TAGO 269A - July 1

TM 11-522

HEADQUARTERS,

Technical Manual DEPARTMENT OF THE ARMY

No. 11-522 Washington 25, D. C., 9 July 1957

CHAPTER 1 .......................................................................................................................................................3INTRODUCTION ..............................................................................................................................................3

Section I. GENERAL.....................................................................................................................................3Section II. DESCRIPTION AND DATA ......................................................................................................3

CHAPTER 2 .......................................................................................................................................................8OPERATING INSTRUCTIONS ........................................................................................................................8

Section I. INITIAL ADJUSTMENTS ...........................................................................................................8Section II. OPERATING INSTRUCTIONS..................................................................................................9

CHAPTER 3 .....................................................................................................................................................10ORGANIZATIONAL MAINTENANCE.........................................................................................................10

Section I. OPERATORS MAINTENANCE................................................................................................10Section II. UNIT REPAIRMAN'S MAINTENANCE.................................................................................12Section III. TROUBLESHOOTING............................................................................................................14

CHAPTER 4 .....................................................................................................................................................17THEORY ..........................................................................................................................................................17

Section I. RADIO SET BLOCK DIAGRAM ..............................................................................................17Section II. RADIO RECEIVER R-508/ARC...............................................................................................17Section III. FREQUENCY CONVERTER CV-431/ARC...........................................................................21Section IV. MINOR COMPONENTS .........................................................................................................24

CHAPTER 5 .....................................................................................................................................................29FIELD MAINTENANCE.................................................................................................................................29

Section I. GENERAL TROUBLESHOOTING TECHNIQUES .................................................................29Section II. TROUBLESHOOTING RADIO SET AN/ARC-60 ..................................................................30Section III. REPAIRS AND ADJUSTMENTS ...........................................................................................37

2 TAGO 269A - July

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

TAGO 269A - July 3

CHAPTER 1

INTRODUCTION

Section I. GENERAL

1-1. Scope This manual covers operation, maintenance, andrepair of Radio Set AN/ARC-60 (fig 1-1). Thismanual contains no installation instructions, howeverit does include typical connection data required tomake this set operative. Installation instructions willvary with each type of aircraft that uses this radioset.

1-2. Forms and Recordsa. Unsatisfactory Equipment Reports.

(1) Fill out and forward DA Form 468(Unsatisfactory Equipment Report toCommanding Officer, Signal EquipmentSupport Agency, Fort Monmouth, N. J., asprescribed in AR 700-38.

(2) Fill out and forward AFTO Form 29(Unsatisfactory Report) to Commander, AirMaterial Command, Wright-Patterson Air

Force Base, Ohio, as prescribed in AF TO00-35D-54.

b. Damaged or Improper Shipment. Fill out andforward DD Form 6 (Report of Damaged orImproper Shipment) as prescribed in AR 700-58(Army); Navy Shipping Guide, Article 1850-4(Navy); and AFR 71-4 (Air Force).

c. Preventative Maintenance Forms.(1) Prepare DA Form 11-238, Operator First

Echelon Maintenance Check List forSignal Corps Equipment (RadioCommunication, Direction Finding,Carrier, Radar) (fig 3-1) in accordancewith instructions on the back of the form.

(2) Prepare DA Form 11-239, Second andThird Echelon Maintenance Check List forSignal Corps Equipment (RadioCommunication, Direction Finding,Carrier, Radar), (fig 3-2) in accordancewith 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 componentsinstalled in an aircraft to provide radiocommunications in the ultra-high frequency band.This radio set provides crystal-controlled amplitude-modulated voice transmission and continuouslytunable reception in the frequency range between228 and 258 megacycles.

1-4. Technical CharacteristicsFrequency Range…………...….225-258 mcTransmitting channels………....16

Crystals required………………16 each of ARC-type17142 or equivalent

Type of modulation……………AmplitudeType of transmission…………..VoiceDistance range:

Transmitting……………...55-60 miles at 5,000 feetaltitude

Receiving…………………Line of sight distanceTransmitting power output.1/2 wattReceiving sensitivity…..…7 microvolts for 10-mw

output with 10-dbsignal-plus-noise tonoise ratio

Antenna…………………..Quarter-wave, base fedinverted L whip

Power input……………....6.8 amperes at 28 volts

4 TAGO 269A - July

1-5. Table of ComponentsQuantity Item Height

(in)Depth

(in)Width

(in)Unit weight

(lb.)2 Frequency Converter CV-431/AR 5 3/4 11 21/32 4 3/4 5.91 Radio Receiver R-508/ARC 6 7/16 11 21/32 4 15/16 9.01 Radio Set Control C-1917/AR 3 3/4 3 3/4 5 3/4 1.41 Relay Frequency Oscillator O-423/AR 5 2 3/4 5 1/16 1.21 Terminal Box J-503A/ARC 4 3/4 1 5/8 7 3/8 1.52 Jack Box J-502/ARC 2 3/4 1 2 0.171 Relay Switch RE-275/AR 1 3/4 3 3/16 2 15/32 0.41

1 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 ConverterCV-431/AR

1 Mount MT-1677/AR Included with Relay FrequencyOscillator O-423/AR

1 Relay K-15 (ARC type)1 Antenna AT-701/AR 6 inches vertical

7 inches horizontal 0.371/4 inch diameter

10 Connector 11337 (ARC type)1 Connector 14050 (ARC type)2 Connector 14951 (ARC type)1 Connector 14320 (ARC type)1 Connector 16115 (ARC type)2 Connector 16743 (ARC type)2 Connector 16744 (ARC type)2 Headset 11935 (ARC type)2 Headset Bracket 11938 (ARC type)2 Microphone 11937 (ARC type)2 Microphone Bracket 11933 (ARC type)1 Cap 14589 (ARC type for Radio Receiver R-508/ARC

Coaxial Cable 11318 (ARC type) Length will vary with each installationMechanical Linkage Assembly 16158 (ARC type) Length will vary with each installation

2 Technical Manual TM 11-522

1-6. Nomenclature and Common Name The following chart lists the AN nomenclature, the equivalent ARC type, and the common names of RadioSet AN/ARC-60.ARC type AN nomenclature Common nameARC-60 Radio Set AN/ARC-60 Radio SetUHF Transverter TV-10 Frequency Converter CV-431/AR TransverterReceiver R-19 Radio Receiver R-508/ARC ReceiverControl Unit C-52 Radio Set Control C-1917/AR Control unitOscillator-relay Unit K-13 Relay Frequency Oscillator O-423/AR Oscillator relayJunction Box J-13A Terminal Box J-506A/ARC Junction boxJack Box J-10 Jack Box J-502/ARC Jack BoxDynamotor D-10A Dynamotor DY-86/ARN-30 DynamotorRelay Unit K-18 Relay switch RE-275/AR Antenna relayMounting M-12A Electrical Equipment Rack MT-1140/ARC Equipment rackMounting M-24 Mount MT-1677/AR MountRelay K-15 Power relayAntenna A-16 Antenna AT-701/AR Antenna

TAGO 269A - July 5

Figure 1-2. Minor components of Radio Set AN/ARC-60 (less ARC type Connectors 16743 and 16744).

1-7. Description of Radio Set AN/ARC-60 The radio set is a group of components installed inan aircraft. The major components are described inparagraphs 1-8 through 1-19 and are illustrated infigure 1-1. The minor components are shown infigure 1-2.

1-8. Description of Frequency ConverterCV-431/AR

a. This transverter is a combined transmitter anda receiver converter. The transmitter portionfunctions as an independent transmitter on afrequency range of 228 to 259 mc; it does not requirethe use of any VHF components for transmission.The converter section converts received signals inthe range 228-258 mc to 118-148 mc, after mixing

with a 110-mc crystal oscillator, and requires the useof a VHF receiver for reception. High voltage for alltransverter circuits is supplied by the dynamotormounted on the receiver.

b. The transmitter is a five-tube, eight-channel,crystal-controlled, voice amplitude-modulated circuitdesigned for aircraft-to-ground transmission in thefrequency range of 228 to 258 mc. Four type 5763and one type 6201 electron tubes are used. One ofthe 5763 tubes is used as a crystal oscillator-doubler,two as amplifier-doublers, and the remaining one asa modulator. The triode sections of the 6201 functionas a push-pull amplifier-tripler. The eighttransmitting channels may all be located in one 4-megacycle band or they may be divided between twobands, each 4 megacycles wide with at least a 2-megacycle separation. The power output is rated at0.5 watt. At an altitude of 5,000 feet, the transmitting

6 TAGO 269A - July

distance range is approximately 60 miles. A type1N82 crystal detector, with AF bypassing, is used toprovide a means of checking the tuning andmodulation with an external dc voltmeter.

c. The converter section of the transvertercomprises a 228-258 mc uhf preselector, a 110-mccrystal oscillator using type 6201 electron tube, acrystal diode mixer, and a 118-148 mc VHFmatching network. Incoming signals between 228and 258 megacycles, after being mixed with the 110-mc crystal oscillator frequency, are converted to118- to 148-megacycle signals. The convertedsignal is fed to the receiver, which is tunable from118 to 148 megacycles. The converter portion of thetransverter contains a 228-258 megacycle band-passnetwork between the UHF antenna connection and a1N82 crystal mixer. The output from the crystalmixer feeds into the 118-148 mc VHF matchingnetwork, whose output feeds into the receiver input.

d. The transverter, as a component of the radioset, is controlled by the control unit.

1-9. Description of Radio Receiver R-508/ARC

a. The receiver is a nine-tube superhetrodyne,continuously tunable over the frequency range of118-148 megacycles. This receiver is used for thereception of voice amplitude-modulated signals. Thereceiver uses three type 9003 electron tubes as thefirst RF amplifier, the second RF amplifier, and themixer, followed by a 9002 employed as the RFoscillator. A 14A7 is used as the first IF amplifier, a14R7 as the second IF amplifier and avc, another14R7 as the third IF amplifier and avc, and a 14F7 asthe detector, noise limiter, and first AF amplifier. A12A6 is used as the final amplifier. A four-sectionganged capacitor is used to tune the RF oscillatorand three RF tuned circuits. The RF oscillatorfrequency is 15 mc below the signal frequency. TheIF section contains eight tuned circuits arranged infour pairs, each tuned to a frequency of 15 mc.

b. Delayed avc is provided which allows theoutput to build up to approximately 170 milliwattsbefore taking hold. The receiver is designed foroperation with the control unit. The avc circuitemploys the diode sections of V106 and V107.

c. One triode section of V108, a type 14F7, isincorporated in a series-diode noise-limiter circuitwhich provides for high attenuation of high-frequency pulses that may interfere with receiveroperation.

d. An input of 3 amperes at 14 volts dc, or 1.5amperes at 28 volts dc is required for operation.High voltage is supplied by the dynamotor whichmounts on the rear of the receiver chassis, and powerconnections are made through mating connectors onthe base of the dynamotor and on the receiverchassis. The receiver mounts on the equipment rack.The receiver includes no operating controls andtherefore may be located in any convenient site inthe airplane; it is tuned remotely through the use ofthe control unit.

1-10. Description of Radio Set Control C-1917/AR

The control unit is an edge-lighted plastic panel,console-mounted unit, designed to control onereceiver for the UHF reception only, one oscillator-relay, and the two transverters. The frequency RECdial, marked MC, is calibrated for use in the UHFband or 228 to 258 mc. The controls comprise acombined VOL-OFF control to control theapplication of primary power and to adjust the audiolevel of the receiver output, and TRANS selectorswitch for interphone connection and selection of upto 16 UHF transmitting channels, and a combinedreceiver tuning control and "whistle-through" controlto operate the oscillator relay. Edge-lighted panelillumination is provided by three midget flange-baselamps of the required rating (28 volts) installed inred-filter light assemblies, and is controlled by theaircraft's panel-lamp control. Electrical connectionsand mechanical linkage connections are made at therear of the unit.

1-11. Description of Relay FrequencyOscillator O-423/AR

Oscillator relay is designed for use with anycontrol unit that includes a "whistle-through"control. It makes possible the precise tuning of theUHF receiver, to a crystal-controlled UHFtransverter frequency. The oscillator relay isoperated when the applicable receiver's tuning crankis pushed. The oscillator relay has the followingfunctions: to connect high voltage to the receiver andtransmitter simultaneously; to reduce the receiversensitivity to a low value; to connect the transvertertransmitter to a 50-ohm dummy load; to switch themicrophone out of the circuit; to turn on a neon lamprelaxation-type oscillator, the AF output of which isinjected into the microphone input circuit to provideabout 20 percent tone modulation; and to connect theheadset (TEL line) to the output of the receiver being

TAGO 269A - July 7

tuned. The oscillator relay includes a VHFWHISTLE LEVEL adjustment and an UHFWHISTLE LEVEL adjustment. These are presetand locked, and must not be disturbed by theoperator. High voltage is obtained from theassociated receiver and a low voltage from theexisting primary power source. The oscillator relayrequires Mount MT-1677/AR for installation. Allconnectors and controls are located on the front ofthe unit.

1-12. Description of Terminal Box J-506A/ARC

Junction box provides 33 terminals plus fourgrounded terminals, and a single-pole, double-throwrelay. The terminals are arranged in pairs with wire-securing nuts, except for those associated with therelay, which have one nut and one bindingheadscrew. Nine rubber-grommet openings areavailable for wire feed-through. The junction box ismounted by means of four holes in the base of thebox. A hole in each corner of the base permitsdrainage of accumulated moisture.

1-13. Description of Jack Box J-502/ARC The jack box provides a microphone input jack anda headset input jack, and two collet-type openingsfor wiring connections into and out of the box. Thejack box is mounted by means of two holes in itsbase.

1-14. Description of Dynamotor DY-86/ARN-30

The dynamotor is completely enclosed and sealed.It is used to furnish high voltage to the receiver (onwhich it is mounted) and to the transverter. Thedynamotor mounts by means of snapslides onto fourshock mounts which are an integral part of thereceiver chassis. Electrical connections are madethrough a connector on the receiver chassis. Thedynamotor has a rated input of 1.7 amperes at 28volts dc, and a rated output of 0.085 ampere at 250volts dc.

1-15. 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. Theantenna relay is used for switching one antenna toeither transverter.

1-16. Description of Electrical EquipmentRack MT-1140/ARC

This equipment rack is a shock-proof vibrationmount type and is used to mount each of thetransverters and the receiver. Suitable holes areprovided for fastening the equipment rack to a shelfor bulkhead. The component is secured to theequipment rack by snapslides engaging the groovedstuds on the equipment rack. This equipment rackhas flat, beryllium copper straps on the underside forground connections.

1-17. Description of Mount MT-1677/AR This mount is a plate type and is used to hold theoscillator relay. Suitable holes are provided forfastening the mount to a shelf or bulkhead. Thecomponent is secured to the mount by snapslidesengaging the grooved studs on the mount. Thismount has disc-type springs on the top of the platefor mounting tension.

1-18. Description of Relay K-15 (ARC type) The power relay connects the 28-volt power sourceto the radio set. This relay is activated by the OFF-VOL switch in the control unit.

1-19. Description of Antenna AT-701/AR This antenna is a quarter-wave, base fed, invertedL-type designed to operate in the UHF band. Itconsists of a 1/4 inch diameter, stainless steel, L-shaped rod mounted on a small aluminum boxcontaining a receptacle for coupling to a 52-ohmcoaxial transmission line.

1-20. Additional Equipment Required A stable 28-volt dc primary power source isrequired for the operation of this equipment. Aseparate circuit to the aircraft's panel light control isrequired to provide control of the edge-lighted panelin the control unit.

8 TAGO 269A - July

CHAPTER 2

OPERATING INSTRUCTIONS

Section I. INITIAL ADJUSTMENTS

Note: This section covers adjustments that should be performed by a unit repairman. Before making adjustments makecertain that the radio set is connected as shown in figure 2-1.

2-1. Tuning Dial Alinementa. Turn OFF-VOL control fully clockwise and

allow the radio set to warm up for two or threeminutes.

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 tuningcontrol until the dial reads the exact frequency towhich the TRANS switch has been set.

e. Reconnect the mechanical linkage. Becareful not to change the relative position of theshafting and the tuning dial.

f. Check alinement at several other crystalfrequencies.

2-2. Whistle Level AdjustmentControls for whistle-level adjustment are on the frontof the oscillator relay unit. To make this adjustmentproceed as follows:

a. Turn OFF-VOL control on the control unit tomaximum.

b. Connect a ME-30A vtvm or equivalent acrossa 300-ohm load to TEL on the jack box.

c. Set TRANS switch on the transverter to anyoperable UHF position.

d. Adjust UHF whistle-level on the oscillatorrelay for an indication of 1 volt output on the vtvm.

2-3. UHF Transverter Adjustments forMaximum RF Output

a. Be sure that the antenna is properlyconnected.

b. Be sure that the crystals are properlyinstalled.

c. Turn the OFF-VOL control on the controlunit clockwise. Allow the radio set to warm up for 2to 3 minutes.

d. Set the TRANS switch on the transverter tothe UHF frequency nearest to the center of the upper4 mc spread being used.

e. Connect a 1,000 ohm/volt or 20,000 ohm/voltmeter (3 volt scale) between TEST jack on frontpanel of the transverter and ground.

f. Press the microphone button and adjust theslotted screws located inside the transverter (fig 5-4)labeled HI 1, 2, 3, 4 for maximum output on themeter.

g. Set TRANS switch on the control unit to theUHF frequency nearest to the center of the lower 4mc spread being used.

h. Press the microphone button and adjust theslotted screws located inside the transverter (fig 5-4)labeled LO 1, 2, 3, 4 for maximum output on themeter.

TAGO 269A - July 9

Section II. OPERATING INSTRUCTIONS

Note: This section covers instructions on the controls and operation of the radio set.

2-4. Control Unit, Operating Controls (fig 2-2)

Operating controls and their functions are listedbelow:

Control FunctionOFF-VOL control Turns on the radio set and permits audio

output adjustment.TRANS switch Selects UHF transmitting frequency,

one position provides interphonecommunications.

REC dial Indicates operating frequency.Tuning crank Tunes receiver to desired UHF

frequency. When pressed, permitsprecise tuning of receiver to selectedUHF frequency.

2-5. Operating Procedurea. Turn the OFF-VOL control on the control

unit fully clockwise. Allow the radio set to warmup.

b. Set the TRANS switch on the control unit tothe desired UHF operating frequency.

c. Press the tuning crank on the control unit andtune 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 onthe microphone and speak into the microphone.

e. To receive, release the microphone button assoon as transmission is ended.

2-6. Stopping Procedure Turn the OFF-VOL switch maximum counter-clockwise position or until a click is heard.

10 TAGO 269A - July

CHAPTER 3

ORGANIZATIONAL MAINTENANCE

Section I. OPERATORS MAINTENANCE

3-1. Scope of Operator's Maintenancea. 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 testequipment.

b. Operator's maintenance for the radio setconsists of the following:

(1) Preventative maintenance (par. 3-2).(2) Operational check list (par. 3-4).(3) Checking cable connections.

3-2. Preventative Maintenancea. DA Form 11-238. DA Form 11-238 (fig. 3-1)

is a preventative maintenance check list to be usedby the operator. Items not applicable to the radio setare lined out in the figure. Reference in the ITEMblock in the figure are to paragraphs that containadditional maintenance information pertinent to theparticular item. Instructions for the use of the formappear on the back of the form.

b. Items. The information in the chart below issupplementary to DA Form 11-238. The itemnumbers correspond to the ITEM numbers on theform.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 controlunit. If necessary, wet the cloth with CleaningCompound and then wipe the parts with a dryclean cloth.

5 All control knobs should work smoothly, betight on the shaft, and should not bind. Tightenall loose knobs and be sure that the knobs donot rub against the control unit panel.

8 Remove all rust from components and touch upbare spots with paint.

9 Repair and cuts in the insulation by coveringthem with rubber tape and then with frictiontape. Replace or repair all broken cords andcables.

Warning: Cleaning Compound is flammable andits fumes are toxic. Do not use near a flame andprovide adequate ventilation.

3-3. Operator's Visual Inspectiona. 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 thepower on.

(1) Wrong settings of TRANS switch andtuning control.

(2) Cables, headset cords, or antenna lead-inwire 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).

3-4. Operational Checklista. General. The operational checklist will help

the operator to locate the trouble quickly. Thecorrective measures are used to repair this trouble. Ifthe measures suggested do not restore normalequipment performance, troubleshooting is requiredby a Field Radio Mechanic. Note on the repair tagwhat corrective measures were taken and how theequipment 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 anycorrective measures necessary.

TAGO 269A - July 11

Figure 3-1. DA Form 11-238.

12 TAGO 269A - July

c. Operational Checklist.Action Normal indication Corrective measure

1. Turn OFF-VOL switchmaximumclockwise

Dynamotor onreceiver runs

Check circuitbreaker

Noise in headset Check powerrelayCheck cable andplug connectionsat transverter,antenna, jack box,receiver andcontrol unit.

Action Normal indication Corrective measure2. Set TRANSswitch oncontrol unit todesiredfrequency.3. Press tuningcrank and tunereceiver formaximumwhistle.

Communicationpossible

Same as 1.Higher echelonrepair required.

Section II. UNIT REPAIRMAN'S MAINTENANCE

3-5. Scope of Unit Repairman'sMaintenance

a. Following is a list of maintenance dutiesperformed by the unit repairman. The scope of theseinstructions has been determined by the availabletools, materials, test equipment, spare parts, andMOS of the unit repairman.

b. Unit repairman's maintenance of the radio setconsists 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.

3-6. Tools, Materials, and Test EquipmentRequired

The tools, materials, and test equipment requiredfor 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.

7930-395-9542).(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.

3-7. Unit Repairman's PreventativeMaintenance

a. DA Form 11-239. DA Form 11-239 (fig. 3-2)is a preventative maintenance check list to be usedby the unit repairman. Items not applicable to theequipment are lined out in the figure. References inthe ITEM block in the figure are to paragraphs thatcontain additional maintenance information pertinentto the particular item. Instructions for the use of theform appear on the back of the form.

b. Items. The information shown in the chartbelow is supplementary to DA Form 11-239. Theitem numbers correspond to the ITEM numbers onthe form.

Item Maintenance procedures22 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 contactswith Cleaning Compound.

29 Lubricate the radio set according to information inparagraphs 3-8, 5-11, and 5-14.

30 Inspect the dynamotor located on the receiver forsigns of overheating. Remove the end covers ateach end of the dynamotor and check to see that nooil or grease is present on the commutators orbrushes. After 200 hours of operation, inspect thebrushes at each end of the dynamotor for wear,spring tension, pitting, and correct fit to thecommutator. Procedures for removal andreplacement of the brushes is given in paragraph 3-13.

31 Do not tighten connectors too tightly. Threads onbolts may become stripped. Tightening terminalnuts in the junction box too tightly will result intwisting off entire terminal bolt.

TAGO 269A - July 13

Figure 3-2. DA Form 11-239.

14 TAGO 269A - July

3-8. Lubrication Remove the flexible mechanical coupling betweenthe control unit and the receiver. Use a thin long

Handled brush and apply a small amount of grease tothe gears located on the control unit and the front ofthe receiver.

Section III. TROUBLESHOOTING

3-9. Unit Repairman's Visual Inspection Before operating the equipment, inspect it. Thiswill save repair time and may also avoid furtherdamage to the radio set. Inspect the following forobvious defects.

a. The proper seating and mounting of thetransverter , receiver, control unit, antenna, antennarelay, oscillator relay, and power relay.

b. That all plugs are securely connected to eachcomponent.

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.

3-10. Equipment Performance Check Lista. General. The equipment performance check

list is a procedure to systematically check equipmentperformance. All corrective measures which the unitrepairman can perform are given in the Correctivemeasures column. When using the check list, start atthe beginning and follow each step in order. If thecorrective measures indicated do not fix theequipment, troubleshooting is required by higherechelon. Note on the repair tag how the equipmentperformed and what corrective measures were taken.

b. Procedure. Place the radio set in operation asshown in c below:

c. Equipment Performance Check List.Step Unit Action Normal indication Corrective measures

1 Antenna and antennarelay

Check for secure antennalead-in connections toantenna and antenna relay.

2 Transverter Check for secure wire andplug connections. Tightenplug connector rings handtight. Remove dust coverand check for properseating of crystals and forcorrelation of crystalfrequency and control unitfrequency.

3 Receiver Check for secure plug andwire connections. Checkand hand tighten plugconnector rings andmechanical linkage nut.

4 Oscillator-relay andpower relay

Check for secure plugconnections. Hand tightenplug connector rings.

5 Junction box Check that all wireconnections and terminalnuts are secure

6 Control unit Check that all plugs aresecure. Hand tighten plugconnector rings andmechanical linkage nut.Set TRANS switch todesired operating channel.

PREP

AR

ATO

RY

7 Headset andmicrophone

Check that headset cordand microphone cord areplugged in jack box.

TAGO 269A - July 15

8 Control unit Turn OFF-VOL controlmaximum clockwise.

Dynamotor on receiveroperates. Backgroundnoise in headset.

Check circuit breaker.Check source voltage.Check connections atpower relay.Replace dynamotor.Check wiring from powerrelay to junction box.Replace receiver.Replace control unit.

9 Receiver Press and rotate tuningcrank.

Loud whistle heard inheadset whenapproaching and onuhf channel.

Check cable connectionsbetween receiver andjunction box oscillator-relay.Adjust oscillator relay forloud whistle (par. 2-2).Replace receiver.Replace oscillator-relay.

EQU

IPM

ENT

PERF

OR

MA

NC

E

10 Microphone Press button and speakinto microphone.

Sidetone heard inheadset

Carry oncommunication

Turn TRANS switch toanother channel orseveral channels.Check wiring betweentransverter and junctionbox and junction box andcontrol unit.Replace transverter.Replace oscillator-relay.Replace receiver.Replace antenna relay.

3-11. Interunit Sectionalizationa. When abnormal indications are obtained at

one operating position, check the operation at theother operating position. If normal results areobtained there, the trouble is probably in the firstjack box, headset or microphone.

b. If operation at both operating positions isabnormal, then depending on the normal indications(par. 3-10c) replace each component with a knowngood component until normal operation is restored.

c. If normal operation is not restored by thereplacing of components then a thorough check ofplugs and cables between components should bemade until the trouble has been found. If a closeinspection does not reveal the trouble, then higherechelon repair and troubleshooting is necessary.

3-12. Tube Testing Techniques When trouble occurs, check all cabling,connections, and source voltage before removingany tubes. Try to isolate the trouble to a componentor stage. If tube failure is suspected, use theapplicable procedure below to check the tubes.

Caution: Do not rock or rotate a tube whenremoving it from a socket; pull it straight out with atube puller.

a. Use of Tube Tester. Remove and test onetube at a time. Discard a tube only if its defect isobvious or if the tube tester shows it to be defective.Do not discard a tube that tests at or near itsminimum test limit on the tube tester. Put back theoriginal tube, or insert a new one if required, beforetesting the next one.

b. Tube substitution Method. Replace asuspected tube with a new tube. If the equipmentremains inoperative, remove the new tube and putback the original tube. Repeat this procedure witheach suspected tube until the defective tube islocated.

(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 andremove the top cover.

16 TAGO 269A - July

Figure 3-3. Tube puller and control unit frequencytab inserts.

(b) Remove and check two type 14R7tubes, one type 14A7 tube, one type14F7 tube, one type 12A6 tube, threetype 9003 tubes, and one type 9002tube, one at a time from the receiver.

3-13. Replacing Brushes in the Dynamotor(fig. 5-6)

When a visual check discloses that the carbonbrushes are shorter than 5/16 inch from end toshoulder, they need replacement. To remove andreplace brushes proceed as follows:

a. Remove the end covers at each end of thedynamotor.

b. Unscrew the bakelite caps at each end of thedynamotor 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 thatthey slide smoothly into their respective brushholders and that they are of correct type.

e. Partly remove each brush and fasten a closefitting strip of fine sandpaper around thecommutator. Reseat one brush at a time by reseatingeach brush in its respective holder with its faceagainst the sandpaper. Rotate the dynamotorarmature until the brush face assumes the samecontour as the commutator.

f. Remove the sandpaper and replace thebrushes and bakelite caps.

g. Blow out all accumulated dust withcompressed air and run the dynamotor until 80percent of each brush makes contact with thecommutators.

h. Replace both end covers.

TAGO 269A - July 17

CHAPTER 4

THEORY

Section I. RADIO SET BLOCK DIAGRAM

4-1. Introductiona. The major components of Radio Set

AN/ARC-60 are shown in figure 4-1. The aircraft'selectrical system furnishes 28-volt dc power to theradio set. When OFF-VOL switch on the control unitis closed, a power relay is activated and low voltageis distributed through the junction box, to the majorcomponents and the dynamotor. The dynamotorgenerates the necessary plate and screen gridvoltages to the receiver, the two transverters, and theoscillator-relay unit. The radio set provides two-waycommunication on any one of sixteen channels, withan additional channel for intercommunicationbetween the aircraft personnel. The setting of theTRANS switch on the control unit selects theoperating frequency and operates the antenna relayto switch the antenna to the transverter in use. Eachtransverter functions as a transmitter and also as afrequency converter for the receiver.

b. The receiver may be tuned to any one of thetransverters' crystal frequencies by pressing thePRESS TP WHISTLE tuning crank on the controlunit. When this tuning crank is pressed it actuates theoscillator-relay unit which performs the followingfunctions through its relays:

(1) Connects high voltage to the receiver andtransverters 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 themicrophone input circuit to provide about

20 percent tone modulation on thetransmitter carrier.

(6) Connects the headset (TEL line) to theoutput of the receiver.

c. High voltage and antenna connections for thetransverters are obtained in the following manner.The microphone and headset, are plugged into thejack box, which is connected to the system throughthe junction box. Closing the microphone switchactuates a relay in the transverter which connects thehigh voltage output from the dynamotor to thetransverter in use. At the same time, anothertransverter relay is actuated which disconnects theantenna circuit from the receiver and connects it tothe output circuit of the transverter. The relays of thetransverter not in use serve to patch the signal andpower connections to the other transverter.

4-2. UHF Transmission and Reception The two transverters in the radio set operate astransmitters and frequency converters. Eachtransmitter section of the transverter operates on afrequency band of 228- to 258-mc. Each transmittercan operate on any one of 8 crystal frequencies, thusproviding a maximum of sixteen operatingfrequencies. The receiver is primarily a VHFreceiver with a frequency range of 118-148 mc. Forreception of UHF frequencies, the converter sectionof the transverter converts the incoming 228-258 mcsignals to the 118-148 mc band by mixing theincoming UHF signal with the output of a self-contained 110-mc crystal oscillator, and applying theresulting 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 nine-tube superhetrodyne, continuously tunable over a

frequency range of 118-148 mc. The RF section ofthe receiver is a preselector assembly which containsfour tuned circuits and four tubes arranged as

18 TAGO 269A - July

Figure 4-1. Radio Set AN/ARC-60, block diagram.

follows: a tuned input circuit, a type 9003 first RFamplifier and tuned output circuit, a 9003 second RFamplifier and tuned output circuit, a 9003 mixer, anda 9002 RF oscillator and tuned circuit. The RFoscillator and RF signal circuits are tuned by a four-section gang capacitor. The IF section, operating at afrequency of 15 mc, consists of eight IF tunedcircuits, a type 14A7 first IF amplifier, a 14R7second IF amplifier and avc, a 14R7 third IFamplifier and avc, and a 14F7 detector and noiselimiter, which also functions as the first audioamplifier. The audio output of the first audio

amplifier is resistance-coupled to a type 12A6 tube,functioning as the final audio amplifier. The outputof the 12A6 is fed through an 8 to 1 stepdowntransformer to the telephone load. The plate andscreen voltages are supplied by a dynamotor. Theheater voltage is supplied directly from the lowvoltage source on the aircraft.

4-4. Preselector Assembly The preselector assembly consists of the antennainput, the first RF amplifier, the second RF

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 inparagraphs 4-5 to 4-8.

4-5. Antenna Input Circuit (fig. 4-3) The antenna input circuit is the first RF tunedcircuit. The signal from the antenna is applied torelay K-18. From this relay the signal is applied tothe transverter in use. The transverter converts thesignal to the frequency range of the receiver (pars. 4-19 through 4-21) and applies it to J306 through anRG-58/U cable or 53-ohm impedance, to the untunedprimary coil L302 and then by mutual induction toL301. Inductor L301 is tuned by C304A. Gangtrimmer capacitors C304B, C304D, C304F andC304H are used to aline all tuned circuits at thepreselector frequency of 144 mc. Capacitor C305 isthe grid coupling capacitor. Resistor R-301 providesthe dc connection from the avc bias source to thegrid of V301. Capacitor C306 is used to decouple thegrid circuits. Filter circuits consisting of C308,R305, C312, R309, C316 and R310 are used todecouple the screen circuits.

4-6. First RF Amplifier Circuit (fig. 4-3) The RF signal is coupled to the grid of V301through C305. Resistor R301 provides a dcconnection to the avc source. Resistor R302 is thecathode bias resistor and C307 is the cathode RFbypass capacitor. Capacitor C304D is the trimmercapacitor used to aline the output RF tuned circuit of

V301 (L303 and C304C). The output of this tunedcircuit is coupled to the input grid of V302 throughC310.

4-7. Second RF Amplifier Circuit (fig. 4-3) The detailed parts of the second RF amplifierfunction in an identical manner as those of the firstRF amplifier. The output of the second RF amplifier,V302, is applied to the input grid of the mixer,V303through the coupling capacitor C314.

4-8. RF Oscillator and Mixer Circuits (fig.4-3)

Tube V304, a type 9002 electron tube, serves asthe RF oscillator in a tuned-plate oscillator circuit.The RF oscillator frequency is below the incomingsignal, the difference being 15 mc (the intermediatefrequency) throughout the tuning range of thereceiver. Capacitor C304G is the RF oscillatortuning section of the gang capacitor. Capacitor C319and R312 are the grid capacitor and resistor. Thelocal oscillator voltage is injected by coupling coilL305 into the cathode of the mixer tube V303, a type9003, so that the total RF grid-to-cathode voltage ofV303 is the sum of the signal applied between gridand ground and the oscillator voltage appliedbetween cathode and ground. Adjustment of theoscillator at the high-end alinement frequency isprovided by trimmer C304H. All tuned inductancesof the preselector are factory-adjusted at the low-endalinement frequency, 122 mc by copper slugsmounted in the ends of the coil shields.

20 TAGO 269A - July

4-9. IF Amplifier Circuits (fig. 4-3) The IF amplifier circuits are similar in design andfunction, except for the fourth IF coupling unit. TheIF amplifier section consists of eight tuned circuitsarranged in four pairs (one pair per tube). Theprimary of the first IF tuned circuit is fed from theplate of mixer V303, and consists of L307, fixedcapacitor C322, and trimmer capacitor C320. Thesecondary is similarly designed. The remaining IFtuned circuits, except for the primary coil and theprimary and secondary fixed capacitors of the fourthIF tuned circuit Z305, are identical. Inductor L316 ismade larger and C355 is reduced in order to obtainsufficient undistorted IF power for the avc rectifier.The IF tuned circuits are inductively coupled andselected to provide almost critical coupling. Theoutput of the seventh IF tuned circuit is connected tothe avc diode plate of V307 through C351 and theoutput of the eighth IF tuned circuit to the diodedetector section of V308.

4-10. Detector, Noise Limiter, and FirstAudio Amplifier Circuit (fig. 4-3)

a. The triode section of V308, pins 5, 6, and 7 isconnected as a diode. The modulated IF signalacross L317 and C356 is rectified by the diode andan AF voltage developed across R340 and R341.The portion of the AF voltage between R341 andground is directly coupled to the first AF amplifier.Instantaneous increases in signal values such asnoise pulses tend to increase the current throughR340 and R341. This increases the biasing effect onthe diode and momentarily reduces the tubes'sensitivity for the period of the noise pulse.Capacitor C349BC is an IF filter, C357 returns L317to ground for IF and RF. Resistor R339 is the dcground return for the grid (pin 4) of the first AFamplifier.

b. The second triode section of V308, pins 2, 3,and 4 is biased by the dc bleeder current from thepower supply through R342 and the cathode biasresistors R343 and adjustable R351. Because nocoupling capacitor is used to couple the AF signal tothe grid of the first AF amplifier, the presence of AFon the grid increases plate current flow through thistriode section. Additional noise limiting is obtainedby this circuit arrangement because an instantaneousincrease in the applied grid voltage instantly reducesplate voltage and, in turn, the output signal, due tothe 180-degree phase shift across the tube. Resistor

R351 varies the bias on the first AF amplifier andfunctions as a volume control.

4-11. Second Audio Amplifier (fig. 4-3) The AF output from V308 is coupled through alow-pass filter circuit consisting of R346, C362 andC363 to the grid of V309, a type 12A6 tube. Theoutput of V309 is applied to T301, an 8 to 1 outputtransformer. Capacitor C365 across the primary ofT301 attenuates all audio frequencies above 4,000cycles and also filters out RF. In early models, asmall neon lamp, V310 was connected across halfthe primary winding of T301. In later models V310was replaced by a thyrite resistor, TY301. Thepurpose of V310 or TY301 is to protect theequipment if exceptionally strong signals arereceived when the normal load is removed. The lampglows at approximately 55 volts ac. As soon as theglow starts, any increase in voltage across the lampterminals causes a relatively large increase in currentthrough the lamp and therefor limits the voltage toapproximately 55 volts ac across half the primary ofT301. The thyrite resistor TY301, functions in thesame manner, except that it depends upon itsinherent resistance behavior to limit the voltage to asafe value.

4-12. Automatic Volume Control Circuit(fig. 4-3)

a. Automatic volume control (avc) is providedby avc diode rectifier (pins 3 and 7 of V307), the avcdiode limiter (pins 3 and 7 of V306), and a filtercircuit consisting of R336, C349A, R324, C324B,R316 and C306. A voltage divider circuit consistingof R321 and R322 applies approximately one-thirdof the total avc bias to V306. The IF voltage thatoperates diode rectifier V307 is obtained from theprimary of Z305 through C351.

b. With the manual sensitivity control atmaximum sensitivity, the avc circuit is designed tobegin control when the RF input level at the antennaexceeds approximately 8 microvolts. This producesan IF level of 30 volts ac at the plate of V307. Withno IF signal the cathode of V307 is positive inrespect to the diode plate because of the voltage dropacross R33 and R334. No voltage is developedacross R335. The diode section of V306 is permittedto conduct because its plate is returned to thecathode of V307 which is plus 30 volts in respect toground. For all signal values a low value of avc isdeveloped across R321 and R322. When the signalvalue at the plate of the diode section of V307exceeds the positive voltage on the cathode of thediode conducts and an avc voltage is developedacross R335. Thus, signal levels in excess of 30 volts

TAGO 269A - July 21

produce an avc rectifier output across R335, willapply 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

4-13. General (fig. 4-4)a. Transverter Block Diagram. The transverter

is a combined UHF transmitter and receiverconverter. The converter section converts signalsreceived in the range of 228-258 mc to 118-148 mcby mixing the UHF signal with a 110-mc crystaloscillator. A simplified block diagram of thetransverter is shown in figure 4-4.

b. Transmitter Section. A detailed blockdiagram of the transverter is shown in figure 4-5.The transmitter section is a five-tube, eight-channel,crystal-controlled, voice amplitude-modulated circuitdesigned for aircraft-to-ground transmission in thefrequency range of 228 to 258 mc. Four type 5763and one type 6201 electron tubes are used. One ofthe 5763 tubes is used as a crystal oscillator-doubler,

two as amplifier-doublers, and the remaining tube asa modulator. The two triode sections of the 6201 areconnected as a push-pull amplifier-tripler. The eighttransmitting channels may be located in one 4-mcband, or they may be divided between two bandseach 4 mc wide. If two 4-mc bands are used, aseparation of at least 2 mc between bands should beobserved. The band section (HI or LO, figure 4-6)will depend on the wiring to the control unit, whichin turn operates relay K4209. Operation of K4209opens the contacts which disconnect the trimmercapacitors from the tank circuits for HI bandoperation. The power output of the transmittersection is rated at 0.5 watt.

c. Converter Section. The converter section ofthe transverter comprises a 228-258-mc UHF

Figure 4-4. Frequency Converter CV-431/ARC, simplified block diagram.

22 TAGO 269A - July

Figure 4-5. Frequency Converter CV-431/ARC, block diagram

preselector, a 110-mc crystal oscillator, using a type6201 electron tube, a type 1n82 crystal diode mixer,and a 118-148 mc VHF matching network (fig. 4-6).After incoming signals are selected by tuned circuitsof the preselector, they are mixed with the 110-mccrystal oscillator frequency, producing convertedsignals in the range of 118 to 148 mc, which are fedto the receiver.

d. Whistle-Through Tuning Procedure. The"whistle-through" procedure is used when it is

desired to tune the receiver exactly to thetransmitting frequency. When the PRESS TOWHISTLE tuning crank on the control unit ispressed, power is applied to relays K4210, K4213,and K4214 (fig. 4-5). Relay K4213 disconnects thepreselector from the antenna, K4210 connects theoutput of the UHF transmitter to a dummy load andK4214 applies the output of the converter to thereceiver. The output of the 1000-cycle oscillator inthe oscillator-relay is applied to the microphonecircuit. This audio frequency modulates the

TAGO 269A - July 23

transmitter's output which is picked up by thereceiver.

4-14. Crystal Oscillator-Doubler Circuit(fig. 4-6)

A pierce crystal oscillator circuit is used togenerate the RF voltage. Eight crystals may beinstalled. Since the radio set uses two transverters atotal of 16 crystals may be used. These crystals areselected individually by the TRANS switch of thecontrol unit. Depending upon the crystal positionselected, one of the relays K4201 through 4208, willbe actuated and connect the desired crystal into theoscillator circuit. The crystal circuit is directlycoupled to the control grid and through C4203 to thecathode of V4201. Capacitor C4202 preventsoscillation when no crystal is present in the circuit.Inductor L4201 is a high-impedance RF choke. Theoscillator output frequency is doubled in the platetank circuit of V4201, and coupled to the grid ofV4202 through C4209.

4-15. Amplifier-Doubler Circuits (fig. 4-6) The output from V4201 is amplified and doubledin the tank circuit of V4202, and further amplifiedand doubled in the tank circuit of V4203. The tankcircuit of V4203 uses a tapped coil L4205 and asplit-stator variable capacitor C4222. The output ofthis tank circuit is applied to the grids of V4205Aand V4205B through C4224 and C4223.

4-16. Push-Pull Amplifier-Tripler Circuit(fig. 4-6)

The amplifier-tripler stage of the transmittersection uses a type 6201 dual triode connected in abalanced push-pull circuit. The use of a push-pullcircuit results in more power output and cancellationof even order harmonics which leaves the preferredthird harmonic to be developed in the tank circuit.The push-pull amplifier-tripler is plate-modulated atbetter than 90 percent by the modulator V4204. The1N82 crystal CR4201 is included in the outputcircuit to allow a comparison check of themodulation and tuning of the transmitter to be made,with a dc volt-meter connected to J4201. CapacitorC4229 functions as an AF bypass capacitor. ResistorR4225 acts as a load when no meter is connected toJ4201.

4-17. Modulator Circuit (fig. 4-6) A type 5763 electron tube V4204 is used as themodulator. The voice-input signal is applied to the

primary of T4201, the secondary feeds into the gridof V4204 through resistor R4211. The output ofV4204 feeds into the primary of modulatortransformer T4202, the secondary modulates theoutput of V4205. Sidetone for interphonecommunication is obtained from the cathode ofV4204 and coupled through C4217 to the headsetline of the receiver.

4-18. 110-mc Crystal Oscillatora. Z4201, the 110-mc crystal oscillator, is an

individual subassembly whose part are located onthe tube socket for V4206 and a ceramic terminalboard. The oscillator circuit is a cathode-coupledoscillator using a 110-mc crystal Y4209. TubeV4206A is connected as a cathode follower. InductorL4211 across Y4209 is used to cancel out the shuntcapacity of the crystal so that only resistance ispresent at the crystal resonant frequency. Therefore,coupling between the cathodes of V4206A andV4206B can only take place at the series resonantfrequency of the crystal. The tanks circuit consists ofL4212, C4248, C4235 and all distributedcapacitance. The filter network consisting of C4232,R4229, and C4234 prevents 110 mc from radiatingor entering into the high-voltage line. CapacitorC4205, connected between the heater of V4206 andground, prevents 110 mc from entering the low-voltage 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 110mc crystal to the cathode of V4206B. Tube V4206Bis a grounded grid amplifier so that no phaseinversion takes place through the tube. The 110 mcsignal is amplified by V4206B and reappears at thejunction of L4212, C4248, and C4235 at a frequencydetermined by the crystal (110 mc) and at a greatermagnitude to maintain oscillation. If V4206 isreplaced, the oscillator must be realigned by L4212,because of the differing tube inherent capacitance.

4-19. UHF Preselector (fig. 4-6) The UHF preselector (Z4202) consists of threeover-coupled tuned circuits, tuned to selectfrequencies between 228 and 258 mc. The first tunedcircuit consists of C4244, L4218, and C4242, withC4242 also functioning to couple the first tunedcircuit to the second tuned circuit. The second tunedcircuit consists of L4216 and C4240, and C4239,which couples the second tuned circuit to the thirdtuned circuit. The third tuned circuit consists ofL4214, and C4236. Jack 4205 provides a convenient

24 TAGO 269A - July

means of testing the crystal current of the mixerCR4202. Inductor L4213 is an RF choke and R4232acts as the load when no meter is connected toJ4205.

4-20. VHF Matching Network (fig. 4-6) The VHF matching network matches theimpedance of the 1N82 crystal into a 50-ohm outputimpedance. A 110-mc trap, consisting of L4219 andC4245, prevents 110 mc from desensitizing thereceiver, since the receiver is capable of being tunedto 118 mc.

4-21. Frequency Conversion Process (fig.4-6)

The 110 mc crystal oscillator develops a signalvoltage that is coupled through V4235 to the 1N82crystal CR4202 mixer circuit. The incoming signalfrom the antenna is also coupled to the mixer circuit.The crystal functions as a nonlinear detector and thedifference frequency is coupled to the receiver. Forexample, if the incoming signal frequency was 248mc, after mixing with the oscillator output of 110 mcthe signal coupled to the receiver would be 138 mc.This difference frequency is developed across L4215and C4238.

Section IV. MINOR COMPONENTS

4-22. Radio Set Control C-1917/ARC The control unit (fig. 4-7) contains all the controlsrequired for the remote operation of one receiver,one oscillator-relay unit, and two UHF transverters.The frequency dial is calibrated for reception in theUHF band of 228-258 mc. The controls consist of acombination primary power switch S4402, andvolume control R4401; a combination receivertuning and "whistle-through" control S4403; and atransmitter channel selector switch S4401 forselection of interphone and up to 16 UHF channels.All electrical connections are made through J4401and J4402, located at the rear of the enclosure. Thereceiver mechanical linkage tuning connect is alsomade at the rear. When the tuning crank is pressed,microswitch S4403 closes, the oscillator-relay unit isactivated and precise tuning of the VHF receiver ispossible.

4-23. Relay Frequency Oscillator O-423/AR(fig. 4-8)

a. A relaxation oscillator within the oscillator-relay 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, untilthe voltage across the tube is high enough to ionizethe gas, the tube presents an almost infiniteimpedance. However, once ionized, a very smallvoltage is sufficient to keep the current flowing.Until the voltage falls below the firing-point value,the tube has a low impedance. When the voltagedrops this value, current flow ceases. In effect, thetube acts as a switch, which is open when de-ionized

b. and closed when ionized. The frequency ofthe circuit is determined by the RC constant.

c. A diagram of the relaxation oscillator in theoscillator relay is shown in figure 4-8. With voltageapplied, C4002 is charged through R4002. SinceV4001 is in parallel with C4002, the voltage acrossV4001 is equal to the charging voltage acrossC4002. When the firing voltage of approximately 90volts is reached, V4001 ionizes and forms adischarge path for the voltage across C4002. Thecapacitor discharges very rapidly until the voltageacross V4001 also decreases to the point where thetube de-ionizes and again presents a high impedance.The cycle is then repeated.

d. The frequency is dependent upon the RC timeconstant. The values of R4002 and C4002 have beenchosen for an oscillator frequency of 1,000 cycles.

e. Separate potentiometers are provided forVHF and UHF whistle-level adjustments. These arescrewdriver-adjusted controls, located on the front ofthe oscillator-relay. Each control is set for a 1-voltoutput. Resistor R4007 is used for VHF whistlelevel, and R4001 is used for the UHF whistle level.Depending upon the position of the contacts ofK4005, either R4007 and R4001 is connected inseries with R4008 to ground.

4-24. Terminal Box J-506A/ARCa. The junction box provides a terminal for all

interunit wiring. All the major components areconnected through the junction box as shown infigure 5-1. The junction box has 30 terminals and 4ground connections, and a single-pole-double-throw(spdt) sidetone relay.

TAGO 269A - July 25

Figure 4-7. Control unit, schematic diagram.

26 TAGO 269A - July

Figure 4-8. Oscillator-relay, schematic diagram.

b. The sidetone relay in the junction boxoperates in the following manner. When themicrophone button is depressed a path to the positiveside of the low voltage power supply is completedthrough the sidetone relay (fig. 5-1). This closes thecontacts on the sidetone relay and the sidetone fromthe cathode circuit of modulator V4204 (fig 4-6) iscompleted to the headset.

4-25. Relay K-15 The power relay (fig. 5-1) operates in thefollowing manner. When the OFF-VOL switch onthe control unit is turned in a clockwise direction apath for dc is completed through the contacts A andB of the power relay coil. This activates the power

relay and closes contacts C and D which completesthe path to the 28-volt supply through the 20-amperecircuit breaker. This action turns on the dynamotor.

4-26. Antenna AT-701/ARC The antenna is a UHF, quarter-wave, base-fed,inverted-L-Type antenna. It consists of a stainlesssteel L-shaped rod, mounted on a small aluminumbox. The box is the base for the antenna rod andcontains a broad-band circuit (fig 4-9). The broad-band circuit consists of 50-uuf ceramic capacitor anda loop constructed from silver-plated strip of copperformed into a rectangular shape. This circuit isconnected across the antenna input. The antennacircuit is tuned to a resonate frequency of 248 mc bymoving the capacitor toward or away from the loop.

TAGO 269A - July 27

Figure 4-9. Antenna, schematic diagram.

4-27. Relay Switch RE-275/ARC (fig. 4-10) The antenna relay permits the use of only oneantenna for the two transverters. The antenna relayconsists of a relay coil and two sets of contacts. TheNO (normally open) terminal is connected to onetransverter and the NC (normally closed) terminal isconnected to the second transverter. The C contact iswired to the antenna. The position of the TRANSswitch on the control unit determines whethercurrent flows through the relay coil and in turnselects the transverter to be connected to the UHFantenna.

4-28. B+ Distribution (fig. 4-11)a. When the OFF-VOL switch on the control

unit is turned clockwise the power relay applies 28volts dc to the dynamotor which in turn supplies250-volts dc to all major components. B+ is

Figure 4-10. Antenna relay, schematic diagram.

applied to the transmitter section of the transverterthrough relay K4211. This relay is actuated when themicrophone button is pressed and removes B+ fromthe converter section of the transverter and from thereceiver.

b. When not transmitting K4211 is normallyclosed and B+ is applied to the converter stage therough relay JK4212 (this relay is closedautomatically when the TRANS switch on thejunction box selects any one of the 16 operatingfrequencies).

c. Power is applied to the second transverter in asimilar manner.

d. B+ is applied to the receiver through thejunction box and the normally closed contacts ofK4211. Thus the receiver normally operates onlywhen the transmitter is not keyed.

e. When the PRESS To WHISTLE tuning crankis depressed relay K4003 closes and B+ is applied toboth the transverter and receiver simultaneously.Thus during the "whistle-through" receiver tuningoperation the transmitter output is used to calibratethe receiver.

4-29. Dynamotor DY-86/ARN-30 The dynamotor is designed to furnish high voltageto the plate and screen circuits of the receiver andtransverters. When 28-volt dc from the aircraft'selectrical system is supplied to the motor section ofthe dynamotor the generator section develops 250volts dc.

28 TAGO 269A - July

Figure 4-11. Radio Set, B+ distribution.

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 anyconnections, turn off the VOL switch on the control unit and temporarily ground terminal 29 in the junctionbox to discharge all capacitors. The high voltage present can cause serious injury or death.

5-1. Test Equipment Requireda. The test equipment required for trouble

shooting and testing the radio set is listed below. Acommon name is given after each component.

Nomenclature Common nameAntenna A-68-A AntennaAudio Oscillator TS-382/A Audio oscillatorMultimeter ME-77/U MultimeterElectronic Multimeter TS-505A/U VtvmElectron Tube Test Set TV-2/U Tube testerSignal Generator TS-497/U Signal generatorBird Electronics Termaline Model 81

with Wattmeter Model 43.Dummy load

6-db pad: Boonton Radio Corp. Type505-a

6-db pad

Electronic Voltmeter ME-30A/U Ac vtvmTest Unit Assembly ARC Type H-18 Test unitBench Test Kit MK-157/GRM Bench test kit

b. In addition to the units listed in a above, thefollowing equipment is required for trouble shootingand testing the components of the radio set whenthey are removed from the aircraft.

(1) High-voltage regulated dc power supply,with output adjustable between 150 and 300volts.

(2) Test crystals: ARC Type 17142, UHFoutput 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 ofsupplying 27.5 volts at 6.8 amperes.

(8) Pair of high-impedance headphones.(9) Microphone RS-38A.

5-2. Troubleshooting Data The organizational maintenance trouble-shootingsection (pars. 3-9-3-12) gives the techniques forsectionalizing operational troubles to a particularcomponent and for use of the equipmentperformance check list. Parts of theory chapters (pars4-1-14-29) outline the signal and control paths of theradio set. Use the text and figures to helpsectionalize 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 figure5-26.

5-3. Troubleshooting Proceduresa. Visual Inspection. Visual inspection

frequently reveals the location of the trouble. Avisual examination usually will reveal the followingdefects:

(1) Defective power or interunit cables andplugs.

(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 importantbecause it frequently indicates the general locationof troubles and often the exact nature of the fault. Allsymptoms must be interpreted in relation to eachother.

30 TAGO 269A - July

c. Voltage and resistance Measurements. Thesemeasurements help locate the individual componentat fault. Use voltage and resistance diagrams (figs. 5-18 and 5-21) to find normal readings at receiver andtransverter tube sockets. Figure 5-1 shows the pointsin the interunit cabling system that are connectedtogether. All wires can be checked by continuityfrom the junction box to the proper terminal on the

connector plug.

d. Troubleshooting Chart. Paragraph 5-4contains a troubleshooting chart that will be useful insectionalizing trouble in the system to a component.Tube-socket voltages and resistances for the receiverand the transverter are shown in figures 5-18 and 5-21 respectively.

Section II. TROUBLESHOOTING RADIO SET AN/ARC-60

5-4. System Troubleshooting Chart The following chart is supplied as an aid inlocating trouble in the radio set. This chart lists thesymptoms that the repairman may observer whileoperating the equipment. The procedures described

in the equipment performance check list, paragraph3-10, should be followed. Troubleshootinginformation for the receiver, the transverter, and theoscillator-relay is contained in paragraphs 5-5, 5-6,and 5-8, respectively.

Symptoms Probable trouble CorrectionNo 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. 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.

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.

Distorted signal. Outside electrical disturbance.Improper antenna connection.Receiver not tuned accurately.

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). Checkfor presence of B+ at transverter (terminals 28and 29 in junction box for respectivetransverters). Refer to paragraph 5-6.

Defective modulator tube in transverter.Defective transverter.

Check V4204 and replace if necessary.Refer to paragraph 5-6.

Faint or fading sidetone. Low input voltage.Defective receiver dynamotor.Poor cable connections.Defective transverter.

Check power source.Refer to paragraph 5-8.Tighten all cable connections.Refer to paragraph 5-6.

No whistle-through. Receiver not tuned to same frequency astransmitter.Defective oscillator-relay.

Retune receiver.

Refer to paragraph 5-7.No transmission. VOL switch turned off.

TRANS switch in wrong position.Defective crystal.Antenna not connected.Defective microphone switch or cable.Microphone not connected.Defective transverter.

Rotate VOL control clockwise.Set TRANS switch to proper channel.Replace crystal.Check antenna connection.Replace microphone and cable.Connect microphone.Refer to paragraph 5-6.

TAGO 269A - July 31

Figure 5-2. Receiver, top view, cover removed.

32 TAGO 269A - July

Figure 5-3. Receiver, bottom view, cover removed.

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 CorrectionDynamotor not running. Low input voltage Replace or recharge aircraft battery.

Loose primary power cable connection.

Wrong cable connections.Primary power circuit breaker tripped.Defective dynamotor.

Check cable connections from primary powersource to receiverCheck all cable connections (fig. 2-1).Check circuit breaker and reset if necessary.Repair dynamotor (par. 5-8--5-12).

Dynamotor running but nooutput.

Dirty commutator.

Open or shorted armature windings.

Defective output connections.

Clean commutator.

Check windings with multimeter. If defect isfound, replace dynamotor.Check connections and repair.

No audible signal. 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.

Test tubes in tube tester. Replace defectivetubes.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 withmultimeter; replace if defective.Check R330; replace if defective.Check C344A; replace if defective.

Faint or fading signal. Defective tube.

IF circuits out of alinement.RF circuits out of alinement.RF oscillator V304 or mixer V303replaced without realinement of RFoscillator shunt trimmer C304H.Defective dynamotor (low output).

Test all tubes in tube tester. Replace defectivetubes.Realine; refer to paragraph 5-24.Realine; refer to paragraph 5-24.Retrim C304H; refer to paragraph 5-24b(5).

Repair dynamotor; refer to paragraph 5-8through 5-12.

Receiver overloads on strongsignal (improper avc action).

Defective RF amplifier tube or mixer tube.

Defective capacitor C351.Defective avc rectifier or avc limiter.

R335 open or changed value.

Check V301, V302, and V303 in tube tester.Replace defective tubes.Replace C351.Test V306 and V307 in tube tester; replacedefective tubes.Check the resistor and replace if necessary.

High noise level. Defective noise limiter V308.Defective capacitor C363.Worn dynamotor brushes or pittedcommutator.

Check the tube and replace if necessary.Check and replace if necessary.Replace dynamotor brushes or refinishcommutator surface (par. 3-13).

Abnormal frequency drift. Low battery voltage.

Defective oscillator tube V304.

Check voltage source with multimeter. If lessthan 27.5 volts, recharge or replace battery.Test tube and replace if necessary.

34 TAGO 269A - July

Figure 5-4. Transverter, top view, cover removed.

TAGO 269A - July 35

Figure 5-5. Transverter, bottom view, cover removed.

36 TAGO 269A - July

5-6. Transverter Troubleshooting Chart The following chart is supplied as an aid in troubleshooting the transverter.

Symptom Probable trouble CorrectionNo UHF transmitter output. Incorrect or defective cable connections from

receiver.Defective high-voltage supply.

Defective tube.

Defective crystal.

Check cable connections from receiverthrough junction box.Check dynamotor mounted on receiver. Repairor replace if necessary.Test all tubes in tube tester. Replace defectivetubes.Replace defective crystal.

No UHF transmitter highvoltage.

Defective high-voltage supply.

Defective B+ changeover/sidetone relayK4211.

Check dynamotor mounted on receiver. Repairor replace if necessary.Repair or replace K4211.

No UHF output at antenna. Defective relay K4210. Repair or replace relay.Incorrect frequencytransmitted

Channel selector switch in wrong position.

Incorrect crystal frequency.

Check position of channel selector switch.

Check crystal frequency.Frequency coverageincomplete.

Improper alinement. Realign; refer to paragraph 5-25.

No sidetone. Defective modulator tube V4204.Defective capacitor C4217.Defective B+ changeover/sidetone relayK4211.

Test tubes and replace if necessary.Check capacitor and replace if necessary.Check relay; repair or replace if necessary.

No UHF converter output. Incorrect or defective cable connections fromreceiver.Defective high-voltage supply.Defective crystal oscillator.

Defective crystal mixer CR4202.

Defective relay K4214.

Check cable connections.

Check dynamotor on receiver.Test tube V4206 in tube tester; replace ifdefective.Check crystal by substitution; Refer toparagraph 5-25f for crystal mixer test.Check relay; Repair or replace if necessary.

No UHF converter highvoltage.

Defective dynamotor on receiver.

Defective relay K4211 or K4212.

Repair or replace dynamotor.

Check relays; repair or replace if necessary.Faint or fading UHFconverter signal.

Defective crystal oscillator tube V4206.

Defective crystal mixer CR4202.

Test tube in tube tester and replace ifdefective.Check crystal by substitution.

No UHF from receiver. Defective receiver. Check operation of receiver on VHF. Ifdefective, repair (par. 5-5).

High UHF converter noiselevel.

Defective crystal mixer CR4202. Refer to paragraph 5-25f for crystal mixer test.

5-7. Oscillator-Relay Troubleshooting When the oscillator-relay is suspected as a sourceof trouble, check the relays for proper operation.Check for good contact at the relay points. If no

whistle-through signal can be obtained, check tubeV4001 by substitution. For complete testingprocedures, refer to paragraphs 5-26 and 5-27. Awiring diagram is shown in figure 5-25.

TAGO 269A - July 37

Section III. REPAIRS AND ADJUSTMENTS

5-8. Inspection of Dynamotor (fig. 5-6)Part Procedure

Armature (34) Inspect commutator for presence ofcarbon or copper dust; also check forpitting or scoring. If commutator isgrooved radially by more than .005inch, dynamotor is unsuitable forrepair.

Brushes (23 and24)

Inspect length of brushes. If anybrush is shorter than 5/16 inch (fromend to shoulder), discard it.

Bearings (33) Inspect lubrication of ball bearings. Ifdry, dirty, or insufficiently lubricated,clean bearings with CleaningCompound and relubricate with alubricant (Navy type 14L3, GradeIII). Do not pack bearings. Check thatbearings run smoothly.

Frame CoilWindings (35)

Inspect for torn insulation andexposed wiring. Measure dcresistance of shunt field withmultimeter. A reading of 225 ohmsmust be obtained. Measure theresistance between adjacentcommutator bars, which isapproximately 25 ohms for highvoltage side and .4 ohm for lowvoltage side. Any appreciablevariation from this indicates an opencircuit, a short circuit, or a partialshort circuit, in which case thearmature must be replaced.

5-9. Disassembly of Dynamotor (fig. 5-6)a. Separate base assembly (1) from dynamotor

(19) by removing screws (2) and unsoldering thewiring 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-voltagebrushes (23). Repeat this procedure for high-voltagebrushes (24).

d. Remove screws (31) from each bearing coverplate (30). Remove cover plate and shim washers(32). The actual number of washers may vary witheach dynamotor.

e. Remove screws (36) to free wiring.f. Unscrew nuts (27) and remove washers (28)

and screws (26) to free armature brackets (25 and29).

g. Carefully remove armature (34) from thedynamotor field subassembly (35).

h. If it is necessary to remove the bearings (33),place the armature in a padded vise and, using abearing puller, remove the bearings. This will alsofree washers (32). Use extreme care to preventdamage to the commutator or shaft.

i. To disassemble base assembly (1), removeretaining ring (14), unscrew screws (5) and studs (4),and separate base (3) from base plate (18).

5-10. Replacement of Dynamotor Bearings If it is necessary to replace the bearings in thedynamotor--

a. Check to see that the bearing runs smoothlybefore placing it on the shaft. With the shield side ofthe bearing facing the commutator, place it on theshaft and with light rap with the palm of the hand,drive it onto the bearing shoulder.

b. Replacement bearings are furnishedlubricated; however, inspect the lubrication. Ifrequired, lubricate as outlined in paragraph 5-11.

5-11. Lubrication of DynamotorTo lubricate the ball bearings of the dynamotor--

a. Remove the end covers and the bearing coverplates.

b. Remove as much of the old grease aspossible, using a cloth or a stiff brush and cleaningcompound.

c. Apply a small amount of Navy type 14L-3Grade III lubricant to cover the bearings. Caution: Do not pack the bearings or allow greaseto get on the commutator.

d. Replace the bearing cover plates and the endcovers.

5-12. Reassembly of Dynamotor (fig. 5-6) To reassemble the dynamotor--

a. Attach the base (3) to the base plate (18) withscrews (5) and studs (4). Replace the retaining ring(14).

b. If the bearings (33) have been removed, referto paragraph 5-10 for replacement instructions.

c. Attach the armature support (25) to thedynamotor field assembly (35) by inserting screws(26) and one washer (28) through the bracket andframe.

38 TAGO 269A - July

Figure 5-6. Dynamotor, exploded view.

TAGO 269A - July 39

d. Holding the bracket in position, insert thearmature (34) with the bearing in the proper positionin the bracket. Attach the remaining bracket (29) andthen secure the assembly with the two remainingwashers (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, checktheir identifying marks and replace them in theiroriginal positions. Secure them with caps (22).

h. Attach the end covers (20) and secure themwith their captive screws.

i. Resolder the wires to the connectors. Attachthe dynamotor to the base assembly (1) with thescrews (2).

j. Test the dynamotor by connecting it to asource of 28 volts dc. Under normal load conditions,measure the output voltage; it should be 250 voltsdc.

5-13. Disassembly of Control Unit(fig. 5-7--5-9)

To disassemble the control unit--a. Detach the cover (1, fig. 5-7) by turning the

fasteners on the rear of the cover counterclockwisewith a screwdriver.

b. Free the plate (2) by removing screws (3) andwashers (4).

c. Unsolder the terminal connections and freethe connectors (5 and 7) by removing the couplingnuts (6 and 8).

d. Using a No. 8 Bristo wrench, loosen setscrew(12) to remove knob (11). Remove screw (14) to freethe 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 housingassembly (22) with the fingers. Extract the lamps(29). Remove grommet (23) and springs (24) ifnecessary.

h. To detach the plastic panel (30), removescrews (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 unsolderingthe 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).

5-14. Lubrication of Control Unita. Lubricate gear teeth, splines, and bearing

surfaces of gear assemblies sparingly with lowtemperature aircraft lubricating grease (MIL-G-3278).

b. If necessary, lubricate mechanical linkageswith clock and watch oil (Lubricating Oil, Watch(OCW) MIL-L-3918).

5-15. Reassembly of Control Unit(fig. 5-7--5-9)

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 andsecure with nut (42).

c. Place washer (40) on the bushing of thevariable resistor (38). Insert the shaft in themounting hole and secure with nut (39).

d. Replace the gear assembly (33) and secure itwith screw (34), screws (35), terminal lug (36), andwashers (37).

e. Replace the panel lamp retainers (26) andsecure them with nuts (27) and washers (28).

f. Secure the plastic panel (30) in place withscrews (31) and washers (32).

g. Replace springs (24) and grommets (23) onthe lamp housings (25). Insert the lamps (29) in theassembled lamp housings (22) and screw them intothe retainers (26).

h. Fasten the spacers (20), the dial (19), and thepressure plate (17) with screws (18). If necessary,install additional spacers to prevent the dial fromrubbing 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 thetuning crank is pressed .050 inch from its normalposition. If adjustment is necessary, bend the switchactuating arm to obtain this setting.

40 TAGO 269A - July

Figure 5-7. Control unit, exploded view.

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 fastenersclockwise.

5-16. Reassembly of Control Unit To adjust the receiver tuning dial in the controlunit--

a. Connect Mechanical Linkage MC-215 to thereceiver and the control unit without regard to thesetting of the dial on the control unit or the tuning ofthe receiver.

b. Carefully turn the control unit tuning crankcounterclockwise as far as it will go. Caution: Do not force the crank beyond thestopping 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-

42 TAGO 269A - July

Figure 5-9. Control unit, wiring diagram.

TAGO 269A - July 43

frequency end of the dial comes directly under thetriangular-shaped reference mark.

e. Replace the linkage, being careful not tochange the positions of the shafting or the spline towhich it is attached.

f. Test the accuracy of the dial positioning bytuning in several stations of known frequency, or byusing a signal generator and checking several pointson the dial.

5-17. Disassembly of Oscillator-Relay(figs. 5-10 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 removeit 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 capacitorsC4001 and C4003 (13 and 14).

e. Free relays (20), (23), and (26) by removingtheir screws and washers.

f. Dismount the resistor assembly (29) byremoving screws (30) and washer (31). If necessary,remove plate (32) with a soldering iron and freeresistors (34) by unsoldering them from the plate(32).

Figure 5-10. Oscillator-relay, exploded view.

44 TAGO 269A - July

Figure 5-11. Oscillator-relay, interior view.

g. Unsolder the wires and dismount theconnectors (35) by removing screws (36) andwashers (37).

h. Unsolder the wires and free the variableresistors *38) by removing nuts (39) and (40) andlockwashers (41).

i. Remove screw (43), washer (44) and terminallug (42).

j. Unsolder terminal connections and dismountconnector (45) by removing its coupling nut (46).

5-18. Reassembly of Oscillator-Relay(figs. 5-10 and 5-11) To reassemble the oscillator-relay--

a. Mount connector (45, fig. 5-10) and secure itwith nut (46).

b. Replace terminal lug (42), screw (43), andwasher (44).

c. Insert the shafts of the variable resistors in themounting holes, replace washers (41) , and replace

TAGO 269A - July 45

and tighten nuts (4). Tighten nuts (39) on thebushings of the variable resistors.

d. Reconnect and solder the wires betweenconnector (45) and the variable resistors.

e. Mount connectors (35) and secure them withscrews (36) and washers (37).

f. If dummy load resistors (34) have beenunsoldered from plates (32) and (33), resolder themwith 3/32-inch leads between the resistors and theplates. Mount resistor assembly (29) in place withscrew (30) and washer (31).

g. Replace relays (26), (23), and (20) with theirscrews and washers.

h. Mount terminal board (17) in place withscrews (18) and washers (19).

i. Solder capacitor C4002 (11) in place. Hookclip (16) into the terminal notches and solder it inplace. Replace the neon lamp in the clip andreconnect and solder the leads to the lamp. Replaceand solder resistor R4002 (10).

j. Reconnect and solder capacitors (14) and(13), resistor (12), and all other wiring. Replace thebaseplate (1) and secure it with screws (2) andwashers (3).

5-19. Mechanical Linkage Fabrication(figs. 5-12 and 5-13)