AB CLX to 1794 RIO wierd comms problem.. help needed!

[AndrewB]

Hi All.. We have a little problem at the plant I work at...

we have been in contact with techconnect and not really achieved much so far.. just while we are waiting for a complete hardware swap to arrive does anyone have ideas for us. I think we are about out!


We have a L55 CLX on V13 with a RIO network with quite a few FLEXIO Racks on Series D 1794-ASB adaptors.

this morning we had one output (valve coil) short and take out the ASB (no lights) on the rack it was controlled from (and yes all the outputs have individual fuses)

we have:
replaced the ASB with the same series
set the dip's the same.
swapped all the TB3's out
restarted PLC (to reinitialise the block transfer)
swapped as many modules out that we have
did a download (rockwells request)
baud rates are correct. 232k
There is only discrete IO fitted IV16's & OM8's


Now the strange part:
1. The new ASB shows up in the IO tree as working with no errors.
2. The ASB has no errors at all. solid green light.
3. we have inputs LED's coming on at the flex IO from the field devices
4. Inputs DO NOT change state in the datatables at all
5. The RIO network daisychains past this cabinet and everything downstream and upstream on the same network is working fine...

in the diagnostics sometimes this cabinet appears as a full rack, other times as 3/4, others as 1/2. A full rack is installed (7 units)


I suspect the hardware.

 

[JohnCalderwood]

Suspect hardware....

1) Power off the rack and remove TB3s, to check if the pins are straight and not bent - I have had that issue before, especially when you are in an awkward position inside a panel...if that does not work then...
2) remove all the I/O blocks and start with just the ASB and the TB3s - you should have a rack fault as the PLC will not see the modules. But does it stabilise the rack size?
3) replace one card at a time to see if you get any response.

Best of luck, as these can be tricky....

 

[AndrewB]

your not wrong on tricky! give me Ethernet Adaptors anyday..

my colleague is in there now with a new rack full of hardware fresh off the plane so fingers crossed at the moment!

Thanks for the reply

 

[JohnCalderwood]

It's not the adapter.....it's the fiddly Flex I/O bases etc....

 

[AndrewB]

yes i'm aware of that..

its just way easier to diagnose on Ethernet (not the fiddly connections though)

 

[AndrewB]

got it going..

pretty much every TB3 and IO module was blown up..

Thankyou for your help!

 

[JohnCalderwood]

serious fault then.....all looks healthy, but in reality all is toast!

I had something similar in the mid-90s with a 1771 rack of analogue cards - all looked good and healthy, but there were no signals coming in to the PLC5. I got called at 2am to look see...
Went to check the 24V DC, got a wee belt from the power supply, which woke me up.....turned out the 415V from a faulty oil-filled Danfoss VSD had found it's way over the mA card to the 24V PSU and trashed the entire 16 slot rack of analogue cards...got it going about a day later once they sourced enough cards for us.

Glad you got it going....

 

[Ken Roach]

The Series B bases were a lot better about lining up and not bending the pins, but you still had to pay at least a basic amount of attention when assembling them.

When FLEX first came out we sold truckloads of it to a GM plant, and they had a lot of out-of-the-box failures. There was a big management meeting, and the installing electricians complained about how hard it was to get the bases to line up.

Our chief engineer took two of them out of a box, with a bit of DIN rail. He showed them how you hook on the retaining hook on the top, then snap the TBs downwards onto the DIN rail, then slid the backplane connector over with his thumb.

"Never seen it done like that," the installation leadman told him. "We hook them on the bottom, then push them down at the top. The damn things are so hard to get set, we have to use a mallet."

They then brought out six hundred 1794-TB3s, all of which had been smashed with a hammer.

 

[Ronnie Sullivan]

Not quite the same but along the same lines - Last week I was fitting a new miniature circuit breaker to a distribution board and noticed all the other breakers had the din-rail fastener clip missing. (they were held in place by the bus bar tag only)

They were all in the bottom of the board broken.

I asked the electrician what had happened: he said that those breakers were impossible to fit, you have to thump them to get them in. (I think it was a Square D Type Q board)
Now I admit, if you have not fitted them before, it can be a puzzle but thumping them in is not usually an option - especially if you have broken the retaining clip off the first one.

 

[Geospark]

Here's some "official" info which outlines "what-to-do" when faced with Flex I/O rack issues...

44791 - Troubleshooting Flex I/O system rail issues
Access Level: TechConnect

& here...

39037 - Physical Problems on1794 Flexbus Adaptor, Terminal Base or Module Cause Errors
Access Level: TechConnect

...in the diagnostics sometimes this cabinet appears as a full rack, other times as 3/4, others as 1/2. A full rack is installed (7 units)

In that second technote, under the section "1794-ASB Remote I/O Module", note one of the possible symptoms you may be faced with: "The Adapter has a different Rack Size than is expected".

You will notice how the rack size is not hardware set. When the rack powers up, it reads the live rack modules, or rack "image", and when it reaches the outmost module it will have determined the current rack size. So when you see an incorrect or sporadic change in the rack size, you can be sure there is a pin, terminal block, or module(s) issue, causing the rack size to be read incorrectly.

While I think most of us can agree that the assembly was always "tricky" for the Flex I/O racks, many issues can still be put down to poorly "fitted" racks, by poorly trained installers.

I once opened a hinged door on a small Flex I/O enclosure that was giving trouble and the rack was hanging upside down off the wires. It wasn't even hooked onto the din-rail correctly. They had propped it up against the din-rail with short pieces of trunking cover at an angle against the inside bottom of the enclosure. These fell away over time and the rack flopped forward. That made me very nervous as to how the pins had been aligned when fitting and sure enough I found some of them were slightly bent. It had been working for some time, but I reckoned the fall forward and knock the rack got was just enough to unseat them and start giving trouble. I can imagine them having torn their hair out trying to get them onto the din-rail correctly before coming up with the ingenious idea of propping them up.

When having to install Flex I/O I remember one guy used to say..."Flex - Fit and Flee!"

Regards,
George