9/15/06
888-2586-001
4-19
WARNING: Disconnect primary power prior to servicing.
Section 4 Overall System Theory
Platinum Z16HD+
Maximum RF output per PA is 350W peak, with typical output of 250Wavg at
nameplate TPO. The power module is designed for single amplifier field replacement.
In the event an RF power MOSFET fails, field replacement is not practical due to the
cost of components, time and test equipment involved in repair and alignment of phase,
gain and response. This is a highly critical area, and if not done correctly, improper
module and transmitter operation will occur.
As an additional consideration, please observe the following warning from the
MOSFET manufacturer regarding beryllium oxide:
!
WARNING:
PRODUCT AND ENVIRONMENTAL SAFETY-TOXIC MATERIALS. THIS PRODUCT
CONTAINS BERYLLIUM OXIDE. THE PRODUCT IS ENTIRELY SAFE PROVIDED
THAT THE BEO DISC IS NOT DAMAGED. ALL PERSONS WHO HANDLE, USE OR
DISPOSE OF THIS PRODUCT SHOULD BE AWARE OF ITS NATURE AND OF THE
NECESSARY SAFETY PRECAUTIONS. AFTER USE, DISPOSE OF AS CHEMICAL OR
SPECIAL WASTE ACCORDING TO THE REGULATIONS APPLYING AT THE LOCA-
TION OF THE USER. IT MUST NEVER BE THROWN OUT WITH THE GENERAL OR
DOMESTIC WASTE.
Failed PA boards should be sent in for repair or exchanged mainly due to the minimal
cost involved. Refer to the Maintenance section of this manual for the RF amplifier
replacement procedure.
4.4.5
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. There is a listing of the
foursomes earlier in this section.
The Wilkinson combiners include isolation loads (ISO loads) which dissipate no power
if all inputs are equal and in phase. These resistors (with a thermistor attached for
temperature sensing) are located on the Isolation Boards and labeled RT1-RT8. The ISO
resistors connect to the points labeled E1-E8 on the Combiner schematic. If any input is
lost due to a failure of a PA module, the associated ISO Load will dissipate some power
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).
4.4.5.1
Isolation Boards
Each Z Plane has an associated Isolation Board which contains the isolation resistors
RT1-RT8 and RF disconnect switches for the two 4-way Wilkinson combiners and RT9
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