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5.S.
5.5.1.
5.5.2.
5.5.3.
Circuit Descri
tion,
E 5002
r3an
Motherboard
The notherboard coticain§ the interconnection be[veen the dif ferent
units and the wiring. The motherbctard also contains the plugs for the
cabinet uiring and the voltage regulators: the 5V regulator. the 12V
regulator supplying the output anplif ier on
302
and the 12V regulator
for the renaining circuits.
On the
301
notherboard the 10 divider for the VC03 loop is located.
1.4 rmz Exciter
The AF input signals are connected t:o the compressor through an in-
put Selector. The microphone and line inputs are open only if the
terminals 4 and 8 are both HIGH. The telex AF input is open only if
terminal 8 is LOW. The tone input is altJays open.
The gain of the compressor is controlled by means of the f ield
e££ect transistor TR2, which functions as a variable enitter resi-
stor for the left hand transistor in IC1. The control voltage is
provided by a rectif ier consisting of the pair of Icl transistors
to the right, which detect the sideband level at the output of the
Crystal filter X1 (or X2). when ceminal 4 ig Low the compressor is
off as the resistance of TR2 is kept at its naximm value.
The compressed audio signal and a I.4 MHz signal £rou tbe carrier
level regulator IC2 are fed to the balanced mixer IC3. The output
is a I.4 rmz double sideband suppressed carrier sigrial that i§
fed through crystal filter X1 (or X2) which removes the upper side-
band (or the lover sideband) and suppresses the carrier Still £urt:her.
The gain of the aplif ier stages following the f ilter i8 controlled
from tertninals 13, 14 and 15 by inserting different eaitter resistors.
In the A3H-rode all terminals are tllen and the gaiti is detemined by
R76. Carrier re-insertion is perfomed by applyit.g the 1.4 rmz sig-
nal I ron the carrier level regulat:or to TR7 via an attetiuator con-
trolled frotn the sane terminals.
The f ilter §hif t is made by means of transistor TR4 cotltrolled by tbe
optional LSD/USE switch on the front panel or the remote control inter-
f ace ,
EE
RE Translator
The 1.4 rmz single sideband signal et`ters the RE translator through
a 1.4 rmz filter. The load resistance of the filter is adjustable
and can be set individually at each band by treans of variable re-
sistors. The signal is converted in the 1.4 to 38 rmz aixer Icl to a
38 mz signal by tnixing the signal with the 36.6 rmz signal from the
36.6 REz VCO. After removing the unwonted mixing products in a 38 mz
crystal filter the Signal is fed to the 38 co 0-30 mz mixer.
5-4
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