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Thread: oudin/tesla coil

  1. #11
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    A friend told me about the rf-method of ionizing gas and referenced to sams laser faq - where its shown as a very soft way to start a tube.

    My idea was to replace the standard ignitor with the rf one. As i understand when i use the rf one i dont have a sparks which spots the cathode.

    Ronny

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    Hi Ronny;

    You may want to take Steve (Mixed-Gas) up on his offer. He's got a large collection of ion lasers at his disposal. If he can get you the factory original ignitor you need for your tube, that would be preferable to anything you might be able to assemble yourself.

    The ignitor pulse can indeed cause damage to the cathode, but you've got to realise that the tube manufacturer knows this and has designed the cathode to be quite robust. Normal starting of the tube isn't the problem. Where you can kill the cathode is when you have a tube that won't start and the ignitor keeps hitting the tube over and over again. Or, if you have a fault in the PSU where it doesn't shut off the ignitor after the tube lights, and once again it keeps nailing the tube over and over.

    Finally, let me say that Steve is a *hell* of a great guy, and is also very knowledgible. If he says he can help you, take it to the bank. He's got the goods.

    Adam

  3. #13
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    Well, i believe in the knowledge and experience of the people here - thats why im here

    I conform with you, the cathode should be robust enough for the job its developed for - but i will make some tests where it is necessay to start the tube every 5-15mins. I cannot imagine how fast the cathode is killed by the sparks (if ever).

    Ronny

  4. #14
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    Quote Originally Posted by ronny View Post
    Well, i believe in the knowledge and experience of the people here - thats why im here

    I conform with you, the cathode should be robust enough for the job its developed for - but i will make some tests where it is necessay to start the tube every 5-15mins. I cannot imagine how fast the cathode is killed by the sparks (if ever).

    Ronny
    I'm the one who wrote that RF starting line in the FAQ, it needs amended a bit to read, "

    "the ringing RF waveform from a proper starting coil aids in starting the tube softly, while insuring formation of the cathode spot using the first sharp pulse of the ringing wave. The pulse heats a small random portion of the cathode surface to start arc electron emission levels. The RF pulse also travels down the bore, ensuring a proper plasma formation, by providing a ionized path to form the arc. Typically the waveform is at 100-500 Khz and the ignitor coils often have a small HV cap across the secondary coil to form a resonant circuit."

    At low tube pressures near end of life that pulse shape really starts to matter as you start boiling off cathode material with the pulses as the tube really ages..

    I wrote that while in college many years ago, it needs updated.

  5. #15
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    Looks like I underestimated it. Perhaps the shockrod might cope though. Another thing is the gas flame igniters powered from the mains, those are usually punchy enough to put some current into their few-thousand-volt arcs. Just take care near glassware, I destroyed a HeNe by carelessly sending the spark through the metal to glass seal.

  6. #16
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    Mixedgas, howbout for saftey do's and dont's elaborate and expand for the users how to properly use the coil or hv wand to start a large ion laser-
    go big or go home

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    "Remember not to scratch your nose with the tip of the BD-10 while it's still plugged in."

    Adam

  8. #18
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    Quote Originally Posted by clandestiny View Post
    Mixedgas, howbout for saftey do's and dont's elaborate and expand for the users how to properly use the coil or hv wand to start a large ion laser-
    after lunch when I get some time to type.

    but for now

    One keep the power down, just turn the knob till it just starts sparkin.

    two , it doenst work with all lasers, like water jacketed 164s , the water doesnt let the RF in. On these, sometimes you can have a go at the ANODE end, but usually its the cathode.

    Three, the BD10 will burn out if left on continiously

    four, keep the hot spark away from brewster windows and glass to metal seals, it can puncture thin glass and the ceramic to metal junctions.

    On complex heads like SP2020s which have computers in the head, well, think twice.

    It works great on ALC/HGM/omnichrome products but stay at least 4" from the little light card in the head, otherwise, replace the 2n2222A and the opamp on the light card.

    watch where the spark is going, if the plasma streamers cant get to the tube, they will find their way to the electronics.

    If your going to test a tube to see if its gas intact, without the power on, disconnect the PSu from the head, set it on a grounded table and do this in the dark. Rememebr, if the HV cant find a ground to flow to, it will light you up, causing you to jerk your hand around and probably knock off a brewster stem in the process.

    This dont work on SOLID STATE YAGS and it will KILL PUMP DIODES instantly, so remove the argon from the projector!

    never stick you between the spark and the ground, you dont glow. Dont even think about sparking your significant other on the A$$! The beautician types used to use these things for electrolytic hair removal, and that wasnt pleasant.

    Dont remove the orange insulator thingy between the coil and the pointy probe thing, that makes the probe 110V live plus HV. Ok to replace the probe with 6" of soft wire to get the spark into tight places, but dont do it often.

    Its a tesla coil at heart, be careful.


    remember, that head has 220 to 700 V in it , not current limited, and you turn into carbon, defibilate and die. So dont do this if you dont know where the HV is in the head.

    DO NOT CONTACT THE PROBE DIRECTLY to THE TUBE OR TERMINALS!

    DONT DO THIS ON A 200,000$ sabre or a SP171 large frame untill you have had some experience doing it on other cheaper tubes. besides the ignitors used in large frames dont go soft that easily, and a BD10 is not going to light a tube with a 560V tube voltage. On larger lasers your seeing if the tube is gas intact, thats about it. This is a good boost for air cooled tubes, it often wont help you do anything then determine if the tube is gas intact on wet systems. On lexels, where the ignitor terminal is up in the air, it can help sometimes. A coherent medical ignitor brick is the next step after a tesla for a professional tech on a large system, and that takes some thinking or training to wire it in, usually with a blocking diode.

    PSUs with the power on are somewhat protected from HV, but with the power off and no voltage across teh tube, the psu is vunerable.

    If it dont light in the first few minutes, it isnt going to go. Setting there for 20 minutes sparking it isnt going to bring it back, if the cathode isnt lit and at the proper power, and if teh PSU is not working, it wont help either. So make sure your PSU can regulate current and there is anode voltage available, otherwise your wasting your time.

    practice on a plasma globe, a big neon tube or a 40 watt flourescent lamp to learn what you have and how to use it.


    Steve
    Last edited by mixedgas; 10-17-2007 at 07:59.

  9. #19
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    In Navy electronics school my friend accidently used a grounding probe on a radar modulator tube.... WHILE THE RADAR WAS ON! Several thousand volts sent directly to ground is something fun to see.

  10. #20
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    No time to type huh steve... I will have to get comfortable for the "full version".
    Love, peace, and grease,

    allthat... aka: aaron@pangolin

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