AMERITRON AL-572, Instruction Manual

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Ameritron AL-572 Instruction Manual
11
ALC
The multimeter measures the output voltage of the ALC detector when in the ALC position. The
full scale ALC reading is 35 volts and is read directly from the ALC/ HV scale. The meter
should flick upwards occasionally during normal ALC action.
ALC SET
The multimeter measures the approximate grid current that will produce ALC activity when the
meter switch is in the ALC SET position. One zero must be added to the reading on the ALC/
HV scale for this function. For example, ALC action will begin at approximately 150 mA of grid
current (typically between 120 mA and 180 mA) when the "ALC SET" control is adjusted until
the meter reads "15."
TUBE LIFE
The 572B is a reasonably rugged tube. The likelihood of premature failure can be reduced by
avoiding excessive tube element temperatures. Element temperature is a function of the duration
and the amount of power dissipated. The elements in the 572B have very good immunity to short
term overload failures.
The anode in the 572B can tolerate large dissipation overloads for short periods of time due to
the thermal mass of the anode. Anode color is a good indication of incorrect tube operation. The
anode in the 572B is designed to operate at moderate temperatures. These temperatures normally
do NOT produce anode color.
The graphite anode is coated or mixed with a "getter" material that de-gasses the tube. This
material is activated by normal operating anode temperatures. The likelihood of gas failure (tube
arcing) is reduced by operating the 572B tubes on a regular basis at normal ratings.
Care must be taken to avoid exceeding the temperature ratings of the tube's glass-to-metal seals.
The life of the tubes in this amplifier may be prolonged if tuning periods are kept short and a
brief "cool-down" periods are provided between tuning periods. Try to allow a one or two minute
non-transmitting "cool-down" period after lengthy CW or RTTY transmissions before shutting
off the AC power switch.
Incorrect operation is most likely to damage the tube's control grid or anode. Applying full drive
power for several seconds with excessively "light" loading (indicated by abnormally high grid
current) can cause control grid damage. Several seconds of high drive power operation with
improper tuning or excessively "heavy" loading (indicated by low output power in concert with
normal plate current) can melt or damage the anode. These undesirable operating conditions can
be avoided by following the tuning procedures in this manual.
In the AL-572, a grid current of 200 mA (at 100 watts of drive) produces rated grid dissipation.
For maximum tube life, the short-term average grid current and drive power should always be
kept below these values.