tube getters

anyone ever (like once a year, or once every two years) let the tubes heat on standby for 24 hours to let the getters pull a better vacuum again? I read this somewhere, but I'm guessing it's better for NOS tubes that last for years, depending on use


scott

No, but if you don't run an amp for a long time, the big electrolytic caps will deteriorate.
Never heard of rejuvenating getters or vacuum. Couldn't find mention of it in a Google search.

Total BS. Worse, it will actually harm the tubes. Running tubes for an extended time with no plate current flowing - ie many hours on standby - is bad for them, it causes 'cathode poisoning'.

If you must do this, run the tubes fully, not on standby. Best of all, don't do anything.

As MrMkIII said, if you're talking about the amp and not just spare tubes, run it regularly to keep the caps in good condition - again fully on, not on standby.

+1. The silver coating that the getters leave on the glass when they are activated in the factory stays active until it is used up which should never occur during the tubes life.

thanks, yeah it seemed like total bs to me. I use them at home fairly regular, so I'm not too worried about caps drying out. I read this on rig-talk, after someone asked about not using their diezel for long periods of time. I mentioned about the caps drying out from no use, and someone else chimed in about the tube getters

scott

Electrolytic caps have some interesting properties. They won't dry out from lack of use, but their plates can
"unform". If you hit them with full voltage they can get very hot and fail permanently. Older caps seem to suffer more though. The "unforming" is a slow process and happens over years and can be reversed just by using them. I just make sure I give my old amps a good run every few years.

Drying out is more to do with use and heat.

Back on the tubes, there are some special things that can be done to reduce gas, but thats more to do with mega expensive transmitting tubes that probably don't have getters. That stuff isn't for audio tubes though.

The getter is not what "pulls a vacuum" in the tube, a vacuum pump is used. The getter is used to remove (or get) any oxygen molecules left in the tube that could burn out the heater filament, not to increase vacuum (although that is a side-effect, but very minimal). The getter is fired using induction, there is no connection to the pins.

If I have any if this wrong, someone please correct me.

Dom

3 day's after I put my pair #2 of Sylvania 6L6s in, I accidentally left the amp on standby overnight after a very hard jam (I always allow the usual good pre-warm, and post-cool down, just forgot to hit the switch). I went back the next morning after coffee and saw the amp on, checked the tubes, checked everything and it was all kosher. I've since put a year in rehearsals and plenty of shows on those tubes (plus the Youtube vids). I didn't leave them cooking powered on though, just the heaters.

Still sounds amazing.

Once the getter is fired as the final stage of tube production,it is no longer active.As dom said it is just a process to burn off any last bit of oxygen that is left to keep the filaments from burning.The silver "stain" is just residue left by the magnesium being flashed.The silver will fade and or turn brown when the tube is old and almost used up.If a tube is stored unused,the flashing will remain silver and the tube wont lose any usefulness.It doesnt need to be rejuvenated as someone told you,that is total b.s.I wouldnt discard a tube whose flashing is browned,but I wouldnt buy a used tube in that condition,it is a sign the tube is on the way out.

The getter is made of Barium which is highly reactive to oxygen. Dom's got it, it's used to absorb any trace amounts of oxygen left in the tube post vacuum sealing. If the tube seal fails (cracks, etc.) or the tube breaks, the silver barium getter will turn white due to the reaction forming Barium oxide. Generally, tubes that fail from a mechanical issue in the glass or any seal etc. will have a white tip instead of a silver one.