Here in the UK, radio amateurs have found many cases of ATX type computer power supplies of far-eastern origin whose conducted emissions are 30 to 40dB above CISPR22 class B limits. These are being distributed by at least two major retailers via Stores and via the web. I believe that similar PSUs have been found in France.
Investigation by RSGB members has shown that these PSUs have plausible DoC's, and are often properly CE marked, but never the less have had all the emc filtering omitted during manufacture (with the inductors replaced by wire links, of course). Various RSGB members have complained about these to their local trading Standards people (who have the front-line responsibility for enforcing CE requirementsin the UK). Formal tests have confirmed the above situation. Action against the importers is being actively considered by Trading Standards, but has to overcome some difficulties since the relevant UK EMC regulations are not a priority for most Trading Standards people. For the models seen here so far, it is possible to check the presence of the EMC filter without breaking the equipment seals. This can be done by looking at the pcb with the aid of a torch between the fan blades. So this is a first step towards building a conforming PC.! Richard Marshall Richard Marshall Limited, The Dappled House 30 Ox Lane, Harpenden, Herts. AL5 4HE, UK Phone: +44 (0)1582 460815 Email: richard.marsh...@iee.org Website: www.design-emc.co.uk From: "Cortland Richmond" <k...@earthlink.net> To: "Derek Walton" <lfresea...@aol.com>; "Reginald Henry" <rhe...@vicon-cctv.com> Cc: <emc-p...@ieee.org> Sent: Friday, December 18, 2009 1:16 AM Subject: Re: FCC PERSONAL COMPUTERS FOR COMMERICAL ENVIORMENT > "Be careful what you ask for; you may get it." > > Firms who wanted relief from having to test for compliance, and who wanted > to be able merely to design to (or just towards) compliance, have now got > all the relief they asked for. No one is checking. > > I wonder what legal obligation exists for one who discovers non-compliance; > must he report what he finds?? Or must it wait until (say) the Coast Guard > can't hear a ship at sea? > > > > Cortland Richmond > KA5S > > > > > > [Original Message] > > From: Derek Walton <lfresea...@aol.com> > > To: Reginald Henry <rhe...@vicon-cctv.com> > > Cc: <jrbar...@iglou.com>; <emc-p...@ieee.org>; <dw...@atcb.com> > > Date: 12/17/2009 10:58:15 AM > > Subject: Re: FCC PERSONAL COMPUTERS FOR COMMERICAL ENVIORMENT > > > > HI All, > > > > This is a timely reminder that assembling of components is a bad idea. > > > > I have just tested a product that is PC based, the radiated emissions > > are under control but the Conducted are 20 dB over the Class A limit. > > > > We have purchased 3 supplies ( all made off shore alas ), and while one > > gets close to Class A, the others are dismal. > > > > So, does anyone make a compliant supply? > > > > I would greatly appreciate, maybe off line is best, a make and model of > > a quiet, 300 Watt PC supply that can be purchased in the 5000/year volume. > > > > Meanwhile, I have a very very irate client using class B hardware that > > cannot even get within 20 dB of class A because of the power supply. How > > is this possible with the FCC requirements? > > > > Sincerely, > > > > Derek Walton > > L F Research > > > > On 12/17/2009 9:38 AM, Reginald Henry wrote: > > > Thank you John and Dennis your input it is greatly appreciated ! > > > > > > Reg Henry > > > > > > -----Original Message----- > > > From: John Barnes [mailto:jrbar...@iglou.com] > > > Sent: Wednesday, December 16, 2009 8:07 PM > > > To: emc-p...@ieee.org; Reginald Henry > > > Subject: Re: FCC PERSONAL COMPUTERS FOR COMMERICAL ENVIORMENT > > > > > > Reginald, > > > > > >> Now I think that I understand.. so there is limited testing to be done > > >> by the assembler in terms of mother board and power supply with the > > >> chassis open covered.. and testing must be performed at > > >> an independent labs If the assembler changes to another PS or MB the> > > >> > > > test must be redone ? > > > > > > Dennis Ward's E-mail talked about the record-keeping issues, and my > > > previous E-mail talked about the technical issues, of assembling > > > personal computers (PC's) from approved motherboards and power supplies. > > > If you abide by these rules, you-- as a personal-computer manufacturer-- > > > do not have to do *any* electromagnetic compatibility (EMC) testing at > > > all! You can mix and match power supplies, motherboards, cases, and > > > other goodies to your heart's content, without getting an EMC test lab > > > involved-- for sales in the United States. Unless, of course, your > > > product causes interference problems (FCC 47 CFR Part 15, 15.102(b)(5)), > > > in which case you are on the hook big-time. > > > > > > If a manufacturer makes a motherboard that meets FCC47 CFR Part 15 > > > Paragraph 15.32(a)(1), or a power supply that meets Paragraph 15.32(b), > > > they will brag about "meeting FCC Part 15" in their: > > > * Advertizing, > > > * Catalogs, > > > * Web pages, > > > * Data sheets, and > > > * On the boxes, because this is a major selling point for them. > > > > > > Of course, just because a manufacturer claims something, does not > > > necessarily mean that it is true. If you have never heard of the > > > manufacturer, and their prices seem too good to be true, you may want to > > > ask around, and get-- and carefully study-- copies of their Declarations > > > of Conformity (DoC's), safety certificates, etc. before you place any > > > large orders with them. > > > > > > > > > > > > In a personal computer (PC), the power supply usually generates the > > > worst Conducted Emissions, and the motherboard the worst Radiated > > > Emissions. Everything else that we stuff into a computer tends to be > > > relatively quiet compared to these two components. A good case can > > > significantly reduce Radiated Emissions, and can reduce Conducted > > > Emissions somewhat. > > > > > > In the 1980's/early 1990's the computer industry was pushing the FCC to > > > let them assemble personal computers without having to put every variant > > > through long, extensive (and expensive) electromagnetic compatibility > > > (EMC) tests. A major consideration, then and now, is that users can > > > easily customize/upgrade personal computers to meet their needs-- and > > > they had been doing so for some time without causing major interference > > > problems. So why were computer manufacturers being given such a huge > > > handicap? > > > > > > The FCC came up with the rules in FCC 47 CFR Part 15 that I discussed in > > > my previous E-mail, basically providing that: > > > * If you have a quiet power supply, the case doesn't matter. > > > * If you have a quiet motherboard, the case doesn't matter. > > > * But if the power supply OR motherboard is noisy, it must be provided > > > with a good case to limit the Conducted and Radiated Emissions. > > > > > > Thus a power supply/motherboard manufacturer can: > > > * Scrimp on development time and cost, and manufacturing cost, to make > > > cheap power supplies/motherboards that can only be sold to > > > high-volume manufacturers with strong EMC expertise. > > > * Spend more development time and cost, making more expensive power > > > supplies/motherboards that can be sold to anyone. > > > > > > High-volume PC manufacturer can buy the cheap power supplies and > > > motherboards, put them in inexpensive cases, and do the development work > > > themselves to meet FCC Part 15 at the lowest-possible total > > > manufacturing cost. The additional engineering time/cost and EMC > > > testing get amortized over many units, so they aren't a big burden. > > > > > > Low-volume PC manufacturers (garage shops) can buy the better power > > > supplies/motherboards, slap them together in any cases that customers > > > want (even for individual custom PC's), and ship them. > > > > > > Users can buy anything from a mass-produced off-the-shelf PC, to a fully > > > custom one that they assemble at home, and anywhere in between. > > > > > > > > > John Barnes KS4GL, PE, NCE, NCT, ESDC Eng, ESDC Tech, PSE, SM IEEE > > > dBi Corporation > > > http://www.dbicorporation.com/ > > > > > > > > > > > > CONFIDENTIALITY NOTICE: This transmission may contain information that > > > is privileged, confidential and/or exempt from disclosure > > > under applicable law. If you are not the intended recipient, you are > > > hereby notified that any disclosure, copying, distribution, or use of > > > the information contained herein (including any reliance thereof) is > > > strictly prohibited. If you receive this transmission in error, please > > > immediately contact the sender and destroy the material in it's > > > entirety,whether in electronic or hard copy format. The views expressed > > > in this > > > communication may not necessarily be the views held by the company. > > > Thank you. > > > > > > > > > > > > CONFIDENTIALITY NOTICE: This transmission may contain information that > is privileged, confidential and/or exempt from disclosure > > > under applicable law. If you are not the intended recipient, you are > hereby notified that any disclosure, copying, distribution, or use of the > information contained herein (including any reliance thereof) is > > > strictly prohibited. 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To post a message to the list, send your e-mail > to<emc-p...@ieee.org> > > > > > > All emc-pstc postings are archived and searchable on the web at: > > > http://www.ieeecommunities.org/emc-pstc > > > Graphics (in well-used formats), large files, etc. can be posted to > that URL. > > > > > > Website: http://www.ieee-pses.org/ > > > Instructions: http://listserv.ieee.org/request/user-guide.html > > > List rules: http://www.ieee-pses.org/listrules.html > > > > > > For help, send mail to the list administrators: > > > Scott Douglas<emcp...@socal.rr.com> > > > Mike Cantwell<mcantw...@ieee.org> > > > > > > For policy questions, send mail to: > > > Jim Bacher:<j.bac...@ieee.org> > > > David Heald:<dhe...@gmail.com> > > > > > > > > > > - > > ---------------------------------------------------------------- > > This message is from the IEEE Product Safety Engineering Society emc-pstc > discussion list. To post a message to the list, send your e-mail to > <emc-p...@ieee.org> > > > > All emc-pstc postings are archived and searchable on the web at: > > http://www.ieeecommunities.org/emc-pstc > > Graphics (in well-used formats), large files, etc. can be posted to that > URL. > > > > Website: http://www.ieee-pses.org/ > > Instructions: http://listserv.ieee.org/request/user-guide.html > > List rules: http://www.ieee-pses.org/listrules.html > > > > For help, send mail to the list administrators: > > Scott Douglas <emcp...@socal.rr.com> > > Mike Cantwell <mcantw...@ieee.org> > > > > For policy questions, send mail to: > > Jim Bacher: <j.bac...@ieee.org> > > David Heald: <dhe...@gmail.com> > > - > ---------------------------------------------------------------- > This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@socal.rr.com> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
