Instruction manual

AL-800 Instruction Manual
23
2.) Adjust the
"ALC SET"
control on the front panel and the rear panel
"ALC Limit"
potentiometer to their full counter-clockwise positions.
3.) Apply full exciter drive power, and adjust the rear panel
"ALC Limit"
potentiometer
clockwise (rear view) until the amplifier's ALC output voltage meter (multimeter
"ALC"
position) indicates 6 to 10 volts. As an alternative, the potentiometer can be adjusted clockwise
until the RF output power reaches 300-500 watts.
"ALC SET" Control
Proper adjustment of the front panel
"ALC SET"
control accomplishes the following:
1. The exciter's power is limited to a value that will produce a fixed amount of grid current in the
amplifier. The front panel
"ALC SET"
control determines the maximum grid current that can
be produced.
2. The
"LOAD"
control setting will determine the maximum plate current and output power for a
given grid current. Never exceed .8 A of short duty cycle (or .6 A of long duty cycle) plate
current. Never exceed 25 mA of operating grid current.
3. For normal SSB operation, the exciter power should be reduced until the ALC voltage
(measured in the ALC multimeter position) flicks upwards on occasional voice peaks. This
will produce the best audio quality. The drive can be increased for DX or weak signal SSB
operation until the ALC steadily registers voltage.
Also see the ALC section on page 6, and the
Multimeter
section on page 9.
Tuning
Follow the instructions below in numerical order. Proper tuning will produce excellent output
power, a clean signal, and good tube life. If the various meter readings are different than indicated
in the text, check the external amplifier connections. Consult the manual for the exciter if
necessary.
WARNING:
The transformer must be wired correctly for your line voltage. This amplifier is normally
shipped wired for standard 120 Vac operation. See the
Transformer Connections
section on page 15 for details.
Tuning Procedure
Important Note:
This amplifier contains an electronic grid protection circuit to prevent control-grid
damage. This amplifier will quit operating and the
"OL"
LED will illuminate if the grid dissipation
exceeds a safe pre-set limit. The overload circuit responds much faster than the grid current meter.
The overload circuit will respond to excessive grid current before the operator can observe the