888-2408-002
4-7
WARNING: Disconnect primary power prior to servicing.
Overall System Theory
4.3.3.2 Main/Alternate IPA Switching
Selection of IPA_AB1 or IPA_AB2 (both input and output) is done via relays K2,
K3 and the IPA DRIVER SELECT control signal from the Life Support Board.
NOTE:
The term “AB” is used to associate a component with Z-Plane A and Z-Plane B.
K2 switches the input RF drive from the exciter to IPA_AB1 or IPA_AB2 while K3
selects the active IPA RF output. The control signal, IPA DRIVER SELECT, is
normally low which places K2 and K3 in the IPA_AB1 position as shown on the
schematic. If IPA DRIVER SELECT goes high, K2 and K3 will be energized and
switch to the IPA_AB2 position. If the Master Controller detects a loss of RF output
from the active IPA it will automatically switch to the second IPA.
IPA switching can also be done manually using the Diagnostics display. Press
[HOME, STATUS, D,B] This should bring up the screen in Figure 4-3. Pressing the
D function key will now toggle K2 and K3, switching from IPA_AB1 to IPA_AB2
or vise versa.
4.3.3.3 IPA Monitoring
The IPA Backplane Board provides for monitoring and/or interfacing of 4 main IPA
parameters:
•
IPA temperature (VTEMP_IPA1 and/or VTEMP_IPA2). If the IPA board exceeds
100°C, the controller will mute the transmitter and/or switch to the alternate IPA.
The sensor is actually located on the IPA board, but is interfaced through the
Backplane.
•
IPA supply voltage (Vd_IPA_SAMPLE). A monitoring sample is sent to the con-
troller through fuse F2. The Supply voltage for the IPA is diode or’ed from both
PA supplies for redundancy.
•
IPA current (Id_IPA). IPA current is measured by measuring the voltage drop
across the series resistor R1. IPA current fault threshold is set at 14.3 amps.
•
IPA Forward Power (IPA FWD PWR). A sample of the IPA forward power is
taken by the directional coupler (shown right after K3 on the schematic) and
detected by CR1. The DC voltage at TP1 will therefore be relative to the IPA out-
put. This is also sent to the controller for monitoring and main/alternate IPA
switching.
Summary of Contents for Z5 CD
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Page 192: ...6 40 888 2408 002 WARNING Disconnect primary power prior to servicing Troubleshooting...
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