1769-L35E Fault

I have a system with the following:

1769-L35E::1769-PA2::1769-IQ16::1769-OB8::1769-IF4::1769-OF2

I went to the job on Monday and found the processor in a major fault. I didn't capture the exact error but it pointed to the OF2 analog output module. The "OK" light on the OF2 was not on at the time. I powered the system down and removed the module, checking the connections. They all looked good. The switch was properly set for internal bus power. The endcap looked good as well. The "OK" light came on upon power-up but eventually turned off again. I called RA and they suggested that I exercise the power selection switch in the module, so I did that. After that, the "OK" light seemed to stay on. I unchecked "Major Fault On Controller If Connection Fails While In Run Mode" for all of the local I/O and left the job for the day.

The next day I got a call that there were problems. The guy on site opened up the panel and noted that "a red light was blinking" on the PLC. He also indicated that the "OK" lights were on for the analog modules. I tried to get remote access and couldn't, but eventually got another vendor on site to connect and report the fault reading to me. Here it is:

(Type 03) I/O Fault
(Code 16) I/O module connection failed on required module.
Port: Backplane
Module: <unknown>
Error: Connection timed out
Info: <none>

Have any of you seen this come up or know what I should look to replace? My local distributor suggests just the OF2 module, but the engineer at RA I spoke with seemed to think I should replace everything, which is probably not going to be possible due to budget and logistics. The RA engineer seemed to have a low opinion of CompactLogix and acted as if this was to be expected due to the "commercial quality" of the line. That's not how the RA sales team described it when they convinced us to switch over! The bottom line is that if possible, I'd like to try to find a solution that I can feel confident in since the job (of course) is not local or convenient.

I had something similar to this on a stretchwrapper that has a 1769-of2 module on it that had the switch set to external and it was hooked up to a separate 24vdc power supply. When maintenance would power down the wrapper for pm's it would fault the processor on power up and dump the program giving the same fault you got. Upon investigation we found the the separate power supply was not coming up to speed (so to speak) on power up as fast as the processor and when it checked the status of the of2 module it didn't see the external 24 volts so it would fault.I fixed it by removing the external power wires and switching the module to internal power and the problem went away. Also we have 2 boilers with those same of2 modules that are there but not even being used and 3 different times our boilers would stop and the processors would be faulted. the ok lights on the of2 module would be off and we had to replace the module to get the boiler back up and running. makes me wonder if there is a problem with premature failure with those units but i haven't seen any recalls on them. Hope this helps.

What output type (voltage or current) did you use on the OF2 modules? Also, what configuration did you use for the channels?

I, too, have seen similar symptoms on a Micrologix with the 1769-OF2 module. In our case, the module LED was off, and the program was dumped. Reseating the card and powering back up recovered the LED and then I downloaded it and it ran fine. It happened again about a month later and then I installed a memory module, so the third time a few months later, I didn't have to drag the laptop out to this machine...also a stretch wrapper for pallets. I don't think it has happened again in the last year or so, and, IIRC, the card was configured for voltage outputs. I don't recall if it was internally or externally powered.

I think that I may just go to an OF4 to solve the issue. That is what I normally use anyway, it's unusual that an OF2 was used. It must've been value engineered.

Un-seat and re-seat the ribbon connectors on the individual modules (up top, in the back). If these come loose, you get goofy problems. Check the ECR as well.

kittydog42 said:

I think that I may just go to an OF4 to solve the issue. That is what I normally use anyway, it's unusual that an OF2 was used. It must've been value engineered.

Click to expand...

I'm not 100% sure about the part number in our machine. It may be an OF4. I will look tomorrow, time permitting, and post again.

My home rig had similar problems last fall & I fixed it by replacing the power supply (mine is a PA72/B).

OkiePC said:

I'm not 100% sure about the part number in our machine. It may be an OF4. I will look tomorrow, time permitting, and post again.

Click to expand...

Yep, it is an OF2, externally powered.

What revision is the firmware? We had problems with this fault after a firmware upgrade from 15 to 19. We ran a fast RPI time of 1.5mS which ran great until 19 was installed. Found that version 15 has only one setting for the RPI that controls all modules. Version 19 you have the option to set each module individually. Just didn't work for us.

Version 19. I'm not sure what RPI time is. I'll research it.

Thanks for checking Okie. These are the worst kind of problems to solve.

We are using 0-10 voltage output and the configuration is raw/proportional. firmware revision is 17.2

What seemed to solve this problem (since Thursday, knock on wood) was disassembling the PLC assembly completely and reinstalling it. The assembly was originally fastened to the backpanel with (8) 8-32 machine screws and I changed that to DIN rail mounting. This may have improved the grounding. So, it was either grounding or a bad phyiscal connection, possibly due to the way it was mounted.

It's usually little annoying things like this that are such mind wrenching problems.

Glad you fixed it