Just purchased a quad if approx. 20 year old matched Sovetek EL34g tubes.
I do not know anything about how they have been stored or anything, but judging by the condition of the boxes, probably nice and dry and I presume normal room temperaturs.
Is there any precaution I should take before listening to the tubes, or is it as simple as "plugg and play"
Thanks, Lars
I do not know anything about how they have been stored or anything, but judging by the condition of the boxes, probably nice and dry and I presume normal room temperaturs.
Is there any precaution I should take before listening to the tubes, or is it as simple as "plugg and play"
Thanks, Lars
Would it not be easier/safer to connect only the heaters for an hour? Or won't they get hot enough?
Most or all audiophiles just plug and play and get just 2K hours time life or less.
This is in the interest of tube manufacturers and tube sellers.
They wont say to the custumer its need activate the getter.
Note that after 6 months the getter goes to sleep and no more clear any possible gass rection inside or external air. Inside a tube there is a partial vacuum, there is millions or molecules or air or metals evaporated.
The correct procedure is activate the getter again to restore a good vacuum, i.e. you have to heat the filaments for various hours and wait a time to the chemical reaction produce a good vacuum again.
The details of how many hours for each step only an expert in that tube can say or the own tube manufacturer. And I sure they wont say it to us.
No. It's never good to only power the filament. And it won't heat the getter, which is the intent with heating in an owen.
How does it not heat the getter? The getter is part of the internal metallic structure, and being that the envelope is a vacuum, heat will conduct throughout the structure. The only other mechanism for dumping heat is radiation (IR).
Is your concern that heater(s) alone can't raise the temperature far enough?
I just tested about 100 pcs 6p3p, which is Chinese version 6L6, made in 70s-90s (40-20 years old) found 30% of them tested initial faulty, e.g. heater don't light up, no cathode current, erratic and unstable. I thought it can't be so many so I re-solder the tube pin of and managed to recover a least 15 pcs otherwise tested faulty. Some have even wrong tube pins on them so can't do anything about it. Even your tubes have been tested before I would advise to resolder the pin, as solder joint deteriorated and eventual would fail over the years.
I'm think of using a small solder pot or bath, since there are many joint to resolder.
I'm think of using a small solder pot or bath, since there are many joint to resolder.
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The getter is the shiny part of the glass envelope, it will have the same temperature as the glass.
A few view points that I have never heard before. Unless a tube is actively leaky, I would think that the vacuum would remain the same. I have never heard of baking the tubes in an oven to reactivate the getter or that the getter "goes to sleep".
Can you expand on this and possibly point out some references for this?
Thank you
BillWojo
Can you expand on this and possibly point out some references for this?
Thank you
BillWojo
I'm curious about this too. I've heard of baking tubes before, but I've never done it or had a need to try it. I've never heard of a getter "going to sleep". What indicates that a getter has gone to sleep, color change? I have hundreds of NOS and OS tubes, all twice as old as I am give or take a handful of years (I'm 30 BTW), I've never had an issue unless the tube is bad or broken.
I'm always open to learning something new though!
I haven't read the article Baking Valves yet by Morgan Jones, here it's. Baking the tubes that are arching (believe to have gas leak) is a good candidate for as heating with electricity can do damage due to arching.
Baking tips
Valves that have no manufacturing defects but have been in storage for many years may accumulate a little gas. If there is any suspicion that this may have occurred to any significant degree, it is better to bake the valves before testing rather than risk damaging fragile oxide-coated cathodes
Baking tips
Valves that have no manufacturing defects but have been in storage for many years may accumulate a little gas. If there is any suspicion that this may have occurred to any significant degree, it is better to bake the valves before testing rather than risk damaging fragile oxide-coated cathodes
I believe that in the factory, the heater at higher than normal voltage is used to activate the getter, this process is (was) called flashing.
Depending on the materials used, some getters are designed to absorb gases only once when flashed, other getter materials are called keepers and will absorb gas at operating temperature.
Which is in any tube is known only by the manufacturer.
I have used many NOS tubes from the late 1940s without any preparation, I think you can do this with most tubes.
As far as loose pins, anything is possible with Chinese quality, the NOS tubes never have this problem.
Depending on the materials used, some getters are designed to absorb gases only once when flashed, other getter materials are called keepers and will absorb gas at operating temperature.
Which is in any tube is known only by the manufacturer.
I have used many NOS tubes from the late 1940s without any preparation, I think you can do this with most tubes.
As far as loose pins, anything is possible with Chinese quality, the NOS tubes never have this problem.
i think koonw has shown one reference.
Remember that the getter ( the silvery surface) bound gas molecules, the process might
be reversed by long storage. Thus heating again will start the absorbation again.
No huge temperatures needed, below 100C and some time ( an hour or two)
This was wellknown for the former generation of engineers, and forgotten like so
many other facts by todays engineers.
Remember that the getter ( the silvery surface) bound gas molecules, the process might
be reversed by long storage. Thus heating again will start the absorbation again.
No huge temperatures needed, below 100C and some time ( an hour or two)
This was wellknown for the former generation of engineers, and forgotten like so
many other facts by todays engineers.
So, all that is happening is that by placing the tube in an oven at 100C, or there about, you are increasing the rate of reaction of potential gases within the tube with the getter flash material. That is sound, but why would a controlled warming of the filaments not accomplish the same thing?
If a tube is arcing due to gas you likely have a pretty gassy tube, I'd say that tube is done. I would be skeptical that an arcing tube, due to gas intrusion, could be saved by a couple hours in an oven. We are talking real catastrophic arcing here, not ionization.
If a tube is arcing due to gas you likely have a pretty gassy tube, I'd say that tube is done. I would be skeptical that an arcing tube, due to gas intrusion, could be saved by a couple hours in an oven. We are talking real catastrophic arcing here, not ionization.
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