BC-191A_N_repair_instructions_TM11-4017_1945.pdf

WAR DEPARTMENT TECHNICAL MANUAL TM 11-4017 RADIO TRANSMITTERS - BC-191-A,-B,-C,-E,-F, AND-N REP AIR INSTRUCTIONS W A R DEPARTMEN T JUNE 1 9 4 5 RESTRICTED. DISSEMINATION OF RESTRICTED MATTER. No person is entitled solely by virtue of his grade or position to knowl- edge or possession of classified matter. Such matter is entrusted only to those individuals whose official duties require such knowledge or possession. , (See also paragraph 23b, AR 380-5, 15 March 1944.) I United Stat.es Government Printing Office Washington : 1945 WAR DEPARTMENT Washington 25, D. C., 4 June 1945 TM 11-4017, Radio Transmitters BC-191-A, -B, -C, -D, - E, -F, and -N, Repair Instructions, is published for the information and guidance of all concerned. AG300.7 (24May45) BY ORDER OF THE SECRETARY OF W AI: OFFICIAL: J. A. ULIO Major Geneml The Ad.iutant Geneml DISTRIBUTION: G. C. MARSHALL Chief of Staff AAF (5); AGF (5); ASF (2); T of Opn (5); Dept (5); Base Comd (5); Island Comd (5); Def Comd (2); Arm S Div ASF (1); Tech Sv (2) ; PC PE (2); Dep 11 (2) ; Gen Over- sea SOS Dep (2); Pro Dist 11 (2); Gen USMA (10); WDGS Lib (5); Lab 11 (2); Rep Shop 11 (2); A (5); CHQ (2); Three (3) copies to each of the following: T/0 11-15; 11-47; 11-107; 11-127; 11-147S; 11-587; 11-592; 11-597. Refer to FM 21-6 for explanation of distribution formula. ii ) CONTENTS Jarayruph Page SECTION I. DESCRIPTION OF RADIO TRANSMITTERS BC-191- A, -8, -C, -D, -E, -F, AND -N. General Frequency coverage . . . . . . Types of transmission . . . Range . . . . . Power output . . . . . . . . . Power input . . Over-all system function , . . . . . II. DIFFERENCES BETWEEN MODELS. General . . . . . . Ill. INITIAL REPAIR PROCEDURES. General . Removal of plug-in parts . . Cleaning, inspection, and lubrication (other than plug-in parts) . . . . . . . . . . . Cleaning, inspection, and testing of plug-in parts . . IV. PRELIMINARY TROUBLE-SHOOTING PROCEDURES. Input resistance test . . . . Preparation of set for operation . . Adjustments prior to operation . . . V. ALIGNMENT PROCEDURE. General Frequency checks and adjustments. . . . Neutralization . . Antenna tuning circuit checks . . . . . Adjustments for C.W. operation . . Adjustments for VOICE operation . . Adjustments for TONE operation. VI. DETAILED TROUBLE-SHOOTING PROCEDURES. General checks for defective stages. Moisture proofing, fungi proofing, and refinishing . . VII. FINAL TESTING. General . . . . . . . . VIII. INDIVIDUAL STAGE AND CIRCUIT REPAIR DATA. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Master oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Power amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Modulator . . . . . , . ,. . . . . . . . 28 Speech amplifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Filament and relay circuits . . . . . . . . . . . . . . . . . . . . . . 30 Switching relay 1165 . . . . . . . . . . . . . . . . . . 31 Checking TONE- C.W.-VOICE switch . . 32 Transmitter tuning units. . . . . . 33 Antenna Tuning Unit BC-306-(*). 34 IX. SUPPLEMENTARY DATA. Parts identification 35 iii 1 1 1 1 1 1 2 3 5 5 6 8 9 9 9 15 15 16 17 18 18 19 21 23 24 28 30 32 35 39 42 52 54 62 64 I WARNING HIGH VOLTAGE is used in the operation of this equipment I DEATH ON CONTACT may result if safety precautions are not observed. iv Figu1e 1. Radio Tmnsmitte1 BC-191-() full View, with Tuning Unit lU-6-A in place. y RESTRICTED SECTION I DESCRIPTION OF RADIO TRANSMITTERS BC-191-A, -B, -C, -D, -E, -F, AND -N1 1. General a. SYMBOLS. Official nomenclature followed by ( *) is used to indicate all-models of the item of equipment included in this Technical Manual. Thus Radio Transmitter BC-191-(*) repre- sents Radio Transmitters BC-191-A, -B, -C, -D, -E, -F, and -N; Transmitter Tuning Unit TU-3-( *) represents Transmitter Tuning Units TU-3-A, TU-3-B, and TU-3-N. Antenna Tun- ing Unit BC-306- ( *) represents Antenna Tun- ing Units BC-306-A and -B. Official nomencla- ture followed by ( ) is used in making general reference to all models of equipment. Thus, Transmitter Tuning Unit TU- ( )-A, or -B represents Transmitter Tuning Units TU-3-A or-B, TU-5-A or-B, TU-6-A or-B, TU-7-A or-B, TU-8-A or -B, TU-9-A or-B, TU-10-A or -B, TU-22-A or -B, and TU-26-A or -B. b. CHARACTERISTICS. Radio Transmitters BC- 1. 91- ( *) (fig. 1), are five-tube, master-oscilla- tor, power-amplifier radio transmitters. They have one stage of speech amplification, operat- ing as a class A driver, to drive the grids of the push-pull class B modulators. On tone, the speech amplifier stage operates as an audio oscillator to supply tone modulation to the car- rier. c. PHYSICAL DESCRIPTION. The transmitter is housed in a shielded metal cabinet, made up of panels fastened with buttonhead screws to the tubular steel frame of the transmitter. The front cover of the tube compartment, located at the upper left front of the transmitter, is se- cured by snap-slide catches. Behind this panel are located the tubes; some of the controls, and the filament-resistor board. The antenna tun- ing controls occupy the right side of the trans- mitter front panel, and the transmitter tuning unit compartment is at the lower left. The transmitter-output terminals are located in the upper right corner of the transmitter, on both the top and the side. The power and control in- put sockets are on the left side and bottom of the transmitter. 1 cc TMII-800 for installation, operation, and other maintenance data mt thi equipment. 2. Frequency Coverage With the use of interchangeable transmitter tuning units, a frequency-range coverage from 200 to 800 kilocycles and from 1,500 to 12,500 kilocycles is possible with the nine tuning units. (See fig. 28.) In some cases, special transmit- ter tuning units are available to cover frequen- cies from 150 to 260 kilocycles, 260 to 400 kilo- cycles, and 800 to 1,500 kilocycles. These special units, however, are not standard equipment. 3. Types of Transmission a. C.W. C. W. refers to unmodulated continu- ous-wave telegraph signals. b. TONE. Tone refers to tone-modulated, con- tinuous-wave telegraph signals. These are am- plitude-modulated signals. c. VOICE. Voice refers to voice-modulated, continuous-wave telephone signals. These are amplitude-modulated signals. 4. Range The range of distances covered by the trans- mitters depends upon several variable factors, such as operating frequency, type of transmis- sion, and type of antenna system, also whether the transmitter is located in an aircraft, at a fixed ground station, or in a vehicle. 5. Power Output Under average operating conditions, the normal power output on continuous-wave telegraph op- eration varies from 40 to 75 watts, depending upon the transmission frequency. 6. Power Input The following different types of power-supply equipment are used in these transmitters: a. Some sets use a 12-volt storage battery floated across the charging generator of a mo- tor vehicle. The battery, a component of the motor vehicle, supplies power directly to the vacuum-tube filaments and to the control cir- cuits. A dynamotor operating from the same battery generates high voltage for the plate cir- cuits of the transmitter. b. A second type of power equipment is a gasoline engine-driven generator which gener- ates both 12 volts and high voltage, and sup- plies all power required for transmitter opera- tion. c. A third type of authorized power-supply equipment is a rectifier type unit, operating from 110-or 220-volt alternating-current (a-c) power supplies. Separate rectifiers in the equipment furnish low and high direct-current (d-e) voltages for the transmitters control and plate circuits respectively. The transmitter tube filaments are heated by low-voltage alter- nating current, supplied by a step-down trans- former in the unit. 7. Over-all System Function a. R-F SECTION. The simplified block dia- gram (fig. 2) shows the transmitter divided in- to separate blocks, each block representing an individual stage or, as with the tuning unit, a component of that stage. The frequency of transmission is determined by the master oscil- lator and the oscillation section of the transmit- ter tuning unit. Power generated by the oscil- lator is then coupled to the power amplifier. The power amplifier, shown by the power- amplifier block and the amplifier section of the I I TRANSMITTER:TU NING UNIT (OSC. SECTION) ! (AMP. SECTION) . I . 2 tuning unit, is then tuned to resonance with the master oscillator. The output of the power am- plifier is coupled to the antenna tuning unit, which can be tuned and adjusted to load the different types of antennas to the proper oper- ating frequency. b. MODULAOR. In the audio section, voice frequencies are picked up by the microphone and coupled to the input of the speech-ampli- fier stage. The amplified signals from this stage are applied to the input of the class B push-pull modulator tubes. These greatly amplified signals from the output of the modulator stage are applied to the primary of the class B output transformer. Any variations of voltage or cur- rent in this primary winding will be present in the secondary winding. Because the plate cur- rent of the final power amplifier flows through this secondary, these variations, of the same frequency as those picked up by the micro- phone, are applied to the plate circuit of the power amplifier and modulate the radio-fre- quency (r-f) carrier. c. POWER SUPPLIES. The block diagram (fig. 2) shows the three types of power supplies which may be used to furnish power necessary to operate the equipment. Any one of the three may be used; the type chosen depends upon where the equipment is installed. - ANTENNA TUNING UNIT - ANT. GND. .JAN-2111 (VT-4-C) .JAN-21 1 1 (VT-4-C) 2-JAN-211 (2-VT-4-c) JAN-lOY (VT-25) MASTER OSCILLATOR DYNAMOTOR AND BATTERY . . POWER PUS H-PULL AMPLIFIER . MODULATOR POWER SUPPLIES A-C POWER SUPPLY - . SPEECH AMPLIFIER (AUDIO OSC ILLATOR) G AS ENGINE G E NERATOR SUPPLY t=:=:(;l TLI9507 Figu1e 2. Radio Tmnsmitte1 BC-191-(*), simplified block diagmm. SECTION II DIFFERENCES BETWEEN MODELS 8. General This text covers seven models of the equipment. Radio Transmitters BC-191-A to -F, inclusive and BC-191-N. All models are identical for all operating functions but vary slightly in small details, usually mechanical in nature. Table I lists the differences in these models. The first 3 column shows the parts affected, and the re- maining columns, each headed by a model num- ber, list the affected parts used in that particu- lar model. In Radio Transmitters BC-191-A to BC-191-E, inclusive, the socket for Tube JAN- lOY (VT-25) is a regular plug-in wafer type, with no holding clamp for the tube. Parts affected Antenna loading coil Switching relay. OFF-ON switch. 12V-14.2 V SThitch. Panel meters. Filament resistor con- nection board. Antenna loading switch. Capacitors. A-C D-C switch. Interstage trans- former. Transmitter tuning units. Resistors 1152 and 1153. BC-191-A 1170. 1165. Rotary type 1132. 1139 and 1140. White face, black letters. A of fig. 7. 1171. 1120, 1155, and 1163. 1136 and 1137. 1157. I TU-( )-A. I I I Beneath speach- amplifier socket. TABLE I-Difje?e?wes Between Models BC-191-B Improved 1170. Improved relay 1165. Rotary type 1132. 1139 and 1140. White face, black letters. A of fig. 7. 1171. 1120, 1155, and 1163. 1136 and 1137. 1157. TU-( )-A. On resistor board BC-191-C Improved 1170. Improved relay 1165. Toggle type 1194. Replaced by 1190. Black face, white letters. A of fig. 7. 1171. 112 1155, and 1163. Replaced by 1195. 1157. TU-( )-A. T U-( )-B. On resistor board. BC-191-D Improved 1170. Improved relay 1165. Toggle type 1194. Replaced by 1190. Black face, white letters. Redesigned as in B of fig. 7. 1198. 1120, 1155, and 1163. Replaced by 1195. 1157. TU-( )-B. On resistor board. BC-191-E Improved 1170. Improved relay 1165. Toggle type 1194. Replaced by 1190. Black face, white letters. Redesigned as in B of fig. 7. 1198. Replaced by single unit, 1197a, b, c. Replaced by 1195. 1157. TU- ( )-B. On resistor board. BC-191- F Improved 1170. Improved relay 1165. BC-191-N Improved 1170. Improved relay 1165. Toggle type 1194. I Toggle type lf9. Replaced by 1190. Black face, white letters. Redesigned as in B of fig. 7. 1198. Replaced by single unit, 1197a, b, c. Replaced by 1195. 1199. TU- ( )-B. On resistor board. Replaced by 1190. Black face, white letters. Redesigned as in B of fig. 7. 1198. Replaced by single unit, 1197a, b, c. Replaced by 1195. 1157. TU-( ) -B. On resistor board. llolc. Transmitter Tuning l:nits TU-( )- A have two insulated binding posts in the upper right corner of the front panel. In Transmitter Tuning l:nits TU-( )-B these binding posts ha,c been remoed. SECTION Ill INITIAL REPAIR PROCEDURES 9. General Note. Before making any repairs or adjustments, all authorized modification work orders should be applied. Sec FM 21-G :f:or list of applicable MWOs. a. TOOLS. Many repairs in the field are me- chanical in nature. When a mechanical defect is encountered, be careful in removing the part b. TOOLS REQUIRED. Tl(m Screw drivers and pliers Diagonal cutters Socket wrenches Soldering iron and soller . Long-handle safety test probes Description Assorted sizes (including off- set screwdrivers). Large and small. Assorted sizes. C. TEST EQUIPMENT REQUIRED. Item Frequency meter . Voltmeter . . Standard ohmmeter Standard oscilloscope R-f antenna meter . . . Capacitors (one each) Resistors (one each). 5 Dcscri ption Crystal or heterodyne type, calibrated for continuous coverage from 125 to 15,000 kc. Sensitivity of not less than 1,000-ohms per volt, prefer- ably greater, measuring a-c or d-e voltages from 0 to 1,500 volts. (Select range to permit center-scale reading.) 0-5 amp range, thermo-couple type. 1,000-mmf; 5,000-vdcw; mica. 600-mmf; 5,000-vdcw; mica. 400-mmf; 5,000-vdcw; mica. 300-mmf; 5,000-vdcw; mica. 200-mmf; 5,000-vdcw; mica. 100-mmf; 5,000-vdcw; mica. 40-ohms; 75-watts; noninduc- tive. 75-ohms; 75-watts; noninduc- tive. 5-ohms; 75-watts; non induc- tive. to be repaired. To avoid damaging the head of a nut or screw always use tools provided with the set or use wrenches and screw drivers of the correct size. Never use force to remove any part. A gentle, steady pressure should remove the part; if not, car