Isn't it that electrocaps that ar strongly over rated in working voltage, wear out sooner as caps that are working close below the max voltage? This due to electrochemical degradation of the electrolytic dielectrum. Actualy the same as due to long storage.
eric -----Original Message----- From: neonixie-l@googlegroups.com [mailto:neonixie-l@googlegroups.com] On Behalf Of JohnK Sent: donderdag 30 juni 2011 15:01 To: neonixie-l@googlegroups.com Subject: Re: [neonixie-l] Re: now a full 7179 clock from the same seller, check out those tubes Yes it was wasn't it. However the scenario I had in mind [and my experience] both allow for 'probably' OK. The mil capacitors of post-war gear have been good for treatment if just lousy due to storage time. The capacitors in old commercial radios any era depend on manufacturer. I don't collect them but had re-furbished two with sentimental value - hence the caps are disconnected and new types 'temporarily' fitted. This is to protect the mains transformer as much as anything else. Added thermal fuse to transformers as insurance -weak as it may be. WWII caps are hit and miss. The capacitors that you mention "a hostile-ish environment (near tubes and other sources of heat)," are in a category that I call Faulty or worn out. I am/was talking about OK caps that were stored for ages - they can be revitalised [generally] and I hear such comments from WWII Rx collectors eg WS19 which is much in vogue over your way. I have had more trouble with 'modern' caps. Even the manufacturers specs don't give you much confidence in commercial quality electros. I can remember the probs we [a gov dept] experienced at inwards goods - eg the Philips electros came in different 'life' categories. They were marked the same; only difference was the physical size. Some suppliers were either trying it on or were as ignorant as some of our inspectors ! With 'modern' gear I replace instead of mucking about; and some collector will rant and rave about it in 50 years :-)) Speaking of modern - a capacitor characteristic often overlooked in current times is the manufacturer specified operating voltage RANGE. Using a cap well below the marked voltage causes it to do two things; lose capacitance and also become resistive [ie leaky, but not liquid if you follow me]. In the 90s I was trouble-shooter at a largish [>2000 employee] local company and there were product recalls due to acceptance of electro caps of higher than specified voltage. eg 50V instead of 6V. The circuit already worked at a non-optimum <2.5V across the cap and that was acknowledged in the design. I guess I was motivated by my hate of needless destruction of old gear. Attempt a reform - replace if required. John K. [PS The very old electros that slosh when you move them are better 'temporarily' replaced as I have done in my old Airzone. An explosion of those is a real mess and dangerous. The explosion of a typical WWII and later type just results in a bit of paste splatter and tons of paper and foil. (says I who had just moved his unprotetced eyes to the other side of my home-made 6 x 807 surplus parts guitar amp. As a schoolboy I just purchased the WWII surplus caps and wired them up. 800V parts and used at 650V. )] [PPS. I suppose this is one of those topics you mentioned that moved off-topic is it?] ----- Original Message ----- From: "Nick" <n...@desmith.net> On Jun 30, 8:53 am, "JohnK" <yend...@internode.on.net> wrote: > Generally, old electrolytic caps that have just been allowed to sit can be > re-formed and henceforth operate properly. From: "Nick" <n...@desmith.net> That's a bit of a sweeping statement. Of the kit I've rebuilt, the electrolytics have typically dried out, and thus cannot be reformed. Many were not sealed well and as they were operating is a hostile-ish environment (near tubes and other sources of heat), they often dry completely. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to neonixie-l@googlegroups.com. To unsubscribe from this group, send email to neonixie-l+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/neonixie-l?hl=en-GB.
