Hello, I am seeking recommendations for troubleshooting an issue with a customer's Compactlogix rack. The CPU model is 1769-L33ER, and the problem is that it intermittently restarts as if the power has been reset. Sometimes it will resume operation, but often it continues cycling through the startup sequence with the LEDs. Initially, the entire Compactlogix system was unresponsive despite 120VAC being present at the power supply. After replacing the power supply, the system was revived, but the recurring restart issue began. One possibility is a faulty module in the rack affecting the chassis voltage. We attempted replacing the processor and other cards in the rack to no avail, except for two modules (1769-OF4VI in slot 7-8) awaiting replacement. In the meantime, we are exploring other potential causes for the problem. Periodically, the system resumes normal operation with no significant faults logged. Have you encountered similar issues or do you have suggestions for further investigation?
Can you provide the model number and location of the power supply within the rack, specifying the slot numbers in between which it is situated?
User clintm inquired about the power supply model number and its placement in the rack, specifically between which slot numbers it is positioned. The model number is 1769-PA4 and it is located in the second slot, with the CPU being the only module on its left side.
After replacing the power supply, what were the results? Did the device successfully power up and for how long did it run? What is the current behavior of the device - does it power up only to reboot after 2 or 3 minutes? Please provide an update on the device's status. - James
After replacing the power supply, the system was able to run normally. However, it now experiences frequent reboots throughout the day. Sometimes, cycling power to the electrical cabinet resolves the issue temporarily, but other times the problem persists even after the power cycle. James Mcquade is seeking assistance in determining the cause of this recurring rebooting issue.
By methodically investigating these possible triggers, you can pinpoint and address the problem leading to the unexpected restarts of your CompactLogix 1769-L33ER PLC. This process will help troubleshoot any issues that may be causing the PLC to reboot unexpectedly.
It seems like you've done a comprehensive job trying to isolate the problem, but one thing that comes to my mind is checking the wiring and grounding of the entire system. Sometimes a minor grounding issue could cause intermittent faults. Also, potential power surges or sags from your electric utility could cause such symptoms. I would recommend using a power monitoring device to record the voltage and current levels and possibly detect any abnormalities. Lastly, if you haven't already, try updating the firmware on the devices. It could be a software glitch that's causing the CPU to reset itself. And of course, replace those two modules still pending, they might just be the culprits!
I've dealt with a similar issue before on a Compactlogix rack. You're on the right track by examining the modules and power supply, but don't rule out issues with the backplane itself, as that can also cause erratic behavior if it's damaged or failing. Intermittent problems can sometimes point to loose or corroded connections. Given that you've replaced most of the components without success, I'd check the wiring and ensure the connectors are clean, secure, and not scored or damaged. I'd consider moving the yet-to-be-replaced modules (1769-OF4VI) to different slots to see if the problem follows these modules. If it does, then those modules might be the culprits. If the system runs without problems without these modules, it's fairly indicative too. Also, examine the environment for factors like temperature fluctuations, electrical noise, or vibration that could impact the system.
It indeed is a puzzling situation you've described. In my own experience, an issue like this could be due to a grounding or electromagnetic interference problem. Have you checked the grounding of your controller and the I/O modules? I've noticed such behavior when we had false grounds in our installation. Also, considering it occasionally resumes normal operation without significant faults, it could be an environmental factor like the degree of surrounding electromagnetic fields causing interference. Furthermore, since you've mentioned two modules awaiting replacement, I would suggest getting those replaced as soon as possible, as a defective module could cause unexpected reboots too even if it might appear unrelated.
It seems like you've tried a number of troubleshooting steps already. Given that the problem still persists after replacing the power supply, processor and other cards, it possibly indicates the issue could be with the bus where the cards sit or the power connections to the rack. I would suggest you pay attention to the two modules (1769-OF4VI) still awaiting replacement. There might just be an issue there. However, if you've not done so already, it could be worth doing a comprehensive hardware check, particularly inspecting the backplane for any signs of damage or cold solder joints, as these could potentially cause intermittent power issues. Regularly log events when restarting happens to perhaps discover a pattern or sequence that can help identify the root cause. Also, verify if environmental factors like heat or electromagnetic interference could be the culprits. It's quite a complex issue you're facing, so keeping a meticulous record of each step you take and each occurrence of the problem could help you corner the problem hopefully.
It sounds like you've done a good job isolating some potential issues with your system. Given that replacing the power supply helped initially but the restarts persisted, I would definitely consider looking into the two 1769-OF4VI modules you mentioned, especially if they're old or have been under heavy load. Sometimes, intermittent problems can be caused by wiring or connections as well, so double-checking the terminals and ensuring they're snug might help. Also, check the backplane for any signs of damage or poor contact, as that can lead to unexpected behavior. If you have the means, running some diagnostics on the modules could uncover hidden faults as well. Good luck!
It sounds like a frustrating issue to deal with! Given the intermittent nature of the restarts, I'd suggest keeping an eye on the temperature and operating environment of the rack; sometimes overheating can cause those kinds of restarts, especially if any modules are overheating. If the 1769-OF4VI modules are still in the rack, it might be worth checking them specifically for any signs of damage or improper wiring. Also, consider looking at the grounding and connections in the entire setup, as loose or poor connections can lead to power fluctuations. Lastly, if possible, try swapping the suspect modules with known good ones to see if that resolves the issue—it's a quick way to narrow it down. Good luck!
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Answer: Answer: The intermittent restart issue could be caused by a faulty module in the rack affecting the chassis voltage, even after replacing the power supply and other cards in the rack.
Answer: Answer: It is recommended to check for faulty modules affecting chassis voltage, replace any problematic modules, and investigate potential causes beyond the power supply and processor cards.
Answer: Answer: In the provided discussion, the modules 1769-OF4VI in slot 7-8 were mentioned as awaiting replacement, indicating a possible connection to the intermittent restart problem.
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