[ct-user] Ethernet Problem

Dennis Egan nb1b@mediaone.net
Wed, 22 Aug 2001 18:02:24 -0400

I went down to work on the station W1KM today and found that the ethernet
network wouldn't work.  In the process of troubleshooting the network I
found that each network card passed the Digital diagnostics, but they still
wouldn't talk to each other.  I went over and over the setup, thinking I had
done something wrong, so I went back to basics and recabled so I only had 2
computers in the network rather than 4.

When I pulled the BNC plug off the NIC, I found that the terminating plug
resistor was warm- so warm that I could hardly hold it.  I don't remember
that from before, so, one at a time, I connected one computer to the cable
and measured the voltage on the cable.  For 3 of the NIC cards, I have -8.7
volts on the BNC pin- and on the fourth NIC, I have .33 volts on the BNC

Could 3 of the 4 cards been blown?  And still pass the diagnostics?  To add
further information, both stack matches had numerous blown diodes and one
had several vaporized traces on the PC board, and a 12V 35Amp power supply
connected to them was putting out a hefty 26 volts! (probably regulator
failure).  I didn't have a chance to replace the NICs today, but is that
voltage on the output normal or do I have 3 blown cards?

Dennis NB1B