TRAK MODEL 9100 MODULAR FREQUENCY/TIME SYSTEM
4-2
TM4400013
REV.
D
4-5.1
GPS Reference Failure
If a primary or backup GPS Reference module fails, the red front-panel FAULT indicator lights. Before replacing
a failed GPS module, verify the following:
1. Through the RS-232 I/O or optional 10BaseT port, identify the failure by issuing the RQBT command to
collect the BIT status of the failed module. Refer to the RQBT message response below for description of
message response.
2. If the failure is due to the GPS Receiver BIT, or the antenna BIT, check the following. For any other failures
the module must be replaced and sent back to the factory for repair.
A. Perform continuity test of antenna cable and verify the cable is not open or shorted.
B. Antenna is mounted vertically and above obstructions that prevent clear view of the sky.
C. Antenna cable connectors are secure and if lightning arrestor is used, verify it is installed according
to manufacturer’s instructions.
D. Antenna cable is within the minimum and maximum length. Refer to Appendix E, Table 2 for the
proper antenna cable lengths.
E. If the Model 9100 has redundant GPS REF modules, swap antenna inputs A and B, and verify if the
failure in the failed GPS REF module clears. If it does the replace the antenna.
X.RQBT<cr><lf>
Module returns:
GPS BIT STATUS ABCDEFGHIJ <cr><lf>
Where:
A is GPS Receiver BIT (G = Good, F = Fail)
B is Rub lock or 10 MHz BIT (G = Good, F = Fail)
C is 5 MHz BIT (G = Good, F = Fail)
D is Composite BIT (G = Good, F = Fail)
E is IRIG B BIT (G = Good, F = Fail)
F is 1PPS BIT (G = Good, F = Fail)
G is CPU BIT (G = Good, F = Fail)
H is Antenna BIT (G = Good, F = Fail)
I is Oscillator cal (G = Good, F = Fail) (F will not cause the front panel
LED to light, unless DAC failure is detected or DAC reaches its limit of adjustment)
J is Module online Y = Yes, N = No)
If it’s determined that a module has failed, follow the instructions below for replacement.
a) Place the FSU Online switch to the non-failed position. For example, if the primary GPS Reference is being
replaced set the FSU A/AUTO/B switch to position B.
b) Loosen the four panel screws securing the module to the chassis.
c) Push down on the ejector handle to disengage the module and carefully pull on handle to withdraw module
from chassis.
d) Install the new GPS module and secure to chassis by tightening the four front panel screws.
e) At the FSU front panel, depress the FAULT RESET switch and assure that all fault indicators are
extinguished.
f) Allow a minimum of 10 minutes for the GPS Reference module(s) to track satellites and an additional 30
minutes to 1 hour for the module to lock. This can be verified by viewing front panel TRACKING and
LOCKED indicators.
g) Place the FSU Online switch back to the AUTO position.
