Platinum Z5 CD - PA Current Foldback; A or B#_UC, PA Under-Current; A or B#_MUTE_FLT, PA Mute Fault

888-2408-002 6-23
WARNING: Disconnect primary power prior to servicing.
Troubleshooting
2 PAs failed, the transmitter could be as high as 97% power or worst case around
84% (possibly less based on individual operating conditions), depending on the
location of the failed PAs. See “Multiple PA Failures in a Foursome ” earlier in this
chapter.
6.11.3 PA Current Foldback
The normal PA Current Foldback threshold is 12.4 amps. This means the PA
Controllers will try to foldback the power of a PA, to keep its current at or below
12.4 amps, by making the PA gate voltage more negative. The PA Foldback current
rating is a moving target depending on the number of working PAs and VSWR. The
PA Current Foldback points can be checked using the Diagnostics Display by
pressing [METERING A,B,D then C or D to check Z Plane A or B].
6.11.4 A or B#_UC, PA Under-Current
PA Under-current is comparing the current readings of the PAs which are common
to each foursome. For example, A1, A2, A3 and A4. All four of these PAs are
plugged into one 4-way combiner. If one of these PAs has a current reading that is
less than 10% of the average current of the other three, the system will be muted for
120mS, the isolation switch for that PA activated (removing the PA from the
combiner), and the mute released on the rest of the PAs. The Master Controller
actually detects this fault since the PA Controller does not have the current readings
on all four PAs in a foursome (each PA Controller only controls 2 PAs on any one
foursome). When a low current fault is detected, the Master sends a command to the
related PA Controller to shut down the PA.
6.11.5 A or B#_MUTE_FLT, PA Mute Fault
Whenever a mute is applied to the PAs, the current draw by each PA is also checked.
If a MUTE is being applied but there is still current flow in a PA, then a
MUTE_FLT will cause the entire transmitter to be MUTED until all currents are
under 1 amp. This is most likely a metering problem. This will show up in the fault
log as an A#_MUTE_FLT or B#_MUTE_FLT (where # is a number from 1-8). Turn
the transmitter off and try turning the PA module over and re-inserting or switching
it with another module to see if it is really the PA or the slot that has the problem.
!
CAUTION:
WHEN A MUTE FAULT OCCURS, BE SURE TO SHUT THE TRANSMITTER
OFF BEFORE REMOVING ANY MODULES TO PREVENT ARCING OF THE
PA EDGE CONNECTORS.