Serge66 said:
You can already do that yourself, if you have an oven. It may even help the getter along a bit in an old valve, as SY noted previously. No company is going to be very successful charging you $200 to stick your 12au7 in their oven for you though, so perhaps it's no surprise no one pushes it much.
edit: spelling
EC8010 said:
Well, according to http://www.thevalvepage.com/valvetek/getter/getter.htm, no oven of mine will ever suffice to flash getters. Wouldn't it be dangerous (or risky to the vacuum) to have the glass at flashing temperature if an oven-heated method were used?
SY said:
For most tubes yes. I understand that the baking you're referring to is just to release gasses from the materials inside the tube to be collected. There are a few I have that I wished they were reflashed, however. Like this one (see attached) and a few tung-sol 5881s I've collected that look like they should have been cooked little longer. It's hard to say if there was insufficient material on the getter ring or just didn't boil it off fully, though. Also, it could have just all collected in that little spot, but the spot is a bit see-though, so I would assume there 'should be more where that came from.'
I would probably never build anything like that though, too much expense and work for too little payoff. Easier to just buy another tube, but I wondered if anyone has done it.
Attachments
Could there be a chance for some sort of reaction to the emitter layer?, say for example thorium, tungsten (not sure whats in a 12AU7) that causes the layer to smooth out, i.e take the miniscule bumps out out the emitting material causing the electron flow to be more even.
This could cause greater linearity and increased trans-conductance owing to the electrical surface density being simply flatter. A great many more electrons can flow from an even surface than just a few at a time boiled off from a pointed area (microns big). We could all get into an argument about how electrical surface density is greater at pointed surfaces, and how an inrush of electrons at that point could affect the operation of the tube but I am just pointing out that science for temperatures that low can sometimes be counter-intuitive... Just look how liquid helium, when chilled to near absolute zero ( classified as a super fluid ) can permeate glass like water through a soggy brown paper bag.
Having said all of this, I would never make a decision without proper testing, and if testing is only "what you hear" then that's not good enough. If the test equipment can tell us every step of the way if a tube has passed or failed the process then you can use the same equipment to show the differences in the tube before and after treatment. Whatever these 'differences' may be......
I believe the purpose of heating the tube in an oven is not to release gasses in the internal material, but rather to elevate the temp of the getter flash to increase its reactivity to recombine with gasses already present inside the tube. It also increases the energy level of the gasses which increases their probability of striking the getter material and combining with it.
I have a cryo rig at home I use.
First, I purchase about a gross of those Chinese 12ax7's. They're only $.18 ea. if you speak Mandarin. Xie, xie!
Then I put each one very carefully in an ice cube tray and use Mountain Myst Spring water to cover them. Freeze for 3 hours or until the impatient guests arrive.
Then I place them in a large bowl and cover them with a pint of ginger ale and 3 fifths of Cosmonaut Vodka.
When scooped, if your cube melts down and has one of the tubes, IT'S YOURS to KEEP as a party gift.
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When looking at the cryo diagram -- what strikes me is all the pass/fail boxes..
snip...
image removed, see post 110.
/snip...
Even if the cryo treatment has no influence on the tubes, all the selection has!
I wonder about that "Vacuum Enhancement Procedure"...
Bake them in an oven?
If that's true, it will flake off and microcrack. Unless it's tightly bound, in which case it will contract, then expand again when the tube is brought back to room temp. I can't conceive of any mechanism that will cause it to smooth out, nor is there any evidence at all that a smoother surface would reduce noise. Do painted bridges in Alaska get smoother over the winter?
Invocation of magic, mysterious forces with no backup data isn't terribly convincing.
Invocation of magic, mysterious forces with no backup data isn't terribly convincing.
True that, however tap a ferrite bar the right way and it will align magnetically, not so obvious from just looking at it. And who knows the bridges in Calgary sure got smoother in the winter when I was there, although this was probably due to black iceIf that's true, it will flake off and microcrack. Unless it's tightly bound, in which case it will contract, then expand again when the tube is brought back to room temp. I can't conceive of any mechanism that will cause it to smooth out, nor is there any evidence at all that a smoother surface would reduce noise. Do painted bridges in Alaska get smoother over the winter?
Invocation of magic, mysterious forces with no backup data isn't terribly convincing.
and I never said a smoother surface would reduce noise, just that a point radiating electrons would suffer increased resistance due to molecular bombardment and therefor reduced linearity over varying current loads..... this is only speculation although. It would have been nice to see real results if you got those tubes....... and I'm not lining up to buy cyro-treated anything anytime soon.
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