AMERITRON ALS-600PS - User Manual

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Table of Contents

Amplifier Features ...........................................................................................................3

Power Supply Features ....................................................................................................4

ALS-600PS ..........................................................................................................4

ALS-600SPS ........................................................................................................4

ALS-600PS and ALS-600SPS.............................................................................4

General Information.........................................................................................................4

Amplifier..............................................................................................................4

Power Supply.......................................................................................................5

Export Modifications ...........................................................................................5

Technical Assistance............................................................................................5

Amplifier Circuitry ..........................................................................................................6

Wattmeter Circuits...............................................................................................6

ALC (Automatic Level Control)..........................................................................6

Thermal Overload ................................................................................................7

Load Fault Indicator.............................................................................................7

SWR Considerations............................................................................................8

Power Supply Circuitry (ALS-600PS) ............................................................................9

Line Voltage Modifications .................................................................................9

High Voltage Section...........................................................................................10

Primary Circuit ....................................................................................................10

Low Voltage Circuits...........................................................................................10

Switching Power Supply Circuitry (ALS-600SPS) .........................................................10

Line Voltage ........................................................................................................10

High Voltage Section...........................................................................................11

Primary Circuit ....................................................................................................11

Low Voltage Circuits...........................................................................................12

Installation .......................................................................................................................12

Amplifier Location...............................................................................................12

Power Supply Location........................................................................................12

Grounding ............................................................................................................12

Power Requirements ............................................................................................13

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The Ameritron ALS-600 is a solid-state linear amplifier designed for amateur radio use, providing a nominal output of 600 watts. It utilizes four rugged RF power FET devices in a double-ended push-pull parallel output configuration, operating at 50 volts. The amplifier offers continuous frequency coverage from 1.5 MHz through 22 MHz without requiring tuning adjustments. For export models or with a valid amateur license, modifications are available to extend operation up to 30 MHz.

Key Features:

No Tune Operation: A simple one-knob selector switch allows operation across frequencies between 1.5 and 22 MHz without manual tuning.
ALC Protection: The amplifier monitors output and reflected power to control the exciter ALC voltage, helping prevent damage. A front panel ALC control allows easy adjustment of the ALC threshold for power output control.
Load Error Protection: The PA load impedance is monitored, and the amplifier is bypassed if the band switch or external load is incorrect.
Illuminated Power/SWR Meter: Features a cross-needle peak reading RF power meter with accurate directional coupler and peak storage circuits, providing simultaneous forward and reflected peak power readings and indicating load SWR.
Operate/Standby Switch: Allows bypassing the amplifier for "barefoot" operation without cycling the main power switch.
Transmit and ALC Indicator LEDs: Front panel LEDs indicate amplifier keying by the exciter and ALC output voltage.
12 Volt Auxiliary Jack: Supplies +12V for low-current accessories.
Thermal Overload Protection: Disables the transmit relay if excessive heatsink temperatures are reached, automatically resetting when temperatures return to a safe value.
Compact Size: Weighs only 12.5 pounds and measures 6"H x 9.5"W x 12"D.

Technical Specifications (Amplifier):

Output Power: 600 watts nominal.
Frequency Coverage: 1.5 MHz to 22 MHz (extendable to 30 MHz with modification).
Drive Power: Less than 100 watts for full output.
Harmonic Suppression: Broad band 5-pole low pass filters provide suppression exceeding FCC requirements.
ALC System: Functions with negative voltage ALC control systems requiring less than 10 volts.
Load Fault Indicator: Lights up and prevents transmit mode if band switch is incorrect, SWR is excessive, or output power is excessive.

Power Supply Options:

The ALS-600 can be paired with two types of power supplies:

ALS-600PS (Standard Power Supply):
- Multi-voltage Heavy Duty Transformer: A "buck-boost" winding allows compensation for up to six different power line voltages (centered on 115V and 230V) to maintain optimum voltages.
- Choke Input Filtering: Provides a low power factor, reducing peak currents and improving voltage regulation.
- Power Line Voltage Options: Operates from 100-130 Vac or 210-240 Vac (50/60 Hz). Factory wired for 120V.
- Output: Supplies approximately 50 volts at a load current of 20 amperes, plus three DC voltages for the amplifier unit.
- Primary Circuit: Includes a 10 ohm resistor (R602) to limit line current during filter capacitor charge time, bypassed by a relay (RLY601) when the 14V control line approaches full voltage. Fused by two 15A (100V), 12A (110-120V), or 8A (220-240V) fuses.
- High Voltage Section: Uses a full-wave bridge rectifier, a large swinging choke (T1), and a high-quality computer-grade capacitor (C5) for DC filtering. Two 100 ohm resistors (R5,6) absorb bleeder current.
- Low Voltage Circuits: Supplies +14V at 2A max for control, lights, bias voltage regulator, and the Bias/Wattmeter board. Protected by a 2A fuse (F602). A separate half-wave rectifier supplies low current for ALC circuitry, protected by a 10 ohm 1/4W resistor (R601).
- Magnetic Fields: The choke in the ALS-600PS emits strong magnetic fields. Avoid placing magnetic tapes, computer disks, or other magnetic-sensitive devices within 18 inches.
ALS-600SPS (Lightweight Switching Power Supply):
- Lightweight: Weighs 3 times less than the choke-type power supply, ideal for travel.
- Hash Free: Specially designed switching and filter circuit ensures hash-free operation.
- Simple Power Line Voltage Options: Safely operates from 90-135 Vac (120V setting) or 185-260 Vac (240V setting). Factory wired for 120V.
- Output: Supplies 50 volts DC at 25 amperes, along with 12 volts positive and negative at low current for control and bias circuits.
- High Voltage Section: Uses a high-current switching circuit with superior filtering to produce a high-current DC voltage, protected by F1 on the printed circuit board.
- Primary Circuit: A 10 ohm resistor limits line current during start-up, bypassed by a relay when the -14V control line approaches full voltage. Protected by a 2A slow-blow fuse. Primary circuits are fused by two fuses on the back panel (15A for 120V, 8A for 240V).
- Low Voltage Circuits: Supplies +14V at 2A max for control, lights, bias voltage regulator, and the Bias/Wattmeter board. A separate -12V supply operates the inrush relay and ALC circuit.

General Operation:

SSB Operation: Normally has no transmit time limits. Reflected power should be kept below 50 watts peak. Linear operation is best maintained with an oscilloscope to observe for clipping. The "ALC SET" control on the front panel should be adjusted until the amplifier's RF output meter just begins to drop when the exciter is at full power (not exceeding 100 watts peak) with normal voice modulation.
CW Operation: Exciter output should be restricted to limit the amplifier to 500 watts output or 50 watts reflected power. The ALC should only barely light or flash.
RTTY, FM, and High Duty Cycle Operation: The "Normal/RTTY" switch on the power supply should be in the RTTY position, limiting voltage to about 42Vdc (350 watts output). This allows 10-minute key-down operation with 50% duty cycle. Output power can be reduced to assist cooling (less than 200 watts output or 25 watts reflected power). Fan speed can be increased for extended high duty cycle operation (e.g., 80 CFM fan for 500W RTTY with 2 min on/1 min off).
AM Operation: Carrier power is restricted to one-fourth of the peak envelope output power (around 150 watts). The "ALC SET" control should be in the maximum clockwise position.

Installation and Interconnections:

Amplifier Location: Avoid excessively warm locations, ensuring free air circulation. Do not obstruct air inlets (rear) and outlets (lower right side).
Power Supply Location: Keep away from magnetic-sensitive devices. Do not obstruct air inlets (rear) and outlets (upper right corner).
Grounding: Connect the amplifier's ground stud to a good earth and RF ground using the heaviest and shortest possible connections (copper flashing or foil recommended). Do not remove or defeat the electrical safety ground connection on the power supply plug.
Power Requirements: The ALS-600 is not designed for 12 Vdc operation. The power supply output voltage should be kept below 65 Vdc at no load for maximum component life.
Connections:
1. Exciter RF output to ALS-600 RF IN (SO-239) with a 50 ohm cable (100W capable).
2. Station antenna system to ALS-600 RF OUT (SO-239) with 50 ohm coax (600W capable).
3. ALS-600 RELAY jack to transceiver/transmitter amplifier relay terminal using shielded audio type cable (male phono RCA).
4. ALS-600 GND stud to station ground buss.
5. ALS-600 ALC jack to exciter ALC terminals with shielded audio type cable (male phono RCA).
6. Power connector from ALS-600PS/SPS to multi-pin male connector on ALS-600 rear chassis.
7. 12V connector can supply 12-14 Vdc (<200 mA) for accessories.

Maintenance:

Periodic Maintenance: Due to the lack of extremely high voltages, periodic maintenance primarily involves monitoring dirt and dust accumulation. Blow out dust with moderate air pressure if noticeable.
Fan Inspection: Inspect the fan area every few months in dusty environments.
Cleaning: Use a soft bristled brush and a small amount of alcohol for stubborn dust, avoiding relay contacts or switches.
Safety: Never remove the cover of the amplifier or power supply while plugged into an electrical outlet.