______________________________________________
HARRIS
888-9058-001
WARNING: Disconnect and lockout AC primary power prior to servicing
190
Finally, if neither of these steps yields success, the problem may lie in a PAL or logic
gate on the module control board. This type of problem is generally rare. Measuring
voltages at various points in the logic circuitry on the module control board can isolate
this type of problem.
A set of troubleshooting procedures, one procedure for each fault code, is given below:
High Output VSWR Fault (1 blink)
The cause for this fault is often external to the
module. First, check the system VSWR on the display panel, and check for a VSWR
foldback or VSWR overload condition on the transmitter. Check the other modules in
the same cabinet for VSWR faults as well. If either is found, suspect a problem in the
system outside the cabinets.
If not, the problem is either in the suspect module or its cabinet. The swap test is the
easiest way to isolate the problem. Swap the VSWR faulting module with a properly
working one from another slot. If the problem remains in the same slot, check the RF
output cable, connector, and combiner reject load for that module slot.
If the problem follows the module, check the solder connections at the directional
coupler and the RF output jack inside the module. If no problem is found, the problem
could be an improperly set VSWR fault threshold or a defective module logic board.
See paragraphs giving procedure used to check and set the VSWR threshold located on
section 8.5.2.5.
Input Overdrive Fault (2 blinks)
Normally, this protects the module from damage due
to excess RF drive (at least 3 dB above the drive required to drive the module to full
power). To isolate the cause of fault, reduce the visual exciter RF output to zero, then
enable the module with a transmitter ON command. If the fault remains, the problem is
likely to be with the module control board.
If the fault clears when RF drive is removed, check to see that the module is not being
overdriven. If not, then the overdrive threshold on the control board may be
misadjusted. See procedure located in section 8.5.2.4 to check the Overdrive Threshold.
ISO Voltage Fault (3 blinks)
The RF input to the quarter module passes through a two-
way divider on the quarter module, and is then fed to two parallel amplifiers on the
quarter module. The outputs of these two amplifiers are recombined in a two way
combiner on the same board. The combiner contains a 10 Watt reject load resistor,
called an ISO resistor because it is used to provide isolation between the combiner input
ports.
If outputs of the two parallel amplifiers are equal in amplitude and phase, the voltage
across the ISO resistor will be very small. Should some component fail on one of the
amplifiers, its output would decrease to a level much lower than the other parallel
amplifier, which would cause the voltage across the ISO resistor to increase
