Members Crunchtime Posted December 16, 2009 Members Share Posted December 16, 2009 I have some RFT 12ax7 preamp tubes in my Chimera. When I turn the amp on, one of them always flashes really bright for a split second then fades to normal. It sounds good and is not micro-phonic. Has anyone ever seen this? I'm afraid it will mean a short lifespan. Link to comment Share on other sites More sharing options...
Members the_bleeding Posted December 16, 2009 Members Share Posted December 16, 2009 I had one that did that, but it only did in the PI position. So i switched it out for another one that didnt -though they were both chinese 9th gens. Apparently some tubes just do that inherently. Link to comment Share on other sites More sharing options...
Members NixerX Posted December 16, 2009 Members Share Posted December 16, 2009 A couple old RCA's i have in my splawn do that. They sound great so I dont worry about it. Link to comment Share on other sites More sharing options...
Members BusterBuster Posted December 16, 2009 Members Share Posted December 16, 2009 Some tubes do this. I think it is some current limiter thing built inside them. Link to comment Share on other sites More sharing options...
Members PaoloJM Posted December 16, 2009 Members Share Posted December 16, 2009 Dunno about a current limiter, but my NOS valves seem to do it more than current production.It can be pretty scary seeing a Link to comment Share on other sites More sharing options...
Members 17 Tubes Posted December 16, 2009 Members Share Posted December 16, 2009 I have some too. Don't know why they do that. Sounds good so no worry... i call it "prewarm-up". Link to comment Share on other sites More sharing options...
Members MRAAJR Posted December 16, 2009 Members Share Posted December 16, 2009 I have a 6L6 in a Herbert that does that. Only after the amp has been off for a awhile though. Link to comment Share on other sites More sharing options...
Members Stephan1980 Posted December 16, 2009 Members Share Posted December 16, 2009 I have a bunch of Mullards that do that. It's normal. Link to comment Share on other sites More sharing options...
Members Guiary Posted December 16, 2009 Members Share Posted December 16, 2009 All my Amperex, Mullard, and Siemens 12AX7s do that. Can't remember if my Mullard CV4024 do as well Link to comment Share on other sites More sharing options...
Members JamesPeters Posted December 16, 2009 Members Share Posted December 16, 2009 RFT 12AX7 do this. It's not isolated to the Chimera, that's for sure. Also from my FAQ: "Some preamp tubes also glow brightly briefly on power-up; this can be normal and not a sign of a bad preamp tube." I have some Chinese 12AX7B which do this too. Link to comment Share on other sites More sharing options...
Members bengerm77 Posted December 16, 2009 Members Share Posted December 16, 2009 [YOUTUBE]ttMoS4dT2fo[/YOUTUBE] Like that? The video says it's a leaky tube with gas in it. Link to comment Share on other sites More sharing options...
Members Uncle_Milton Posted December 16, 2009 Members Share Posted December 16, 2009 Sounds like it's time to turn out the lights and invite some girls over Link to comment Share on other sites More sharing options...
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