I have a modulator that uses four 100TH tubes, it has had the same tubes for the last 25 years, they look clear, and work fine. I have a bunch of spare 100 TH and TL's, all look ok last I looked...
I have noticed a bunch of white tubes in the 7 and 9 pin tube stashes, maybe the seals fail, the pins rust, or something happens and the air gets in. You have a lot of thermal cycling on tubes that get used, from cold to very hot, to cold again, but tubes just sitting going bad? Brett ----- Original Message ----- From: "rbethman" <[email protected]> To: "AM Radio List" <[email protected]> Sent: Tuesday, August 25, 2009 12:06 PM Subject: [AMRadio] 100TH and 250TH advice and or comment > Question: > > I have noticed that the 100THs and 250THS that are in their original > boxes, either not used at all, or maybe use for less than an hour to > test them, seem to be doing fine. > > Their envelopes are crystal clear an can not see any sort of defect. > > Then the ones that are in one of the two BC-610s that has the hours on > it, even though it last performed flawlessly, now appears to have gone > gassy with some milky white inside the envelope. > > Is this perhaps due to over heating or maybe I should phrase this as the > convection cooling of these radios since they do NOT have fans. > > Ideas? Comments? > > It has always been metered and watched with a scope for observing > waveforms, and the wattmeter is the newer Model Bird with peak reading > built-in. (However true they really are!) > > Bob - N0DGN > > > ______________________________________________________________ > Our Main Website: http://www.amfone.net > AMRadio mailing list > Searchable Archives: http://www.mail-archive.com/[email protected]/ > List Rules (must read!): http://w5ami.net/amradiofaq.html > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Post: [email protected] > To unsubscribe, send an email to [email protected] with > the word unsubscribe in the message body. > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
