EDWARDS SYSTEMS TECHNOLOGY IRC-3 Maintenance And Troubleshooting Manual page 13

Maintenance and Troubleshooting Manual
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Figure 1 . The Pulses should not be excessively curved, and the
turn-on pulse must be present. If some pulses appear excessively
rounded and/or the start pulse is missing, too much capacitance is
the problem.
Referring to Figure 1, the pulse width for all values below 5
Note:
VDC must be at least 70% of the pulse width for values above 5 VDC,
or the waveform is said to be excessively curved.
ZAS line capacitance problems are typically caused by long wire
runs, ground faults on the ZAS line, improper T-taps, or improper
shielding.
The shield must be treated as a third conductor. It must be free of all
ground faults and have continuity throughout. If the wire
capacitance is too large for the run length, the only remedies are to
replace the wire with a cable having a lower capacitance per foot or
install additional ZAS modules, dividing the line into acceptable
lengths.
3. Ground Faults:
Eliminating ground faults on the ZAS line reduces the amount of
capacitance on the ZAS wiring.
Verify the ZAS line is free of ground faults. Remove all field wiring
except the ZAS line under test from all panels which share a
common power supply with the CM1/2(N) containing the ZAS card.
Verify jumper J1 is installed the trouble sense (lower) card of the
power supply and J2 has been removed. If the CM1/2(N) displays
either a GND0 or P 002 then the ZAS line has a ground fault, which
must be corrected.
If the ZAS circuit is wired with improper T-taps (described earlier)
corrective measures include designing the ZAS line properly and re-
pulling the wire, or balancing the line. Balancing the line can help in
some cases but is not a substitute for proper wiring practice. If line
balancing is required, call EST Technical Services for additional
information.
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