1769-OW16 Output Cards, Are they fused?

gbradley

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gbradley
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Apr 2002
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I had a couple of Output cards go bad out in the field last week. AB 1769-OW16
This happened on two completely separate machines, during the same week.
The thing is, that it wasn’t just one Output, or the first 8, but the entire card.
When the Output is energized, the LED lights up, but no continuity between VAC-VDC and OUT.
I’m guessing maybe its dirty power that kilt them.
Is there a fuse inside these cards?
 
The data sheets do not say that they are fused, but as relay outputs, there are limits on what load they can take.

What voltage and current load have they been taking, and was there a fault on that load that could have taken out the card?
 
If you can get the module into a quiet environment, trigger the outputs manually. You can always hear the click of the relay.

If the relays aren't clicking, then something's wrong with the circuit or the supply that powers them off the backplane connector.

You've already seen that the OW16 is divided into two groups, of course; there are two separate banks of relays, with two separate common source terminals.
 
If you had a very high overload condition on more than one of the outputs, you could have melted the common connections to both AC-DC Common pins.

I would have expected the upstream fusing to protect the relays, but that doesn't mean it did.

I don't think there's any confusion here: continuity is easy to measure and a reliable indication of a conductive path.

While I haven't examined those cards specifically, typically A-B selects relays with a 100% or more service factor relative to the card specs. Have a close look at your loads and your fusing to be sure somebody didn't stick a 20A fuse someplace because they didn't have a 5A handy.
 
Since I was throwing out the card, I pulled apart a couple of the Contacts. One looked pretty bad. some of the others were pristine, so I don't know why none of them worked?
It will be a while before I can get over to look at the actual machines, but when I do, I'll definitely look to make sure that nobody replaced a fuse with a bolt or something.
Those NY24W-K relays are Fragile.

NY24W-K_Contact.PNG
 
Thanks very much for taking the time to perform an autopsy on the card and post the photograph and details.

I'm surprised that the relays are only 3A rated; A-B rates the module at 2.5 A per point at 120/240V AC and 2 A per point at 24 V DC. There's always a tradeoff between over-building and size, I suppose.

If just one of the contacts was worn, that's the load you want to check on, of course. Can you tell us what voltage and type of load it was ?
 

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