Control logix, flex i/o comms issue!!!

[Roy13j]

Hello everyone!

I have a control logix plc that is set up to communicate with 6 1794-asb flex i/o racks.

Everything has worked good over the years until about a month ago. They lost communication on rack 16, or 6, and we can't get it back.

Found a replacement module, no luck. Switched with a known good one. No luck. Just that stupid yellow triangle in studio 5000.

I was not the first guy to try and figure this out, and I can see dip switch settings in the original have been toggled, so no correct previously good settings are known.

I'm going to attach the configuration settings from studio to see if anyone can point us in the right direction.

Rockwell has been no help.

The old man that got me into pics is stumped.

I'm getting now gray hair every time I go out there.

It seems to be a rack size issue as you see from the pictures, but trying to figure out standard, compact and other addressing is confusing per rockwell instructions.

Halp.

 

[cardosocea]

I may be very wrong here. Where I had these issues turned out to be a little capacitor or varistor inside a DH+ splitter box that led to that particular PLC. Obviously I don't know if you have them, but worth looking at it. I remember spending a day battling it with a colleague of mine that actually installed these things and decide to ring Rockwell who gave us this tip. We replaced it and comms started going straight away. That alone was worth the 3 years Tech Connect.

 

[kekrahulik]

I got my butt kicked on a flex IO talking to controllogix via EthernetIP. It turned out to be a bad card or backplane module. At first we assumed it was the 1794-AENT card not talking, but it ened up being a problem somewhere in the rack that made the 1794-AENT think it was a 5 card rack instead of a 6 card rack. I think we ended up doing a full swap out since that was the fastest way to get production back up versus the trial and error approach.

 

[5618]

Your project says 3/4 rack but the module shows 1/2 rack. That leads me to suspect you have a bad connection between bases or a bad base, maybe between modules 2&3 or between 3&4. (first module is zero)

If that doesn't get you there, I remember dip switches changing over the different series (A through at least E) and some documentation was wrong. Double check what series you have and see if you can find documentation for the one you have plus the following series to see if it has any corrections for the previous series.

Last thing that comes to mind that I doubt is your problem: have you flashed to newer CLX firmware? I remember converting a PLC5 to L72 CLX with 40+ physical racks on DHRIO module. Whatever random firmware version I had was 30, 31, or 32 and not the latest in that major revision. I couldn't get RIO working. It seemed like I had one or two magic racks that always worked and the others might only occasionally connect. I didn't fool with that much. I discovered everything RIO worked fine with the latest V20 firmware.

 

[Roy13j]

Your project says 3/4 rack but the module shows 1/2 rack. That leads me to suspect you have a bad connection between bases or a bad base, maybe between modules 2&3 or between 3&4. (first module is zero)

If that doesn't get you there, I remember dip switches changing over the different series (A through at least E) and some documentation was wrong. Double check what series you have and see if you can find documentation for the one you have plus the following series to see if it has any corrections for the previous series.

Last thing that comes to mind that I doubt id your problem: have you flashed to newer CLX firmware? I remember converting a PLC5 to L72 CLX with 40+ physical racks on DHRIO module. Whatever random firmware version I had was 30, 31, or 32 and not the latest in that major revision. I couldn't get RIO working. It seemed like I had one magic rack that always worked and the others might only occasionally connect. Everything RIO worked fine with the latest V20 firmware.

We have 5 modules on that rack, 0-4, but I couldn't get a solid answer from the manual what rack size that is.

I forgot to add we also have a blinking module active light on the module

 

[5618]

Five modules would be 3/4 rack, like the project says. The comm module diagnostic says 1/2 rack so it looks like it only sees 3 or 4 I/O modules.