AB Compact Logix PLC 1769-L24ER-QB1B High failure rate.

kbradio

Member
K
Join Date
Oct 2003
Posts
11
Been seeing a high failure rate on these PLC's on 2 of our process. The control power is feed through a APC UPS to a 24VDC power supply to power the unit. Getting a hard fault where the OK LED comes on red and stays red. It never sequences through all the LED on power up. Tried the hard boot by holding in the reset button and applying power.

Has anyone else seen a high failure rate on this model PLC? TIA..
 
I've only used one of these on one project in the past couple years, and it hasn't had any issues yet. Might need to put a power analyzer on the UPS?

EDIT: Ours was also on a 24VDC power supply fed from a UPS (Tripp Lite SU1000XLa).
 
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I would replace the UPS, I have maybe 100-150 out running and never had an issue, are you getting them repaired? I would like to see if we can repair them.

Thats also a expensive failure these days because the lead time on them is terrible, I had a customer looking for one with a machine down and they end up going with a different processor.
 
geniusintraining said:
I would replace the UPS, I have maybe 100-150 out running and never had an issue, are you getting them repaired? I would like to see if we can repair them.

Thats also a expensive failure these days because the lead time on them is terrible, I had a customer looking for one with a machine down and they end up going with a different processor.
Click to expand...
Just had another one fail, same problem. changed the UPS as recommended last time.
 
Thank you for the reply. Us using a AB 24 VDC power supply and an APC UPS for the 115V feeding the AB power supply. The Compact logix PLC is brand new from AB.
 
to eliminate UPS issue, i would bypass UPS and directly connect 110V AC to 24V DC power supply.
we have many brand new APC UPS failure, some even fails 1-2 weeks.
in our plant there are more than 10 1769-L24ER-QB1B, never have any issue.
 
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This system ran for 2 years without the APC UPS and lost 2 PLC. So thought if add a UPS it would help.
 
My experience with APC is the same as with Mike. Causing more headache and not worth the trouble.
APC was the product that geared towards more computer equipment. It is now owned by Schneider btw. Do you have the part #?

If I understood you correctly: you have more than 2 PLC systems, but system #1 & #2 failed more than once,
and you have since added UPS to them, but they are still failing, correct?
If that was the case, I’d start looking at the IO. I did have an input failed, and had to switch to a different input.
 
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There is one of these installed in the cabinet. Allen Bradley 4983-DC120-10 Surge and Filter Protector
Filter, Surge Protective Device, 120 Volt AC, 10 Amp, Din Rail Mount, 150 AC, Maximum Continuous, Operating Voltage
 
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Can you still connect to the PLC via any interface? USB/Ethernet? Is the hard fault a real fault that has a fault code somewhere? If we are just trying from a "Red Light" troubleshooting standpoint, as others said, the best way forward is to keep isolating things, making power smooth, and preventing ground faults in circuitry.

Regards,
-PreLC
 
APC is trash.

If you lean on:
- consumer gear, go CyberPower.
- IT/enterprise gear, go Eaton.
- In-cabinet/industrial gear, Phoenix Contact.

As for the 24V supply being suspect, the only way to be sure is to log its output voltage.

This is an L24, so the embedded field I/O might be subject to something in the field. Opto-isolation ought to be a thing here, so the mainboard should be protected against whatever hits the IO terminals.

Another corner possibility is if the controller is attached to a PoE switch port. Because there’s about 272945 different PoE versions, modern switches try sensing the load and setting an appropriate output voltage. Some earlier stuff doesn’t and fries unprotected equipment. The 5380 controllers have robust isolation transformers placed in series with their Ethernet ports, but I’m not sure how or even if the 5370 models do.
 
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I've used a few L24's over the years.
Only problem ever was when a coworker tried to connect to one over Ethernet, It faulted out. Told him to try USB and the same results.


5 mile drive for me. Tried Ethernet, didn't work. Plugged in the trusty USB cable, downloaded my program. Viola!


I think there were some issues with those back then when you had to have the original laptop connection to make it work.


Who the hell knows what Rockwell is ****ing up for everyone???
 

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