I have a Norstar CICS sytem in a building with three mig welders. The CID card gets hosed up 2-3
times a week.I have changed card and even the CICS
and all surge equipment. I do have a te-600 ups on it also. The CICS I took out of this location, I installed at another location with absolutely no problems. The weird thing is the system doesnt go down just the trunk card. When you press L1 or 2,3,4, it says no service.I believe it is a power issue related to mig welders. How do I prove it, the customer wants me to change all voice cables to shielded wire on my dime. Help me PLEASE!

I don't think changing the voice cable that go to the stationswill help. You say when the system goes down it's just the lines, the sets remain operational since your are receiving a screen message.

You say the system removed works in another location, but do the trunk cards work in other systems after they've been removed?

You might want to try a ferrite bead on the CO cable to shield it from the RF burst caused by the arc.

We did replace trunk card after it had happened a couple of times. Then we replaced entire system with another new trunk card. The trunk cards and systems were both new not refurbished. All previously installed equipment at this site has worked perfectly at the other locations we installed them. We were a little bit nervous about them so we followed up with the new owners a few times and absolutely no problems.

How close is the demarc and CICS to the welders? If they are commercial welders their power supplies sould be isolated from standard 110V circuits. Unless its a confined space I dont believe EMI would cause an issue unless they had leads laying on or coiled up on conduits or cables. Is it a metal building?

The phone company demarc is very close to one of the welders. The CICS is 80 feet away and yes it is
a metal building. the other two welders are on the plant floor but this is very small commercial building probably 90 feet by 120 feet.

I would try to isolate or relocate the phone companies demarc from that one welder before I recabled. From what I understand its only affecting the trunk cards.

This may or may not help...

I had a system reboot from time to time, system was replaced and these line cards also:
NT7B75AAAF GATC CLIDNT7B75AAAE CII NT7B66DW

Fix in the end was using card that eneded in G

"There was a problem with cII card ending in D and E and first version F. These cards would just fail for no reason and a reboot would correct the problem. this was resolved in the G cards"

Thanks guys, you all had some good ideals and I am going to move the demarc which is only 6-8 foot from 3 phase welder to another location upstairs next to the CICS. I dont know the card numbers but
I will look into that also, by the way that 3 phase welder was installed after demarc was already there.
I do really appreciate your help.

I had a Panasonic 824 that would die when the MIG welder was in use. The RF field generated by the MIG welder was feeding through the demark back to the KSU. I ended up grounding the MIG welder with a copper ground rod drilled through the slab, grounding unused pairs from the demark to the KSU and sheilding the actual demark block.