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A Question about tube materials

G

guitargrump

Active Member
While I was browsing Ebay I came across some Soviet 6p14p / el84 tubes these tubes were listed as having a gold plated grid...

Another auction had a Soviet 6n2p adaptable to a 6.3 volt filament 12ax7 / ECC83 with a silver grid...

Why use a semi and precious metal on the grid of those tubes?

I get electroplating the pins with gold to prevent corrosion but the tube is filled with gas...
 
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I wonder if those claims are true....
Those metals are better conductors. Probably makes sense if those tubes were designed for very low noise amplifying very low-level signals.
 
I don't read or speak Russian so...

But I know that the military dose error on the side of caution when it comes to equipment durability and nobody has deeper pockets...

It can't be much that's for sure or the sellers would scrap them for quick cash...
 
guitargrump said:
I don't read or speak Russian so...

But I know that the military dose error on the side of caution when it comes to equipment durability and nobody has deeper pockets...

It can't be much that's for sure or the sellers would scrap them for quick cash...
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I have a friend in his 70s, who used to work at one of the military electronics plants in Lviv, Ukraine. I'll see him tomorrow and will update
 
My understanding is that the getter flash is creating a high temperature in the bulb while drawing a vacuum. This allows achieving a deeper vacuum level, otherwise impossible at sea level.
 
avionic said:
Wrong--- Vacuum tube ie. void of any atmospheric gases.
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I'm pretty sure in traditional vacuum tube making the vacuum is created by the same expansion and contraction concept as canning uses only it's the final heating of the tube in a centrifuge that causes the internal gases to expand and take up more room.

Then while the hot sealed tube is cooling, is when it actually becomes a vacuum because without the heat the remaining few gases and materials contract and you have your vacuum...

At least that's what I understand the process is basically...
 
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guitargrump said:
I'm pretty sure in traditional vacuum tube making the vacuum is created by the same expansion and contraction concept as canning uses only it's the final heating of the tube that causes the internal gases to expand and take up more room.

Then while the hot sealed tube is cooling, is when it actually becomes a vacuum because without the heat the remaining few gases and materials contract and you have your vacuum...

At least that's what I understand the process is basically...
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Your understanding is incorrect.
 
Usual practice is a vacuum pump to a high vacuum (32 to 34" of hg), RF Induction Heating of the getter material (a mixture of Barium and other minerals (yes I'm being overly simplistic as it's late and my COPD is acting up again!)) causing the mixture to flash against the envelope and instantly cool to a bonded solid to the glass. When the getter flashes, the exhaust tube is sealed from the vacuum source by a flame and pulling the glass exhaust tube from the envelope, sealing the tube. The getter will react chemically with any impurities left over in the envelope (atmospheric and material wise) each time the tube is energized. Eventually the getter will wear out and become absorbed by itself. (tube cannibalizism). A white getter signifies a vacuum leak and the tube is only good for tossing into a circular file, or setting up on a wood rail for plinking on the rifle range...........

There is an "OLD" (1950's) MULLARD Tube video on Youtube that shows this process during the making of tubes.
 
The gold is less likely to emit( there is a table for this property). Just like the opposite sort of characteristic is chosen for cathodes( Thoriated Tungsten ), excluding the coated types that are a step towards the unipotential style( cathode sleeves independent from the heater). Ideally you'd flash the getter when the guts are the hottest and least likely to condense the mostly-Barium flashing material on them.
cheers,
Douglas
 
. Dimitri;

"Commercial vacuum tubes are evacuated at manufacture to about 0.000001 mmHg (1.0×10−6 Torr; 130 μPa; 1.3×10−6 mbar; 1.3×10−9 atm).[69][70]" From Wikipedia "Vacuum Tubes"

I have no idea of how to convert that to "hg. But I would presume it's a lot more than what's needed for an Automotive A/C system. Already have the Aspirin out for the Migraine that's brewing.
 
grindfix said:
I have a friend in his 70s, who used to work at one of the military electronics plants in Lviv, Ukraine. I'll see him tomorrow and will update
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I asked him about gold grids. His immediate answer was impedance reduction for a cleaner signal. Then he added that military products were made with no expenses spared. If using gold for grids shows any improvement at all, who cares how much more it costs to build it? In the late 80s he serviced phone line cable equipment and 6P14P-EV was one of the tubes used. He said that all Soviet-era made tubes with -E as a part of the suffix had gold grids.
 
grindfix said:
I asked him about gold grids. His immediate answer was impedance reduction for a cleaner signal. Then he added that military products were made with no expenses spared. If using gold for grids shows any improvement at all, who cares how much more it costs to build it? In the late 80s he serviced phone line cable equipment and 6P14P-EV was one of the tubes used. He said that all Soviet-era made tubes with -E as a part of the suffix had gold grids.
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And that includes the 6P3S-E output tube.

Jack
 
grindfix said:
I asked him about gold grids. His immediate answer was impedance reduction for a cleaner signal. Then he added that military products were made with no expenses spared. If using gold for grids shows any improvement at all, who cares how much more it costs to build it? In the late 80s he serviced phone line cable equipment and 6P14P-EV was one of the tubes used. He said that all Soviet-era made tubes with -E as a part of the suffix had gold grids.
Click to expand...

So there was definitely something to the the useage of gold and silver.

And it's not a Hoax... Yay...:) all the Soviet cold war era tubes with the suffix of E

Oh boy that really is so awesome there's alot of those surplus tubes available in great condition I definitely need to pay more attention to them when I am looking for tubes...

I guess that if the military was making guitars there might be gold plated wire windings on the pickups too.

Must be nice to have a almost unlimited budget...

larryderouin said:
Usual practice is a vacuum pump to a high vacuum (32 to 34" of hg), RF Induction Heating of the getter material (a mixture of Barium and other minerals (yes I'm being overly simplistic as it's late and my COPD is acting up again!)) causing the mixture to flash against the envelope and instantly cool to a bonded solid to the glass. When the getter flashes, the exhaust tube is sealed from the vacuum source by a flame and pulling the glass exhaust tube from the envelope, sealing the tube. The getter will react chemically with any impurities left over in the envelope (atmospheric and material wise) each time the tube is energized. Eventually the getter will wear out and become absorbed by itself. (tube cannibalizism). A white getter signifies a vacuum leak and the tube is only good for tossing into a circular file, or setting up on a wood rail for plinking on the rifle range...........

There is an "OLD" (1950's) MULLARD Tube video on Youtube that shows this process during the making of tubes.
Click to expand...

So Sorry about your COPD acting up... There's not too much golden about the golden years as I am just discovering... I wasn't trying to start your headache...

I need to look up that mullard video on YouTube dose it show the sealing of the tube/envelope? Is that how they get their point on the newer tubes? Nevermind I'll find out by watching it...:beatnik:

Thank You Both All for helping commenting
 
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I wouldn't think that impedance reduction of the control grid material would be much of a reason for Au-plating it, since such tiny currents flow in that grid. For a coupla uA or so, who cares if it's 10milliohms or a 100? Maybe back emission from the grid that gets to hot being near the heater might be a better reason.
 
There were a number of industrial/ milspec exotic tubes that had precious metal parts that were were worth more as scrap than as surplus. Many were crushed and chopped for salvage in the past, including types that are now repurposed for audio.
 
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