Harris Platinum Z2 CD, Manual

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4-10 888-2406-002
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.3.4.2 8-Way Combiner
Refer to the Combiner schematic for the following. Each 8-way combiner consists
of two 4-way Wilkinson combiners, called FOURSOMES, followed by a 2-way
Wilkinson combiner which combines the outputs of the two Foursomes. The
Foursomes are split up as follows:
•
1, 2, 3 and 4 - Front Foursome
•
5, 6, 7 and 8 - Rear Foursome
The Wilkinson combiners include isolation loads (ISO loads) which dissipate no
power if all PA outputs are equal and in phase. These resistors are located on the
Isolation Board and labeled R1-R8. The ISO resistors connect to the points labeled
E1-E8 on the Combiner schematic. If any input is lost due to failure of a PA module,
the associated ISO load dissipates some power, approximately 150 watts, until the
RF switch on the Isolation board disconnects the ISO load and grounds that point
(E1-E8) on the combiner. This now looks like an open to the 4-way combiner output
at E9 or E10 (the input to the 2-way combiner).
4.3.4.3 PA Modules
Each of the 8 PA Modules contain one PA Amplifier board mounted on one side of
the PA Module heat sink, with the opposite side empty. The modules are numbered
1 through 8 with the top module in the front being #1 and counting to #4 at the
bottom. The top rear module is #5 counting down to #8 at the bottom rear, see
Figure 4-4 for the front view and Figure 4-5 for the rear view. All DC, signal and RF
connections to a PA board are through one edge connector.