HF frequency

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Group working on a problem here... does anyone know the frequency of the HF signal used in TIG welding?I am trying to fix a problem with this causing RFI, but i need to know what the frequency is so that I maybe able to determine to and of choking necessary to suppress it.TNX Jim
Reply:It depends on the machine, but simple machines run on 60hz., in the U.S., anyway.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by KF6OWCGroup working on a problem here... does anyone know the frequency of the HF signal used in TIG welding?I am trying to fix a problem with this causing RFI, but i need to know what the frequency is so that I maybe able to determine to and of choking necessary to suppress it.TNX Jim
Reply:I have a scope to measure it, but all my machines are invertersReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Unfortunately, most TIG welders use a spark gap circuit to make the HF. Judging from your handle, I'm sure you know that's not good news JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:Running a dedicated ground at the machine can help control it. But it is tough to eliminate. Share your progress if you don't mind. Joe
Reply:Yes stray RF is not a good thing.  the reason I ask is knowing the frequency of the HF signal helps me to determine the amount of choking impeadence I need.  the lower the frequency the more that is needed.  I need to spend a little more time on miller site to come up with something.  I know grounding is very important,  all my test equipment, radios, welders, tools etc are grounded.  I run 3' wide copper strap to copper buss bars and lom impeadence braid.  The reason for this post was I just bought a everlast 250ex.  yes it is green but that is not the point of this discussion,  apparently this machine has an issue where stray rf get back to one of the boards and takes out a multiplex switch IC  (4053 chip),  Everlast has done some rok to minimize this but i think it needs more... when i opened up the machine for a quick peeak i found 5 of the 7 wires from the remote controll switch are wrapped around a ferrite core(this is good), ironically the two wires that go directly to the 4053 IC are not wrapped around a core and as part of the solution the put in a DIP socket for ease of replacing the IC, no more unsoldering and soldering again  from what i gather talking to one of the service guy from everlast the machine is picking up stray RF one the remote lead and bringing it back into the machine and blowing the 4053 IC.The 4053 in itself is a CMOS chip which is very susceptible to RF.Now I dont want this to turn into a blast the everlast product forum, so far I think the welder is pretty good, especially for the price!!!  It just has some growing pains and i hope to help with this.  This is my first experience with Inverter welders, prior to this I had a Miller Syncro 180SD, that was great but big, lacked some features I really wanted. I have also used the new Syncro 250 at work and think it is a blast to run,  just too much $$$ and way to big from a home welder.I had problems with the 180SD in the past with the HF knocking out my LAN, but a little ground and abunch of ferrite ont he CAT5 and CAT6 wires fixed that.  Stray RF is nothing new to me,  just one of those things you have to learn to adapt to.Lastly anyone out there have the issue of blowing the 4053 IC on their 250EX? If so what were you doing?  did this happen repeatedly?  what did you do to fix it?  I am looking for common demonimnators to help isolate the issue.I do not work for Everlast.  I am simply trying to address and issue before it arises,, I dont know about you guys but I dont have a stick of 4053 IC's in my tools boxyour input pleaseJimyeah spelling was never my thing.
Reply:I think you are one of the few that would actually know if an IC is blown.   I have one AC tig machine, but the start is different than a spark gap HF.   Its more like a coil ignition on a car.  It will draw a blue spark a few inches and they are only a few sparks per second. (Hz).  It ALWAYS starts the arc.   And Do Not step on the foot pedal while changing tungsten.   It does not seem to affect anything in my shop.  Nothing is grounded, beyond the plug.Good luckDavidReal world weldin.  When I grow up I want to be a tig weldor.
Reply:Sounds like your Chinese POS is designed to "self destruct".Ever consider that that may have something to do with what they charge for them?At least, in the past, with the old Heathkit electronic kits, the parts were designed to be compatable with each other.Syncro 250 DX Dynasty 200 DXMM 251 w/30A SG XMT 304 w/714 Feeder & Optima PulserHH187Dialarc 250 AC/DCHypertherm PM 1250Smith, Harris, Victor O/ASmith and Thermco Gas MixersAccess to a full fab shop with CNC Plasma, Water Jet, etc.
Reply:And you asked that it not turn into a ( bash the brand ) and then it goes downhill.  I hope you find the fix and then post the the findings, so that others can reap the reward of have a decent machine at a lower cost. Some do not seem to understand that there will always be the 80/20 factor or the Monday, Friday build that can have an bad out come on a build, good luck, ki6pxf.
Reply:Yep, everything has a problem  truth is if no one tries to fix and improve how are things supposed to get better?  Why did miller come out with a second welder, simple it was an improvement on the first.  if we dont provide these companies feed back they will have no idea that there are problems.  I want your constructive criticism.anyone else had this problem?  Jimoh and you ham guys my actual call is W7OWC, KF6OWC was my old call, I gues I ned to change my user name on here.  my favorite thing to build is antenna brackets out of aluminum, I have done all sorts for friend who use the big screwdriver antennas for HF...
Reply:The HF is generated by a spark gap tuned oscillator circuit, They tell  me it is around 2 megahertz.  AN  L C circuit.  Starts out with over 6K volts.  The cap is a .002 mfd. Good grounds and bypass caps work to control the HF.Have seen a computer Ether net card die because the Ether net cable ran up the electrical system ground cable. HF from the welders we were working on went down the ground cable and bled over to the Ether net cable.
Reply:were/who did you talk to to find that info? that's  what i was looking forTNX Jim
Reply:Jim, Hf is in essence a spark gap transmitter, I read some on it in the ARRL manual. I am not familiar with how its accomplished in your particular machine but in my linmited experience it covers most of the rf spectrum.I have a Miller Dynasty 200 and it is better than the older systems but still produces rf that gets into the computer on the cnc mill and shuts down the usb ports periodically.Good luck with your problem. I would try ferrite beads close to the problem ic if  its possible. Maybe order a stick of 4053's in the meantime as a backup measure.we0lmike sr
Reply:According to a source,for TIG high frequency starting circuits, the oscillation frequency for the high frequency staring is "preferably 1.5 MHz, although alternatively between about 1 MHz and 2 MHz"The repetition rate of the arc starting signal (e.g. the rate of the spark gap firing), is preferably on the order of 700 Hz or between about 1 Hz and 1 Khz and may even vary vary randomly within the range.The voltage of the arc starting signal is preferably 15,000V peak to peak but could alternatively be between 2,000V and 25,000V peak to peak.This seem to corroborate / supplement ccawg's info.Last edited by jakeru; 04-23-2012 at 11:12 PM.Reason: corrections
Reply:I have a Chinese no-name Super 200P AC/DC Tig/Stick/Plasma and the manual (loose term ) has the HF as 100kHz.I have only used the plasma part so far.Mike VK6MB
Reply:yep from what I have been able to come up with is choke the s out of it,  because i can not determine the impeadence of the circuit it make sit impossible to accurately come up with an exact amount of choking to put on it.  for now i am going to wrap as many turns as pratical 1/2 around a 2.5" mix 31 core and hope for the best.    oh the machine is the everlast 250ex, lets not go china welder bashing; it fit the budget and i heard enough good things to take the leap, plus i can actually replace parts on this thing, now SMD crap.  hello to all the ham welders
Reply:Originally Posted by KF6OWChello to all the ham welders
Reply:It's in the MHz range, as has been mentioned. It would not surprise me if this varied pretty widely, though, with part tolerances and environmental conditions. It will even depend on how coupling transformer is built.The 100kHz mentioned is the switching frequency for the internal inverter. 60Hz is line frequency. Neither of those are it. It is in the MHz range because the faster the slew rate of the signal, the easier it is to ionize the air and make a spark. You mix high voltage and high frequency and you get a hefty spark out of it. I've explained the high frequency circuit to people before as essentially a modified Tesla coil, because that's what it is. Many people think the spark gap "limits" the voltage to safe levels, but in reality, the spark gap is actually what causes the oscillations to begin. Line voltage is generally stepped up through a simple transformer to a few KV or so. This voltage is fed into the tank circuit. At the point in the 60Hz AC cycle where the stepped up voltage is high enough to jump the gap, it will. This surge of current starts the oscillations between the L-C tank circuit. THIS oscillation is the one that is usually in the MHz range. The current is actually jumping the gap, back and forth, back and forth, until there is not enough energy left to continue the oscillations. Depending on  how long the oscillations last though, this action will be re-started by the negative side of the 60Hz cycle, or the next positive side. Actually, I just read what Jakeru said, and he is right. Whatever is feeding the tank circuit doesn't have to 60Hz, it can be higher too, but that frequency is not the oscillation frequency you are wanting to filter out. Take this oscillating current and couple that through another transformer into you work lead, and there you have a HF arc stater. Or you can take that oscillation current and couple it through another step up transformer and make a Tesla coil. To be honest, you might think about making an external filter board for those lines. You could put a common-mode choke on there along with ferrite beads for each line with a little bit of parallel capacitance to earth behind them to really knock out the RF junk. I doubt you are going to filter it to the point of being too slow, especially if it's just the torch switch.