A-B 1771-BCM/BEM glitches

J

Thread Starter

JD

Two 8 slot racks, a 5/60 in each, a BCM module in slot 0, BEM module in slot 1 for each. When the primary is put into program mode, the secondary does not take over. I have no experience with A-B's backup system, but have heard horror stories. Does anyone have any tribal knowledge, as far was what to look for?

Another problem, and what started all of this was a RIO fault that took out all the racks (1/4 rack block I/O) on one of the channels. NONE of the racks came back until one of the blocks was removed from the link. The customer did the troubleshooting in the beginning, so unfortunately we do not have firsthand knowledge of what was done.

So I guess there's two issues:

1) an existing problem of a backup system not working.

2) some glitch in the BCM/BEM module hardware that we we are suspecting as the cause of the initial RIO problem.

Thanks for any help.
 
B

Bill Braband

I did a 5/20 backup 3 years ago. I was a nightmare. The main obstacle to get over is all the BTW's and BTR's. They must match up. Also the blue hose connections must be correct. I will go back and look up my doc's for you to see if I can help you a little more
 
1/2 slot addressing. What happens if it's not 1/2 slot? Just curious.

It has never worked, to the best of their knowledge.

In one of A-B's bulletins on testing the system, they mention resetting all O: bits relating to the rack/slot where the BEM/BCM are installed. It just so happens that O:1/0,1, and 2 are on (not used in the logic, don't know why their on). Any experience with this?
 
BEM-BCM that I used once was used along with a standard block transfer program. We never faced any backup problems.

Check cabling and block programs.

What about having different programs on primary and standby or programs not synchronised.

Anand
 
> 1/2 slot addressing. What happens if it's not 1/2 slot?
> Just curious.

When using the BCM and BEM the chassis must be set for 1/2 slot addressing or the system will not function. If only using the BCM module the chassis may be configured for 1 slot.

> It has never worked, to the best of their knowledge.

No one ever tests the system to see if it will fail over? How did the vendor ever get paid?

> In one of A-B's bulletins on testing the system, they mention
> resetting
> all O: bits relating to the rack/slot where the BEM/BCM are
> installed. It
> just so happens that O:1/0,1, and 2 are on (not used in the
> logic, don't
> know why their on). Any experience with this?

Those bits should be off. Bit 0-7 in O:000 may appear ON/OFF because these bits are used for the Block Transfer communication. But the bits you show above in O:001 should all be off.

Have you verified that both processor are the exact same Model, Series, and Revision numbers? The processors have to be identical. I think someone else already mentioned that the programs have to be identical in both processors.

Are the BCM and BEM modules identical in both processors?

Does the program contain the necessary BTR instruction to enable the proper operation of the BCM/BEM module?

If you want you could send me a copy of the program.

Bradley G. Hite
Intertech Inc.
mailto:[email protected]
http://www.myplc.comTeaching Practical Skills for a Technological World
 
Hello,

Have you checked the dip swihc setting on the BCM and the BEM in both the Chassis? Check the connections and the Dip Switch setting. Changeover is purely a hardware function. If changeover is not taking place at all that means that there is something wrong with the hardware, most probably the hardware is not set correctly.

Hope this helps!

regards,

Vikas
 
Thanks for all your help. We found 2 problems during a scheduled shutdown:

1) CLR/BLUE backwards on one of the BCM's.
2) BEM in one of chassis' had a bad channel

After the wiring was fixed and the BEM was replaced, the system switched over just fine, multiple times.

Thanks again.


 
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