tubes age 124
Thought this tip from Nolan would be of use to someone, somewhere, some
time.......found it while searching for something else. Barry
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I had a few more than a half dozen inquiries wanting more info about my
mentioning "fixing" gassy tubes, so here's an explanation of the method I use.
I've been doing this for ages and have had a pretty good rate of success.
Sometimes a tube will break while doing this. Your mileage may vary... It's a
very simple procedure involving the use of a glove, a Zippo cigarette lighter, and
a tube tester. I suppose that eye protection would be a good idea. Also a fire
extinguisher if your're a little clumsy. <grin> I wouldn't advise doing this to any
tube containing radioactive isotopes. You wouldn't want have one break and
possibly contaminate you or the shack. I make it a point to test all applicable
"amplifier" tubes for gas anytime I plug a tube into the tube tester. I've had
some odd ball problems with gear in the past that ended up being caused by
gassy tubes. At any rate, lets say that I just pulled one of the 5814A's out of the
R390A and it tested as gassy. The first step is to leave it in the tester for about
ten minutes at it's normal filament voltage to get the envelope good and hot.
Think of it as preheating. Next, while wearing a suitable glove, I pull the tube out
of the tester and using the Zippo, play a flame over and around the getter of the
tube, evenly for a few moments. I've never measured the amount of time that it
takes, it's just something that you'll develop a feel for after you've done it a
number of times. The Zippo coats the tube with a layer of soot while doing this.
This is good. It helps prevent hot spots and helps to decrease the odds of
stress cracking the tube. I have had a lot more tubes break heating them with a
butane lighter than with a Zippo. A candle would probably work OK too. If you
think you heated it enough, wipe it off and plug it back into the tube tester and
test it for gas again. Maybe it's fixed, maybe it ain't and needs another
treatment, and maybe the treatments just flat out ain't going to work on that
particular tube.
If you did heat it enough originally, you can often see a change in the
appearance of the getter. But not always. Don't you just love something that's
cut and dry? <grin> If it doesn't test gassy anymore, leave it in the tester for
about a half hour and test it again to make sure. Usually gassy tubes show up
a lot easier after they've run for a while. When doing octal tubes, sometimes the
getter is in the bottom of the tube below the edge of the tube base. This is one
reason that I don't like RCA 6K6GT's and prefer Sylvania or GE 6K6GT's. :-) The
Zippo method isn't practical for tubes built like this. ;-( If you put your eye out,
don't come crawling to me whining that I owe you an eye or something... my
disclaimer below applies, nolan
*** Disclaimer: Opinions are my own and in no way reflect those ANYONE else!
This disclaimer does not cover misuse, accident, lightning, flood, tornado,
tsunami, volcanic eruption, earthquake, hurricanes and other Acts of God,
female misinterpretation, neglect, damage from improper or incorrect line
voltage, improper or unauthorized use, broken antenna or marred cabinet,
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