It might be that the tube is more susceptible to variations in voltage that the other tubes, but it's only showing up a difference that is there in the voltage generation. The difference in sensitivity is probably there because of a slow leak or manufacturing tolerances. I'm pretty sure the underlying issue is one of voltage generation, not poisoning. I don't think tubes poison that quickly, or repair that quickly either.
On a related topic, has anyone ever investigated re-gassing tubes? I have quite a few broken IN-18's and they are almost worth repairing. Some of them were broken in transit, and have the original gassing nipple snapped off, which would be an easy physical fix. Even tubes with a slow leak around the pins might be possible to fix with a re-flashing of the seals or the nail-varnish trick. It could even be possible to re-seal them with candle wax: this is a trick in mechanical circles for releasing stuck bolts, but it could also have an application here: molten wax appears to have incredible penetration capabilities.
I know that the technology exists to gas new tubes (
, we're talking about you), but I've never heard of anyone re-gassing old tubes.
Last edit: 4 years 8 months ago by Ian. Reason: removed remark about improvement, already noted in a previous post