Service Manual Part 1

8"  
  
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The nominal supply voltage of the T2000 is 13.8VDC but satisfactory operation is possi-
ble from supply voltages of between 10.8 and 16V. Power for the radio is switched via
the volume control and switch on the control head.
Overvoltage protection is provided in the form of an 18V zener diode. This will sup-
press transient spikes but prolonged overvoltage will cause the device to fail short cir-
cuit.
On the RF PCB, two regulated power supply rails of 8V and 5V are provided as well as
a 30V supply from an inverter. The 30V supply is used to feed the synthesiser loop filter
and the receiver front end tuning. A switched 8V line is used to enable the transmitter
and disable the receiver.
13.8V is applied directly to the RF and audio power amplifiers, with the audio power
amplifier rated for a standard output of 4Wrms into 4Ω, at a nominal supply voltage of
13.8V.
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The TCXO/Tx audio PCB provides the temperature compensated 12.8MHz reference
frequency for the synthesiser and a times-three multiplier in the receiver. The PCB also
contains the Tx audio limiter, deviation level potentiometer and low pass filter. The
TCXO fine frequency adjustment is provided by a ten turn potentiometer. Narrow or
wide band deviation and TCXO frequency stability with temperature are determined
solely by this PCB.
       