Martin's 'anode trick' is indeed a neat one. I've always shied away from reversing the polarity when playing with dekatrons because I read somewhere vaguely authoritative that it rapidly destroys the quality of the cathode surfaces. However that's probably not an instantaneous event, and anyway if the tube is otherwise unusable, there's nothing to lose. Will definitely give it a go next time I find a sticky tube which resists the usual methods. I think the 6909 is probably an early one - my sense is that Sylvania tubes labelled in green ink predate the yellow ink ones. Can't read the date code though, and nobody I've asked seems to have the scoop on it. Or maybe they do and they're not telling. Week 52 of 1959? With regard to the glow colour, I wonder if it's a partial outgassing effect which has effectively changed the gas mix in the tube? The more exotic fill mixes often contained hydrogen to reduce the effecive deionisation time, and this may be preferentially leaking out or reacting with tube contents over time. I have seen something which may be similar - most of my 7978 dekatrons show a orange peach/blue glow, but one has a much more typical neon orange colour. If this explanation is right, then I would predict: a) the odd-glow colour 6909 cannot be operated as quickly as a 'normal' glow colour 6909 b) ithe deionisation time should be longer in the odd 6909. I've never tried to do this, but I guess you could look at deionisation by striking a glow and then watching the decay of tube current following a sharp step of the anode voltage to below the tube maintaining voltage (eg ground). Would have to be careful that the measurements don't get confounded by stray capacitance differences between tubes. Sounds like a fun job for a rainy afternoon with a scope! Cheers, Jon.
On Friday, October 19, 2012 2:00:43 AM UTC+1, threeneurons wrote: > Its working, properly now. Both at low current (~350uA) and at its > specified higher operating current (1.5mA), in both the pendulum and > spinner. Never got around to trying the "alternate anode" trick. Just left > it in the pendulum circuit for the last 3 or 4 days, 24/7. I'm keeping > that "anode" trick under my hat, just in case. Thank you. > > Glow color is still different than the other tubes I have of this type. > Its a Sylvania 6909. Green "Sylvania" text silk screened on a black base. > The "6909" is on the glass. Other text on the base is "952" vertically, and > "PAZ" horizontally. Just in case someone knows the Sylvania date codes. > > >>> >> -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To post to this group, send an email to [email protected]. To unsubscribe from this group, send email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msg/neonixie-l/-/qpTQbd8gTI8J. For more options, visit https://groups.google.com/groups/opt_out.
