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Steel

Discussion in 'Amplifiers' started by C2, May 24, 2006.

  1. C2

    C2 Sr. Member

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    One guy is selling all his tubes and says they all got to go because he is upgrading to steel.

    What does this mean? Tubes have a tungsten steel filament, right? or does he mean the glass tubes vs the steel "tube."



    What is it about steel that makes it an "upgrade" from regular(?) tubes?
     

  2. Moleculo

    Moleculo Administrator
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    I think he's talking about changing over to an amp that uses the newer steel ceramic tubes instead of old sweep tubes (or maybe some newer glass tubes). I don't know all the advantages of the steel ceramic, but I do know they are much more durable and capable to taking abuse.
     
  3. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    Most of the ceramic tubes are usefull over a much wider range of freqs.,not that it matters for a single band amp.They are able to provide much more power from a single tube than you can obtain from glass tubes so a single 3CX1500 can provide more than a gaggle of sweep tubes. ;) I must disagree with you Mole on the durable aspect.It all depends on the tube.Most ceramic tubes,like the 4CX250B for example,can be destroyed very easily by overdriving them.The grids just can not handle much power.Also they are just as susceptable to internal damage due to shock and vibration as glass tubes,they just do not have a glass envelope to break.If you drop a ceramic tube or give it a sudden jar it may not show any damage on the outside but the internal structure may be a right off.The only way to tell is to ohm it out and that may not even tell you.Then comes the big bang theory,turn it on and if it goes BANG then chanches are it was damaged. ;) As a rule the 4CX series (tetrodes)have very high gains and can usually be driven to max output with just a few watts.The 3CX series (triodes) requires more drive and has less gain.Cooling for the ceramic tubes is more complicated as well.Generally when not over driven the signals are cleaner due to lower IMD products from ceramic tubes.BTW NEVER CUT A CERAMIC TUBE OPEN!! The ceramic contains beryllium oxide and cutting it or sanding it can lead to the dust entering your lungs and it can cause very bad problems and even death. :!: As long as the ceramic remains intact there is no problem.

    BeO MSDS sheet
     
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  4. Moleculo

    Moleculo Administrator
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    Good info QRN. For some reason I always thought they could handle being over driven better, or worse SWR conditions, or bad load / tune conditions better than the tubes. Guess I just had the wrong info.
     
  5. C2

    C2 Sr. Member

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    Thanks guys :)
     
  6. Captain Kilowatt

    Captain Kilowatt Professional Amateur
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    I know a few guys that think that as well. I guess they think that way due to the lack of a glass envelope that is obviously fragile. The feel of a ceramic (steel) tube is that it is more solid feeling and generally heavier leading to a more robust feel.The elements inside however are basically the same as a glass tube except for the plate which is actually the steel top with the fins.These tube are also called "external anode" types because the anode,or plate,is physically outside the vacuum chamber of the tube.As for being damaged by overdriving it all depends on the individual tube just like glass tubes.The 4CX250B has a grid dissipation of only about 2 watts before it is destroyed while higher power tubes like the 3CX800A7 have a grid dissipation of only 4 watts.A 3-500Z however has a grid dissipation of 20 watts.Note that grid dissipation levels do not mean drive levels,only what the grid is capable of handling when grid current flows in the tube.These levels can quickly be exceeded in an overload condition such as improper tuning or improper bias levels.
     
  7. nomadradio

    nomadradio Analog Retentive

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    Whoa! Mr. uh, "Steel" is in for a surprise if he picks up a bar magnet and gets it near his "steel" tubes.

    Most of the metal in an external-anode tube is , oh yeah, a 'banned' word. Latin name "cuprium", giving it the symple "Cu" on the periodic table, NOT steel. The small 250-Watt tubes have a metal ring around the base, which tends to be steel of some kind.

    But the big ring with the fins inside it will usually be a cuprium alloy, and NOT magnetic. The whole point of using a metal cup to hold the vacuum is that the heat travels out of it much more efficiently. A tube like the 3-500Z that has the anode enclosed in glass can't transfer heat as efficiently. Makes it larger, to spread the heat over a larger area, and keep the temperature below melting point.

    Take that gray anode you see in the 3-500Z and make IT into the vacuum "container", with an insulator on the bottom where the pins are, and now the heat can travel THROUGH the metal to the outside world, directly. Makes an external-anode tube far smaller per Watt of rating, since more heat per square inch of surface can be pulled out of it.

    Bear in mind that not all external-anode tubes are made with ceramic insulation. Plenty of glass-metal tubes are out there, especially Russki military types.

    Using glass as the insulating ring under the metal anode limits how hot you can safely get it. A metal-glass tube called the "4X150" is nearly identical to the ceramic-metal "4CX250"-type tube. The stuff inside is all the same, but the "C" in the second number means "ceramic". This raises the tube's maximum-safe temperature, rasing the wattage it can dump into the air that flows over it.

    Wonder if your 'steel' guy will want to pick up a bar magnet and see just how much of his 'steel' tubes it will stick to?

    73
     
  8. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Good info on steel tubes, bump.
     
  9. BJ radionut

    BJ radionut Supporting Member and 6m addict

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    I am like Nomade and CK, I don't understand where this "Steel" tube nomenclature ever came from.
    They are composite Glass/Ceramic tubes. Even some of the Russian tubes are Hybrids,
    I guess it stems from the Anode cooler on top, "appears" to be steel but they are not.
    Nomade is correct (as others have stated) the "C" in the tubes like the 4CX250/4CX1000-1500-3000 etc. is a Glass/Ceramic Hybrid.
    The (4) in front means Tetrode (4 elements) ... Filament/Grid/Screen/Anode
    The (3) in front means Triode (3 Elements) Filament-Cathode/Grid/Anode
    Ex: 3-500Z ... 3-1000 ...3CX800 ...3CX3000
    However some Tetrode tubes can be operated as Triodes 4-400 ...4-1000 and others.
    However, in doing so, they can require more drive to get approximately the same power as their Triode cousins.
    I have an amplifier here that is designed to use a 3-1000z Glass, I can also sub in a 4-1000A or 4T-1100 tube in the same amplifier. The 4-tubes require more drive in Grounded Grid configuration than the 3-tube. The way to compensate for that is to have an adjustable Plate voltage supply. Thus being able to increase the Plate voltage gives the 4 - tube the same "Gain" as the 3 - tube. (or in some cases more)
    However again may require the additional drive to do so.

    OK CK/Shockwave you or others/ Engineers etc., if I have misstated anything, please correct me.
    I am just a Layman wire twister and this is how I have learned to understand this.:D
    The Russian tubes have a different number or identifier system. However many of their configurations are direct subs for the American (USA) versions. They also have many of their own designs which work well in amplifiers. Ex. Some of their Ceramic/Glass examples are the GI (6)7 series ...GS31 ...GS35 and many more. It just depends on the Frequency and supply voltages/ drive requirements etc. parameters they were designed for.
    A good source for many Transmit Datasheets here:

    http://www.ok1rr.com/index.php/rustr/2P302A.pdf

    https://mafiadoc.com/eimac-power-gr...ce-catalog-1969_5a13405a1723dd3e08081208.html

    Russian tube source:
    http://qro-parts.com/index.php?cPath=21
    http://rutubes.com/category/power-vacuum-tubes/

    https://archive.org/details/vacuumtubemanuals

    OK...Got to run...
    All the Best
    Gary
     
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  10. Shadetree Mechanic

    Shadetree Mechanic 808 On The North Side of Dover

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    Thanks for the info Gary, now I have some reading to do.
     
  11. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    UY224 tetrode plate current negative resistance svg - Wikimedia Commons.png
    If I remember correctly there is a "Dynatron Region" in which a increase in plate voltage will not cause an increase in tube conduction.
    Tetrode tubes can and will oscillate like crazy if not properly neutralized or compensated with negative feedback.

    I also think the ones with the fins need forced air cooling. Not for the people who get irritated by the sound of the Megawatt 50 amp supplies.
     
    #11 Tallman, Nov 30, 2019
    Last edited: Nov 30, 2019
    Shadetree Mechanic likes this.
  12. Doc813

    Doc813 Member

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    The steel came from the same place as pills did lol.....
     
  13. nomadradio

    nomadradio Analog Retentive

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    Triodes and tetrodes are different.

    Raising the plate-voltage of a grounded-grid triode increases the power gain. Period. Up to the point where things melt, explode or gas in the tube's vacuum breaks down.

    The power gain of a tetrode is a lot more sensitive to the screen than the plate voltage. Especially if the tetrode is grid-driven with the cathode grounded. Raising the plate voltage alone makes almost no difference once it's past that 150% to 200% region. It does let you increase the drive level at which the tube will "flat top" or slice off modulation peaks. The tube tends to "accept" more drive with a higher plate voltage alone. Doesn't change what comes out at a particular drive level. Just increases the max drive the tube will accept before flattopping.

    Oh, yeah, the Dynatron. Just think of the screen grid as a signal input. One that you don't feed a signal into. It still wants to behave that way just the same. The sensitivity of the plate current to changes in screen-grid voltage (power gain) is highest when the plate voltage is lowest. Accidental feedback-signal input to the screen grid can make the tube sing like a bird.

    A bypass capacitor from the screen grid to ground is there for this reason, but sometimes won't do the whole job of keeping it stable. Found that a 'swamping' resistance from the screen grid to ground will suppress this tendency. Works best placed nearest to the tube socket.

    73
     
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  14. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Agreed. Triodes and tetrodes are different. Tetrodes are inherently unstable. I don't know exactly why, but it could be because of inter-element capacitance.
    There was a piece of medical equipment that used a tetrode. The therapy was referred to as "Diathermy." The machines have been regulated out of use since they were hazardous to patients. The chart I included was showing plate voltage versus conduction. The chart above is from :https://commons.wikimedia.org/wiki/File:UY224_tetrode_plate_current_negative_resistance.svg
     
  15. Slowmover

    Slowmover Sr. Member

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    Lee DeForest & the Audion Diathermy Device.

    9843D095-7C44-43BD-92D2-52B5AE815636.jpeg


    Now we know what dledinger was up to re RF lip burn when really it was the double-dog-dare-ya HAM radio equivalent of touching tongue to metal freezer shelf.

    .
     

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