Can't get on-line with 1756-CNB/D

I cannot get online with my controlnet network. I have verified the communications path. The card is Rev 5.22. The 'OK' light is blinking green, and the CH A light is blinking red. The readout is reading A#01(Address), NET ERROR. I tested the controlnet cable for shorts and resistance(OK). Verified terminated 75ohm resistors in place, and taps correct. 1756-CNB is connected to a 1794-ACN. The 'OK' light is blinking green. The CH A light is blinking green. Comm path is correct. When I try to go online, I get a 'Communications Interface Device did not respond' error, transition to on-line failed. Below is a pic of my comm path.
Error CNET:80AE



I found the following info in the user manual:
“If you configure a keeper on one network and then use it on another network,the conflicting information can make it difficult to use RSNetWorx software toschedule the new network. In extreme cases it may be impossible to go online,more commonly you get many apparently irrelevant error messages aboutdevices that existed on the old network but do not exist or are different on the new one.
• For more information on the network keeper, refer to the section Understanding the Network Keeper.
• For more information on how to reset valid keepers to an unconfiguredstate to resolve mismatches, see the RSNetWorx software online help

I tried to reset the valid Keeper as per the RSNetworx help, but when I right click on the module, the class instance editor is greyed out and not selectable.

Could it possibly be a bad CNB card?

That red Channel A LED and the NET ERR message indicates that the module doesn't see a good ControlNet signal. Until it does, you won't be able to use it to "go online" with the ControlNet.

It is possible to damage a ControlNet channel without damaging the module. I'd try to substitute the 1756-CNB into a network with a known good cable and tap to see if it picks up a green Channel A LED there.

Thanks Ken. My problem is that this is a couple of demo units set up in my home office, with about 10' of cable between units. Below are the readings I get on my cable from cnb connector to cnb connector through the taps with the 75 ohm terminating resistors in place.

cnb to cnb signal - 1.2 ohms
cnb to cable ground with resistors in place - 38.2 ohms
cnb to cable ground without resistors in place - open

As this is a project I'm working on in home office, I have no way of testing the card, in a working system.

Can you let me know if you see a problem with the above readings?
I appreciate the help.

Is this a card that has been previously used? Did you use the ClearKeeper utility?


Is the card inhibited in the program?

Oakley, no this card has never been used before. For all I know it maybe an 'EBAY' special.

I did try to use the 'Clear Keeper Utility'as per the help,but the 'Class Instance Editor' is greyed out and not selectable. I'm not sure why it won't let me do this.

Thanks

Are these readings what you would expect?

See previous post. Are the resistance readings what you think?

With 2 terminating resistors of 75 ohms in place you are spot on with those values.
Applying ohms law, 75 ohms divided by 2 resistors = 37.5 ohms,

In reality anything between 30 or 75 ohms will be OK even wider values are probably OK.

With such a short piece of cable only 10' , it may even work with no terminating resistors, but its good habit to use resistors, as real world cables are longer and do cause reflections, and do need resistors

Would everyone suggest that maybe I should get another 1756-cnb?
I have tried everything I can think of with this one, and have come to my wits end.

Have you tried to update the firmware?

CH A light is blinking red. The readout is reading A#01(Address), NET ERROR.

Click to expand...

Until those symptoms go away, this 1756-CNB won't be able to connect to any ControlNet network.

It is possible (and consistent with the symptoms) that this module has a damaged ControlNet Channel A transciever. A module with a possible history of aftermarket/surplus sales sounds more suspicious than one new out of the box.

If you can't get a distributor or Rockwell office in your area to help you out on this, send me a PM and you can send me this card to test. I have active CNet networks, known-good taps and trunks, and ControlNet signal analyzers available.

How would I go about updating the firmware. I am using RSNetworx Version 8. I'm pretty sure I have the latest buy not positive.

Ken Roach - I will check with my boss and see if sending it to you should be my next approach. I thank you very much for the offer. I will get back to you.