AB output card question

djw

Member
Join Date
Mar 2003
Location
Olympia, WA
Posts
5
Hello all. Asked a question of a couple of guys the other day. We have an AB PLC and one of the output cards had a problem the other day. The old card was a 1746-OA16, series C and the only replacement I had on the shelf was a series D. The question was, "Can I substitute the series D for the Series C?". After trying it, the answer is no. It messed up the logic on the PLC on other cards. Any body got any ideas why? Thanks. Jeff W
 
The old card was a 1746-OA16, series C and the only replacement I had on the shelf was a series D
And the OA16 is just your garden variety 120VAC triac output module regardless of the revision level. There are no smarts on the card so using either one should be of no consequence.
The question was, "Can I substitute the series D for the Series C?". After trying it, the answer is no. It messed up the logic on the PLC on other cards. Any body got any ideas why?
The answer is yes, you can substitute the D for the C series and if you found a problem on other cards or in the program because of it, then there is some other problem afoot. I suspect you need to look a little further. Rev levels on this card are not your culprit.
 
yup

Thanks Randy, that's what I thought, but my boss says it won't work. Can't tell me a reason, so that's why I asked. Appreciate your help.
 
Series c/d

When the series D card was installed, the plc would not let the setworks (hydraulic positioner) on the machine adjust when the operator selected different positions. Interestingly enough, the other machine on the PLC appeared to be working normally. Two different machines are controlled by the same plc, seperate input cards and output cards for each machine. The problem may be that I did NOT change the output card in the setup for the plc. Or maybe not. I just swapped cards, thinking they should be functionally identical.
 
Curious question here, but, did you power down the rack before you changed the cards?

The revision level on the output card should have no, none, zero, nada bearing on the situation. There's no configuration to change, no logic, for all intents and purposes they might has well not even marked the revision change on the piece, for your purposes they are identical, NOTHING AT ALL TO DO EXCEPT CHANGE IT OUT!

Reason I ask is that if you did indeed power down the rack, then nothing that you've listed here should be happening at all. NOW, that being said, if you did NOT power down the rack, then there's no telling what will happen, or what you may destroy.

Case in point, recently one of my I&E techs discovered a faulty thermocouple card in a data acquisition system. It was running on an SLC 5/03. He quite literally forgot that the SLC family is not hot swappable, and simply pulled the card out replacing it with a new one.

About an hour later, when he cam and found me, we determined that not only had he ruined the new thermocouple card, but also the rack and the processor. Now, this was a little odd because usually it doesn't get the processor. But, toasting the new card and the rack is quite the norm.
 
pwr dwn

Thanks Bakerman,
Yes, I did power down. That's the reason I'm so confused. I thought it would swap without a change too. When we reinstalled the old card, the system operated as designed. Puzzled does'nt begin to describe my mental state. I was hoping someone here might have experienced a similar problem and have a reason. Then I could show my boss why it was happening. Well, I'll keep answering, maybe someone will have an idea. Thanks again for the answers guys.
 
I think it's time to call in an AB rep. The situation you've described shouldn't have happened. A 1746-OA16 of any revision level should replace any other 1746-OA16. If a newer version is incompatible with earlier ones, they should give the new one a new part number. If there are any incompatibilities with CPU models or firware versions, these should be spelled out in the documentation that accompanies the module.

Some things to consider: Are you sure the series D module was functional? Does it work in a different PLC? Are you positive you put in a 1746-OA16? By that I mean, could the box have been mislabeled? Less likely, but not impossible, could the wrong circuit board have been assembled into the plastic housing labeled as a 1746-OA16? Did the PLC report any faults when the series D card was installed? Could the terminal strip have been not seated properly when you had the series D card in place so that external power wasn't getting to the card? Was RSLogix showing the output(s) to be on? Were the LEDs on the face of the module showing outputs on? Does this module have onboard fuses?
 
I am curious too. Where is Ken.

I am curious as to why the hydraulic positioner didn't work.

Now djw says the hydraulic positioner did not work. Now I will make an assumption. I bet the hydraulic position card is a 1746-QS. Did you check to make sure the M0, M1 configuration was right when it failed? Perhaps the SLC5/0x' configuration was erased or invalidated when the series D card was installed. This may have happened when the configuration wasn't changed to match the new card.

I like the idea of reading the rack again and making sure the 1746-QS is still configured correctly. I would bet that the system will work with the seried D after reading the I/O and making sure all the intelligent modules are correct.

The series D should work.

Let us know what happened.

[TANGENT]
If you look the the bus inteface chip for the 1746-QS it says potato chip on it. Some one at Rockwell has a sense of humor.
[/TANGENT]
 
Ok, now that we've exhausted the obvious, I'll mention one thing that did happen to me.

I was installing some new panels in a paint shop. I had one card that went DOA (I said "went" since it only worked for about a day). It happened to be 1771-OAD. I powered down the rack, pulled the old card out, and slid in a new one expecting everything to be hunky dory. I might add that this was the first time I had a 1771 card die in about 7 years. Anyways, fired it back up and NOTHING worked right. I had stuff all over the place going crazy, just wild. Whole thing was screwed.

Turns out, when the electricians had installed the conduits into the panel's top plate, they had neglected to always cover the rack. I say always because apparently they made sure to cover it when I was there, but neglected to anytime I was not there, as I later found out. Anyways, a metal burr had been sitting ontop of this card, and when I removed it, the burr fell down into the rack. The problem came when I re-inserted the new card. I caught the burr and crammed it into the backplane connector. I lost the card, the rack, the power supply, and a few other cards.

I learned a lesson. Never forget to take the time to check the rack before you power it up. Turns out the rest of the rack had shavings in it as well.

Bakerman to the electricians: "Now.......what did we learn?????"
 

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