1747-ASB Remote I/O problem but without error diagnostics

I have a machine that includes a PLC5/40 with two PLC5 remote racks, a PV1000e, and a SLC remote rack. About 24hrs ago, our second shift electricians discovered the problem when trying to put the mahcine back in service after it had be idled for some time (approximately 1 week).

For some reason, the SLC remote rack is not updating the outputs nor sharing with the PLC the inputs. All of the other remote items are working fine. (Panelview, local rack, and other DH+ PLC5 racks.)

The SLC rack is as follows:
The chassis is a 1746-A7.
The adapter is a 1747-ASB.
Then I have a 1746-OW16, a 1746-IA16,1746-OW16, a 1746-IA16,1746-OW16, and a 1746-IA16 in that order.

The ASB is configured as follows:
SW1: 11101011
SW2: 01011100
SW3: 01000011

I have confirmed that the PLC is set to 230.4 kilobaud.
I have confirmed that the rack is supposed to be "Rack 5" in the PLC.
I have confirmed that we start with Group 0.
I have confirmed that my ASB configuration is set to 2-slot and 4 groups.

My comm LED is solid green.
My fault LED is off.
The diagnostic display says 'run'.
However, my outputs are not turning on even though the PLC is telling them to. The PLC is not seeing the inputs.

If I unplug the blue hose at either the ASB or the PLC, the diagnostic display changes from 'run' to 'noc'.

If I change sw2 bit 7 from off to on, then the diagnostic display changes from 'run' to 'ade'. This confirms to me that my logical group number is correct.

I have removed the plugs of all of the outputs. Same situation (solid green comm and 'run').

I have removed the plugs of all of the inputs. Same situation (solid green comm and 'run').

I have swapped out the ASB card with another. Same situation (solid green comm and 'run').

I have swapped out the chassis with a new one. Same situation (solid green comm and 'run').


As I told the electrician who was working with me today... I have run out of bright ideas.

looks like you've already nailed down all of the obvious troublemakers ...

here are a few extra straws at which to grasp:

try changing SW3-3 to ON (selects Restricted mode) ...

try changing SW2-7 to ON (selects room for 4 groups) ...

and I hate to bring this up, so no offense intended, but is the PLC processor in the RUN mode? ...

again, no offense intended, but the PLC addresses that you're using are something like the following:

O:050/0 thru O:050/17 ... and ... I:050/0 thru I:050/17
O:051/0 thru O:051/17 ... and ... I:051/0 thru I:051/17
O:052/0 thru O:052/17 ... and ... I:052/0 thru I:052/17

NOTE: all of these are OCTAL in the PLC-5 - but the LEDs on the SLC modules are usually numbered in DECIMAL ... sometimes that causes confusion ...

so, just to nail this down, the system was WORKING correctly with all of the settings that you've listed ... then the system was shut down for about a week ... no changes were made to the system ... then the system was powered back up ... now it "looks like" the remote chassis is communicating with the PLC-5 processor – based on the LEDs and the codes on the ASB ... but ... the output bits will not turn on ... and the PLC-5 doesn't see the input bits changing ...

this is truly weird ... regardless of what you find – PLEASE come back and tell us ...

and I truly hate to keep bringing up the obvious – but you ARE "online" communicating with the PLC-5 when you're toggling the output bits – and monitoring the inputs – right? ... again, I mean no offense – but I HAVE seen people make that mistake before ...

if all else fails, I'd disconnect – or power OFF – all of the other remote components except for this one that's giving you trouble ... then use the Auto Configure feature on the PLC-5's Channel Configuration screen for 1B ... see if the rack pops back up with the proper settings and addresses ...

I hope this helps ...

Ron,
Thanks for the suggestions. Yes, you are right about the group number. Somehow I messed that up in my narrative. Even though I typed it in incorrectly, I had the correct dip switch selection for 4 groups on the ASB itself.

Anyway, I shared your suggestions to the third shift engineer on watch. He decided to get a fresh ASB card out of the crib and try it. This card worked correctly with the listed configuration.

SW1: 11101011
SW2: 01011110
SW3: 01000011

In summary, for those who will look at this posting 3-6 years from now with the same problem. We swapped out to a new ASB card. The only difference between the one that we swapped out before and the one from the crib is that the one from the crib was never used before. It might be a newer series or manufacture but I don't know for sure.

Thanks.

well, we're glad that you've got it working again ...

I've heard of cases where a particular DIP switch has been "pressed" to the proper ON position - but then didn't quite make proper contact ... there's only a small amount of voltage on those things - so any amount of "dust" or "film" deposit in there could prevent an electrical connection ...

so - the DIP switch could be in the "correct" physical position - but still not be giving the "correct" configuration setting ...

let's just chalk it up as one of those "electronic hairball" issues and move on ...

thanks for the update ...