AMERITRON AL-572, Instruction Manual

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Ameritron AL-572 Instruction Manual
12
WARNING: NEVER drive this amplifier with more than 100 watts of
short term average envelope power. NEVER allow the
grid current to exceed 200 mA under any operating
condition.
Maximum power output normally will occur with approximately 125 mA of grid current on CW,
or less than 45 mA of grid current (125 mA instantaneous peak) on SSB (two-tone test). Grid
dissipation, with 125 mA of grid current and 70 watts of drive, is approximately ten watts.
If you wish to add control grid protection to the AL-572, always remember fuses and resistors are
too slow and unpredictable to adequately protect tubes. While grid protection is generally not
required with tubes like the 572B, Ameritron does offer an optional fast-acting electronic circuit
that will rapidly disable the amplifier if excessive grid current occurs. This circuit also reduces or
eliminates the chance of tank component damage from incorrect loading or load failure. The part
number of this add on board is 50-0080-5.
The continuous commercial plate current rating of each 572B is 275 mA. For maximum tube life,
total plate current should be maintained below 1100 mA on CW and other "steady" carrier
modes. Brief periods of plate current exceeding 1100 mA will not cause loss of emission or
shorten the amateur service life of the tubes in this amplifier.
The application of filament voltage causes thermal stresses from rapid and uneven temperature
changes. Avoiding needless cycling of the filament can prevent premature failure or unnecessary
stress in the tube's filament.
An accumulation of gas (or stray debris) in the tube can cause the tube to arc between the anode
and the other elements of the tube. The resulting "gas arc" will generally manifest itself as a loud
"pop" when the amplifier is first turned on. A "gas arc" will often damage diode D117 on the
negative rail of the filter capacitor bank and open the fuses in the amplifier. If this problem
occurs frequently, the tube should be tested or replaced. The use of low quality tubes, tubes that
have been stored for extended periods, or abused tubes increase likelihood of a "gas arc".
Ameritron recommends using only current code date 572B tubes.
EXPORT MODIFICATIONS
A simple modification will allow operation on frequencies above 15 meters. Instructions for this
modification are available by sending a written request for "Export Modification Instructions"
along with a copy of a valid amateur license. There is no charge for this information. Export
models are shipped with this modification installed and have an "X" or "Y" following the serial
number.
Address: Ameritron
116 Willow Road
Starkville, MS 39759
FAX: (662) 323-6551