AMERITRON AL-1500 Manuel d'instruction - Page 5

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METERING FUNCTIONS

The AL-1500 has two illuminated meters. The Grid Current meter

provides a continuous indication of the 3CX1500/8877 grid

current. This exclusive feature of Ameritron amplifiers indicates

proper amplifier operation better than any other parameter. Do

not exceed 75 mA on this meter during normal operation of this

amplifier. The other meter reads Plate Voltage (HV), Plate

Current (IP), Peak RF Watts (PO) and ALC. These functions are

selected with the Multimeter Switch.

Plate Voltage (HV): Read DC Plate Voltage on the 4000 volt

scale. This scale is 100 volts per division. Normal voltages are

3600 volts no load, 3300 volts full load.

Plate Current (Ip): Read DC Plate Current on the 1000 mA scale.

This scale is 25 mA per division.

Peak RF Watts (PO): Read Peak RF Watts on the 2000 watt

scale. This scale has 50 watt divisions below 1000 watts and 100

watt divisions above 1000 watts.

NOTE:

This circuit uses an emitter follower to charge a

capacitor to the peak envelope voltage detected by the

ALC/Power Board. Accurate peak envelope power readings are

given when the amplifier is connected to a 50 ohm nonreactive

load. If the amplifier is used with a mismatched load, the power

meter will read higher or lower than normal by a ratio up to the

value of the SWR. Potentiometer

The high voltage present on the plate choke and air variable

capacitors attracts dust and dirt out of the air stream. It is

particularly important that the high voltage areas at the bottom of

the plate choke and the insulators on the air variable capacitors be

dust free. These areas should be inspected every few months if

the amplifier is operated in a dusty environment. Unplug the line

cord, and wait about 90 seconds until the power supply capacitors

discharge. Check the HV scale for zero voltage before removing

the cover. Remove the cover. You must first connect a jumper

wire from ground or chassis to the anode connection

TRANSFORMER INSTALLATION

Remove the cover of the amplifier. Remove the small package

that is wrapped around the anode connector. This is the fuse pack

and contains the fuses, fuse caps and the remainder of the chassis

screws. Remove the top 7/16" nuts from the four transformer

mounting bolts inside of the amplifier. Carefully remove the

transformer from its shipping carton.

Place the transformer on the four

because the transformer is heavy. The side with the two high

voltage secondary RED leads must be adjacent to

PERIODIC MAINTENANCE

the tubes.

INSTALLATION

/4-20 mounting bolts. Use care

R5 on the Meter Board (50-01140-1) adjusts the calibration of the

power meter.

ALC: Indicates a relative drive level (average, not PEP) that can

be estimated by dividing the Peak RF Watts scale by 10.

TECHNICAL ASSISTANCE

Technical assistance is available during our normal business

hours on weekdays. The following information is required to

assist you with operational problems:

1. Model and Serial Number

2. Date of purchase and dealer

3. An accurate description of the problem

Meter readings at all stages of the tuning proceedure 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 writ

ten reply.

AMERITRON 116

Willow Road

Starkville, MS 39759

Tel: (662) 323-8211

Fax: (662) 323-6551

NOTE: This is a safety wire that must be installed when

beginning service work. After service is complete, reverse the

procedure to remove the safety wire. Remove the wire from the

anode connection first and then from ground.

Use a soft bristle brush dipped in alcohol to clean areas men-

tioned previously. In the event that cleaning is required at

frequent intervals, place a low restriction air filter material over

the air inlet holes on the left front side of the cabinet near the

filter capacitors. Most hardware stores stock suitable materials

that are used as replacement filters for window air conditioners.

the center panel(see Fig. 1). Now place a 7/16" nut on each bolt

(see Fig. 2). Snug the nuts down manually. Do not tighten with a

ratchet wrench.

Remove the brass

hex nuts and the top flat washer from the

/4"

two 6-32 screws on the rectifier board (see Fig. 1). Install the

RED lead ring terminals on the screws and replace the flat

washers and

hex nuts. Position the wires so that the black

/4"

insulated areas are at least

objects. Now tighten the

/4"

from each other and any metal

/4"

hex nuts.