Hello, I'm not an electrical engineer so I wanted to get your opinion also about this strange situation.
3 weeks ago the factory that I'm working for changed its UPS system. Now 3com btx network interface cards (3c905b-tx) are not working properly (I get many request timeout when I ping different servers, I can't connect to shares). When I check with sniffer we get many CRC's and some alignment errors. It's weird because it's not working in the technicians room. It's working in my room. When I plug it to the socket in my room it's working (with the same network connection) but when I plug it in the technicians room it's not working. I've tried the network card in the new computers, but it's not working also (in the technicians room). I have tried as many 3c905b-tx as I've found but it is not working. Electrical technicians has measured the voltage, the ground, the frequencies and they say that all is OK. I'm in europe so 220 V, 0 ,50 khz (I think). I'm 100% sure that it's not a network or network cabling problem. What can I tell them, what can we do to solve this problem. Is there any other measurement that we can do (I don't know much about electric)? Thank you Erman Ulusoy