CNBR Channel A flashing red

We are using CNBR's (D)to communicate between the main rack and the remote rack. Then the system goes out through flex i/o to the nodes. Both my CNBr's have channel A flashing red and channel B good. I can take my channel A feed to the nodes and place it on B channel and B works. Green. To me that means my channel A cabeling is good. (it runs to all the nodes good). B feed out will not work on A. I'm new to controlnet but it seems like channel A is bad in one of the cards. The connection between the CNBR's is good and the cable seems good so I'm lead to believe it's a card. So, I took a new CNBR and installed it in the remote rack and still had channel A flashing red and B was good. (the version is the same). I then placed the original card into the remote rack and tried placing the new card into the PLC main rack and lost my entire controlnet. (same revision) So I placed the old card back into the main rack and channel B came up but channel A was still down. I'm not versed in keepers and signatures. Is the reason all the control net went down with the new card because of signatures ir keepers? Also Has anyone ever ran into this and can you give me some advice on correcting this? I do have a Cnet CHRK on order. Thanks for any help.

Is this a system that worked previously, or is it the first time you are configuring this network ?

When the system is in its original configuration with Channel A on both of the 1756-CNBR modules flashing red, are the Channel A indicators on the FLEX I/O devices in the field also flashing red ? That is the typical behavior.

Because both of the 1756-CNBR modules have Channel A flashing red, it is unlikely to be a module problem. The odds of both modules having a bad channel is low.

The 1788-CNCHKR device is the very best tool for troubleshooting ControlNet cable systems.

Channel A Only, Channel B Only, or Channel A/B Redundancy is an overall Network setting done in RSNetworx for ControlNet when the schedule is created. The "Keeper" keeps this setting along with the RPI and the Maximum Scheduled and Maximum Unscheduled node numbers.

A new device connected to the network should accept those values from the Keeper, but with ControlLogix modules I send them a Reset message to clear out their nonvolatile memory before moving them to a new network.

Ken,
The system has been running for 4 years fine until the A channel went red flashing. The flex I/O's are also showing A out and B ok. I did have to change a flex cnet adapter on node 20 but its showing B up now. When I first arrived at the system, 3 panelview 600's were showing a 9021 and 9022 comm errors. Once the main cnet cmbr was reseated, they all came up and work fine on B channel, A was still flashing red. I checked all the connections and they look good and are secure. The dam has all functionality on B with A still flashig red accross all CNBR's and flex I/O's. Originally, both A & B were green.

I found the problem, The Phoenix Digital F/O card feeding channel A from the main PLC to the remote rack was sending trash even though the link and data lights were showing good. It's all good now.