Steve Etter
Lifetime Supporting Member + Moderator
Ok. Riddle me this one.
I have a machine that's been running for a couple of years. It is outfitted with a AB 1768-L43S Processor with a 1769-IQ16 digital input module in the first slot. Today one of the inputs from a 2-wire prox went out - no light on the prox and no signal on the input module. Once all of the field hardware was verified to be working (and indeed it all was), I identified that the PLC input, itself, had to be the culprit. I was able to do this by lifting the wire from the "bad" input and touching it to a known "good" input. Doing this, prox works again and a signal is received by the PLC. Putting it back on it's original input, however - nothing.
Bad input on the card you say? Seemingly not.
I replaced the card with a new one and the same input still does not work. What is going on? The only thing left, it seems, is the processor and something with it. At least that's all I can think of. Fortunately there was a spare input on the same module and by moving the wire and some minor reprogramming, I was able to get the machine going again.
Finally, I took the old module back to my office and connected it to a processor I have on the bench. The suspect input (12) works just fine on it.
Any thoughts?
I have a machine that's been running for a couple of years. It is outfitted with a AB 1768-L43S Processor with a 1769-IQ16 digital input module in the first slot. Today one of the inputs from a 2-wire prox went out - no light on the prox and no signal on the input module. Once all of the field hardware was verified to be working (and indeed it all was), I identified that the PLC input, itself, had to be the culprit. I was able to do this by lifting the wire from the "bad" input and touching it to a known "good" input. Doing this, prox works again and a signal is received by the PLC. Putting it back on it's original input, however - nothing.
Bad input on the card you say? Seemingly not.
I replaced the card with a new one and the same input still does not work. What is going on? The only thing left, it seems, is the processor and something with it. At least that's all I can think of. Fortunately there was a spare input on the same module and by moving the wire and some minor reprogramming, I was able to get the machine going again.
Finally, I took the old module back to my office and connected it to a processor I have on the bench. The suspect input (12) works just fine on it.
Any thoughts?