I've been using several med. pwr. HF amplifiers ( 2KW +/-) for years, - none og them has or had a separate HV switch...
what has to do heater with getter ?!
anyway, by using valve normal way will not create heat like this on getters
Near all tubes works with hi voltage to me:
A small preamp 12AX7 tube plate can receive over 300VDC
A thin EL34 plate can sink 800VDC.
6C33 plate usually run from 200VDC to 250VDC.
GM70 plate start working at 800VDC to 1500VDC
Chinese 211/845/805 Triode plates start working at 900VDC
This is very hi voltage to me, but even a low 30 VDC can kill a man.
Tube amps owners must use a clock to mark the time to press the second power on switch, I sure it not difficult even for Pop music fans.
I know many very famous, respectable and expensive tube brands that dont use a second power on switch or even a time delay for the HV plate.
All I can say to it is these amps are outrageously faulty and are obviously tube eaters.
I hate this kind of scamming in audio.
I sorry your amp dont had two power on switches or even a HV delay.
But it can be moded, a switch cost so low as 0,25 dolar in China.
Very few money to protect your tubes and amp.
Otherwise if you use this tube is a ham radio, it surely had a knob for output power, which is the hi voltage control; and dont need a second power on switch.
HF PAs have a standby function which disables keying, - HV is on at all times... no problems at all
- and HV is 2.5-3 KV, depending on OP mode.
No need to modify, - and switches don't like 3 Kilovolts.......
- and HV is 2.5-3 KV, depending on OP mode.
No need to modify, - and switches don't like 3 Kilovolts.......
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Personal experience is circumstantial, and Google is not good source of real scientific evidence. You need to read more books.
Fortunately, valves have different ideas about high voltage.FullRangeMan said:
The scam is low power valve amps with a totally unnecessary 'stand-by' switch, which may reduce valve and capacitor life by creating current surges and running valves unnecessarily with full heater and no HT.
Don't valve rectifiers (5ar4) provide delayed/slow increase of high voltage while heaters are warming?
I unknow this amp but this standby option looks a second switch, it may keep on just the cathode heating and disable the grid and HV, hence the name ''stand-by''.
Some amp builders, use a pot to control the HV plate, which is OK.
3kV is the output from the power supply, the input where the second switch locate may be 120V from the wall outlet.
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How minutes are this delay??
Looks it is a soft start(some seconds) to avoid the inrush from the mains wall;
Interesting question, FullRangeMan.
I was wondering whether setting up a simple burn-in fixture (a socket and a power supply) and applying power to the filament only would work. A quick google search turned up this link:
AE1S Amateur Radio Blog: "Gettering" GU74b / 4CX800A
Granted, I haven't done this myself (although I intend to do so in the very near future with some old tubes I just acquired on eBay), but it sounds quite safe and reasonable.
The heater in the tube provides a rather high temp and will also heat the cathode element. Heating both elements will serve to absorb any stray gas molecules in the tube.
I tend to agree with the other posters that the getter itself is a one-time use device. Baking the entire tube in an oven is problematic in both the blistering of the bakelite base (on octal tubes) and getting clearance from the XYL 😀
If you're concerned about gas in your older tubes, it seems just running the filament hot for several hours would do the best possible thing.
BTW - for most of the audio tubes used by us, you won't need the cooling fan apparatus described in the link. The 4CXxxx is a VERY hot tube, with a ceramic body, and absolutely needs forced-air cooling or it will be destroyed.
As a practical note, most of the amplifiers we build run on modest (<500V) plate supplies. The danger of arcing in the tube due to gas is remote - but this seems like a very easy procedure and at this point I'm of the opinion, "why not?"
This seems to apply only to old tubes either pulls or NOS that have been in storage for many years. A new tube will not need this kind of treatment.
As for the cryogenic stuff - I will leave that to others...
Good luck!
RF Dude
I was wondering whether setting up a simple burn-in fixture (a socket and a power supply) and applying power to the filament only would work. A quick google search turned up this link:
AE1S Amateur Radio Blog: "Gettering" GU74b / 4CX800A
Granted, I haven't done this myself (although I intend to do so in the very near future with some old tubes I just acquired on eBay), but it sounds quite safe and reasonable.
The heater in the tube provides a rather high temp and will also heat the cathode element. Heating both elements will serve to absorb any stray gas molecules in the tube.
I tend to agree with the other posters that the getter itself is a one-time use device. Baking the entire tube in an oven is problematic in both the blistering of the bakelite base (on octal tubes) and getting clearance from the XYL 😀
If you're concerned about gas in your older tubes, it seems just running the filament hot for several hours would do the best possible thing.
BTW - for most of the audio tubes used by us, you won't need the cooling fan apparatus described in the link. The 4CXxxx is a VERY hot tube, with a ceramic body, and absolutely needs forced-air cooling or it will be destroyed.
As a practical note, most of the amplifiers we build run on modest (<500V) plate supplies. The danger of arcing in the tube due to gas is remote - but this seems like a very easy procedure and at this point I'm of the opinion, "why not?"
This seems to apply only to old tubes either pulls or NOS that have been in storage for many years. A new tube will not need this kind of treatment.
As for the cryogenic stuff - I will leave that to others...
Good luck!
RF Dude
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No. Firing the getter is a one-time event. The getter then continues to mop up gas for the life of the valve. It works at all temperatures, but better at higher temperatures.rfengineer2013 said:
An exception is some high power valves, which use a different getter system. This is attached to the anode and only works at high temperature. Some big RF ceramic tetrodes may use this system, so you can't necessarily apply techniques for them to ordinary audio/radio valves.
DF96, I would agree with you that firing the getter is a one-time event. And the theory presented in the link I posted does indeed suggest that he is "activating" the getter by heating the tube.
While heating the getter in the 4CX tube was seemingly the object of the exercise, I think the process is still valid in this discussion.
Earlier in this thread was a link to a white paper that involved baking tubes in an oven at 100C or so. The theory there was that the filament and cathode surfaces, when heated, would absorb any stray gas molecules in the tube.
It seems that IF a person wants to "bake-out" a tube after long-term storage, and IF the process involves heating the tube, then it only seems logical to use the tube's own built-in heater.
Whether it makes any difference or not, I can't say. Certainly, we're talking about very trace amounts of gas here. If the plates glow blue in operation, this process is not going to fix the tube (unless it's supposed to glow blue, that is)
So while it may not help much, IMHO it can't hurt to run the filaments on tubes that have been in long-term storage.
If nothing else, it looks pretty 🙂
While heating the getter in the 4CX tube was seemingly the object of the exercise, I think the process is still valid in this discussion.
Earlier in this thread was a link to a white paper that involved baking tubes in an oven at 100C or so. The theory there was that the filament and cathode surfaces, when heated, would absorb any stray gas molecules in the tube.
It seems that IF a person wants to "bake-out" a tube after long-term storage, and IF the process involves heating the tube, then it only seems logical to use the tube's own built-in heater.
Whether it makes any difference or not, I can't say. Certainly, we're talking about very trace amounts of gas here. If the plates glow blue in operation, this process is not going to fix the tube (unless it's supposed to glow blue, that is)
So while it may not help much, IMHO it can't hurt to run the filaments on tubes that have been in long-term storage.
If nothing else, it looks pretty 🙂
In most valves the heater does not heat the getter very much, as the getter is on the envelope so kept fairly cool. In many cases simply running the valve (i.e. heater and anode current) will do the job, as the anode will heat the getter more effectively than the heater will. Baking it is an alternative, which may be better as the cathode is not exposed to danger from ions.
Oh dear, I got quite misunderstood here.
Done that - on theoretical scale. Using Lenard Jones Potential for the adsorption, calculating partition functions, temperature dependet pressure etc..
Know that quite well 🙂 We do some nanostructures in my University with molecular beam epitaxy. This is done in UHV conditions. Maybe the department pays your job, when something is ordered 😀
Exactly what I mentioned. Baking is not particularly neccessary.
In terms of chemical bonding, yes. But simple sorption happens on nearly every surface. When it minimizes the free Energy (A tube can be seen as a nice Canonical Ensemble) it will happen.
I assumed that the structures were heated properly when the turbo pump/diffusion pump was applied and that there were very few molecules left on the surface. Under these circumstances, any air that goes in the tube will be caught by the metal structures (chemical potential !) and of course the getter.
And to clear things up a bit, here is a table with some Getter types:
Usually, barium getters are used (silver dome), sometimes also Ferrum-Zirconium (invisible on the glass)
Done that - on theoretical scale. Using Lenard Jones Potential for the adsorption, calculating partition functions, temperature dependet pressure etc..
Know that quite well 🙂 We do some nanostructures in my University with molecular beam epitaxy. This is done in UHV conditions. Maybe the department pays your job, when something is ordered 😀
Exactly what I mentioned. Baking is not particularly neccessary.
In terms of chemical bonding, yes. But simple sorption happens on nearly every surface. When it minimizes the free Energy (A tube can be seen as a nice Canonical Ensemble) it will happen.
I assumed that the structures were heated properly when the turbo pump/diffusion pump was applied and that there were very few molecules left on the surface. Under these circumstances, any air that goes in the tube will be caught by the metal structures (chemical potential !) and of course the getter.
And to clear things up a bit, here is a table with some Getter types:
An externally hosted image should be here but it was not working when we last tested it.
(source: Getter Materials)
Usually, barium getters are used (silver dome), sometimes also Ferrum-Zirconium (invisible on the glass)
My electronics knowledge is so small I do not know if these probs you mentioned even exist, but seems make sense at first glance.
I would be careful with these famous Triodes amps, as these audiophile tubes are very expensive(45, 2A3,300B) and are marketed as jewelry.
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the actual procedure is really running the tubes with just the heater supply on and no high voltage B+ for 8-12 hrs. tubes don't ionize as bad as crt's do for some reason, but its ionization is most likely caused by improper storage techniques.
Surely running the valves *once* to operating temp, would be enough? When you turn it off, the valve is still really hot, and that remaing thermal energy should be plenty for any "gas" to find its way to the getter...yeah? As long as that getter still looks good after cooling, all is well..right? 😉
cheers, Jacob
cheers, Jacob
you would think so, especially since the tubes don't have a big empty space conpared to CRTs.