DeviceNet Bus Off Issues

Hey all, I've been working with DeviceNet for 6 years now and have done several large projects. On a project we didn't get we were called in about a year ago to fix the mess they had gotten from the previous contrator. We used the Media Checker and also the NetAlert meter to verify that our corrections were good and all the segments were working great. I also performed a full power audit and full calcualtion method for the larger highways that needed multiple power supplies.

THey are currently having an issue we have gone and checked out twice. They can run for 2 days or 2 months without a problem on this one segment then they go bus off. Once it happens it will occur several times then clear up.

The NetAlert readings are all close to the baseline we orignally took. The segment is as follows:
Trunk: Mid cable, 468' in lenght
Drops: Mid Cable, cumalitive drop length is 156'
5 Turck multiport taps
14 total device (12 vavles and 2 AB digital armor blocks)
1 power supply at the begining of the highway and grounded

We have check voltages, ground loops, comm voltage and nothing is out of line. Everything is installed properly.

I'm thinking it's a connection issue or a bad device. I'm now grasping at straws to help this company out.

Any ideas?

It sounds like a short somewhere on the power supply pair or power to gnd. I'd have to say a bad field connector, tap, or nicked up cable somewhere is intermittently causing the power to short and that sends the scanner into a Bus-Off condition. Only way I know of to clear the fault is to reset the scanner. I think you are on the right track with your troubleshooting. If you have an inline plug in resistor check that as well.

Just from what I read, 1 power supply is not enough for that long of a run.

you said you checked the power etc. but the voltage drop over the distance might cause that sort of problem?
and you didn't post the amperage of that supply either, even still that would exceed AB's specs on length from the PS.

Ohh, and I'm very experienced in deviceNet systems(but still learning)