Radio Sets SCR-608-A and SCR-628-A - TM 11-620 War Department Technical Manual

Performance Characteristics Radio Transmitter BC-684- A Remote Control Unit RM-29-D Dynamotors DM-34-( ), DM-35-( ), DM-36-( ), DM-37-( )

Mountings FT-284- ( ) and FT-285-( ) and Frame FM-43..

Ii. Installation and Operation.

19. Preparation for Use 30 21. Presetting Push Buttons 36 III. Functioning of Parts.

23. Functioning of Radio Receiver BC-68 3- A 43 24. Functioning of Radio Transmitter BC-684- A 57 23. Functioning of Remote Control Unit RM-29-D 63 26. Functioning of Dynamotors DM-34-( ), DM-35-( ), DM-36-( ), DM-37-( ) 63 27. Functioning of Control Circuits 63 28. General Maintenance Information 71 29. Routine Check of Mounting 73 30. Routine Check of Radio Receiver BC-683-A 73 31. Routine Check of Radio Transmitter BC-684- A 77 32. Routine Check of System 84 33. Emergency Check of Receiver Output Volume and Circuit Alignment 84 34. Emergency Alignment of Radio Receiver BC-683-A 86 33. Emergency Alignment of Radio Transmitter BC-684-A 95 36. Emergency Sources of Test Tones 100 37. Precision Alignment of Radio Receiver BC-683-A 100 38. Precision Alignment of Radio Transmitter BC-684- A 105 39. Location of Trouble in Radio Receiver BC-683- A 109 40. Location of Trouble in Radio Transmitter BC-684- A 124 41. Maintenance of Dynamotors 130 42. Replacement of Parts 133 43. Modifications During Manufacture 139 44. Color Codes on Components 149 43. Table of Replaceable Parts 156 grouped according to components 1 Radio Set SCR-608-A: 2 Radio Set SCR-628-A: 3 Radio Set SCR-608-A: Over-all and Unit Dimensions 8 23 Radio Set SCR-608-A: System Block Diagram -41 69 Radio Set SCR-608-A: System Schematic Diagram 189 8 Left-hand Interior View 14 9 Right-hand Interior View 15 10 Push-button Assembly, Right-side View 16 1 1 Push-button Assembly, Front View 16 25 Functional Diagram of R-f Amplifier, Modulator, and R-f Oscillator 44 26 Functional Diagram of I-f Amplifier and Limiter 46 27a Functional Diagram of Discriminator 48 27b, c, d Vector Diagrams Showing Phase Relations in the Discriminator 49 28 Functional Diagram of A-f Amplifier 51 29 Functional Diagram of Delayed-automatic-volume-control Circuit 52 30 Functional Diagram of Squelch Circuit 54 31 Functional Diagram of I-f Oscillator 56 32 Functional Diagram of the Heater Circuits 57 43 Wiring Diagram of Front Panel 72 44 Apparatus Location Diagram, Front View of Panel 73 45 Apparatus Location Diagram, Left-side View 74 46 Apparatus Location Diagram, Right-side View 75 51 Location of Alignment and Tuning Controls 93 58 Resistance Diagram 119 70 Schematic Diagram Showing Modifications During Manufacture 191 72 Wiring Diagram Without Front Panel 195 Radio Transmitter BC-684 A:

12 Front View With Crystal Compartment Open 17 13 Assembly and Exploded View of Crystals 18 14 Right-hand End View with Cover Plate Removed 19 1 5 Interior View with Top Cover and Dynamotor Removed 20 16 Push-button Assembly, Left-side View 21 17 Push-button Assembly, Right-side View 21 18 Interior View with Bottom Cover Removed 22 34 Functional Diagram of Oscillator and First R-f Amplifier 58 35 Functional Diagram of Modulator and Rectifier 59 36 Method of Modulation 60 37 Functional Diagram of Tripler, Doubler, Power Amplifier, and Antenna Coupling Circuits..

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