QRO Technologies HF-2500DX Instruction Manual page 14

5. Turn the load control counterclockwise, and the screen current should start to fall. Continue
to turn the load control counterclockwise until the screen current reads 25 mA.
6. Turn the tune control clockwise until the screen current reads between 50 - 100 mA. Again, turn
the load control counterclockwise until the screen current reads 25 mA. Keep repeating this
procedure until you see the screen current's maximum peak occurs somewhere on the
screen current scale. Then, adjust the loading control counterclockwise (reduce) or
clockwise (increase) until the screen current reads approximately 50 mA. You are now tuned
to resonance for the input power applied. Again, on 160 meters and 80 meters the screen current
may drift downward the longer you keep the amplifier keyed. We are not concerned about an
absolute steady state of screen current on these bands. Simply adjust the tune control for a on
scale screen current peak, and adjust the load control for a 50 mA reading.
7. Increase your dive power in 20 watt increments. With each increment repeat the procedure in
item six until you have your desired level of power output.
REMEMBER THIS AMPLIFIER DOES NOT REQUIRE MUCH DRIVE POWER. SO
START WITH LOW DRIVE POWER, AND THEN TUNE TO RESONANCE AS
OUTLINED ABOVE. OTHERWISE, ARCING MAY OCCUR INSIDE YOUR
AMPLIFIER.
NEVER RUN YOUR AMPLIFIER FOR ANY SUSTAINED PERIOD WITH A
SCREEN CURRENT READING GREATER THAN 50 MILLIAMPERES. IF YOU
DO, DAMAGE AND FAILURE OF THE 4CX800A TETRODES WILL RESULT, AND
THEY WILL NOT BE COVERED BY SVETLANA'S WARRANTY!
To facilitate your initial tune up, we have included a tune up chart. These settings and readings
are into a 50 ohm dummy load. Your actual reading may vary do to any reactance in your
antenna. Record your settings for future reference. You can control the power level of your voice
peaks on SSB by advancing the ALC Control clockwise assuming you have the ALC line
connected between your transceiver and amplifier.
TUNE-UP TABLE (50 Ohm Resistive Load) with 10 ohms
Frequency Power
(MHZ) Input
1.80
1.90
3.60
3.90
7.20
14.20
of Cathode resistance.
Tune Load Power Screen
Output Current
(IP) Plate
Current
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