Noise Limiter fig

The triode sections of Tube JAN-6N7 (V9) are connected in parallel to form a single triode (fig. 30) which is used as a shunt-type limiter. The heater voltage is reduced to approximately 3 volts by 4-ohm series resistor R31 (fig. 56). The control grids (pins 4 and 5) are connected to 0.05-mf capacitor C42, which is grounded at one end, and through 1-megohm (meg) resistor R49 to the most negative point (A) on the diode resistance. The cathode (pin 8) is connected through...

Preparation for

Check to see that the tubes are in the proper sockets before turning on the receiver. (1) Receiver. To inspect the receiver tubes, remove the dust cover by removing the thumbnuts which hold the cover to the front panel and rear edge of the chassis. A receiver tube location diagram is shown in figure 13. Their proper location, as well as the marking of their respective sockets, is clearly shown also in the etched location plates attached to the top of the tuning unit. All of the...

Capacitor Tests

It is often necessary to check capacitors for leakage or open or short circuits which are caused by break-down of the dielectric between the plates. This applies only to capacitors of the tinfoil paper or mica type, since the dielectric film of wet electrolytic capacitors is self-healing. b. Open Capacitors. To check a capacitor suspected of being open, place a good capacitor in parallel with it. In r-f circuits, keep the capacitor leads as short as those of the suspected capacitor....

IF Amplifier fig

Super Selectivity With Crystal

Input Stage Tube JAN-6K7 (V5). (1) CRYSTAL SELECTIVITY switch at OPE. With the CRYSTAL SELECTIVITY switch, SW7, at OFF, the crystal filter is shorted. Consequently, the i-f signal is applied directly from input transformer L26 to the parallel-resonant grid circuit (permeability-tuned inductor L27 and 85-mmf capacitor C33) and to the control grid (top cap) of V5. C34 places the lower end of L27 at r-f ground potential. Grid bias is applied from the a-v-c line (par. 65) through 10,000-ohm...

Power Supply Unit Test

The power supply test prevents further damage to the receiver from possible short circuits. This test also indicates whether the power supply unit is functioning properly. o. With the receiver and power supply unit connected for operation, place the OFF-ON switch in the ON position. If the receiver fails to operate, check all connections to the power supply unit and to the power source to determine whether the proper voltage is being delivered to the receiver. b. As the receiver warms up,...

Destroy Everything

In case of electric shock, shut off the high voltage at once and ground the circuits. If the high voltage cannot be turned off without delay, free the victim from contact with the live conductor as promptly as possible. Avoid direct contact with either the live conductor or the victim's body. Use a dry board, dry clothing, or other nonconductor to free the victim. An ax may be used to cut the high-voltage wire. Use extreme caution to avoid the resulting electric flash. a. Breathing stops...

Siting

The receivers must be correctly situated to be sure of good performance. In many instances, particularly where the receiver is part of a larger set, the necessary tactical and technical requirements for proper operation of the system as a whole will determine the receiver location. In any case, remember the following points a. The antenna should be high, and clcar of surrounding objects. b. The receiver should be situated away from power lines, generators, and power units, or other unshielded...

Description of Power Supply Unit

The five power supply units are similar in appearance. Each one is mounted on a steel chassis. Like the receiver, the power supply unit can be used for either rack or table mounting. The rack mounting model is secured to an aluminum panel 19 Figure 7. Pozuer Supply Unit RA-94-A. Figure 7. Pozuer Supply Unit RA-94-A. Figure lt . Radio receiver installed on Mounting FT-510. Figure lt . Radio receiver installed on Mounting FT-510. inches wide by inches high with appropriate mounting notches. It...

Equipment Performance Checklist

Set band switch control at any desired position. Tune across entire band by rotating MAIN TUNING control. Check each of the tuning ranges. Use procedure given in step 16 above. Rotate band switch to a high-frequency band and rotate the BAND SPREAD control from 100 to 0. Tune in any station by rotating the MAIN TUNING control. Then rotate the SENSITIVITY control in either direction. Turn to SEND position. When check is completed, return to REC position. Rushing noise is heard in loudspeaker....

Capacitors

Inspect I . 1 Inspect the terminals of large fixed capacitors for corrosion and loose connections. Carefully inspect the mountings to discover loose mounting screws, studs, or brackets. Examine the leads for poor insulation, cracks, and evidences of dry rot. Cut away frayed strands on the insulation. Wrap exposed wire with friction tape. See that the terminals of the capacitors are not cracked or broken. 2 Thoroughly inspect the case of each large fixed capacitor for leaks, bulges, and...

Replacing Parts

Careless replacement of parts often makes new faults inevitable. Note the following points a. Before a part is unsoldered, note the position of the leads. If the part, such as a transformer, has a number of connections, tag each of the leads to it. b. Be careful not to damage other leads by pulling or pushing them out of the way. c. Do not allow drops of solder to fall into the set, since they may cause short circuits. d. A carelessly soldered connection may create a new fault. It is very...

Battery Operation

Although primarily designed for a-c operation, in an emergencv the receiver can be operated from a 6-v storage battery, five 45-v plate supply batteries, and a 45-v bias battery. The 7-foot connector cable which is supplied for battery operation is connected as shown in figure 35. One end of the cable is provided with a terminal strip which connects to the terminal strip on the receiver. Terminals 2 and 8 of the connector cable terminal strip are shorted. b. The plate supply voltage is...

Beat Frequency Oscillator fig

Beat frequency oscillator V10 uses Tube JAN-6SJ7 in a pentode-operated electron-coupled oscillator circuit. The cathode, control grid, and screen grid form a series-fed Hartley oscillator. The screen grid of the tube acts as the plate of the Hartley oscillator circuit. When the SIGNAL MOD-CW switch SW3 is in the CW position, screen and plate voltage are applied through decoupling circuit R35, C27, dropping resistor R33 and load resistor R34. R-f current is fed back-to the grid tank circuit...

Radio Receivers Bc Bc Bc and RU

Hammarlund Super Pro Receiver

Make all repairs and adjustments necessary for proper operation of the receivers. b. Disassembly. 1 Remove the two screws holding the terminal strip cover to the chassis, and remove the cover. 2 Loosen the 10 screws holding the cable to the terminal strip, and remove the cable. Tighten the screws on the terminal strip. 3 Remove the eight screws holding the front panel of the receiver in Cabinet CH-104- .A or in the relay rack, and pull out the chassis. 4 Remove the 11 knurled...

Packaging Data for Domestic Shipment

Radio receivers and power supply units packed for domestic other than oversea shipment may be received in shipping containers similar to those described for export, with the following changes, depending upon the amount of handling anticipated and the length of storage contemplated 1 The use of a dehydrating agent, or desic- Figure 5. Packaging and packing of radio receivers. Figure 5. Packaging and packing of radio receivers. Table I. Packaging data for export shipment Table I. Packaging...

Differences in Models

Power Units RA-74- , RA-84- , and RA-94-A are electrically alike except for variations in power transformers Tl, T2, and T3 figs. 50, 51, and 52 . The output of these transformers is the same, but the input requirements vary. a. Power Unit RA-74- operates from a 95-130-volt v , 190-260-v, 25-60-cycle power source. The transformer primary is provided with eight taps marked 95, 105, 117, 130, 190, 210, 234, and 260. b. Power Unit RA-84- is designed to operate from a 105-115-125-v, 50-60-cycle...

Part One Introduction

The radio receivers described in this manual are of the superheterodyne type intended primarly for fixed station use although mountings for vehicular use may be provided. The receivers use a conventional superheterodyne circuit and are designed for the reception of either continuous-wave c-w , or amplitude-modulated a-m voice or tone signals with either manual or automatic volume control avc . b. The receivers use an external power supply. Both the receiver and power supply fig. 1 are...

Power Supply Units RA RA and RAA figs and

Make all repairs and adjustments necessary for the proper operation of the power supply units. b. Disassembly. 1 Remove the two screws holding the terminal strip cover to the chassis, and remove the cover. 2 Loosen the 10 screws holding the cable to the terminal strip and remove the cable. Tighten the screws on the terminal strip. 3 Remove the eight screws holding the front panel to the rack, and remove the power supply from the rack. 4 Remove the eight knurled nuts and...

Power Transformers Fifter Chokes and Audio Transformers

Since power transformers, filter chokes, and audio transformers used in the equipment are of similar potted construction, preventive maintenance for them is similar. a. Feel F . As soon as possible after shutdown, feel filter chokes LI and L2 for abnormal heating which may indicate an overloaded condition, or imminent failure due to moisture absorption or other causes. Likewise feel audio transformers T7 and T8 for abnormal heating. Power transformer T3 normally operates at a warm temperature....

Mixer and HF Oscillator fig

For simplicity, capacitor C71, main tuning ganged capacitor C1C, and band spread ganged capacitor C2C are represented as a single variable capacitor C across the inductance trimmed secondary of r-f transformer L18. Signal voltages across C are applied through 600-mmf capacitor Cll to signal grid G1 top cap of pentagrid mixer Tube JAN-6L7. Fixed bias from the voltage divider fig. 31 is applied through a filter circuit 10,000-ohm resistor RIO and 0.01-mf capacitor C12 and...

AVC Circuit fig

Beat Frequency Oscillator

An a-v-c circuit which is independent of the detector provides improved a-v-c action. In Radio Receiver BC-779-B the separate a-v-c circuit consists of an a-v-c branch i-f amplifier Tube JAN-6SK7 VI1 and an a-v-c rectifier Tube JAN-6H6 V12 . The rectified and filtered output of V12 is applied as a-v-c voltage to both r-f stages and to the first two i-f stages. a. A-V-C Amplifier Tube JAN-6SK7 VI1 . The output of the 2d i-f stage, V6, is applied simultaneously to the 3d i-f stage, V7 fig. 29 ,...

Crystal Filter fig

The equivalent electrical circuit of a crystal is shown in A, figure 28. The circuit, and hence the crystal, are resonant at two frequencies The frequency at which the reactance of L is equal to the reactance of C series resonance , and the frequency at which the effective reactance of L-C in series is inductive and equal to the capacitive reactance of CY parallel resonance . At the series-resonant frequency the crystal acts as a low-impedance connection between 1...