AMERITRON ALS-600 Operation manual
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
Interconnections...............................................................................................................13
Operation .........................................................................................................................15
SSB Operation .....................................................................................................15
CW Operation ......................................................................................................16
RTTY, FM and Other High Duty Cycle Operation .............................................16
AM Operation ......................................................................................................16
Drive Power Requirements..................................................................................17
Periodic Maintenance ..........................................................................................18
ALS-600 Parts Lists & Schematics .................................................................................19
Meter/ALC Board ................................................................................................19
PA Board..............................................................................................................21
Output Filter Board..............................................................................................22
LED Board ...........................................................................................................24
SWR Detect Board...............................................................................................25
ALS-600 Chassis Components ............................................................................26
ALS-600PS Parts Lists & Schematics .............................................................................27
Power Supply Board ............................................................................................27
ALS-600PS Chassis Components........................................................................28
ALS-600SPS Wiring Diagram.........................................................................................29
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AMPLIFIER FEATURES
Rugged devices. The ALS-600 uses four rugged RF power FET
Fast warm-up time. The ALS-600 has no vacuum tubes to warm
No tune operation. Tuning adjustments are not necessary. A simple one knob selector
switch permits operation on frequencies between 1.5 and 22 MHz.
ALC protection. The output and reflected powers are monitored and control the exciter
ALC voltage. This helps prevent damage to the amplifier.
Front panel ALC control. This unique Ameritron feature allows easy front panel
adjustment of the ALC threshold to control power output.
Load Error Protection. The PA load impedance is monitored and the amplifier is
bypassed if the band switch or the external load is incorrect.
Illuminated Power/SWR meter. The ALS-600 has an illuminated cross-needle peak
reading RF power meter. Accurate directional coupler and peak storage circuits give
simultaneous forward and reflected peak power readings and also indicates load SWR.
Operate/Standby switch. This switch allows the amplifier to be by-passed for "barefoot"
operation without turning the main power switch off and on.
Transmit and ALC Indicator LED's. Front panel LED's provide an indication of
amplifier keying by the exciter during operation and ALC output voltage.
12 volt auxiliary jack. This jack supplies +12v to operate low current accessories.
Thermal Overload Protection. The transmit relay in the amplifier is disabled if
excessive heatsink temperatures are reached.
Compact size. The ALS-600 weighs only 12.5 pounds and measures 6"H x 9.5"W x
12"D.
3
POWER SUPPLY FEATURES
ALS-600PS
Multi-voltage heavy duty transformer. A unique "buck-boost" winding allows
compensation for up to six different power line voltages centered on 115 and 230 volts.
This versatile Ameritron feature maintains optimum voltages on the amplifier
components for maximum performance and life.
Choke input filtering. The ALS-600PS standard power supply uses an input choke to
provide a low power factor to the power lines. This reduces the peak currents drawn from
the line and improves the voltage regulation of the supply.
ALS-600SPS
Light weight. The ALS-600SPS is a light weight switching power supply to use with the
ALS-600 amplifier. The switching supply weighs 3 times less than the choke type power
supply. The ALS-600 amplifier with the switching power supply is ideal for travel.
Hash free. The specially designed switching and filter circuit makes the power supply
hash free.
Simple power line voltage options. The power supply will safely operate from 90-135
Vac in the 120 setting and 185-260 in the 240 Vac setting.
ALS-600PS and ALS-600SPS
Step-start circuit. This circuit uses a relay and resistor to limit the inrush current to the
power supply. This circuit extends the life of the power supply components.
Current and output voltage metering. An illuminated cross needle meter monitors the
output voltage and current of the 50 volt output line.
GENERAL INFORMATION
Amplifier
The Ameritron ALS-600 is a 600 nominal watt output, solid state, linear amplifier using
state-of-the-art, high voltage, RF TMOS FET devices in the power output section. The
ALS-600 provides continuous frequency coverage from 1.5 through 22 MHz with no
tuning adjustments. Broad band 5 pole low pass filters provide output harmonic
suppression in excess of all FCC requirements. Export modifications are available to
extend operation up to 30 MHz with a copy of a valid amateur license.
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The ALS-600 uses four MRF-150 FET's operating at 50 volts in a double ended pushpull parallel output configuration. High quality RF components combine with an
accurate peak detecting directional coupler, front panel adjustable ALC circuit with
automatic SWR foldback, and one switch frequency selection to make this one of the
easiest to operate amplifiers available. The matching power supply, ALS-600PS or ALS600SPS, is shipped factory wired for 120 volt, 50/60 Hz power mains and is easily
converted to other supply voltages between 100 and 240 volts.
Power Supply
The ALS-600PS power supply is designed to power the ALS-600 amplifier from 50 to 60
hertz AC power mains that range from 100 to 130 and 210 to 240 volts. The ALS600SPS has a terminal strip where the AC voltages can be 120 or 240 50/60 Hz. The
power supply will safely operate from 90-135 Vac in the 120 setting and 185-260 in the
240 Vac setting. All ALS-600PS/ALS-600SPS supplies are wired for standard 120 volt
systems and are shipped with a NEMA 5-15P three wire plug.
These supplies will safely provide the power required to operate the ALS-600 in typical
continuous amateur service at 600 watt output levels. The ALS-600PS/SPS power
supply supplies the three DC voltages required by the amplifier unit. The high voltage
section supplies approximately 50 volts at a load current of 20 amperes.
Export Modifications
A simple modification will allow operation on frequencies up to 30 MHz. A parts kit to
make this modification is available by sending a written request for the export
modification kit, item no. MOD-10MB, along with a copy of your valid amateur license
to Ameritron. There is charge for this kit. Export models are shipped with this
modification installed. The ALS-600(S)Y is the export for 115-130vac operation and the
ALS-600(S)X is the export model for 220-240 operation.
Technical Assistance
Technical assistance is available by calling (662) 323-8211 during our normal business
hours (8:00 to 4:30 Central Time on weekdays) for questions that are not answered by the
technical information sheets. We are happy to provide personal assistance if you need
more detailed help. Please have the following information available so that we can
accurately assist you with any problems:
1. The model and serial number of the unit.
2. The date of purchase and the dealer.
3. A brief description of the station equipment and antenna system.
4. A complete description of the problem along with any abnormal meter readings.
Written assistance is also available. Due to time delays in processing mail, please allow
at least three weeks for a written reply. See warranty page for mailing address.
5
AMERITRON
116 Willow Road
Starkville, MS 39759
Tel: (662) 323-8211
Fax: (662) 323-6551
AMPLIFIER CIRCUITRY
Wattmeter Circuits
The BIAS/WM/ALC board contains the peak power detector circuits. The rear panel
directional coupler connects to IC101D/C. IC101D/C drives Q101/102 to charge
C103/106 to the peak voltage from the directional coupler. C103/106 is lightly loaded by
IC101A/B and R103/107. This allows enough "hang" time for the meter to accurately
indicate peak power levels.
Accurate forward peak power reading are obtained under mismatched load conditions
when the reflected power is deducted from the forward power readings.
The average and peak envelope power values are EQUAL on CW, FSK and FM (modes
that do not have amplitude changes in the carrier). The average power level of voice or
other complex waveform signals has NO SET RATIO of peak to average power.
ALC (Automatic Level Control)
The ALC circuit functions by using a comparator (IC103A) to reduce the exciter drive
power if the output power of the ALS-600 exceeds a preset value. The ALC circuit also
reduces the drive power if the SWR increases while operating with the ALC controlling
the amplifier output power level. The ALS-600 ALC output should be connected to the
proper exciter external ALC connection point with a shielded audio type cable. Consult
the exciter manual for the proper exciter connection details.
Operation at high audio gain levels on SSB with ALC has the same effect as an RF
speech compressor. RF compression increases SSB "talk power". Background noise
pickup also increases when the exciter gain is operated at high levels to increase
compression. Audio distortion does not normally occur with this type of speech
processing if the ALC circuit in the exciter is properly designed.
Do not attempt to limit the CW power more than a few percent solely with the amplifier
ALC circuit. Using the amplifier ALC to reduce CW power levels may result in pumping
of the output power during dots and dashes. The "ALC SET" control will be correctly
adjusted when the "ALC" LED gives a small flash while transmitting on CW. This can
be accomplished by adjusting the "ALC SET" control on the front panel so that the
"ALC" LED just barely lights when the desired power level (below 400 watts) is reached
with a steady carrier.
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The ALC circuit can be used to reduce power by any amount on constant amplitude
carrier modes such as RTTY or FM. The ALC cannot cause modulation distortion or
pumping on these modes.
Never use the ALC to control the level of AM transmissions. Using the amplifier's ALC
circuit to control AM output power will cause pumping of carrier amplitude on AM
transmissions during modulation.
The ALC indicator on the front panel of the ALS-600 is driven by comparitor IC3B.
Resistors R24 and R25 set the turn-on level of the front panel "ALC" indicator. Factory
selected resistor values cause the "ALC" LED to illuminate as soon as negative ALC
voltage begins to appear at the ALC output jack.
If the exciter used with this amplifier does not "fold back" until appreciable ALC voltage
is developed, the "ALC" LED may become fully lit even under operating conditions that
are producing very light ALC action.
Caution: There are no industry standards for transceiver or exciter ALC input voltage
levels, input resistance, or attack and decay times. While every attempt has
been made to make the ALC circuit in this amplifier compatible with various
exciters, the exact operation of the ALC circuit will vary with the exciters
response to external ALC control voltages. This ALC circuit will function
with negative voltage ALC control systems requiring less than 10 volts.
Thermal Overload
The ALS-600 has a built in thermal cut-out that by-passes the amplifier if excessive heat
sink temperature is produced. This circuit minimizes the risk of excessive temperature
damage to the FET's and other components.
If the amplifier "XMT" LED remains lit while the amplifier suddenly stops transmitting
the thermal overload has probably tripped. If the thermal overload has tripped full exciter
power will appear on the RF output meter.
The thermal overload resets automatically and all amplifier functions are restored when
heat sink temperature returns to a safe value. The usual cause of thermal overload is
excessive heat buildup during a transmission period longer than a few minutes. To
correct this condition be sure that the power level and duty cycle limits are being
followed, that the SWR is as low as possible, and that the cooling is not being hampered
by air flow restriction or excessive inlet air temperatures.
Load Fault Indicator
The "LOAD FAULT" LED indicator will light and the amplifier will not go into a
transmit mode if the band switch is set on the wrong frequency range, if the load SWR is
excessive, or if the output power level is excessive.
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To reset a "LOAD FAULT" indication:
1. Determine and correct the cause of the problem.
2. Place the amplifier "STANDBY-OPERATE" switch to "STANDBY" and then
back to "OPERATE".
The load fault detector circuit is located on the output filter board and measures the
reflected power presented by the output filter network and the SWR directional coupler.
The sensitivity of the circuit is adjusted by R304 and R601. C324 is a factory adjustment
that controls the impedance of the detector circuit. This capacitor is adjusted for
minimum detector voltage on 7 MHz with a 50 ohm load. Do not adjust any components
in this circuit without consulting the factory.
SWR Considerations
A high SWR (Standing Wave Ratio) causes higher voltages and/or currents to appear at
the output connector of the amplifier. This problem occurs with all amplifiers regardless
of whether tubes or semiconductors are used in the output stage.
Vacuum tube amplifiers have the reputation of handling high SWR's quite well. This
reputation probably exists for two reasons. First, most vacuum tube amplifiers use
adjustable output networks. Second, nearly all vacuum tubes handle momentary
overloads extremely well.
In tube amplifiers that have tunable Pi or Pi-L networks, the only components affected by
a high load SWR are those between the loading adjustment capacitor and the output
connector. When the output network is properly adjusted the SWR cannot affect tube
life.
The TMOS FET devices used in the ALS-600 have nearly the same momentary overload
tolerance as vacuum tubes. The low pass output network in the ALS-600 is much
broader in bandwidth and less sensitive to load changes than the networks used in tube
type amplifiers.
This makes the ALS-600 much less sensitive to frequency and SWR changes than the
best "no- tune" tube amplifiers but not as good as adjustable pi-networks. The ALS-600's
multiple section output network and push-pull output configuration offers much better
harmonic suppression than most tube amplifiers regardless of load SWR.
The only danger presented by a high SWR in this amplifier is that the current and power
dissipation in the output devices may exceed safe limits. Lengthy operation with high
SWR at high power levels can result in heat damage and failure of the FET devices. If
the reflected power exceeds 50 watts the power level should be reduced until the reflected
power indicated on the internal meter is 50 watts or less on peaks. At approximately 75
watts of reflected power the internal safety circuitry will disable the amplifier.
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ALS-600PS POWER SUPPLY CIRCUITRY (ALS-600PS)
Line Voltage Modifications
The line input voltage of the ALS-600PS can be changed by moving jumper wires on the
power supply printed circuit board to new locations. The ALS-600PS is wired for
standard 120 Vac operation unless otherwise indicated.
Warning: Never remove the cover of this unit while it is connected to the power line.
Never solder or unsolder without eye protection.
Refer to the following chart for the proper location of the primary wiring. This chart lists
the proper jumper connections for different ranges of MAXIMUM line voltage.
The standard line voltage in the USA is NOT 110 and 220 volts. It is almost ALWAYS
above 120 volts or 240 volts.
Caution: Never exceed the voltage in this chart for each wiring configuration. If the
output voltage of this supply exceeds 65 volts damage to the amplifier may
occur.
ALS-600PS Power Supply Board
Jumper Pad Diagram
For the following line voltages
jumper the correct pads.
AC LINE
VOLTAGE
RANGE
95-110 A TO B C TO D E TO 2 F TO 1
105-120 A TO B C TO D E TO F
115-130 A TO B C TO D E TO 1 F TO 2
200-220 B TO C E TO 2 F TO 1
210-230 B TO C E TO F
220-240 B TO C E TO 1 F TO 2
PRIMARY
BUCK BOOST
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