Replace receiver. Replace oscillator-relay. Turn TRANS switch to another channel or several channels. Check wiring between transverter and junction box and junction box and control unit. Replace transverter. Replace oscillator-relay. Replace receiver. Replace antenna relay Interunit Sectionalization a. When abnormal indications are obtained at one operating position, check the operation at the other operating position. If normal results are obtained there, the trouble is probably in the first jack box, headset or microphone. b. If operation at both operating positions is abnormal, then depending on the normal indications (par. 3-10c) replace each component with a known good component until normal operation is restored. c. If normal operation is not restored by the replacing of components then a thorough check of plugs and cables between components should be made until the trouble has been found. If a close inspection does not reveal the trouble, then higher echelon repair and troubleshooting is necessary Tube Testing Techniques When trouble occurs, check all cabling, connections, and source voltage before removing any tubes. Try to isolate the trouble to a component or stage. If tube failure is suspected, use the applicable procedure below to check the tubes. Caution: Do not rock or rotate a tube when removing it from a socket; pull it straight out with a tube puller. a. Use of Tube Tester. Remove and test one tube at a time. Discard a tube only if its defect is obvious or if the tube tester shows it to be defective. Do not discard a tube that tests at or near its minimum test limit on the tube tester. Put back the original tube, or insert a new one if required, before testing the next one. b. Tube substitution Method. Replace a suspected tube with a new tube. If the equipment remains inoperative, remove the new tube and put back the original tube. Repeat this procedure with each suspected tube until the defective tube is located. (1) Check tubes in the transverter as follows: (a) Remove the dust cover. (b) Remove and check four type 5763 tubes, one at a time, from transverter. (c) Remove and check two type 6201 tubes, one at a time, from transverter. (2) Check tubes in receiver as follows: (a) Slide back the slide fasteners and remove the top cover. TAGO 269A - July 15

16 Figure 3-3. Tube puller and control unit frequency tab inserts. (b) Remove and check two type 14R7 tubes, one type 14A7 tube, one type 14F7 tube, one type 12A6 tube, three type 9003 tubes, and one type 9002 tube, one at a time from the receiver Replacing Brushes in the Dynamotor (fig. 5-6) When a visual check discloses that the carbon brushes are shorter than 5/16 inch from end to shoulder, they need replacement. To remove and replace brushes proceed as follows: a. Remove the end covers at each end of the dynamotor. b. Unscrew the bakelite caps at each end of the dynamotor and remove the carbon brushes. c. Sand the commutators with fine sandpaper. Clean the commutators with Cleaning Compound. d. Insert the new brushes, making certain that they slide smoothly into their respective brush holders and that they are of correct type. e. Partly remove each brush and fasten a close fitting strip of fine sandpaper around the commutator. Reseat one brush at a time by reseating each brush in its respective holder with its face against the sandpaper. Rotate the dynamotor armature until the brush face assumes the same contour as the commutator. f. Remove the sandpaper and replace the brushes and bakelite caps. g. Blow out all accumulated dust with compressed air and run the dynamotor until 80 percent of each brush makes contact with the commutators. h. Replace both end covers. 16 TAGO 269A - July

17 CHAPTER 4 THEORY Section I. RADIO SET BLOCK DIAGRAM 4-1. Introduction a. The major components of Radio Set AN/ARC-60 are shown in figure 4-1. The aircraft's electrical system furnishes 28-volt dc power to the radio set. When OFF-VOL switch on the control unit is closed, a power relay is activated and low voltage is distributed through the junction box, to the major components and the dynamotor. The dynamotor generates the necessary plate and screen grid voltages to the receiver, the two transverters, and the oscillator-relay unit. The radio set provides two-way communication on any one of sixteen channels, with an additional channel for intercommunication between the aircraft personnel. The setting of the TRANS switch on the control unit selects the operating frequency and operates the antenna relay to switch the antenna to the transverter in use. Each transverter functions as a transmitter and also as a frequency converter for the receiver. b. The receiver may be tuned to any one of the transverters' crystal frequencies by pressing the PRESS TP WHISTLE tuning crank on the control unit. When this tuning crank is pressed it actuates the oscillator-relay unit which performs the following functions through its relays: (1) Connects high voltage to the receiver and transverters simultaneously. (2) Reduces receiver sensitivity. (3) Connects the output of the transverter in use to a 50-ohm dummy load. (4) Switches the microphone out of the circuit. (5) Turns on a relaxation-type tone oscillator, whose output is injected into the microphone input circuit to provide about 20 percent tone modulation on the transmitter carrier. (6) Connects the headset (TEL line) to the output of the receiver. c. High voltage and antenna connections for the transverters are obtained in the following manner. The microphone and headset, are plugged into the jack box, which is connected to the system through the junction box. Closing the microphone switch actuates a relay in the transverter which connects the high voltage output from the dynamotor to the transverter in use. At the same time, another transverter relay is actuated which disconnects the antenna circuit from the receiver and connects it to the output circuit of the transverter. The relays of the transverter not in use serve to patch the signal and power connections to the other transverter UHF Transmission and Reception The two transverters in the radio set operate as transmitters and frequency converters. Each transmitter section of the transverter operates on a frequency band of 228- to 258-mc. Each transmitter can operate on any one of 8 crystal frequencies, thus providing a maximum of sixteen operating frequencies. The receiver is primarily a VHF receiver with a frequency range of mc. For reception of UHF frequencies, the converter section of the transverter converts the incoming mc signals to the mc band by mixing the incoming UHF signal with the output of a selfcontained 110-mc crystal oscillator, and applying the resulting VHF signal to the receiver. Section II. RADIO RECEIVER R-508/ARC 4-3. General Radio Receiver R-508/ARC (fig. 4-2) is a ninetube superhetrodyne, continuously tunable over a frequency range of mc. The RF section of the receiver is a preselector assembly which contains four tuned circuits and four tubes arranged as TAGO 269A - July 17

18 Figure 4-1. Radio Set AN/ARC-60, block diagram. follows: a tuned input circuit, a type 9003 first RF amplifier and tuned output circuit, a 9003 second RF amplifier and tuned output circuit, a 9003 mixer, and a 9002 RF oscillator and tuned circuit. The RF oscillator and RF signal circuits are tuned by a foursection gang capacitor. The IF section, operating at a frequency of 15 mc, consists of eight IF tuned circuits, a type 14A7 first IF amplifier, a 14R7 second IF amplifier and avc, a 14R7 third IF amplifier and avc, and a 14F7 detector and noise limiter, which also functions as the first audio amplifier. The audio output of the first audio amplifier is resistance-coupled to a type 12A6 tube, functioning as the final audio amplifier. The output of the 12A6 is fed through an 8 to 1 stepdown transformer to the telephone load. The plate and screen voltages are supplied by a dynamotor. The heater voltage is supplied directly from the low voltage source on the aircraft Preselector Assembly The preselector assembly consists of the antenna input, the first RF amplifier, the second RF 18 TAGO 269A - July

19 Figure 4-2. Radio Receiver R-508/ARC, block diagram. amplifier, and the RF oscillator and mixer circuits. The details of this assembly are described in paragraphs 4-5 to Antenna Input Circuit (fig. 4-3) The antenna input circuit is the first RF tuned circuit. The signal from the antenna is applied to relay K-18. From this relay the signal is applied to the transverter in use. The transverter converts the signal to the frequency range of the receiver (pars through 4-21) and applies it to J306 through an RG-58/U cable or 53-ohm impedance, to the untuned primary coil L302 and then by mutual induction to L301. Inductor L301 is tuned by C304A. Gang trimmer capacitors C304B, C304D, C304F and C304H are used to aline all tuned circuits at the preselector frequency of 144 mc. Capacitor C305 is the grid coupling capacitor. Resistor R-301 provides the dc connection from the avc bias source to the grid of V301. Capacitor C306 is used to decouple the grid circuits. Filter circuits consisting of C308, R305, C312, R309, C316 and R310 are used to decouple the screen circuits First RF Amplifier Circuit (fig. 4-3) The RF signal is coupled to the grid of V301 through C305. Resistor R301 provides a dc connection to the avc source. Resistor R302 is the cathode bias resistor and C307 is the cathode RF bypass capacitor. Capacitor C304D is the trimmer capacitor used to aline the output RF tuned circuit of V301 (L303 and C304C). The output of this tuned circuit is coupled to the input grid of V302 through C Second RF Amplifier Circuit (fig. 4-3) The detailed parts of the second RF amplifier function in an identical manner as those of the first RF amplifier. The output of the second RF amplifier, V302, is applied to the input grid of the mixer, V303through the coupling capacitor C RF Oscillator and Mixer Circuits (fig. 4-3) Tube V304, a type 9002 electron tube, serves as the RF oscillator in a tuned-plate oscillator circuit. The RF oscillator frequency is below the incoming signal, the difference being 15 mc (the intermediate frequency) throughout the tuning range of the receiver. Capacitor C304G is the RF oscillator tuning section of the gang capacitor. Capacitor C319 and R312 are the grid capacitor and resistor. The local oscillator voltage is injected by coupling coil L305 into the cathode of the mixer tube V303, a type 9003, so that the total RF grid-to-cathode voltage of V303 is the sum of the signal applied between grid and ground and the oscillator voltage applied between cathode and ground. Adjustment of the oscillator at the high-end alinement frequency is provided by trimmer C304H. All tuned inductances of the preselector are factory-adjusted at the low-end alinement frequency, 122 mc by copper slugs mounted in the ends of the coil shields. TAGO 269A - July 19

20 4-9. IF Amplifier Circuits (fig. 4-3) The IF amplifier circuits are similar in design and function, except for the fourth IF coupling unit. The IF amplifier section consists of eight tuned circuits arranged in four pairs (one pair per tube). The primary of the first IF tuned circuit is fed from the plate of mixer V303, and consists of L307, fixed capacitor C322, and trimmer capacitor C320. The secondary is similarly designed. The remaining IF tuned circuits, except for the primary coil and the primary and secondary fixed capacitors of the fourth IF tuned circuit Z305, are identical. Inductor L316 is made larger and C355 is reduced in order to obtain sufficient undistorted IF power for the avc rectifier. The IF tuned circuits are inductively coupled and selected to provide almost critical coupling. The output of the seventh IF tuned circuit is connected to the avc diode plate of V307 through C351 and the output of the eighth IF tuned circuit to the diode detector section of V Detector, Noise Limiter, and First Audio Amplifier Circuit (fig. 4-3) a. The triode section of V308, pins 5, 6, and 7 is connected as a diode. The modulated IF signal across L317 and C356 is rectified by the diode and an AF voltage developed across R340 and R341. The portion of the AF voltage between R341 and ground is directly coupled to the first AF amplifier. Instantaneous increases in signal values such as noise pulses tend to increase the current through R340 and R341. This increases the biasing effect on the diode and momentarily reduces the tubes' sensitivity for the period of the noise pulse. Capacitor C349BC is an IF filter, C357 returns L317 to ground for IF and RF. Resistor R339 is the dc ground return for the grid (pin 4) of the first AF amplifier. b. The second triode section of V308, pins 2, 3, and 4 is biased by the dc bleeder current from the power supply through R342 and the cathode bias resistors R343 and adjustable R351. Because no coupling capacitor is used to couple the AF signal to the grid of the first AF amplifier, the presence of AF on the grid increases plate current flow through this triode section. Additional noise limiting is obtained by this circuit arrangement because an instantaneous increase in the applied grid voltage instantly reduces plate voltage and, in turn, the output signal, due to the 180-degree phase shift across the tube. Resistor R351 varies the bias on the first AF amplifier and functions as a volume control Second Audio Amplifier (fig. 4-3) The AF output from V308 is coupled through a low-pass filter circuit consisting of R346, C362 and C363 to the grid of V309, a type 12A6 tube. The output of V309 is applied to T301, an 8 to 1 output transformer. Capacitor C365 across the primary of T301 attenuates all audio frequencies above 4,000 cycles and also filters out RF. In early models, a small neon lamp, V310 was connected across half the primary winding of T301. In later models V310 was replaced by a thyrite resistor, TY301. The purpose of V310 or TY301 is to protect the equipment if exceptionally strong signals are received when the normal load is removed. The lamp glows at approximately 55 volts ac. As soon as the glow starts, any increase in voltage across the lamp terminals causes a relatively large increase in current through the lamp and therefor limits the voltage to approximately 55 volts ac across half the primary of T301. The thyrite resistor TY301, functions in the same manner, except that it depends upon its inherent resistance behavior to limit the voltage to a safe value Automatic Volume Control Circuit (fig. 4-3) a. Automatic volume control (avc) is provided by avc diode rectifier (pins 3 and 7 of V307), the avc diode limiter (pins 3 and 7 of V306), and a filter circuit consisting of R336, C349A, R324, C324B, R316 and C306. A voltage divider circuit consisting of R321 and R322 applies approximately one-third of the total avc bias to V306. The IF voltage that operates diode rectifier V307 is obtained from the primary of Z305 through C351. b. With the manual sensitivity control at maximum sensitivity, the avc circuit is designed to begin control when the RF input level at the antenna exceeds approximately 8 microvolts. This produces an IF level of 30 volts ac at the plate of V307. With no IF signal the cathode of V307 is positive in respect to the diode plate because of the voltage drop across R33 and R334. No voltage is developed across R335. The diode section of V306 is permitted to conduct because its plate is returned to the cathode of V307 which is plus 30 volts in respect to ground. For all signal values a low value of avc is developed across R321 and R322. When the signal value at the plate of the diode section of V307 exceeds the positive voltage on the cathode of the diode conducts and an avc voltage is developed across R335. Thus, signal levels in excess of 30 volts 20 TAGO 269A - July

21 produce an avc rectifier output across R335, will apply an avc bias equal to this excess to the input grids of V301, V302, V305, and partially to V306. Section III. FREQUENCY CONVERTER CV-431/ARC General (fig. 4-4) a. Transverter Block Diagram. The transverter is a combined UHF transmitter and receiver converter. The converter section converts signals received in the range of mc to mc by mixing the UHF signal with a 110-mc crystal oscillator. A simplified block diagram of the transverter is shown in figure 4-4. b. Transmitter Section. A detailed block diagram of the transverter is shown in figure 4-5. The transmitter section is a five-tube, eight-channel, crystal-controlled, voice amplitude-modulated circuit designed for aircraft-to-ground transmission in the frequency range of 228 to 258 mc. Four type 5763 and one type 6201 electron tubes are used. One of the 5763 tubes is used as a crystal oscillator-doubler, two as amplifier-doublers, and the remaining tube as a modulator. The two triode sections of the 6201 are connected as a push-pull amplifier-tripler. The eight transmitting channels may be located in one 4-mc band, or they may be divided between two bands each 4 mc wide. If two 4-mc bands are used, a separation of at least 2 mc between bands should be observed. The band section (HI or LO, figure 4-6) will depend on the wiring to the control unit, which in turn operates relay K4209. Operation of K4209 opens the contacts which disconnect the trimmer capacitors from the tank circuits for HI band operation. The power output of the transmitter section is rated at 0.5 watt. c. Converter Section. The converter section of the transverter comprises a mc UHF Figure 4-4. Frequency Converter CV-431/ARC, simplified block diagram. TAGO 269A - July 21

22 Figure 4-5. Frequency Converter CV-431/ARC, block diagram preselector, a 110-mc crystal oscillator, using a type 6201 electron tube, a type 1n82 crystal diode mixer, and a mc VHF matching network (fig. 4-6). After incoming signals are selected by tuned circuits of the preselector, they are mixed with the 110-mc crystal oscillator frequency, producing converted signals in the range of 118 to 148 mc, which are fed to the receiver. d. Whistle-Through Tuning Procedure. The "whistle-through" procedure is used when it is desired to tune the receiver exactly to the transmitting frequency. When the PRESS TO WHISTLE tuning crank on the control unit is pressed, power is applied to relays K4210, K4213, and K4214 (fig. 4-5). Relay K4213 disconnects the preselector from the antenna, K4210 connects the output of the UHF transmitter to a dummy load and K4214 applies the output of the converter to the receiver. The output of the 1000-cycle oscillator in the oscillator-relay is applied to the microphone circuit. This audio frequency modulates the 22 TAGO 269A - July

23 transmitter's output which is picked up by the receiver Crystal Oscillator-Doubler Circuit (fig. 4-6) A pierce crystal oscillator circuit is used to generate the RF voltage. Eight crystals may be installed. Since the radio set uses two transverters a total of 16 crystals may be used. These crystals are selected individually by the TRANS switch of the control unit. Depending upon the crystal position selected, one of the relays K4201 through 4208, will be actuated and connect the desired crystal into the oscillator circuit. The crystal circuit is directly coupled to the control grid and through C4203 to the cathode of V4201. Capacitor C4202 prevents oscillation when no crystal is present in the circuit. Inductor L4201 is a high-impedance RF choke. The oscillator output frequency is doubled in the plate tank circuit of V4201, and coupled to the grid of V4202 through C Amplifier-Doubler Circuits (fig. 4-6) The output from V4201 is amplified and doubled in the tank circuit of V4202, and further amplified and doubled in the tank circuit of V4203. The tank circuit of V4203 uses a tapped coil L4205 and a split-stator variable capacitor C4222. The output of this tank circuit is applied to the grids of V4205A and V4205B through C4224 and C Push-Pull Amplifier-Tripler Circuit (fig. 4-6) The amplifier-tripler stage of the transmitter section uses a type 6201 dual triode connected in a balanced push-pull circuit. The use of a push-pull circuit results in more power output and cancellation of even order harmonics which leaves the preferred third harmonic to be developed in the tank circuit. The push-pull amplifier-tripler is plate-modulated at better than 90 percent by the modulator V4204. The 1N82 crystal CR4201 is included in the output circuit to allow a comparison check of the modulation and tuning of the transmitter to be made, with a dc volt-meter connected to J4201. Capacitor C4229 functions as an AF bypass capacitor. Resistor R4225 acts as a load when no meter is connected to J Modulator Circuit (fig. 4-6) A type 5763 electron tube V4204 is used as the modulator. The voice-input signal is applied to the primary of T4201, the secondary feeds into the grid of V4204 through resistor R4211. The output of V4204 feeds into the primary of modulator transformer T4202, the secondary modulates the output of V4205. Sidetone for interphone communication is obtained from the cathode of V4204 and coupled through C4217 to the headset line of the receiver mc Crystal Oscillator a. Z4201, the 110-mc crystal oscillator, is an individual subassembly whose part are located on the tube socket for V4206 and a ceramic terminal board. The oscillator circuit is a cathode-coupled oscillator using a 110-mc crystal Y4209. Tube V4206A is connected as a cathode follower. Inductor L4211 across Y4209 is used to cancel out the shunt capacity of the crystal so that only resistance is present at the crystal resonant frequency. Therefore, coupling between the cathodes of V4206A and V4206B can only take place at the series resonant frequency of the crystal. The tanks circuit consists of L4212, C4248, C4235 and all distributed capacitance. The filter network consisting of C4232, R4229, and C4234 prevents 110 mc from radiating or entering into the high-voltage line. Capacitor C4205, connected between the heater of V4206 and ground, prevents 110 mc from entering the lowvoltage line. b. The voltage at the junction of L4212, C4248, and C4235 is presented at the cathode of V4206A. The output of V4206A is coupled through the 110 mc crystal to the cathode of V4206B. Tube V4206B is a grounded grid amplifier so that no phase inversion takes place through the tube. The 110 mc signal is amplified by V4206B and reappears at the junction of L4212, C4248, and C4235 at a frequency determined by the crystal (110 mc) and at a greater magnitude to maintain oscillation. If V4206 is replaced, the oscillator must be realigned by L4212, because of the differing tube inherent capacitance UHF Preselector (fig. 4-6) The UHF preselector (Z4202) consists of three over-coupled tuned circuits, tuned to select frequencies between 228 and 258 mc. The first tuned circuit consists of C4244, L4218, and C4242, with C4242 also functioning to couple the first tuned circuit to the second tuned circuit. The second tuned circuit consists of L4216 and C4240, and C4239, which couples the second tuned circuit to the third tuned circuit. The third tuned circuit consists of L4214, and C4236. Jack 4205 provides a convenient TAGO 269A - July 23

24 means of testing the crystal current of the mixer CR4202. Inductor L4213 is an RF choke and R4232 acts as the load when no meter is connected to J VHF Matching Network (fig. 4-6) The VHF matching network matches the impedance of the 1N82 crystal into a 50-ohm output impedance. A 110-mc trap, consisting of L4219 and C4245, prevents 110 mc from desensitizing the receiver, since the receiver is capable of being tuned to 118 mc Frequency Conversion Process (fig. 4-6) The 110 mc crystal oscillator develops a signal voltage that is coupled through V4235 to the 1N82 crystal CR4202 mixer circuit. The incoming signal from the antenna is also coupled to the mixer circuit. The crystal functions as a nonlinear detector and the difference frequency is coupled to the receiver. For example, if the incoming signal frequency was 248 mc, after mixing with the oscillator output of 110 mc the signal coupled to the receiver would be 138 mc. This difference frequency is developed across L4215 and C4238. Section IV. MINOR COMPONENTS Radio Set Control C-1917/ARC The control unit (fig. 4-7) contains all the controls required for the remote operation of one receiver, one oscillator-relay unit, and two UHF transverters. The frequency dial is calibrated for reception in the UHF band of mc. The controls consist of a combination primary power switch S4402, and volume control R4401; a combination receiver tuning and "whistle-through" control S4403; and a transmitter channel selector switch S4401 for selection of interphone and up to 16 UHF channels. All electrical connections are made through J4401 and J4402, located at the rear of the enclosure. The receiver mechanical linkage tuning connect is also made at the rear. When the tuning crank is pressed, microswitch S4403 closes, the oscillator-relay unit is activated and precise tuning of the VHF receiver is possible Relay Frequency Oscillator O-423/AR (fig. 4-8) a. A relaxation oscillator within the oscillatorrelay unit consists of V4001, R4002, and C4002. This circuit is called a neon tube sawtooth generator. In a neon tube, or any cold-cathode gas tube, until the voltage across the tube is high enough to ionize the gas, the tube presents an almost infinite impedance. However, once ionized, a very small voltage is sufficient to keep the current flowing. Until the voltage falls below the firing-point value, the tube has a low impedance. When the voltage drops this value, current flow ceases. In effect, the tube acts as a switch, which is open when de-ionized b. and closed when ionized. The frequency of the circuit is determined by the RC constant. c. A diagram of the relaxation oscillator in the oscillator relay is shown in figure 4-8. With voltage applied, C4002 is charged through R4002. Since V4001 is in parallel with C4002, the voltage across V4001 is equal to the charging voltage across C4002. When the firing voltage of approximately 90 volts is reached, V4001 ionizes and forms a discharge path for the voltage across C4002. The capacitor discharges very rapidly until the voltage across V4001 also decreases to the point where the tube de-ionizes and again presents a high impedance. The cycle is then repeated. d. The frequency is dependent upon the RC time constant. The values of R4002 and C4002 have been chosen for an oscillator frequency of 1,000 cycles. e. Separate potentiometers are provided for VHF and UHF whistle-level adjustments. These are screwdriver-adjusted controls, located on the front of the oscillator-relay. Each control is set for a 1-volt output. Resistor R4007 is used for VHF whistle level, and R4001 is used for the UHF whistle level. Depending upon the position of the contacts of K4005, either R4007 and R4001 is connected in series with R4008 to ground Terminal Box J-506A/ARC a. The junction box provides a terminal for all interunit wiring. All the major components are connected through the junction box as shown in figure 5-1. The junction box has 30 terminals and 4 ground connections, and a single-pole-double-throw (spdt) sidetone relay. 24 TAGO 269A - July

25 Figure 4-7. Control unit, schematic diagram. TAGO 269A - July 25

26 Figure 4-8. Oscillator-relay, schematic diagram. b. The sidetone relay in the junction box operates in the following manner. When the microphone button is depressed a path to the positive side of the low voltage power supply is completed through the sidetone relay (fig. 5-1). This closes the contacts on the sidetone relay and the sidetone from the cathode circuit of modulator V4204 (fig 4-6) is completed to the headset Relay K-15 The power relay (fig. 5-1) operates in the following manner. When the OFF-VOL switch on the control unit is turned in a clockwise direction a path for dc is completed through the contacts A and B of the power relay coil. This activates the power relay and closes contacts C and D which completes the path to the 28-volt supply through the 20-ampere circuit breaker. This action turns on the dynamotor Antenna AT-701/ARC The antenna is a UHF, quarter-wave, base-fed, inverted-l-type antenna. It consists of a stainless steel L-shaped rod, mounted on a small aluminum box. The box is the base for the antenna rod and contains a broad-band circuit (fig 4-9). The broadband circuit consists of 50-uuf ceramic capacitor and a loop constructed from silver-plated strip of copper formed into a rectangular shape. This circuit is connected across the antenna input. The antenna circuit is tuned to a resonate frequency of 248 mc by moving the capacitor toward or away from the loop. 26 TAGO 269A - July

27 Figure Antenna relay, schematic diagram. Figure 4-9. Antenna, schematic diagram Relay Switch RE-275/ARC (fig. 4-10) The antenna relay permits the use of only one antenna for the two transverters. The antenna relay consists of a relay coil and two sets of contacts. The NO (normally open) terminal is connected to one transverter and the NC (normally closed) terminal is connected to the second transverter. The C contact is wired to the antenna. The position of the TRANS switch on the control unit determines whether current flows through the relay coil and in turn selects the transverter to be connected to the UHF antenna B+ Distribution (fig. 4-11) a. When the OFF-VOL switch on the control unit is turned clockwise the power relay applies 28 volts dc to the dynamotor which in turn supplies 250-volts dc to all major components. B+ is applied to the transmitter section of the transverter through relay K4211. This relay is actuated when the microphone button is pressed and removes B+ from the converter section of the transverter and from the receiver. b. When not transmitting K4211 is normally closed and B+ is applied to the converter stage the rough relay JK4212 (this relay is closed automatically when the TRANS switch on the junction box selects any one of the 16 operating frequencies). c. Power is applied to the second transverter in a similar manner. d. B+ is applied to the receiver through the junction box and the normally closed contacts of K4211. Thus the receiver normally operates only when the transmitter is not keyed. e. When the PRESS To WHISTLE tuning crank is depressed relay K4003 closes and B+ is applied to both the transverter and receiver simultaneously. Thus during the "whistle-through" receiver tuning operation the transmitter output is used to calibrate the receiver Dynamotor DY-86/ARN-30 The dynamotor is designed to furnish high voltage to the plate and screen circuits of the receiver and transverters. When 28-volt dc from the aircraft's electrical system is supplied to the motor section of the dynamotor the generator section develops 250 volts dc. TAGO 269A - July 27

28 Figure Radio Set, B+ distribution. 28 TAGO 269A - July

29 CHAPTER 5 FIELD MAINTENANCE Section I. GENERAL TROUBLESHOOTING TECHNIQUES Warning: When servicing the radio set, avoid contact with the B+ circuits. Before touching any connections, turn off the VOL switch on the control unit and temporarily ground terminal 29 in the junction box to discharge all capacitors. The high voltage present can cause serious injury or death Test Equipment Required a. The test equipment required for trouble shooting and testing the radio set is listed below. A common name is given after each component. Nomenclature Antenna A-68-A Audio Oscillator TS-382/A Multimeter ME-77/U Electronic Multimeter TS-505A/U Electron Tube Test Set TV-2/U Signal Generator TS-497/U Bird Electronics Termaline Model 81 with Wattmeter Model db pad: Boonton Radio Corp. Type 505-a Electronic Voltmeter ME-30A/U Test Unit Assembly ARC Type H-18 Bench Test Kit MK-157/GRM Common name Antenna Audio oscillator Multimeter Vtvm Tube tester Signal generator Dummy load 6-db pad Ac vtvm Test unit Bench test kit b. In addition to the units listed in a above, the following equipment is required for trouble shooting and testing the components of the radio set when they are removed from the aircraft. (1) High-voltage regulated dc power supply, with output adjustable between 150 and 300 volts. (2) Test crystals: ARC Type 17142, UHF output frequencies. (3) Antenna wire, 10 to 20 feet long. (4) Three Electrical Equipment Racks MT- 1140/ARC (ARC type M-12A). (5) Receiver R-508/ARC. (6) Noninductive resistor, 300-ohm, 1-watt. (7) Low-voltage dc power supply, capable of supplying 27.5 volts at 6.8 amperes. (8) Pair of high-impedance headphones. (9) Microphone RS-38A Troubleshooting Data The organizational maintenance trouble-shooting section (pars ) gives the techniques for sectionalizing operational troubles to a particular component and for use of the equipment performance check list. Parts of theory chapters (pars ) outline the signal and control paths of the radio set. Use the text and figures to help sectionalize trouble. Wiring diagrams (figs. 5-19, 5-22 and 5-23) and interior views, such as figure 5-24, will help to locate individual parts in the equipment. For repair of coaxial-cable connectors, refer to figure Troubleshooting Procedures a. Visual Inspection. Visual inspection frequently reveals the location of the trouble. A visual examination usually will reveal the following defects: (1) Defective power or interunit cables and plugs. (2) Broken wires within the components. (3) Loose or defective tubes. (4) Burned relay contacts. (5) Blistered or discolored resistors and capacitors. b. Operational Test. The equipment performance check list (par.3-10) is important because it frequently indicates the general location of troubles and often the exact nature of the fault. All symptoms must be interpreted in relation to each other. TAGO 269A - July 29

30 c. Voltage and resistance Measurements. These measurements help locate the individual component at fault. Use voltage and resistance diagrams (figs and 5-21) to find normal readings at receiver and transverter tube sockets. Figure 5-1 shows the points in the interunit cabling system that are connected together. All wires can be checked by continuity from the junction box to the proper terminal on the connector plug. d. Troubleshooting Chart. Paragraph 5-4 contains a troubleshooting chart that will be useful in sectionalizing trouble in the system to a component. Tube-socket voltages and resistances for the receiver and the transverter are shown in figures 5-18 and 5-21 respectively. Section II. TROUBLESHOOTING RADIO SET AN/ARC System Troubleshooting Chart The following chart is supplied as an aid in locating trouble in the radio set. This chart lists the symptoms that the repairman may observer while operating the equipment. The procedures described in the equipment performance check list, paragraph 3-10, should be followed. Troubleshooting information for the receiver, the transverter, and the oscillator-relay is contained in paragraphs 5-5, 5-6, and 5-8, respectively. Symptoms Probable trouble Correction No audible signal. No power to receiver; aircraft battery switch off or circuit breaker tripped. VOL control not turned on. Headset defective or not connected. Power cable loose or not connected. Defective receiver or transverter. Turn battery switch on; check circuit breaker. Rotate control clockwise. Plug in headset; Repair or replace if necessary. Connect or tighten cable. Refer to paragraph 5-5 or 5-6. Faint or fading signal. Distorted signal. Gain not advanced enough. Receiver not tuned accurately. Loose cable connections. Low input voltage. Defective tube. Distant station. Antenna not connected. Low B-supply voltage (defective dynamotor). Defective receiver or transverter. Outside electrical disturbance. Improper antenna connection. Receiver not tuned accurately. Turn VOL control full clockwise. Retune receiver. Tighten cable connections. Check power source. Refer to paragraph 5-5 or 5-6. Tune to nearer station. Reconnect antenna. Check dynamotor; refer to paragraph 5-8. Refer to paragraph 5-5 or 5-6. Tune to another station. Check and reconnect antenna. Retune receiver, using whistle-through. No audible sidetone. No high voltage applied to transverter. Check receiver dynamotor (par. 5-8). Check for presence of B+ at transverter (terminals 28 and 29 in junction box for respective transverters). Refer to paragraph 5-6. Faint or fading sidetone. No whistle-through. No transmission. Defective modulator tube in transverter. Defective transverter. Low input voltage. Defective receiver dynamotor. Poor cable connections. Defective transverter. Receiver not tuned to same frequency as transmitter. Defective oscillator-relay. VOL switch turned off. TRANS switch in wrong position. Defective crystal. Antenna not connected. Defective microphone switch or cable. Microphone not connected. Defective transverter. Check V4204 and replace if necessary. Refer to paragraph 5-6. Check power source. Refer to paragraph 5-8. Tighten all cable connections. Refer to paragraph 5-6. Retune receiver. Refer to paragraph 5-7. Rotate VOL control clockwise. Set TRANS switch to proper channel. Replace crystal. Check antenna connection. Replace microphone and cable. Connect microphone. Refer to paragraph TAGO 269A - July

31 Figure 5-2. Receiver, top view, cover removed. TAGO 269A - July 31

32 Figure 5-3. Receiver, bottom view, cover removed. 32 TAGO 269A - July

33 5-5. Receiver Troubleshooting Chart The following chart is supplied as an aid in locating trouble in the receiver. Symptom Probable trouble Correction Dynamotor not running. Low input voltage Replace or recharge aircraft battery. Loose primary power cable connection. Check cable connections from primary power source to receiver Check all cable connections (fig. 2-1). Check circuit breaker and reset if necessary. Repair dynamotor (par ). Dynamotor running but no output. No audible signal. Faint or fading signal. Receiver overloads on strong signal (improper avc action). Wrong cable connections. Primary power circuit breaker tripped. Defective dynamotor. Dirty commutator. Open or shorted armature windings. Defective output connections. Defective tube. Dynamotor not running. Dynamotor running but no output. Circuit breaker tripped. Shorted or open winding in T301. Defective R330. No screen-grid voltage at any tube socket. Defective tube. IF circuits out of alinement. RF circuits out of alinement. RF oscillator V304 or mixer V303 replaced without realinement of RF oscillator shunt trimmer C304H. Defective dynamotor (low output). Defective RF amplifier tube or mixer tube. Defective capacitor C351. Defective avc rectifier or avc limiter. R335 open or changed value. High noise level. Defective noise limiter V308. Defective capacitor C363. Worn dynamotor brushes or pitted commutator. Abnormal frequency drift. Low battery voltage. Defective oscillator tube V304. Clean commutator. Check windings with multimeter. If defect is found, replace dynamotor. Check connections and repair. Test tubes in tube tester. Replace defective tubes. Refer to first symptom in this chart. Refer to second symptom in this chart. Check circuit breaker and reset if necessary. Check output transformer T301 with multimeter; replace if defective. Check R330; replace if defective. Check C344A; replace if defective. Test all tubes in tube tester. Replace defective tubes. Realine; refer to paragraph Realine; refer to paragraph Retrim C304H; refer to paragraph 5-24b(5). Repair dynamotor; refer to paragraph 5-8 through Check V301, V302, and V303 in tube tester. Replace defective tubes. Replace C351. Test V306 and V307 in tube tester; replace defective tubes. Check the resistor and replace if necessary. Check the tube and replace if necessary. Check and replace if necessary. Replace dynamotor brushes or refinish commutator surface (par. 3-13). Check voltage source with multimeter. If less than 27.5 volts, recharge or replace battery. Test tube and replace if necessary. TAGO 269A - July 33

34 Figure 5-4. Transverter, top view, cover removed. 34 TAGO 269A - July

35 Figure 5-5. Transverter, bottom view, cover removed. TAGO 269A - July 35

36 5-6. Transverter Troubleshooting Chart The following chart is supplied as an aid in troubleshooting the transverter. Symptom Probable trouble Correction No UHF transmitter output. Incorrect or defective cable connections from receiver. Defective high-voltage supply. Check cable connections from receiver through junction box. Check dynamotor mounted on receiver. Repair or replace if necessary. Defective tube. Test all tubes in tube tester. Replace defective tubes. Defective crystal. Replace defective crystal. No UHF transmitter high Defective high-voltage supply. Check dynamotor mounted on receiver. Repair voltage. or replace if necessary. Defective B+ changeover/sidetone relay Repair or replace K4211. K4211. No UHF output at antenna. Defective relay K4210. Repair or replace relay. Channel selector switch in wrong position. Check position of channel selector switch. Incorrect frequency transmitted Incorrect crystal frequency. Check crystal frequency. Improper alinement. Realign; refer to paragraph Frequency coverage incomplete. No sidetone. Defective modulator tube V4204. Defective capacitor C4217. Defective B+ changeover/sidetone relay K4211. No UHF converter output. No UHF converter high voltage. Incorrect or defective cable connections from receiver. Defective high-voltage supply. Defective crystal oscillator. Defective crystal mixer CR4202. Defective relay K4214. Defective dynamotor on receiver. Test tubes and replace if necessary. Check capacitor and replace if necessary. Check relay; repair or replace if necessary. Check cable connections. Check dynamotor on receiver. Test tube V4206 in tube tester; replace if defective. Check crystal by substitution; Refer to paragraph 5-25f for crystal mixer test. Check relay; Repair or replace if necessary. Repair or replace dynamotor. Defective relay K4211 or K4212. Check relays; repair or replace if necessary. Faint or fading UHF Defective crystal oscillator tube V4206. Test tube in tube tester and replace if converter signal. defective. Defective crystal mixer CR4202. Check crystal by substitution. No UHF from receiver. Defective receiver. Check operation of receiver on VHF. If defective, repair (par. 5-5). High UHF converter noise Defective crystal mixer CR4202. Refer to paragraph 5-25f for crystal mixer test. level Oscillator-Relay Troubleshooting When the oscillator-relay is suspected as a source of trouble, check the relays for proper operation. Check for good contact at the relay points. If no whistle-through signal can be obtained, check tube V4001 by substitution. For complete testing procedures, refer to paragraphs 5-26 and A wiring diagram is shown in figure TAGO 269A - July

37 Section III. REPAIRS AND ADJUSTMENTS 5-8. Inspection of Dynamotor (fig. 5-6) Part Armature (34) Brushes (23 and 24) Bearings (33) Frame Coil Windings (35) Procedure Inspect commutator for presence of carbon or copper dust; also check for pitting or scoring. If commutator is grooved radially by more than.005 inch, dynamotor is unsuitable for repair. Inspect length of brushes. If any brush is shorter than 5/16 inch (from end to shoulder), discard it. Inspect lubrication of ball bearings. If dry, dirty, or insufficiently lubricated, clean bearings with Cleaning Compound and relubricate with a lubricant (Navy type 14L3, Grade III). Do not pack bearings. Check that bearings run smoothly. Inspect for torn insulation and exposed wiring. Measure dc resistance of shunt field with multimeter. A reading of 225 ohms must be obtained. Measure the resistance between adjacent commutator bars, which is approximately 25 ohms for high voltage side and.4 ohm for low voltage side. Any appreciable variation from this indicates an open circuit, a short circuit, or a partial short circuit, in which case the armature must be replaced Disassembly of Dynamotor (fig. 5-6) a. Separate base assembly (1) from dynamotor (19) by removing screws (2) and unsoldering the wiring from the connector(13). b. Pry out the lead seals on end covers (20),. Loosen the captive screws and remove the covers. c. Unscrew caps (22) and remove low-voltage brushes (23). Repeat this procedure for high-voltage brushes (24). d. Remove screws (31) from each bearing cover plate (30). Remove cover plate and shim washers (32). The actual number of washers may vary with each dynamotor. e. Remove screws (36) to free wiring. f. Unscrew nuts (27) and remove washers (28) and screws (26) to free armature brackets (25 and 29). g. Carefully remove armature (34) from the dynamotor field subassembly (35). h. If it is necessary to remove the bearings (33), place the armature in a padded vise and, using a bearing puller, remove the bearings. This will also free washers (32). Use extreme care to prevent damage to the commutator or shaft. i. To disassemble base assembly (1), remove retaining ring (14), unscrew screws (5) and studs (4), and separate base (3) from base plate (18) Replacement of Dynamotor Bearings If it is necessary to replace the bearings in the dynamotor-- a. Check to see that the bearing runs smoothly before placing it on the shaft. With the shield side of the bearing facing the commutator, place it on the shaft and with light rap with the palm of the hand, drive it onto the bearing shoulder. b. Replacement bearings are furnished lubricated; however, inspect the lubrication. If required, lubricate as outlined in paragraph Lubrication of Dynamotor To lubricate the ball bearings of the dynamotor-- a. Remove the end covers and the bearing cover plates. b. Remove as much of the old grease as possible, using a cloth or a stiff brush and cleaning compound. c. Apply a small amount of Navy type 14L-3 Grade III lubricant to cover the bearings. Caution: Do not pack the bearings or allow grease to get on the commutator. d. Replace the bearing cover plates and the end covers Reassembly of Dynamotor (fig. 5-6) To reassemble the dynamotor-- a. Attach the base (3) to the base plate (18) with screws (5) and studs (4). Replace the retaining ring (14). b. If the bearings (33) have been removed, refer to paragraph 5-10 for replacement instructions. c. Attach the armature support (25) to the dynamotor field assembly (35) by inserting screws (26) and one washer (28) through the bracket and frame. TAGO 269A - July 37

38 Figure 5-6. Dynamotor, exploded view. 38 TAGO 269A - July

39 d. Holding the bracket in position, insert the armature (34) with the bearing in the proper position in the bracket. Attach the remaining bracket (29) and then secure the assembly with the two remaining washers (28) and the nut (27). e. Attach the wiring to terminals with screws (36). f. Place a sufficient number of shim washers (32) on the shaft ends. Place the cover plates (30) against the shaft ends, securing each with screws (31). g. If the original brushes are to be used, check their identifying marks and replace them in their original positions. Secure them with caps (22). h. Attach the end covers (20) and secure them with their captive screws. i. Resolder the wires to the connectors. Attach the dynamotor to the base assembly (1) with the screws (2). j. Test the dynamotor by connecting it to a source of 28 volts dc. Under normal load conditions, measure the output voltage; it should be 250 volts dc Disassembly of Control Unit (fig ) To disassemble the control unit-- a. Detach the cover (1, fig. 5-7) by turning the fasteners on the rear of the cover counterclockwise with a screwdriver. b. Free the plate (2) by removing screws (3) and washers (4). c. Unsolder the terminal connections and free the connectors (5 and 7) by removing the coupling nuts (6 and 8). d. Using a No. 8 Bristo wrench, loosen setscrew (12) to remove knob (11). Remove screw (14) to free the tuning crank (13). e. Using a No. 6 Bristo wrench, loosen setscrew (16) and remove knob (15). f. To free the pressure plate (17), the dial (19), and the spacers (20), remove screws (18). g. Unscrew the panel light lamp housing assembly (22) with the fingers. Extract the lamps (29). Remove grommet (23) and springs (24) if necessary. h. To detach the plastic panel (30), remove screws (31) and washers (32). i. Unsolder the wiring to the gear assembly (33). Free the gear assembly by removing screw (34), screws (35), terminal lug (36), and washers (37). j. Free the variable resistor (38) by unsoldering the wiring. Remove nut (39) and washer (40). k. Unsolder the wiring to the rotary switch (41). Dismount the rotary switch by removing nut (42) and washer (43). l. Remove switch (44) by removing screws (45) Lubrication of Control Unit a. Lubricate gear teeth, splines, and bearing surfaces of gear assemblies sparingly with low temperature aircraft lubricating grease (MIL-G- 3278). b. If necessary, lubricate mechanical linkages with clock and watch oil (Lubricating Oil, Watch (OCW) MIL-L-3918) Reassembly of Control Unit (fig ) To reassemble the control unit-- a. Replace switch (44) and secure with screws (45). b. Place washer (43) on the bushing of rotary switch (41). Insert the shaft in the mounting hole and secure with nut (42). c. Place washer (40) on the bushing of the variable resistor (38). Insert the shaft in the mounting hole and secure with nut (39). d. Replace the gear assembly (33) and secure it with screw (34), screws (35), terminal lug (36), and washers (37). e. Replace the panel lamp retainers (26) and secure them with nuts (27) and washers (28). f. Secure the plastic panel (30) in place with screws (31) and washers (32). g. Replace springs (24) and grommets (23) on the lamp housings (25). Insert the lamps (29) in the assembled lamp housings (22) and screw them into the retainers (26). h. Fasten the spacers (20), the dial (19), and the pressure plate (17) with screws (18). If necessary, install additional spacers to prevent the dial from rubbing against the plastic panel. i. Mount the knob (15) and tighten setscrew (16). Mount the tuning crank (13) and tighten screw (14). j. Switch (44) must make contact when the tuning crank is pressed.050 inch from its normal position. If adjustment is necessary, bend the switch actuating arm to obtain this setting. TAGO 269A - July 39

40 Figure 5-7. Control unit, exploded view. 40 TAGO 269A - July

41 Figure 5-8. Control unit, interior view. k. Assemble connectors (5 and 7) on plate (2) with their coupling nuts (6 and 8). l. Reconnect and solder all wiring. m. Secure plate (2) with screws (3) and washers (4). Replace the cover (1) and turn the fasteners clockwise Reassembly of Control Unit To adjust the receiver tuning dial in the control unit-- a. Connect Mechanical Linkage MC-215 to the receiver and the control unit without regard to the setting of the dial on the control unit or the tuning of the receiver. b. Carefully turn the control unit tuning crank counterclockwise as far as it will go. Caution: Do not force the crank beyond the stopping point. c. Remove the linkage at one end. d. Turn the tuning crank until the small dot that is located about 1.8 inch to the right of the high- TAGO 269A - July 41

42 Figure 5-9. Control unit, wiring diagram. 42 TAGO 269A - July

43 frequency end of the dial comes directly under the triangular-shaped reference mark. e. Replace the linkage, being careful not to change the positions of the shafting or the spline to which it is attached. f. Test the accuracy of the dial positioning by tuning in several stations of known frequency, or by using a signal generator and checking several points on the dial Disassembly of Oscillator-Relay (figs and 5-11) To disassemble the oscillator-relay-- a. Detach the baseplate (1 fig. 5-10) by removing screws (2) and washers (3). b. If necessary, remove resistor R4002 (10). Unsolder the leads to the neon lamp (15) and remove it from the clip (16). c. Unsolder the clip (16) and capacitor C4002 (11). Free terminal board (17) by removing screws (18) and washers (19). d. Unsolder resistor R4008 (12) and capacitors C4001 and C4003 (13 and 14). e. Free relays (20), (23), and (26) by removing their screws and washers. f. Dismount the resistor assembly (29) by removing screws (30) and washer (31). If necessary, remove plate (32) with a soldering iron and free resistors (34) by unsoldering them from the plate (32). Figure Oscillator-relay, exploded view. TAGO 269A - July 43

44 Figure Oscillator-relay, interior view. g. Unsolder the wires and dismount the connectors (35) by removing screws (36) and washers (37). h. Unsolder the wires and free the variable resistors *38) by removing nuts (39) and (40) and lockwashers (41). i. Remove screw (43), washer (44) and terminal lug (42). j. Unsolder terminal connections and dismount connector (45) by removing its coupling nut (46) Reassembly of Oscillator-Relay (figs and 5-11) To reassemble the oscillator-relay-- a. Mount connector (45, fig. 5-10) and secure it with nut (46). b. Replace terminal lug (42), screw (43), and washer (44). c. Insert the shafts of the variable resistors in the mounting holes, replace washers (41), and replace 44 TAGO 269A - July