Sanity check

[DarrylR]

Hello all, I have a Controllogix 1756-L61 with some RIO. There are a couple of 1734-OB4E's that have gone bad. (no output voltage) My boss found some online and we received them the other day. 7 of them. Same part number, same series, revision 3.022. The configuration for keying is setup as "compatible module" with the major revision at 3 and the minor at 1. My understanding is if the replacement is the same, or higher, with the minor revision we should have no problem. Correct? Because all 7 of these modules we received do not work. I suppose it's possible, but I find it difficult to believe they're all bad.

 

[A_G]

I am not sure. But I would try to select Disable Keying just for troubleshooting purposes

 

[DarrylR]

Thanks- That was tried, no difference.

 

[plvlce]

The configuration for keying is setup as "compatible module" with the major revision at 3 and the minor at 1. My understanding is if the replacement is the same, or higher, with the minor revision we should have no problem. Correct?

This is my general understanding as well, although I have seen a (third-party) device where a higher firmware would not work with 'compatible keying', but did with keying disabled. Regardless, unless it's giving you configuration errors the keying is almost certainly not the issue.

I agree that having all your modules fail with the same symptom suggests a different problem. Where are the problematic modules located in the rack; do you have other modules to the right that are still functioning? I suggest checking out the terminal bases on both the problem modules and to the left of them -- output power is supplied from the internal bus, so I could see an issue with the bus connections in the terminal bases causing a loss of voltage.

 

[glennz]

"My boss found some online..."

There are counterfeits out there, and we've been bitten by that same bug. Maybe check with Rockwell or your distributor to determine authenticity.

 

[joseph_e2]

I would try a different slot that has a working module in it, just to rule out the chassis. But I'm a little sus about the source of your modules, honestly. There are a couple of used part resellers I'll trust, but someone random on e-bay...not unless I was desperate.

 

[Picklemon]

Are the new cards showing communication errors on the Point I/O adapter or PLC or is it just the missing output voltage problem?

If there are no communication problems, then check the wiring of the device(s) being controlled.
These cards have an electronic fuse that will stop the output voltage if it detects a short circuit.
The output status LEDs will be red, when the output is on if it's faulted.

 

[ASF]

When you say "all the same series"...which series, specifically?

A 1734-AENT or 1734-AENTR requires series C I/O modules. In general terms, series A modules only supported DeviceNet adaptors, and series B supported DeviceNet and Profibus adaptors. There are a few exceptions, but your module is not one of them.

See this technote (techconnect required) for additional detail.

 

[joseph_e2]

When you say "all the same series"...which series, specifically?

A 1734-AENT or 1734-AENTR requires series C I/O modules. In general terms, series A modules only supported DeviceNet adaptors, and series B supported DeviceNet and Profibus adaptors. There are a few exceptions, but your module is not one of them.

See this technote (techconnect required) for additional detail.

That's interesting. Definitely something to keep in mind if I need an alternate source for scarce modules in the future.

 

[DarrylR]

Good info everyone, thanks. Definitely the cards. Purchased another batch from alternate source and they work fine.

 

[A_G]

Good info everyone, thanks. Definitely the cards. Purchased another batch from alternate source and they work fine.

Wow bad luck with those cards I guess. If you feel comfortable can you share where you got them from, so we can avoid them?