AMERITRON AL-80B Specifications download pdf (Page 3)

GENERAL INFORMATION

SAFETY INTERLOCK

The interlock switch closes to allow AC line voltage to reach the

power transformer as long as the AL-811's top cover is in place.

When the top cover is removed, the interlock opens and

disconnects the line voltage. This does not discharge the bank

of power supply filter capacitors. Be sure to allow the filter

capacitors to discharge before you touch anything inside the

amplifier. You can select the High Voltage function of the

Multimeter to check the high voltage potential.

WARNING:

never remove the cover of this amplifier with the unit

plugged into the power line.

DRIVING POWER

This amplifier is designed to operate at full ratings when it is

driven by an that has aproximately 70 watts of RF output. You

can use an exciter that has lower output power, but the

amplifier's output may be less. If you use an exciter that delivers

more than 70 watts, carefully adjust the driving power to avoid

"over drive" and the creation of spurious signals, which create

needless interference to other operators. We highly recommend

that you use a monitor scope for continuous output monitoring.

The display on an oscilloscope is the best readily available way

of determining the amplitude of the voice peaks which, if

excessive, can cause "flat topping" and splatter.

IMPORTANT: In no case should you advance the power

output control of your exciter beyond the point where the

amplifier's power output indication ceases to increase.

Nonlinear operation may occur if you turn the control past

this point.

FILAMENT SUPPLY

The filament circuit of this amplifier satisfies all requirements of

the tube manufacturer related to tube performance and life.

Inrush current is controlled by the transformer internal resistance

and impedance, filament choke resistance and filament wiring

resistance. To insure maximum life of the tube never replace

any circuit components or wiring with substitute parts.

ALC CIRCUIT

The ALC circuit converts a portion of the RF drive voltage at

the exciter end of the tuned input circuit to a negative going

control voltage. This voltage should be used to limit the exciter

drive to safe drive levels for the

AL-811 for exciters that

develop more than

70 watts of output power.

A capacitive divider consisting of C27 and C28 is used to reduce

the RF voltage and drive a rectifier circuit consisting of D17 and

D18. The resulting voltage is filtered by C29 and R12 and

applied to the ALC potentiometer R14. R13 provides RF and

DC isolation for the ALC jack. The DC isolation prevents

loading of the exciter ALC input line by the ALC potentiometer.

The ALC circuit can be adjusted by loading the AL-811 slightly

beyond the recommended maximum values with the ALC line

disconnected. The ALC line can then be connected and the

ALC control on the amplifier adjusted to a point just before the

drive begins to decrease.

NOTE:

The primary use of the ALC function is the prevention

of excessive drive levels. This circuit will not prevent small

changes in output power from occurring on different bands.

Destructive levels of drive power are those above 100 watts

under most conditions. Slight changes may occur in maximum

output power on different frequencies with the ALC connected.

A compromise in ALC adjustment may be necessary to achieve

acceptable performance on all bands.

PLATE SUPPLY

The power supply in this amplifier uses a combination plate,

filament and control transformer. A buck boost winding is

provided to allow the user to compensate for low, medium or

high power line voltage. This amplifier is normally supplied

wired for the highest power line voltage setting. Never change

this setting unless you are positive that performance is suffering

due to low filament and plate voltages. The life of components

will be shortened drastically if the high voltage exceeds 1800

volts at rest. The diagram on page 4 shows proper wiring for

each voltage.

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 and have an "X" following the serial number.

Standard frequency coverages are indicated in the chart on page

TECHNICAL ASSISTANCE

Technical assistance is available during our normal business

hours on weekdays. The following information is required to

assist you with operational problems:

•

Model and Serial Number;

•

Date of purchase and dealer;

•

An accurate description of the problem;

Meter readings at all stages of the tuning procedure are very

important along with a complete description of the other

equipment used with our product.

Written assistance is also available. Due to time delays in

processing mail, please allow at least three weeks for a written

reply.

AMERITRON

116 Willow Road

Starkville, MS 39759

Telephone: (662) 323-8211

FAX: (662) 323-6551

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AMERITRON AL-80B Specifications Page 3

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