LCN Suspect Alarm


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We have upgraded TDC3000 to Experion Release 300. For this Process Manager has been Upgraded to High Performance Process Manager. The LCN software release has also been upgraded to Release 670 from Relesse 435. Since commissioning we have been facing a frequent issue in the form of LCN suspect alarm. At first we used "Net Media Dead" option to see the max number of dead packets per nodes. The nodes that had max number of nodes were thoroughly inspected for rectification. But now dead packets count varies node to node and we are unable to diagnose faulty node.

It should be noted that all nodes access the LCN network via a device called "MAU--Media Access Unit". And we have also replaced one MAU for rectification.

Rahul P Sharma

We had a very similar problem that kept on throwing LCNB cable to suspect mode always. Finally we could solve the problem in a very 'unconventional' manner. We just put an insulating material (some paper or rubber) below the MAU making sure it did not touch any chassis of the console or anything similar. And the problem got rectified permanently. (The problem hasn't come up in last one year!!!)

au revoir
The majority of our cable suspect errors have been remedied by replacing failed terminating resistors at the ends of the LCN coax segments.
LCN troubleshooting is a bit tricky and requires patience.

If the noise pattern is random on different nodes at different times u need to dig in deep.

Go to system menu->event history retrieval and query for a log of both system errors and system status.

Carefully observe, the time at which your LCN went to suspect and the system errors at that time.

You will have a flood of errors, but the error which came immediately before/after the LCN suspect, may be the culprit.

Then based on the error you can further go on with troubleshooting.

Let me know if this helps.