1794-ASB Failure Issue

[BColnago 0]

I have a 1794-ASB series A (13 years in operation) that just failed and in doing so it activated all 16 outputs on each of two OB16's. As you might imagine this created havoc in our process. Has anyone else experienced an ASB failure that caused digital outputs to activate? FYI at the time of failure the local fault led was on and the adapter fault led was off. We powered all modules off then on and the digital outputs reset to not activated, and both the Local and Active fault leds were on, so we replacd the ASB with a spare and then everything worked fine. I have read elsewhere on this forum that ASBs are rather unreliable. Is this just anecdotal or factual? Has AB ever admitted a problem with the ASB design? Just wondering as we have other ASB Ser A in service and wondering whether we should replace these. Edited 25 Sep 2014 by BColnago

[Ken Roach 194]

Failing in the ON state is very rare but not impossible. Yours is just the second incident I've ever heard of. My opinion is that the 1794-ASB is very reliable. A quick check of the RA Knowledgebase filtered for Service Advisories for the 1794-ASB finds none. The number of less serious compatibility notes is also fairly low. I've personally commissioned many dozens of them, and the only failures I had were from damaged connectors due to ham-fisted installers. The FLEX backplane can be damaged by incautious assembly, which is one of the reasons RA developed the POINT product line, and improved the connectors on the FLEX backplane (while preserving backward compatibility). Virtually all of the 1794-ASB posts I see are related to replacement of old ones with Series E, which is when the DIP switches were partially re-mapped to support 32-bit modes.