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R & S E K 8 9 5 / R & S E K 8 9 6
User Manual
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Power Supply
1.3.8 Power Supply
1.3.8.1 Design
The power supply consists of the printed circuit
board A66, a rear panel, a transformer, a
switch and the interface to the carrier board.
The rear panel contains the external interfaces.
Via cables the external HF interfaces are
directly connected to the respective modules.
The external AF interface (R&S EK 896) is
connected to the control unit via cables. To the
rear panel a heat sink is fixed.
Variable jumpers in the power supply permit
the line driver (600>] transformer) to be used
bidirectionally.
1.3.8.2 Functioning
(See Fig. 1.11)
If the power switch is closed by actuation of
the respective key on the control unit, the ex>
ternal AC voltage (100 to 240 VAC / 47 to
420!Hz) is fed from the mains connector via a
mains filter and a voltage selector to the trans>
former. By means of the voltage selector the
transformer is set to the external mains volt>
age. A protection facility in the voltage selec>
tor protects the input circuit against too high
currents. In case the temperature in the trans>
former rises above 113 ∞C, the input circuit is in>
terrupted as a result of the heat protection fa>
cility (Æ send power supply for repair).
The DC voltages generated from the secondary
voltage of 20 VAC by way of rectification and
filtering are stabilized via two fixed>voltage
regulators to +15 VDC and > 15 VDC. The +15>
VDC fixed>voltage source feeds for example a
5>VDC voltage regulator as well as the reset
and monitoring circuit.
Another secondary voltage of 20 VAC is
rectified and filtered. The DC voltage thus pro>
duced is stabilized by a fixed>voltage regulator
to +15 VDC. The stabilized DC voltage supplies
the AF amplifier in the control unit. The 15>
VDC voltage regulators contain internal
current limiting facilities and a protection
against excessive heat.
The DC voltage produced from the secondary
voltage of 9.1 VAC by way of rectification and
filtering is fed to an externally adjustable volt>
age regulator as well as to the reset and moni>
toring circuit. The voltage regulator is set to an
output voltage of +5.2 V. The voltage regula>
tor is automatically switched off, as soon as the
output current exceeds the nominal value set
(short>circuit current). Current supply of the
option 'TTY Line Current Source R&S GH!890' is
made via the secondary voltage of 25.6 VAC.
The reset circuit ensures that for switch>off of
the mains voltage all receiver settings are
stored in the processor and for switch>on all
stored receiver settings are again read in. The
monitoring circuit controls the LED MAINS on
the front panel of the control unit via the
signal CM.
The AF signal AFL from the IF / AF processor is
fed via an amplifier and a 600>] transformer to
the interface OUTPUT. The AF level is
adjustable via the variable resistor LINE in the
range between >10 and +10 dBm.
In case the level of the PZG signal is exceeded,
the processor switches an open>collector tran>
sistor. The open collector is connected to the
interface OUTPUT.
The option 'TTY Line Current Source R&S
GH!890' is connected via a cable to the power
supply. The carrier board is connected via EMC
filters and a cable to the interface OUTPUT as
well as via another cable to the RS232C!>!RS485
interface. The connector BCD INTERFACE is
connected via a cable to the optional 'BCD
Interface R&S GC 890'.
The external HF interfaces are connected via
HF cables to the following modules:
External
interface
Module
1/5/10 MHz
IF
1.44 MHz
IF / AF processor or option
'R&S FK 890H1'
not used
Synthesizer
IF / AF processor
HF unit, mod. 03 or option
IF Processor R&S GM 893
IF
0...40 kHz
OPTION
6164.0717.02_01
> 1.20 >
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