de-gassing power tubes???

[speakerfritz]

Ran across this article about de-gassing power tubes. Basically different techniques to get the gas to interact with the getter. Thoughts?

SM 5 BSZ - A procedure to recondition power tubes

[Wavebourn]

Search for baking tubes in oven, we discussed it here.

[speakerfritz]

Originally Posted by Wavebourn

Search for baking tubes in oven, we discussed it here.

interesting...thanks for pointing this out....it helps me understand why a very large percent of guitar amp power tubes get gassy over time vs traditional tube amp power tubes....the guitar amp power tubes spend their time upside down...heat rises....but with an inverted tube....the getter does not get as hot as a non inverted tube....harder for the getter to absorb the gas.

[v4lve lover]

ive read of hams regenerating sweep tubes by putting all the grids shorted to the cathode and pulling a huge current through the cathode wich is very taxing to the tube . wich breaks down the old layer of barium strontium , natrium carbonates to oxidesinto No2- wich is then in turn absorbed by the getter

if you want to regenerate the tube in one shot . try this whit i cheap tube : preferably a series heater one just light the fillament whit twice the heater voltage this will bring the cathode above degassing temperature and expell all the trapped gasses wich will be absorbed by the getter . i have actually seen PCF80's YES i have a few 100s of them . lose their gettering while practicing this . but ofcourse they shined as bright as a halogen bulb

edit those are tough . things i had one survive about four times its rated voltage for some time it drew 1 amps instead of .3 can you imagine a tube the size of a ecc dissipating about 20 watts of heater power ? HMM they give of that smell of vinegar and toasted skin oil .

[Alastair E]

Had a PL519 just recently show a nice blue glow inside the plate structure....

This was a used and rather old, sad looking example, blackened glass, and that horrible brown stuff on the inside of the glass that Mullard valves always seem to get after hundreds of hours use, and silver patches near the base-pins.....

I just left it in the amp, (Simple-OTL, running at 150V, 150mA) and let it get good and hot...

After 10-15 mins, the blue-glow had reduced to just a little, around the plate.

After about half hour, there was no trace of blue at all, and the valve functioned--and still does--normally...

[v4lve lover]

yeah that is a nice case where the oxygen got eaten by the barium metal on the cathode and restored vacuum . the steepnes and emission should tho have changed some . as a thin layer of barium has evaporated making the cathode a little thinner just a bit . means it will do something whit the steepness of the valve

btw those horrid stains are harmless little lead oxide getting free afther electron bombardment nothing to worry about

[ChrisA]

Originally Posted by speakerfritz

interesting...thanks for pointing this out....it helps me understand why a very large percent of guitar amp power tubes get gassy over time vs traditional tube amp power tubes....the guitar amp power tubes spend their time upside down...heat rises....but with an inverted tube....the getter does not get as hot as a non inverted tube....harder for the getter to absorb the gas.

"Heat" does not rise. Hot air rises. The tubes are filled with vacuum so there is nothing to raise. The tubes cool by radiation and so they cool just as well base up or base down

[Wavebourn]

In guitar amps output tubes die younger because they dissipate more power and run hotter.

[Sch3mat1c]

The getter is essentially at an identical temperature to the glass it's deposited on. Moreover, the getter is shiny metal and therefore reflects any radiation nearby. If the getter is at the top of the tube, and the tube is inverted, it will be the coolest point on the tube because the coolest air is reaching it first and because it isn't dissipating much heat over that area to begin with.

If the getter is at the base, the opposite is true, with the added factor that pins are also carrying a little heat through the glass.

Tim