You are absolutely right. I was thinking room temperature, but at high temperatures barium bonds with nitrogen to form a stable nitride.
So we can conclude that during storage, the barium getter will catch oxigen, but nitrogen gas remains present untill the getter gets hot enough to initiate the reaction.
This explains the improvement that MJ found in his baking experiments.
The question remains however, if using the valves in a regular circuit would not have given the same results.
Thermal runaway, ok. But how often does this occur?
Except for '80s chinese power valves I have not seen valves running away.
I do have noisy old valves. Perhaps due to high gas that the getter can't absorb under normal operating conditions. Baking might improve those.
Preventive baking (doing so without testing for gas first), for me is overdoing it a bit. Not to mention introducing thermal stress that could have been avoided.
Except for '80s chinese power valves I have not seen valves running away.
I do have noisy old valves. Perhaps due to high gas that the getter can't absorb under normal operating conditions. Baking might improve those.
Preventive baking (doing so without testing for gas first), for me is overdoing it a bit. Not to mention introducing thermal stress that could have been avoided.
Good to know: I have collected quite a few years ago.
When I finally get to using them I will test and monitor them closely
Sorry my ignorance, but how is this gas test for tubes?? (small and power tubes).
It will be quite useful to me.
Thanks
Just clip a couple of test leads across your grid-leak resistor and measure the voltage, if any. If you're drawing grid current, you will see a voltage produced across this resistor.
The current is I=E/R - simple.
Sorry to join the conversation so late, but...
I, too, had problems with 6Н1П-EB (among others), and I used to bake NOS tubes (a la Morgan Jones), but have found an equally effective (for IHT's anyway) method that takes a good deal less effort and presents no risk to bakelite bases:
By running the heater off of a current-regulated (benchtop lab) supply with no B+, the same improvement that Morgan describes in his article can be had overnight while I sleep.
The current-limiting causes the filament to come up very slowly - (it takes about 100-200 seconds for a 6Н6П, for example, to reach 6.3V @ .75A) - and then the heat from the filament does the baking just as well as the oven used to.
The by-product, of course, is that in the morning, I have an already-warmed-up tube ready for testing - I ramp-up B+ to the plate (over about 15 seconds), check grid leak, then read cathode currents at a couple different bias volts for matching/QC purposes at this point.
I take two senile 6C33C-B tubes to baking, both are Ulianov SET1983 OTK 11.
V1 had no more vacuum, a glass/metal pin top nipple broke and its structural pins are non aligned probably due a huge G force in a jet.
Getter had a subtle blow away gray area near the top due air entrance. Plate is very clean. no sign of dust getter.
V2 is factory sealed yet, seems good vacuum, very few signs of dust getter on the plate.
I put a bread to baking in the gas stove at minimum temperature= 180ºC and also include these two tubes.
They cooked for two hours, after it both tubes had few getter on top, the plate seems more clear, with less black dust getter.
After a week or so, I baking both tubes again and the top getter decreased again, seems very little now in both tubes, almost vanished, the top glass is near transparent in both tubes.
Seems to me 180ºC is too hot for thiese tubes, I would suggest 100ºC for one or two hours for the first time.
V1 had no more vacuum, a glass/metal pin top nipple broke and its structural pins are non aligned probably due a huge G force in a jet.
Getter had a subtle blow away gray area near the top due air entrance. Plate is very clean. no sign of dust getter.
V2 is factory sealed yet, seems good vacuum, very few signs of dust getter on the plate.
I put a bread to baking in the gas stove at minimum temperature= 180ºC and also include these two tubes.
They cooked for two hours, after it both tubes had few getter on top, the plate seems more clear, with less black dust getter.
After a week or so, I baking both tubes again and the top getter decreased again, seems very little now in both tubes, almost vanished, the top glass is near transparent in both tubes.
Seems to me 180ºC is too hot for thiese tubes, I would suggest 100ºC for one or two hours for the first time.
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