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In Reply to: RE: Why bother posted by thetubeguy1954 on September 15, 2011 at 13:05:48
I've written about this before.I use an old toaster over and stuff it full of tubes, If you have inquisitive household members, cover the tube with some fiberglass cloth to avoid thermal shock from curious eyes.
Once loaded I turn the oven on at the lowest setting and let the load sit for 3o minutes, I raise the temperature every 3o mites another 5o degrees till I reach about 300 degrees, and then I just let the tubes bake at that temperature for as long as I feel comfortable ( I've let the tubes bake over night). Once the baking period is over, simply unplug the oven and let it cool slowly to ambient room temperature, about3 or 4 hours.
I often do this to even new tubes as some residual gas seems to leach out after sitting for long periods ( NOS types). The result is a more dynamic sounding tube with a better top end.
Incidentally polishing tube pins also gives a much improved top end ( at least for 7 and 9 pin tubes where the pins enter directly through the glass). You also can effect big sonic changes in octal type tubes by changing the solder in the pins!
StuPS I should add that you could go higher in the bake out temperatures, but I do not recommend going past 350 degrees, primarily because the printing will yellow. Makes it difficult to resell. Ive gone up to 450 degrees with no issues to the tube however.
Edits: 09/19/11Follow Ups:
You know that vacuum is a heat insulator, of course?
The tube envelop will get hot and the pins will conduct heat to the interior structures, but inefficiently.
I don't have a clear idea how hot you could get the innerds of a tube by your method.
Nothing is going to 'leach out' of a tube.....ever...while it is under vacuum.
Too much is never enough
Can I use a fan-forced oven?
Note that a post in response is preferred.
Warmest
Timothy Bailey
The Skyptical Mensurer and Audio Scrounger
And gladly would he learn and gladly teach - Chaucer. ;-)!
'Still not saluting.'
Yeah, you know us metrically deprived Americans. Convection ovens are fine, the key is to heat and cool the tubes slowly, or at least slow enough to insure that the differential between expansion rates of the metal and glass do not cause any issues.
Stu
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