Troubleshooting Micrologix 1000 fault tomorrow...

AutomationTechBrian

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A customer sent me these pictures, wondering if I can help with the fault on a critical machine tomorrow. I think I've seen this before, and it seems to me there was something about the situation I should remember... but it's been so long ago.

To the legacy Allen Bradley gurus: Do you see something here that might indicate what I'll need to do to clear the fault? ....maybe point me in the right direction? Is my RSLogix 500 going to work? There's a round connector on the PLC... I think I've got the right comm cable... I've been carrying it unused in my bag for ages, wondering if I'll ever need it. I'd like to confirm that it is correct... does anyone know the right cable part number?

I'll grab the manuals before leaving home tomorrow. I can dig deeper into this on the jobsite. If you see something that looks familiar, please let me know. I think this is only the 2nd ML1000 I've ever touched in my life. I suspect there are some well-known quirks that pop up on these PLCs.

Thanks for any input!

MicroLogix1000.png Panelview_300.png Panelview_300Backside.png
 
The cable you need is the 1761-CBL-PM02 ( null modem cable).

From the picture of the PV it shows a cable with what looks like a cable with a null modem adapter on the end. The PV you have requires a straight thru cable
So you may have one already.

The PV you have supports DH485 protocol. This could be a problem if you don't have the proper hardware to get connected. The ML1000 does have Auto Protocol detection if you have a series D controller (see pdf). Otherwise you may need a 1747-UIC ( DF1 to DH485 converter)

To find the fault go online and check controller status.
 
It looks like they have a 1761-CBL-PM02 plugged into a null modem adapter connected to the RS-232 port on the HMI. So if you have a good serial port on your laptop, you could use that cable to communicate with the ML1000. The DF1 driver in RSLinx should work with either DH485 protocol or DF1 with that cable since it is electrically still RS-232.

Assuming the photo of the HMI was taken after the fault, it appears to be reading values from the PLC. This would indicate that the PLC has not lost its program. Old ML1000 can go flaky and wipe themselves out but if that happens there should be a communication error on the HMI.

RSLogix 500 will work. That analog version of the ML1000 could be replaced with a 1766-L32BWAA (ML1400, AC power, DC inputs, relay outputs, analog i/o) I think depending on the details of the analog input. IIRC the ML1000 could take a 4 to 20mA or a 0 to 10vdc input, not sure about the 1400.

We always use expansion cards for analog inputs, so I have not used either of those with analog built in. I have replaced a handful of ML1000 analog controllers with newer micrologix over the years and replaced the PV300 with Red Lions.

You'll probably find a fault that can be cleared and get the PLC running again.
 
Last edited:
That went exceedingly well.

I connected with the USB/PM02 cable that I bought from Tim at TW Controls. Auto-configure worked great. I found the cause of the fault quickly, and the manual said that I can just reset the fault on the Status window, on the Error tab (see picture). The one thing that got me was finding out that there isn't a physical program/remote/run switch on the ML1000. I had to re-connect the laptop to switch the mode to run via the software.

Thanks again for the help! The customer was very happy.

Clearing fault on ML1000.png
 
Thanks for sharing this - I have had a few calls in the past where the the 1000 wouldn’t boot into run mode properly after it was a victim of receiving dirty power
 

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