Pathway DMX Pathfinder CR Manual - Manual (Page 28)

DMX Distribution System Page 28
Maintenance and Testing
2.3 ADVANCED TROUBLESHOOTING
As described earlier, basic troubleshooting usually involves isolating a troublesome
or defective opto-repeater circuit or module and replacing it with a known good
module instead. It may also include checking for obvious things such as incorrect
addressing on DMX receiving devices, absence of a line terminator, defective DMX
patch cables, or even incorrect control console configuration.
Once all basic troubleshooting checks have been completed, without the desired
resolution of the problem, more sophisticated fault finding may be carried out. It is
recommended to use a portable computer connected to the Master Module’s PC
Com Port jack so that test patching and diagnostics can be done right at the rack
itself. First, however, the DMX'ter should be used to either transmit DMX in place of
the control console, or receive DMX in place of the receiving device(s). Check the
receiving device by connecting the DMX'ter directly to it in transmit mode, or if that is
not practical, to the corresponding front panel auxiliary connector in the
DMXPathfinder (NOTE: Be sure that the circuit’s isolation relay is open before doing
this -- SEL LED off). Then set the DMX'ter to receive mode and monitor the data
coming to the distribution rack from the console (SEL LED on). If this test does not
point to the data source or the receiving device as being the cause of the problem,
there may be a slight incompatibility between them as far as DMX512 is concerned.
However, if the two units had previously worked together, these tests will point to a
problem in the DMX cable installation or in one of the DMXPathfinder modules.
At this point, the suspect Output Module should be withdrawn from its frame and the
spare unit inserted in its place (remember to match the spare’s switch settings with
those of the suspect module). If this proves that the original unit is defective,
withdraw the module and inspect it for blown data link fuses or any other obvious
cause. For more serious defects, disconnect the module entirely and take it to the
test bench for repair. If the unit has proven to be good, test the DMX cable
installation for open or shorted lines using the DMX'ter's cable check function. The
best way to do this is by interconnecting the DMX'ter's two XLR jacks with the A/B
or C/D auxiliary send jack pairs at each Output Module in the rack, and looping a
patch cable between the receive jacks at the suspect receiver station. Then
perform a “Cable Check” test for all five pins. A similar test can be done for input
cabling.
If the above tests yield passing results and the problem persists, it may be
necessary to use the Fluke LAN Cable Meter to do a high-frequency analysis of the