Hi Group Many thanks for the replies. I had not considered this would be acceptable under 60950 - just shows I don't know it well enough!
With my technical writer's hat on, should the user document make a reference to the fact that a user COULD perceive a shock (albeit acceptable) if touching certain parts at the same time and may see sparks when connecting the data cable after turning on the drive (I do see sparks), I know what the marketeers would say... Incidentally, the Maxtor user guide requires the power to be connected and switched on, before connecting the data cable, so a user may see sparks when connecting the data cable and may perceive a shock if they touch the drive case and the connector outer at the same time (assuming the power unit we have is the only type shipped with the product). It does not refer to sparks or tingles. Regards Stuart Stuart Miller - Ablewisp wrote: > Hi group > I hope I can get some advice on an issue with a power supply. It was > supplied, as a separate unit, with a Maxtor portable hard disk drive > that we use for backups in the office (UK based). The drive sits on a > pc case. > The supply is manufactured by DVE, model number 0421S. It provides 12V > dc at 3A. Rated input is 100-240V, 50/60Hz, 1.2A. > Its CE marked, UL listed and has a TuV mark stating BSEN60950. It's > marked as double insulated. > I guess its around 18 months old and has had an "easy" life in the > office, with no visible case damage. > > After connecting the data cable (Firewire, already connected to the > pc) to the drive, I touched its metal case while touching the outer of > the dc connector and got an unpleasant tingle. > I measured 230 V from the metal case to the outer of the dc connector > (not connected to the portable hard disk). > To isolate the drive from ac ground, I removed the data cable from the > drive and measured 230V from the metal case to ac power ground (the > drive is insulated from the pc case by plastic feet). Current was > around 0.2mA. > > When the dc connector is connected, the drive performs normally. > The drive was removed for secure storage when we left the office over > the Easter holiday. In normal use it remains connected to one pc for > weeks at a time. It would be exciting to move the drive from pc to pc! > > I couldn't find a recall notice for the DVE part number on Google. > > I'm interested in possible failure modes (I'm not a switch mode power > supply expert) that could result in this shock hazard. I assume its > due to degrading components and will get worse! > > Many thanks in advance > > Stuart Miller > Ablewisp Limited > www.ablewisp.com > ph: 01803 843502 > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] 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 [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
