Ericsson MASTR II 4EF4A1, Руководство по обслуживанию

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DESCRIPTION
General Electric Power Amplifier Models 4EF4A1, 2
and 3 operate in the 25-54 megahertz band. They are used
with an external driver and power supply to provide a power
output between 150 and 300 watts. The amplifier employs a
4CX250B as a power amplifier tube, with forced-air cooling
providedby a blower mounted on the power supply. Standard
RETMA rack-mounting dimensions are used. The tuning
controls most frequently used are located on the front of the
unit.
All the power connections, except the high voltage con-
nection, are made with a 6-pin plug from the front of the
unit. High voltage is brought to the plate at the rear of the
plate compartment.
Antenna relay keying voltage connections are made be-
hind the output Power Indicator, using screw connections.
The RF drive connection is made by an RG-58/U cable
plugged into the driver from the front of the unit.
CIRCUIT ANALYSIS
Excitation of the Power Amplifier at P482 is fed to cou-
pling loop L482 and coupled to coil L484, which, with
C481, forms the grid tank of the amplifier. By adjusting the
PA GRID control (C481), the grid tank may be tuned to the
operating frequency. Coil L481 isolates RF from the power
cable.
In order to obtain optimum tube life the filament voltage
on the Power Amplifier tube V481 is set at the factory for 6
Volts with R4 on the High Power Power Supply. The fila-
ment voltage can be set for a higher value but with a corre-
sponding decrease in tube life. C482, C483, and C484 are
RF by-pass capacitors and R481 is used as a screen RF de-
coupling resistor. Built into the tube socket, XV481, is a
ring-type capacitor which is used as a screen grid by-pass.
All input voltage connections to the Power Amplifier, ex-
cept the B-plus voltage connection, are made at P481 on the
front side of the panel. The 2000-volt B-plus lead is con-
nected at terminal P0-2 located in the rear on the plate cavity
cover. C485 provides bypassing for the B-plus and L485 is
an RF choke. The plate tank is composed of C488 and
L494. The plate tank is tuned to the operating frequency by
adjusting the PA PLATE control C488.
Adjusting the PA COUPLING control varies the cou-
pling from the plate to the output by controlling the amount
of magnetic flux linking the plate coupling loop to the out-
putloop. The filter consists of L490, L491, L492, L493,
C492, C493, L494 and C495.
Antenna coupling is adjusted by the PA ANTENNA con-
trol C489. The signal is fed from the filter to J481. The sig-
nal from J481 is connected to the antenna through P1 and P2
on the Reflectometer and through the contacts on the an-
tenna relay K482.
POWER REFLECTOMETER
The Power Reflectometer gives a relative voltage which
indicates forward and reflected RF power output.
The Reflectometer samples the magnetic field caused by
current in the transmission line and the electrical field from
the voltage on the line. on a properly matched line, these
two voltages are equal and cancel each other when reading
REFLECTED power ("0" reflected power). When the probe
is rotated 180, these two voltages add to indicate FOR-
WARD power.
When the load is not matched, these two voltages be-
come unequal and provide a ratio of incident (forward) to re-
flected power. Any significant change in this ratio (if other
than 1:1) after initial installation and check out, should be
cause for examination of the antenna and feed line. Actual
V.S.W.R. as measured on a calibrated bridge, should remain
below 1.5:1 at all times.
ANTENNA RELAY
K482, the antenna relay, switches the antenna from the
receiver to the transmitter when the transmitter is keyed.
MAINTENANCE
PREVENTIVE MAINTENANCE
To obtain optimum performance from the equipment, a
program of regular preventive maintenance should be fol-
lowed. This preventive maintenance should include the fol-
lowing:
1. A check of the operating frequency as required by
the Federal Communications Commission.
2. A check of the PA PLATE current, Power Amplifier
GRID current and PA PLATE voltage meter read-
ings.
3. A check of the PA PLATE tuning and reflected
power (if any) and realignment if improper opera-
tion is indicated.
Copyright © 1978, General Electric Company
TABLE OF CONTENTS
DESCRIPTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
CIRCUIT ANALYSIS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Power Reflectometer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Antenna Relay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Power Amplifier Tube Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Blower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
ALIGNMENT PROCEDURE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
OUTLINE DIAGRAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
SCHEMATIC DIAGRAM (Models 4EF4A1 & 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
SCHEMATIC DIAGRAM (Model 4EF4A3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
SPECIFICATIONS
*
MODEL NUMBER 4EF4A1,2,3
USED WITH Driver Type KT-56-A and Power Supply 19D402530G1, G2 to
provide a 150-300 Watt (KT-39-A) Transmitter
FREQUENCY RANGE 4EF4A1: 25-30 MHz
4EF4A2: 30-42 MHz
4EF4A3: 42-50 MHz
POWER INPUT 117 VAC, 50/60 Hz
Standby: 2 amps
Transmit: 9 amps (maximum)
POWER OUTPUT 150 to 300 Watts
TUBE COMPLEMENT (1) 4CX250B or 7203/4CX250B
AM HUM AND NOISE LEVEL Down 34 dB
MAXIMUM FREQUENCY SPREAD:
(2 or more channels) Full Specifications 1 dBDegradation
25-30 MHz 0.12 MHz 0.24 MHz
30-36 MHz 0.12 MHz 0.24 MHz
36-42 MHz 0.16 MHz 0.32 MHz
42-50 MHz 0.18 MHz 0.36 MHz
DUTY CYCLE Continuous --Blower recommended for cabinet ventilation under
conditions of high ambient temperatures or continuous duty
operation.
AMBIENT TEMPERATURE RANGE -30°C to +60°C (-22°F to +144°F)
DIMENSIONS (HxWxD) 7" x 19" x 11"
WEIGHT 18 pounds
* These specifications are intended primarily for the use of the serviceman. Refer to the appropriate Specification Sheet for the
complete specifications.
No one should be permitted to handle any portion of the equipment that is supplied with high voltage; or to connect any exter-
nal apparatus to the units while the units are supplied with power. KEEP AWAY FROM LIVE CIRCUITS!
WARNING
LBI-4938 LBI-4938
1