| whit3rd <whit3rd@gmail.com>: May 19 01:12PM -0700 On Saturday, May 18, 2019 at 8:22:32 AM UTC-7, Cursitor Doom wrote: > 27k became 38.6k > another 27k ----> 29k > 100k ----> 107k Good to know, but the aging of composition resistors doesn't tell us much about carbon film resistors (the common low-spec type nowadays) or metal film (the common high-spec type) and manufacturer coatings and such are likely to be changing from year to year as well. Probably, because conductive (metallic or semimetallic) items are positive valence, oxidation will raise resistance with time, for almost anything. How much time, is still a mystery (for almost anything we build today, at any rate). There's too much chemistry involved to make a really good long-life high accuracy projection for most real components. Humidity, ozone, fungus, air pollution... so MANY variables. |
| tabbypurr@gmail.com: May 19 01:24PM -0700 On Sunday, 19 May 2019 21:12:54 UTC+1, whit3rd wrote: > There's too much chemistry involved to make a really good long-life > high accuracy projection for most real components. Humidity, ozone, > fungus, air pollution... so MANY variables. You can eliminate all those with glass, vacuum & getter. Then you find one day that the getter is oxidised & the bulb contains hydrogen. NT |
| Cursitor Doom <curd@notformail.com>: May 19 10:45PM On Sun, 19 May 2019 13:24:18 -0700, tabbypurr wrote: > You can eliminate all those with glass, vacuum & getter. Then you find > one day that the getter is oxidised & the bulb contains hydrogen. I was under the impression that glass was impermeable even to omnipresent hydrogen. Or is there a path via where the base pins protrude? -- This message may be freely reproduced without limit or charge only via the Usenet protocol. Reproduction in whole or part through other protocols, whether for profit or not, is conditional upon a charge of GBP10.00 per reproduction. Publication in this manner via non-Usenet protocols constitutes acceptance of this condition. |
| Fox's Mercantile <jdangus@att.net>: May 19 07:50PM -0500 On 5/19/19 5:45 PM, Cursitor Doom wrote: > I was under the impression that glass was impermeable even to omnipresent > hydrogen. Or is there a path via where the base pins protrude? Hydrogen atoms are really really small. Trying to keep hydrogen in or out is always problematic. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Clifford Heath <no.spam@please.net>: May 20 11:14AM +1000 On 20/5/19 10:50 am, Fox's Mercantile wrote: >> hydrogen. Or is there a path via where the base pins protrude? > Hydrogen atoms are really really small. > Trying to keep hydrogen in or out is always problematic. Also, a kilogram of hydrogen at a given pressure takes more space than any other gas. |
| tabbypurr@gmail.com: May 19 09:48PM -0700 On Sunday, 19 May 2019 23:45:14 UTC+1, Cursitor Doom wrote: > > one day that the getter is oxidised & the bulb contains hydrogen. > I was under the impression that glass was impermeable even to omnipresent > hydrogen. Or is there a path via where the base pins protrude? Glasslinger did a mass spec analysis to discover that gassy valves contain hydrogen. I don't know whether that permeates through the glass (unlikely since most valves stay hard), leaks in through pin sealing defects or is the result of remaining water vapour reacting with the getter. Either way a getter that could capture it would be a good thing probably. https://www.youtube.com/watch?v=16vOoF_XUB8 NT |
| Mike Coon <gravity@mjcoon.plus.com>: May 20 08:11AM +0100 In article <rvOdnSbLyqpFZHzBnZ2dnUU7-TmdnZ2d@giganews.com>, jdangus@att.net says... > Hydrogen atoms are really really small. > Trying to keep hydrogen in or out is always problematic. In practice you get molecules on the two-fer principle which are much bigger. Helium is bad too because then the atoms come at you singly... Mike. |
| John Robertson <spam@flippers.com>: May 20 08:40AM -0400 On 2019/05/18 11:22 a.m., Cursitor Doom wrote: > 400k ----> 509k (bad) > These were all marked with a silver tolerance band, so clearly Taylor > back then at least not *that* bothered about accuracy. No, those resistors have drifted since their original construction. People did have ohm-meters back then and would verify values on resistors particularly if they were colour deficient or colour blind as I did, testing Rs when building kits - red/green deficient vision. I still check almost all resistors I come across with a meter as I don't trust my green, dark red, and brown differentiation. If they are in power circuits - plate or cathode or voltage dropping then those do drift as they were only compressed carbon and heat/cooling cycles would cause them to change value - usually upwards as you have discovered. I consider your values typical of tube gear that is 40 or more years old. 1920s resistors were a chunk of carbon rod with a wire wrapped around each end then dipped in a sealant - how long do you think that value would last within X%? Wire wound resistors external connections were pressure bonded to the resistance wire, not uncommon for that joint to fail over time... Like I said earlier you HAVE to verify all the resistors as they wander over time. Modern Rs are much more reliable when operated under their rated wattage. John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
| Hash L <hashx123@gmail.com>: May 19 10:39AM -0700 YouTube videos of U.S. Congress money laundering hearing of Saudi Billionaire " Maan Al sanea" with bank of America and The owner of Saad Hospital and Schools in the Eastern Province in Saudi Arabia and the Chairman of the Board of Directors of Awal Bank in Bahrain With Arabic Subtitles موقع اليوتيوب الذي عرض جلسة استماع الكونجرس الأمريكي لمتابعة نشاطات غسل الأموال ونشاطات السعودي معن عبدالواحد الصانع مالك مستشفى وشركة سعد ومدارس سعد بالمنطقة الشرقية بالسعودية ورئيس مجلس ادارة بنك اوال البحريني مترجم باللغة العربية http://www.youtube.com/watch?v=mIBNnQvhU8s |
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