TBA0STU/TBA0STP CTU Operation Manual Modification History 9
© Tait Electronics Limited September 2005
2 Modification History
This chapter provides details about any production modifications made to
the CTU that may affect its performance, or the way in which it interacts
with the TB7100, TB8100 or TB9100 base stations.
AC Coupled
Unbalanced Audio
Input
The unbalanced input on the CTU was changed from DC to AC coupled
in August 2005. This modification (fitting a capacitor) was necessary
because the unbalanced input on TB8100 TaitNet and TaitNet RS-232
system interface boards was changed at that time from AC to DC coupled.
This change was made for paging, and the version of these boards was
changed from 0 to 1. If your reciter is fitted with a version 1 TaitNet or
TaitNet RS-232 board, you must use a CTU that is AC coupled. If the
CTU and system interface board are both DC coupled, and the test
equipment is not AC coupled, the DC signal will directly pull the modulator
carrier frequency.
CTUs with the serial number 18012507 and higher incorporate the change
on the PCB, but earlier CTUs must be modified as described in TN-1082.
To check if your CTU has been modified, use a multimeter to check the
continuity between the centre pin of the unbalanced input BNC connector
(UB INPUT) and pin 6 of the 15-way system interface connector (or pin 5
of the 25-way connector). An open circuit indicates the capacitor is fitted,
a short circuit indicates the capacitor is not fitted.
To check the version of a system interface board, run the Service Kit and
select Monitor > Module Details > Reciter. In the Versions area, the
System Interface field displays the version number.
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