We have three 620-35 redundant PLCs (Nodes 15-16, 17-18 & 19-20) on UCN along with one redundant pair of HPMM (Node 9-10)...

"Node 16" is continuously displaying a "Nosynch" message... We carried out the following checks:

1) Synchronised Node 16 (Redundant) with Node 15 (Primary) by turning the "Key to Program Mode"... (No improvement)

2) No visible fault or status LED seen in the PLC Rack...

3) Program reloaded in the LMM from HM... (No improvement)

4) Checked Node 16's LMM by plugging it in a working node (Node 19)... It was found that this LMM was very noisy... Cable noises began increasing at a rate of thousands of counts per sec finally leading to the failure of Node 19 from UCN.... Hence replaced Logic Manager Module (LMM) of Node 16 with a working module... (No improvement)

5) Restarted the entire PLC rack of Node 16... (No improvement)

Please suggest what further checks can be done and what can be done to restore the status of "Node 16"....

Will the changeover take place from Node 15 to Node 16, should some problem occur with Node 15....????

au revoir
Rahul

 

At first check the UCN Taps and cables, seems that you have a problem in cables going from LMM16 to the tap. Or could be that the the tap has a problem. Find in what cable you have more problems and check that tap and Drop cable.

 

i have same problem. Check your if power supply is redundant. Change it and the problem is solved. If it is, send a message.

 

Gentlemen,

I have also faced this problem. Make sure your connections between the RCM, LMM, SLM modules in the processor rack and the SLS card in the I/O rack(s) are secure. It that is OK, then swap each of the above mentioned cards with a known good card.

I suggest you review the documentation from Honeywell publication LM13-X00 (X being the software version of the LCN) for procedures and cautions for performing this work.

John Beck
Control System Spec., Retired
[email protected]