1756-L61S Major recoverable fault when attempting to go online

Hi all,

We have a machine with a 1756-L61S/1756-LSP processor. The programme is stored on a compact flash card inserted inside the L61S.

The processor is set at revision 19.011 and the RSLogix software being used is version 19.01.

Over the weekend, the processor suffered some kind of fault (I'm unsure what the fault was as the people on shift dealt with it without calling for engineering support). The people on shift wrote in their log that the processor had a flashing red 'OK' led. To recover the situation, they installed a new L61S, inserted the Compact Flash card and then toggled the key switch from PROG to RUN and then to REM and the system came back to life.

However, the machine HMI showed an alarm which they traced to a limit switch, but the only way they could get it to clear was by removing the cable from this limit switch input. The machine then could run and has been running since.

The line engineer today has attempted to go online using a Windows 10 PC connected to the machine via our site Ethernet network to try and determine why the alarm message relating to the limit switch would not clear after the programme was reloaded. However, every time he tries to go online via the EN2T Ethernet card in the rack, the new processor crashes (Major Fault) and he cant get online to find out why or what the Major Fault is (the OK LED flashes red, as per the weekend).

I then got involved and I tried to go online via another Ethernet card in the rack, a 1756-ENBT (a different network to the EN2T card) and the same thing happens.

I then thought it maybe the PC, so tried to go online using a Windows 7 Laptop, but the same thing happens when attempting to go online via either of the two Ethernet cards. The system can always be recovered by moving the key switch PROG, RUN, REM

From both the PC and the laptop, I can Ping Ethernet both cards from Command Prompt and I can see the controller properties from RSLinx

The error that comes up in RSLogix on both machines is "Failed to go online with controller. Can't communicate with RSLinx". The error number is 701-80042535.

So I dont really understand why we cant go online with this PLC.

This machine has a sister machine with exactly the same hardware config and more or less the same software (the controller version is the same) and we can get online with this no problem.

The only difference I can see is that both the original processor from the affected machine and the processor in the sister machine say on the side F/W Rev 1.10. The new processor says F/W Rev 1.9.

Can any of you help? I dont really know how to tackle this.

We have rung Rockwell UK today and they have pointed to some knowledgebase articles suggesting that deleting harmony files etc from the PC/Laptop might help, but why would we have the same problem on 2 programming terminals?

Thank you for any suggestions you have.

Was the new CLX flashed to the correct firmware?

Any reason you can't connect via the serial port instead?

Can you access the web interface of the ENBT and check the diagnostics?

It is possible you are exceeding the total number of CIP connections? I.e connections to the old processor are sill being maintained, along with a new set of connections to the new processor?

Are you using the same project file as before? You can't connect, but maybe you can upload the project file and see if that behaves differently.

I missed your comment about the FW versions, so scratch that. Another thought, is there any reason you can't swap the old one back? They never identified the fault so perhaps its something easily fixed like an overflow.

Thank you for you reply Dryhops

Project file is the same as it is the one that was on the compact flash card.

Haven't tried the web interface, but I'm having the same problem across two different types of Ethernet card in the same rack, an ENBT and an EN2T

I cant upload because I cant go online with the processor, I cant even go online with a blank project with just the controller path inserted to bring up the processor properties. As soon as you click Online, the processor faults and you get the message bout not being able to connect.

The processor would not have been flashed, as the shift guys would not have the capability to do this. However, as far as I can tell, the processor is set to revision 19.011 as I can see this by right clicking the controller and accessing properties from RSlinx. I'm not sure what the firmware revision 1.9 vs 1.10 is? Can I flash that?

Only reason for not connecting by serial lead is that I haven't considered it. I'd have to buy/make a serial lead if we go this route, but I'd prefer to get the Ethernet route sorted.

I don't know about CIP connections, I'm not sure how to check this.

Update, just seen your second reply - We are going to switch back to the old processor tomorrow, as we don't believe there is anything wrong with it.

Attached is an example of the web interface to check your connection load. If you have a lot of Ethernet connected modules or VFDs, etc. it can be an issue with older processors that don't have effectively unlimited network resources:

Got back to this today.

Connection load seems ok.

Replaced the processor with the original one that was removed Sunday and have the same problems.

I think we are going to get Rockwell involved.

Will let you know how we get on once they have visited.

Did you manage to correct this problem? Now I am going through the same situation.