5
DX-3 LINEAR AMPLIFIER
Serial No
…………
OPERATING MANUAL
April 2005
CAUTION
1 GENERAL DESCRIPTION
The Emtron DX-3 Linear Amplifier is a 3000 watt average output power, for the 160m through 10m amateur bands
(9 bands),
housed in a desk-top cabinet with self-contained power supply and cooling system.
It utilises a single high performance tetrode, type GU78B (4CX3000A),
a ceramic metal tube with a plate dissipation of 2500W.
The tube is air cooled by a commercial grade forced air turbine blower system under the chassis and a computer type fan sucking
air and positioned above the tube. Both fans operate at two speeds, controlled by a temperature sensor.
Tetrodes offer exceptionally stable operation and levels of quality performance far exceeding that which can be expected from
triodes. The harmonic output and intermodulation distortion achieved with this tube are exceptionally low. This is especially
important when dealing with a high output power.
The Emtron DX-3 is supplied as standard with a host of features including solid state metering, comprehensive
protection systems
and very long duty cycle.
In addition, a unique Emtron QSK module allows for extremely rapid switching times between transmit and receive, with
consequent advantages when using CW or the digital modes. QSK is standard in all DX-3 amplifiers.
Operation of the DX-3 is greatly simplified by the absence of meter switching, mechanical display and front panel level setting
controls. The front panel moving LED display systems indicate simultaneously: the output forward and reverse power, screen grid
current (positive and negative), the plate voltage and the plate current, while 5 single LED’s indicate: Ready, Overdrive warning,
High SWR cut-off indication, On Air and Fault.
The Emtron Electronic Bias Switch (EBS) automatically switches the standing current (typically 0.75 A) off when there is no
modulation. This reduces the average tube dissipation.
On initial switch on, the unique Emtron "soft start" circuitry ensures that no damaging AC surge currents are generated.
Professional, fine output tuning adjustment is possible, due to the 6: 1 reduction mechanism fitted.
The DX-3 has been designed for 100% safe operation and long life. Interlocking
sensing circuitry constantly monitors conditions inside the amplifier. It must be
noted however, that the high voltages present inside the DX-3 are EXTREMELY
DANGEROUS. Do not remove the top cover under any circumstances if any leads
are still plugged into the rear of the amplifier
-
especially if the AC lead is plugged in
the power outlet.
Before any component inside the high voltage, power
supply or output section is touched, unplug all rear panel leads and
allow at
least 5 minutes of 'off time'.
After that, you should further check this
by momentarily shorting the tube anode to the chassis with a suitable insulated lead.
