Assembly Instructions
Table Of Contents
MXi501/1002U POWER AMPLIFIER HEATSINK ASSEMBLY
1 POWER AMPLIFIER HEATSINK ASSEMBLY
The MXi Power Amplifier Heatsink Assembly 41D2272G1 consists of a fan-cooled heatsink and ten printed circuit
board sub-assemblies. The first module is a pre-amplifier, known as the Front-End Module. This first stage is
operated in Class A mode. Next is the Driver pallet, which is biased so as to pre-correct for the non-linearity in the
final amplifier stage. The next stage is a five-way splitter that splits the RF power so it can be fed to the PA
pallets. The final amplifier stage is the PA pallets. After the pallets is the five-way combiner which combines the
output power from the PA pallets. The last sub-assembly on the heatsink is the directional coupler which detects
the forward and reflected power and provides samples to the control board and a RF test point on the rear panel.
Also mounted on the heatsink is a thermal switch, which protects the amplifiers from over-temperature conditions
such as the absent of cooling or amplifier over dissipation. This heatsink assembly is mounted in the Amplifier
Chassis Assembly 41D2270G1 or G2. Descriptions of each stage are detailed in the following pages.
Figure 1 MXi Sub-Assemblies
The above picture illustrates the arrangement of the sub-assemblies on the amplifier heatsink assembly. From
right to left are the Front-End and Driver modules. Centered and towards the back are the Splitter, PA modules
and the Combiner. At the very back is the Directional Coupler. Strategically installed on the heatsink, is a thermal
switch which protects the amplifier from over temperature conditions.
Cooling for the heatsink is provided by a fan array assembly consisting of four 4-inch axial flow +12VDC muffin
fans. This array is situated near the front section of the MXi housing underneath the MXi Amplifier Controller PC
board. The fans blow air into the finned portion of the heatsink, which exhausts through the rear.
PUB11-014 Rev 1 July 2011 11-014-1 MXi501/1002U Power Amplifier Heatsink Assembly