Alex: Good Show.
I am curious as to HOW the unfamiliar manufacturer's driver got into your product. It seems this was a costly substitution in terms of time and lab fees. I wonder if you are a victim of the "Purchasing as a Profit Center Syndrome." This is the characteristic of too many organizations, where the purchasing agent has the authority (or takes it) to make parts substitutions on the basis of lower cost, or sometimes, social relationships. I've seen many cases of "equivalent" or "as good as" parts that were anything but. I shudder at the engineering hours I have seen wasted due to substitutions. The best approach I can offer is that parts should have approved and released engineering drawings which cannot be changed except by going through a formal change control process - which engineering either controls or participates in. Purchasing cannot purchase parts from a vendor who is not approved on the part drawing, except at their own career risk. Engineering change notices (a.k.a. Design change notices DCN) should require the approval, in some fashion, of the EMC and homologation person in the organization. I have used a check box on ECNs which say: _____may affect EMC/EMI ______ may affect approvals/homologation or something to that effect. This lets the originator do the alerting, and hopefully actually think about the broader implications of a change that is being contemplated. I'm sure that others on this forum have their own approaches, either personal or organizational. Perhaps they will share them. One last remark, and this applies also to vendors who change parts but not part numbers. An example being the smaller die sizes of FETs being discussed here lately. I have always found it helpful to keep a "S-H-one-T" list (SH1T) of rogue vendors not to buy from, and freely share the list with engineers and, yes, even purchasing. Cheers, Jack Jacob Z. Schanker, P.E. 65 Crandon Way Rochester, NY 14618 Phone: 716 442 3909 Fax: 716 442 2182 [email protected] ----- Original Message ----- From: Alex McNeil <[email protected]> To: <[email protected]> Sent: Thursday, October 25, 2001 10:04 AM Subject: EFT Failures..Solved!+ ESD symbol question | | Hi Group, | | The problem was an oversensitive Display driver. Replacing this driver | solved my problem. | | It was diagnosed by: | 1. Was the problem due to conductive or radiated or both? By using the | DC lead, made a small loop, as my noise source with EFT test running, I | noticed the problem occurring near the display circuitry. The fault was | actually a Display lock whereas I thought it was a keyboard lock (same | symptons). I then attached my large ferrite core to the DC cable, several | turns, and repeated the test. No problems. I assumed from this that radiated | was the problem. | 2. What was actually picking up the noise and was the fault the display | driver? I assumed the cable connected to my display was picking up this | noise and conductively passing it on to the display driver. I could not | bypass the problem using caps, functionality started to play up a bit | depending on my value of capacitor. It was at this time I noticed that we | were using an unfamiliar driver manufacturer! I went to the stores and found | the proper part, fitted it and BINGO it now passes up to 3KV!!!! | | I am relatively new to this forum. but I think it a good idea if we all | share our problems and diagnostics. I am sure this would be a great help to | many of us!! | | However, for my next question? | | I want to place a "Static Sensitive Area" symbol on my product molding, | avoiding words, as it will be a worldwide product. The suymbol will be | explained in the user guide. | | Q. Is there a worldwide symbol to denote a "Static Sensitive Area" or a | European one and another North American one or.... I would need the .bmp | file if possible? | | Kind Regards | Alex McNeil | Principal Engineer | Tel: +44 (0)131 479 8375 | Fax: +44 (0)131 479 8321 | email: [email protected] | | -----Original Message----- | From: Alex McNeil | Sent: Tuesday, October 23, 2001 9:44 AM | To: '[email protected]' | Subject: EFT Failures..Update! | | | Hi Group, | | THANKS for your very much appreciated responses!! I was in | panic mode!! | | I thought it would be appropriate to let you know the | status. | | My product is a small all plastic enclosure Point if Sale | (POS) Class III terminal. It has an external SMPS, Class II, no earth, | supplying SELV, 12Vdc 1.5A to my product. The power supply works OK with | some of our other products, for EMC. The problem is with my product. | | I solved the problem at the test house by wrapping a few | turns of the DC PSU cable through a "Large" Ferrite Clamp at the Product | input (it did not work so well at the PSU I/P nor O/P). The fix cannot be | considered final due to obvious reasons. | | I am now at my Lab, now the serious diagnostics begin. I | have been trying various "quick fixes" to no avail i.e. Caps, TVS, MOV etc. | | If you have any further comments feel free to email me. | | THANKS again to all those who responded with their thoughts. | I can tell you they were wide and varied just as you would expect to trying | to resolve an EMC problem over the NET!! | | Best Regards | [email protected] | | | | | | | | | -----Original Message----- | From: Alex McNeil | Sent: 22 October 2001 11:23 | To: [email protected] | Subject: EFT Failures..Help! | | Hi Guys, | | I am at an EMC test centre today and tomorrow. | Unfortunately, my product failed EFT testing on the AC power port at 1KV. | This is for various combinations of Line, Neutral and Earth (L, N, E, LN, | LE, NE and LNE) | | My product is Class II, no Earth. It is supplied by | an external power supply. This supplies SELV to my product. The power supply | manufacturer has stated that his power supply meets EN61000-4-4 for 2KV and | has emailed me this report to verify this. | | Has anyone got a quick solution to my problem so | that I can implement here at the EMC test house? | | Kind Regards | Alex McNeil | Principal Engineer | Tel: +44 (0)131 479 8375 | Fax: +44 (0)131 479 8321 | email: [email protected] | | | ------------------------------------------- | 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: | Michael Garretson: [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: | No longer online until our new server is brought online and the old messages are imported into the new server. | ------------------------------------------- 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: Michael Garretson: [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: No longer online until our new server is brought online and the old messages are imported into the new server.
