Platinum Z5 CD - Air Flow Sensing; IPA_AB1 and IPA_AB2 Interlocking; IPA Power Divider (3 Db Hybrid); Z-Plane Combiner;Divider Boards

4-8 888-2408-002
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.3.3.4 Air Flow Sensing.
Airflow is sensed as the difference in temperature between a heated sensor, RT1,
and an ambient sensor, RT2. RT1 is actively biased via R3 which will cause a steady
increase in temperature with no air flow. Under normal operation, the voltage
difference between the two sensor outputs will stabilize at some value depending on
the amount of air flow. If the airflow is reduced or non-existent, then RT1 will heat
up increasing its voltage output, whereas RT2 will stay the same. Eventually the
voltage difference between the two sensors will reach a threshold where the
controller will turn the fan to high speed to compensate for the reduced airflow. If
the airflow is still insufficient, the transmitter will be shut off.
4.3.3.5 IPA_AB1 and IPA_AB2 interlocking.
The signals IPA1_PCB_OK and IPA2_PCB_OK are the interlock signals for the
IPA boards. The interlock connections on the IPA board (and the PAs as well) are
shorter than the other pins. This causes the interlock connection to break before the
RF and voltage contacts when the module is unplugged. This gives the controller
time to shut off the IPAs (via the IPA gate voltage, IPA1_GATE) so that the
connector contacts do not arc.
4.3.3.6 IPA Power Divider (3dB Hybrid)
The IPA power divider is actually a 3dB hybrid which splits the IPA output into 2
equal amplitude signals 90 degrees out of phase to drive the Z Planes at J5 and J6.
Remember that the output of the Z Planes is recombined using another 3dB hybrid
which requires a relative 90 degree phase angle between the two input signals. The
reject port on the hybrid is connected to an external Reject Load. The hybrid
integrated onto the IPA Backplane Board.
4.3.4 Z-Plane Combiner/Divider Boards
There are two Z-Plane Combiner/Divider Boards in the Z5 transmitter. These two
boards provide all inputs to and outputs from the PA modules. The Z Plane is the
overall term for the combination of the Combiner and Divider boards. There is a
separate schematic for each part of the Z Plane in the schematic package. The first
page of each schematic is identical and is a block diagram of the entire Z Plane.
Each Z-Plane assembly contains:
• Edge connectors for 8 PA amplifier boards (4 in front and 4 in the rear). These
connectors are labeled J1-J8.
• An 8 way Wilkinson Divider, driven by the IPA, which feeds RF drive to each of
the 8 PA amplifiers.
• An 8 way Wilkinson Combiner which combines the output of the same 8 PA
amplifiers.