Heater Voltage of tubes

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This text is a little bit parody, but I still mean it. What a miracle, tubes work so well, because everything inside is a compromise, between parameters, performance, cost, reliability, and many more items.

The main 3 parameters to make the heater and cathode last longer are: The heater voltage, it's tolerance, and in case you are looking for a third factor: The way you switch the heater off.

Too fast cooling down will cause cracks in items which were very hot. So any baked tiles, pottery, glass and ceramics, but also metals can crack. When metals crack, they form more, and new crystals inside, mainly where the tension is, and then eventually break at those points. This building of crystals is greatly prevented by slow cooling down.

Slow heating up doesn't prevent this, as we all know crystals form not a warming up, but at cooling down. (It's a bit strange we have to say, what everybody already knows....)

But: Slow heat up causes emission loss, and it's overall disadvantage. You can do it for fun, and if you use the tubes very little, it doesn't matter much. In all other cases, it's not a very good idea.

Information Sources

The tube manufacturer
 If you think it is possible, the manufacturers of the tubes know what they are talking about, follow their advice. If you think manufacturers don't know much abut tubes, and good information comes only from anonymous experts on the tube forums... , well then you know who to ask.
Good DIY tubes magazines
 Glass Audio, or similar, but old issues are hard to find. Also most old American magazine from 1925...1965. Just dig into those old articles, and you will be surprized about the 10.000's of excellent articles you can find in those. So not, first a tube was developed, and then the application knowledge came by doing. Go to 4tubes.com under literature and find some of the top class magazines and articles from the 1930's..
Experienced Service people and good DIY builders
Good DIY builders are to my opinion the most reliable.
Amplifier Manufacturers
 Some are excellent. But some are hard learners, and never admit a mistake. Like when the tube data sheet writes maximum 33uF Capacitor on 5U4G, only a fool takes 100uF and say the data sheet is wrong.
Manufacturers of 'clever' tube module electronics.
 NO. Don't bother me with it. Such modules are a source of problems before you know it. These solve artificial problems, like weird slow start sequences, or anything 'interesting' which is supposed to sound 'better'. In the end these items cause problems, by not understanding what prolongs tube life, and what shortens it. (See more text below here, about this)
Internet babble
 If anonymous talk, it's for the birds. Look at it like this, who writes something great, would be proud to have his name on it. If they intentionally hide their name, that makes it easier to disappear after writing nonsense.

Mistakes

Overheating. Yes we all know, that is not good. Let me explain the meaning of 5V +/-5%, when the data sheet writes so. To understand that, just look at those questions:

Under heating. It says in the data sheet 5V +/- 5%, under heating. will have similar problem behavior. So at -6% is not possible, otherwise the data sheet would have said so. At under heating, the tube will give up on you, much sooner as you like. The difference between over- and under heating is, with under heating problems come MUCH faster. So after 50...100 hours, the tube may already get bad.

Interesting, with under heating., the tubes will often recover for the greater part of it, when heater voltage is corrected. Whereas with overheating however the damage is lifetime loss, and what is lost, is lost.

This is the reason, why heater voltage tolerance is always written so clearly in the data sheet, at it's first page.

Slow start of heaters. Actually this ok, BUT..... only if there is no anode current. If you never heard about this requirement, don't ask other amateurs. Better ask specialists, like those who build tubes, for instance.

On just a few lines.... The best was to blast off (invisible) micro chips from the heater, is FORCE full current at a half warm heater. That works really good, because the heater surface heats up with little islands at first, and these islands, though initially the best spots, get thermally blasted off, by forcing full current through these narrow spots.

Note, switch off abruptly is JUST AS bad, and the reason for unexplained heater breakage. But many of those module makers never heard of this. They do their 'great job' in slow start, but just within 4 seconds is fine. But, stupidly, when it comes to slow ramp down, which would be SO EXCELLENT (provided anode current is off), they never heard of it, and just switch off the tube radical.

This page is about Errorz and Misstakes. Here is another one:

Just cut and past that in the Google Earth search: 32°40'33.94'N 117° 9'27.84'W