Max,
You may be exciting a resonant cavity with the video card.
If you can identify cavity modes being set up you may be
able install straps to reroute current flow within the
cabinet away from vulnerable slot coupling. Alternatively,
you may be able to install some kind of shield on the video
card to sink the excitation currents before they can couple
to the cabinet.
Cheers,
Cortland
Disclaimer: The opinions expressed in this message are my
own and do not necessarily reflect those of my employer.
______________________________ Reply Separator _________________________________
Subject: Re: Need EMC Help With Video Card
Author: Max <[email protected]> at internet
List-Post: [email protected]
Date: 8/29/96 12:44
Mike,
Thanks for the information. I wish I had tried moving the wires against
the chassis or putting ferrites on the fan wires.
I'm not sure what I could do about this from a practical view point,
though, except to look for another PC. I doubt if the FCC would allow
you to modify the PC.
Max
%>
%>> I still have the problem when I remove all of the
%>cables from the system,
%>> including the printer cable, etc. The emissions are
%>coming out of the
%>> holes in the PC cabinet and this is a very good PC
%>and is well sealed. The
%>> largest emissions seem to be coming from the fan
%>vent holes.
%>>
%>
%>
%>> [email protected]
%>>-- End of excerpt from Max
%>
%>
%>Max,
%>We have had problems with fans and fan vent holes very
%>often.
%>
%>All the rules about hole sizes and emissions don't
%>apply when the body of the fan is mounted right up
%>against them and the fan itself is "hot" with RF. We
%>have had to keep the power wiring to the fan held flat
%>against the chassis and then put ferrites on it to
%>choke off any pickup from emissions inside the box.
%>
%>Once we had to put ferrites on the fan leads from a
%>Pentium cooling fan. It seemed to pick RF up
%>capacitively right off the case of the Pentium it was
%>cooling and then the leads radiated thruout the case.
%>
%>Good luck!
%>
%>
%>--
%>Mike Donnelly
%>[email protected] WD7M
%>Standard disclaimer: These are my own words, not the Company's.
