Yup
Old electrolytics need “time” and, IIRC, a gradually increasing voltage to reform before one applies the “full voltage”! I’ve probably told this story before, but, when at school “some decades” ago I built a valve/tube oscillator from stuff in a “junk pile” that I had bought from a local old guy, but I didn’t have a suitable HV (it needed around 160-200V dc) supply to power it. So I took it to school and connected it to a working supply, and then left the room (luckily!) – 5-10 mins later there was a “big bang” from the room, went back there to find the whole place covered in Al foil from the capacitor which had “ejected” its contents “explosively” J. That was a 1950’s era component, but I suspect that even somewhat later capacitors would probably have similar “issues” if not rejuvenated “carefully”!! John E Allen W. London, UK From: Doug Powell [mailto:doug...@gmail.com] Sent: 18 January 2020 04:45 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Capacitor Friday question Thanks Ken, I had not realized anyone else on this forum had ever worked around vacuum tubes. Good to know. Yes, I've always understood capacitor formation is a gradual thing. And especially not with high ripple current as is likely in the method described in the video. Doug -- Douglas E Powell doug...@gmail.com https://www.linkedin.com/in/dougp01 From: ibm...@gmail.com Sent: January 17, 2020 8:32 PM To: doug...@gmail.com Cc: EMC-PSTC@listserv.ieee.org Subject: Re: [PSES] Capacitor Friday question Hi Doug! Reforming capacitors is definitely a thing but it sounds like your skepticism comes from the allegation that capacitors can reform themselves in-circuit. I think this is also 'a thing', though probably not recommended in the way shown in the video (dumping full line voltage across the equipment and waiting). I recall hearing a common suggestion for working on older (vacuum tube) radios and such; that it was a good idea to bring them up slowly on a variac to allow for precisely this (capacitors to reform themselves). Another thing that rubs me the wrong way about the approach shown in the video: If there's a question about a piece of equipment (whether old or new) it would be wise to open it up and check some things out first, even if only a visual inspection to look for bulged, vented, or leaky caps. This is doubly a concern due to the industry-wide problem of 'capacitor plague' from the 90's to the early 2000's. The general public may only have tangentially been aware of this due to significant fallout in Dell computers, but many manufacturers were affected. The story behind it is actually quite fascinating: https://www.theguardian.com/technology/blog/2010/jun/29/dell-problems-capacitors -Ken On Fri, Jan 17, 2020 at 8:22 PM Doug Powell <doug...@gmail.com> wrote: This is somewhat off topic but still I feel it can be relevant to equipment reliability. My daughter found this article on Facebook and successfully got her sewing machine running again, after a fairly long period of storage. The link has an interesting theory about old electrolytic capacitors restoring themselves and I'm not sure I buy it. I've never heard of this before sort of thing before. What do you think? https://m.facebook.com/DrDavesSewingMachines/posts/1273259472698687 Have a great weekend. ~Doug -- Douglas E Powell doug...@gmail.com https://www.linkedin.com/in/dougp01 - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
