High frequency start box


When welding with an AC arc welder, it is often necessary to “scratch start” them to get the arc going. For those unfamiliar, it is just like it sounds. You drag the head across something just like a giant match. There are some that come with an arc stabilizer or “high frequency starter”. This is preferred, but they can be hard to find. [Bill] shows us how to make one of our own. Though you may have an easy enough time finding a big transformer, you might run into some difficulty finding the capacitors, and tungsten spark gaps. If you manage to get your hands on them, you can follow [Bill]‘s schematic and build one of these starters for yourself.


  1. blubb says:

    looks intressting but the parts are not easy to find ;)

  2. Zorink says:

    when I was building my tesla coil I got some tungsten spark gaps and similar caps form ebay.

  3. Doug says:

    My first thought an auto ignition coil will not stand up to continuous duty. Second thought was that my be why it’s labeled a start box not a HFHV arc stabilizer and what appears to be foot switch. Third though was #8 wire in pretty puny when compared to my welding cables. The only other feature I could think to add is current sensing, along with time delay. That would sense an attempt to start the arc, turn the box on and, turn it off when the welder had time to establish the arc. Allowing one to get rid of the foot switch

    • adam2 says:

      That is the basic idea behind a lift arc start welder. When you touch the tungsten to the workpiece, the welder senses a short circuit, than when you lift the tungsten back up the welder senses that the circuit is now open and starts a high frequency arc.

  4. Josh says:

    Very interesting. Only question I have is “why tungsten spark gaps?” Wouldn’t regular spark gaps work?

  5. Tachikoma says:

    Why Tungsten? I would imagine Tungsten has an extremely high melting point and has a good resistance to arc oxidation. So they last a lot longer.

  6. calvin says:

    Electronics Goldmine sells 35kv capacitors like the one pictured.

  7. nnx says:

    Why spark gaps at all? Wouldn’t a good Power Semiconductor do the Work, the same kind they use in tesla coils.

  8. bobby says:

    green coded tig welding electrodes are almost pure tungsten. they are available from welding suppliers in many different diameters. a spark gap can be made from a couple pieces of an electrode that are shimmed apart.

  9. Daniel Raftman says:

    Great Hack !!

  10. Tim says:

    Spark gaps because its simple, spark gaps never blow up like a transistor. Im sure theres probably also some better reason related to the incredibly high frequency.

  11. Arc Welder says:

    To be able to superimpose this high frequency signal on the secondary of the welding transformer, you also need a high-pass filter connected in paralel with the secondary winding.
    Otherwise the high frequency signal will feed back into the primary.

    • thesaint says:

      Hi, I am very new to tig welding and have just got an inverter tig welder thats scratch start. my question is, do the keep the arc starter connected all the time while i am welding or is it just switched on to get the arc then switched off. thansk for help.

  12. Arc Welder says:

    see this schematic of the Miller HF-15 arc starter: http://www.yoreparo.com/foros/files/hf15.gif

  13. Newton Brawn says:

    The arc starter works really good !
    You dont need touch the stick electrode with the work to initiate the arc. Very usefull for low current weld.
    Thanks to Willian F. Dudley Jr. that published the schematic PLEASE NOTE THATH THE 500 pF capacitor is TO BE CONNECTED IN SERIES with the primary of auto ignition coil. 100ohms not required im my assembly.
    Also the auto ignition coil was replaced with a homemade transformer primay 10 turns #22awg, secondary 300 turns #28awg, core from a tv flyback “c” 200mm2 cross section, insulation between layers 0.12mm polyester paper. No more than 38 turns in each layer. Alkid (exterior spar vernish or sparlac)impregnation.

    The termminal of buzz box to be shunted with 0.5mF x 400v cap to prevent HF voltage enter into the main weld machine



  14. Newton Brawn says:

    By the way, the 500pF x 30000V capacitor was replaced by a 1000pf x 20000V home made capacitor

    Material required : aluminun foil used at kitchen and glasses from home windows.



  15. Adams says:

    How wide do you set the gaps on the tungsten? If its like a spark plug, its gonna need a certain size gap.

  16. DAVE says:

    What voltage is supplying this start box?

  17. what Amount HF Generator Voltage?

  18. Newton Brawn says:

    Yes, it works very fine. Connected to the buzzbox allows u weld very confortable at 30-80A.

    The schematic has a mistake: 500uuF in parallel with the 10 turns primary.
    To fix make the 500uuF cap in SERIAL with the primary 10 turns coil.

    The 500uuf capacitor was made with windows glass e aluminiun cook foil.

    The tesla coil was simplified too, using simple ferrit beats found in scraped computer monitor.

    Assembled with 2 gaps only,

    At all is very effective device to help weld at low currents.

    Newton Brawn,

  19. Stephem Wrona says:

    Info gleaned from Miller HF-15 manual(TM-610A ,Sept 1997):
    Can be used with other processes such as Plasma Arc Cutting! (hint hint)

    Spark gap is .008 inch.

    High voltage transformer steps up voltage from
    115v to 3000v(three thousand).

    High freq produced is approximately 1 to 2 megahertz.

  20. GONÇALVES says:

    please, send me de schematic of the high frequency start box. thanks

  21. Spink says:

    I know the post talking about the coil standing up to continuous duty is way old but I would like to point out that a car coil should do fine durability wise. On a V8 engine a conventional coil would fire around 400 times per second at 3000 rpm. 3000/60=50 full engine rotations per second. The coil fires once per spark plug. For a V8 that would be 8 firings per revolution so 50*8=400. An automotive coil has a service life of years and is cheap to get as well as easy to deal with.
    Just wanted to point that out for anyone coming across this information.

  22. Rob Candey says:

    I recognise that this article (and posts) are very old,but can asnybody provide schematics for this project please.
    Thanks Rob.

  23. james says:
  24. Lawrence Day says:

    Can someone build me one of these? I like to work with old vintage welding equipment and this would be a nice add-on to an old dinosaur stick machine I have.

  25. what is the name ds parts to complete this assembly not understand that piece that are connected wires Green black and white I thank

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