Muriel,
If it is conducted emission through the power cord, then chances are that (the layout for) the EMI filters had been compromised. Immediately upon entering the shielded box the mains leads should meet a mains EMI filter enclosed in a metal box bonded to the Earth on your shielded box. Every precaution must be taken to separate the proximity between the filtered mains and the outgoing (DC o/p) cables from the incoming 'unfiltered mains'. The incoming cable carrying the unfiltered mains should be a twisted-type and should not be passed through fuses, switches, or whatever before filtering. These switches, fuses or whatever that carries the filtered mains must 'ideally' be inside your shielded box. The filtered mains cable should also be twisted and run by as direct route as possible to the SMPS pcb. Any cables to switches, fuses or indicator lamps (whatever) should be as far as possible from the SMPS circuits. The objective is to reduce the chance of any near field coupling into the unfiltered mains cable, causing a CE test failure. Hope this helps. Tim Foo ------------------------------------------- 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: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
