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C. Disconnect BNC connector P18 from J18 on the rear of the RF amplifier assembly.
D. Disconnect BNC connector P17 from J17 on the front of the RF amplifier assembly.
E. Remove the six screws from the underside which secure the assembly to the chassis.
F. Remove the RF amplifier assembly from the exciter chassis.
10.3.2
INSTALLATION PROCEDURE.
To install the RF amplifier assembly after repairs have been completed, proceed as follows:
WARNING
DISCONNECT EXCITER PRIMARY POWER BEFORE
PROCEEDING.
WARNING
A. Disconnect the primary power from the exciter.
B. Follow the REMOVAL PROCEDURE in reverse order.
10.4
THEORY OF OPERATION
This section presents the theory of operation for the exciter RF amplifier assembly.
10.4.1
RF AMPLIFIER ASSEMBLY DESCRIPTION.
The RF amplifier assembly consists of: 1) two series-pass voltage regulator transistors, 2) a +20V regulator
circuit, 3) a temperature sensing circuit, and 4) an RF amplifier circuit board. All wiring to and from the
assembly is routed through plugs and jacks to facilitate maintenance. An exhaust fan is installed on the exciter
rear-panel to maintain proper operating temperature.
10.4.2
RF AMPLIFIER CIRCUIT BOARD DESCRIPTION.
The RF amplifier circuit board contains a three-stage FM broadband amplifier with a maximum output power of
50 watts. Output levels from 3 to 50 watts are attained by adjusting the power transistor control voltage. Due
to the broadband characteristics, tuning of the amplifier is not required.
In addition, the RF amplifier circuit board contains forward and reflected power directional couplers and an
input mute circuit. The directional coupler outputs and operating potentials are routed from the circuit board
through the chassis with feed-through capacitors to prevent RF interference.
10.4.3
FUNCTIONAL DESCRIPTION.
A simplified schematic diagram of the RF amplifier circuit board is presented in Figure 10-1. Refer to Figure 10-1
as required for a description of the following circuits.
A. RF amplifier circuit.
B. Directional coupler circuits.
C. Input mute circuit.
RF AMPLIFIER CIRCUIT. The RF amplifier circuit consists of an input amplifier, a driver amplifier, a power
amplifier, and associated components. Interstage impedance matching networks are designed with microstrips
to provide maximum broadband frequency stabilization.
Input Amplifier. The input amplifier consists of thick-film hybrid amplifier U2, and resistor pad R6 and R7. A 1
milliwatt RF input signal from the modulated oscillator is input to U2. This stage provides approximately 1 watt
of output power across R6 and R7 to the following stage.
Содержание FX-50
Страница 12: ...x 2011 Broadcast Electronics This page intentionally left blank ...
Страница 20: ...8 2011 Broadcast Electronics Figure 2 1 FX 50 E REAR PANEL CONNECTIONS SHEET 1 OR 2 ...
Страница 21: ...9 2011 Broadcast Electronics Figure 2 1 FX 50 E REAR PANEL CONNECTIONS SHEET 2 OR 2 ...
Страница 32: ...20 2011 Broadcast Electronics Figure 3 1 FX 50 E CONTROLS AND INDICATORS ...
Страница 35: ...23 2011 Broadcast Electronics Figure 4 1 FX 50 E OVERALL SIMPLIFIED SCHEMATIC ...
Страница 40: ...28 2011 Broadcast Electronics Figure 5 1 FX 50 E ASSEMBLY ...
Страница 46: ...34 2011 Broadcast Electronics Figure 6 1 CONTROL CIRCUITRY SIMPLIFIED SCHEMATIC ...
Страница 49: ...37 2011 Broadcast Electronics Figure 6 2 POWER SUPPLY SIMPLIFIED SCHEMATIC DIAGRAM ...
Страница 53: ...41 2011 Broadcast Electronics Figure 6 4 PARALLEL LOAD CONNECTION ...
Страница 56: ...44 2011 Broadcast Electronics Figure 6 5 NO PA VOLTAGE TO THE RF AMPLIFIER ...
Страница 58: ...46 2011 Broadcast Electronics Figure 7 1 METERING CIRCUIT REMOVAL AND INSTALLATION DIAGRAM ...
Страница 60: ...48 2011 Broadcast Electronics Figure 7 2 METTERING BOARD SIMPLIFIED SCHEMATIC ...
Страница 68: ...56 2011 Broadcast Electronics Figure 8 1 MODULATED OSCILLATOR SIMPLIFIED SCHEMATIC DIAGRAM ...
Страница 74: ...62 2011 Broadcast Electronics Figure 9 1 AFC PLL CIRCUIT BOARD SIMPLIFIED SCHEMATIC ...
Страница 81: ...69 2011 Broadcast Electronics Table 9 2 FREQUENCY SYNTHESIZER PROGRAMMING ...
Страница 84: ...72 2011 Broadcast Electronics Figure 9 4 NO RF OUTPUT LOCK IS EXTINGUISHED ...
Страница 85: ...73 2011 Broadcast Electronics Figure 9 5 NO MODULATION LOCK INDICATOR ILLUMINATED ...
Страница 89: ...77 2011 Broadcast Electronics Figure 10 1 RF AMPLIFIER SIMPLIFIED SCHEMATIC ...
Страница 92: ...80 2011 Broadcast Electronics Figure 10 2 RF AMPLIFIER CIRCUIT BOARD CONTROLS ...
Страница 95: ...83 2011 Broadcast Electronics Figure 10 3 RF AMPLIFIER TROUBLESHOOTING INFORMATION ...
Страница 100: ...88 2011 Broadcast Electronics Figure 11 1 SLAVE FM BOOSTER SIMPLIIFED SCHEMATIC ...
Страница 101: ...89 2011 Broadcast Electronics Figure 11 2 MASTER FM BOOSTER SIMPLIFIED SCHEMATIC ...
Страница 161: ...149 2011 Broadcast Electronics Figure 14 1 OPTIONAL LOW PASS FILTER ASSEMBLY ...
Страница 162: ...150 2011 Broadcast Electronics Figure 14 2 EXCITER FRONT RAIL MOUNTING APPLICATIONS ...
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