TEX30/50/100/150/300LCD
ELETTRONICA
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User Manual
Rev. 1.0 - 29/11/12
7.4 TEX300LCD Different Parts
7.4.1 Power Supply
The
TEX300LCD
power supply unit is a switching-type unit whose +50 V main
stabilizers for generating cont5 V, +18 V and -18 V voltages for supplying
the other equipment circuits. Note that the power supply is a “direct from mains”
type, or rather it is without a transformer, and it can be connected to any voltage
between 90 and 260 V without any adjustments or manual settings.
7.4.2 Power Amplifier
The final power stage is enclosed in a totally shielded metal container fastened
in the centre of the device.
The RF signal coming from the “main” card reaches the pilot, is amplified and is
then sent to the final stage that sees to its final amplifications up to 300W.
The amplifier is made in three stages. The first is made with BFG35, the second
with one BLF175 and the last with one SD2942.
In addition to the actual RF amplification, this circuit carries out the following
functions:
•
Control of the power level in output, depending on the setting
•
Reduction of the power supplied when in presence of high-level reflected
power
•
Measures of the forward and reflected power by means of directional
couplers
•
Measures of the current absorbed by the power amplifier
•
Measures of the temperature
•
Low-pass filtering of the RF signal in output
This board also features an RF sampling of approximately -60dB RF with respect
to the output, which is available on a BNC connector below the transmitter output
connector. This sample is is useful for verifying the characteristics of the carrier,
but not for verifying those of the upper harmonics.
7.4.3 Control Board
The main function of this board is to check and correct the MOSFET polarization
voltage of the RF amplifier section.
It also provides the measurement of the absorbed current and contains a circuit
for signaling power supply unit faults.
If no alarms are present, the voltage is adjusted only depending on the set output
