I suppose that vibration may be good to a point, but I offer the following. I bought a pair of PC's (These were Dell Dimension 500 and they did pass Class B) out of the box. I found however that after many repeated trips to the lab in my car, they no longer did. The I/O connectors did degrade somewhat, but the noise leakage was traced to the case. It appeared that the problem was fretting due to vibrating metal to metal contacts along various seams in concert with some kind of coating on the surfaces. Where metal fingers met metal surface, a kind of black marking had developed and I found it couldn't be cleaned with alcohol etc. Light sandpapering didn't help much either, although I suppose a dremel tool might have worked. Copper tape along the affected seams did work, but of course then, I had modified it....
George Stults WatchGuard Technologies Inc. From: Cortland Richmond [mailto:72146....@compuserve.com] Sent: Thursday, March 27, 2003 11:10 AM To: lfresea...@aol.com; ieee pstc list Subject: Re: OK, what's going on? Derek wrote: >> the EUT should have been exposed to simulated shipping and installation by a user... << FWIW, in the 1980's I worked in an audit lab where we tested samples of shipped equipment for FCC, vibration, heat, humidity, temperature, TEMPEST... it was not uncommon for equipment to do BETTER in EMC tests after it had been subjected to vibration testing. With oils, oxides and so on having been abraded, metal parts made better contact with each other. Cortland This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
