Revision 2
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Circuit Boards
There are ten basic circuit boards plus two power amplifier modules in the ALS-1306. The text
below gives a brief description of each board’s function.
2KWF6
The 2KWF6 is a high-power low-pass filter. It is the very large topmost board with several large
toroids and air wound inductors. This board contains filter SWR fault detection, power amplifier
imbalance detection, and multiple high-power low-pass 5-pole filters. Additionally, the antenna
relay board RLY attaches directly to the 2KWF6 board.
BS2
The BS2 is located behind the BAND switch. It provides all band selection functions, as well as
band indicators.
CB2
The CB2 is located near the front of the amplifier just behind the meters. The CB2 control board
provides most control functions. This includes bias, fan speed, overload and wrong-band
protection, and transmit-receive relay sequencing. It is the hub for nearly all functions, including
external interfaces, power metering and 12-volt busses.
MB1
The MB1 is located behind the front panel below the meters. It contains peak-envelope-power
detection circuits, multi-meter switching, fault indicators, and ALC circuitry. There are four
power meter adjustments on this board; forward power, reflected power, forward peak hold time,
and reflected peak hold time. Shunts on a header located on the board’s upper edge adjust panel
meter brightness.
PA Boards
PA boards are located on top of the heatsinks under the filter board shield panel. The PA boards,
along with heatsinks, are integral units of the PA modules. There are no user adjustments on
these boards, and the FETs and assemblies are gain matched at the factory. The PA modules are
serviced by removing the bottom panel.
PD8
The PD8 is located on the right side of the amplifier just above the panel containing the cooling
fans. It contains a power splitter and two 5 dB attenuator pads. The splitter and attenuator pads
isolate the two power amplifiers from each other, and terminate the PA inputs in 50 ohms over a
wide range of frequencies. This is necessary to stabilize the PA modules. Do not modify,
remove, or bypass the attenuators.
RJ45
The RJ45 board mounts on the rear panel. It contains two RJ-45 jacks for remote control
interface.
RLY
The RLY board contains two transmit and receive relays, one for RF output switching and the
other for RF input switching. T/R relays activate with a low on terminals K (key) J1-3 and RJ1-
7. The CB2 board contains the relay timing controls.
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