# High Frequency arc Stabilizer



## Hawkeye

I picked up this Century HF Arc Stabilizer earlier this week at an estate sale. It is a Model 115-007. Output is 3500 volts and the unit is rated for a maximum welder output of 295 amps.



Has anyone had any experience with this type of equipment? I found the manual, but it consists of a few lines on connecting and a whole bunch of the usual dangers of welding, plus high voltage issues. I'm planning to use it with my Century 70 amp inverter or, to play with aluminum, a 90 amp transformer stick machine.

I have already made a module to provide post-flow argon timing when the arc is extinguished and can expand that to give a choice of continuous HF or start-only.

I've read references to adding capacitors between the supply welder and the HF unit to protect the supply. Do you have any links that go into detail? I imagine the cap would have to be able to handle 5 kV (3500 v x 1.414), but how much capacitance is required? There is no mention of the frequency for this particular unit, but I read a blurb on another one that said 20 kHz. Where is the capacitance connected? Across the output terminals of the welder?

Thanks for any help you can give me.

BTW, if you are using a scratch-type TIG setup, you can use a piece of tungsten clamped near your starting point to reduce or eliminate contamination caused by contacting the steel or aluminum work piece. Just scratch the torch tungsten against the clamped piece to start the arc.


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## November X-ray

I have an old Miller Radio Wave (High Frequency) Generator and is basically the same unit. On it, it has built in capacitors that keep you from back feeding the power source, and I remember the manual gave parts numbers for these but I highly doubt I can find it anymore. It has settings for AC & DC and Frequency Adjustment but quite honestly I have not used it in 25 + years. As far as scratch starting goes, it depends on your base material, the amperage you are using and the technique used to ensure no tungsten inclusions occur. We used to use a "sacrificial" electrode where it was really critical. However with the advent of the high frequency unit super-imposing the high voltage in the process, there is no longer any need to "scratch" start.

Oh, one other thing, On the highest voltage setting it can and will arc thru a person's glove, thru your finger, thru the other side of the glove and into the base metal. I can tell you from first hand experience that it is an extremely painful occurance and it took forever for my finger to quit hurting.


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## Hawkeye

Thanks for the warning on the fingers. Mine has no frequency or voltage adjustments, but I think 3500 volts could find its own path. I'll try not to be it.


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## Joe in Oz

Hang on, HF is not meant to do ANYTHING to a person's tissues (e.g. fingers) the little current that it carries should flow only on the surface.

Yes, mine will arc onto my hand and give me the occasional startle, and if you grab the electrode (making good contact) it will spark from your skin elsewhere on your body to any good ground (surprising sometimes which part of your body is ACTUALLY closest to "ground"). But it doesn't injure me - or cause pain! I guess you could burn yourself eventually if you put up with the spark and keep it going for a long time....
Something is wrong with your HF attachment November-Xray - I suspect.


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## Joe in Oz

Just to confirmRick - I am actually a nurse, with lots of industrial accident and electrical experience (the latter from an engineering background in a previous career).
We are possibly talking about several different things here - HF is conducted quite differently to low frequency or DC currents. That topic is however way outside this forum.
If the HF from an arc welder injures you, there is something wrong with the HF unit (probably too low a frequency) and it won't work properly as a pilot arc or HF overlay for aluminium welding.

Let's just say that sparks (think in terms of static electricity) can startle you and go across large distances, gloves an all and acrs can burn your skin, no matter what the current is. Low frequency and DC voltages can injure your tissues by damaging cells inside and outside your body - including cooking your tissue, if sustained long enough with a high enough current (which depends on voltage of course). Incidentally, if you have metal spinters in your scin (from burrs or swarf for example) you will feel MUCH lower voltages - down to 12 V even - as a noticable electric shock - I know that from experience!

Cheers,
Joe


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## geotek

The purpose of the HF (they call it HF because it is a high frequency generated by a small Tesla coil type device) is to establish an arc between the tungsten electrode and the work, without having to scratch start. Since AC current passes through zero, when welding with AC the arc stabilizer is used continuously to restart the arc 120 times per second. The danger of using the HF while stick welding is do to the fact that the HF can establish the arc through the operator! It's not the tiny current of the HF that is dangerous, it's the aperage from the welding machine that can get you. Normally open circuit voltages on welding machine do not exceed 100 volts. The electrode holder and gloves keep you from getting zapped. But if an arc is established through the operator by the HF, it can become a path for the full power of the welding machine.
BTW, if you want to use scratch start, place a small piece of copper near the weld area. Scratch the copper and carry the arc to the work area.


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## Hawkeye

Rick,

You are correct in that the Century unit is a pilot arc source. It will only be useful for aluminum if I use it after a suitable AC welder. Once I get it hooked up and working, I'll probably run it through my current detector to give the option of start-only operation on DC. The CD also adds post-flow timing to my Frankensystem.

I'm a bit scared to try it out in case it fries my welder.

I've used carbon for a scratch pad, but now prefer a piece of tungsten as a scratch point.

I think I'll take the same approach with welding electricity that I do at work - consciously avoid setting myself up as a path.

Cheers. Mike


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## geotek

I used to have one of these many years ago. I used it with a Dayton cracker-box AC welder. It did a real nice job on heavier aluminum such as 1/8 - 1/4", but because the Dayton welder had poor control on the low end, it was difficult to use with thinner material. I would not be afraid to use it with any welder, the energy generated by the HF is so low it couldn't damge anything.
Use a Tig torch with a gas valve on the torch. Turn on the gas and go. Run about 20cuft/hr gas rate, pure Argon.
For using the unit as start only, just use a foot switch to turn on and off the HF unit. You can buy foot switches that have the AC plug and outlet built into the cord like this one:
http://www.grainger.com/Grainger/LINEMASTER-Foot-Switch-2A190?Pid=search


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## Hawkeye

Geo,

I used to use the torch valve, but I had a lot of fun designing the current detector and post-flow timer. I'm an Electronics Engineering Technologist, among other things, so it's nice to actually use it now and then. The foot pedal (also home made) includes a switch to turn on the gas as soon as it's moved from zero. That switch could also be used to turn on the HF, but starting the welding arc can be used to shut off the HF when that option is selected.

All this is currently run on a Century 90 amp inverter, so it's the solid state components I'm concerned with. Obviously, when I get into aluminum welding, I'll be switching to an AC source of some sort. Does sine-wave AC work at all? I know square-wave AC with all the bells and whistles is best, but budget is a factor.

Thanks for the input, guys.

Mike


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## Hawkeye

Thanks, Rick. I've been dabbling more that delving, but I'll get there eventually. That kind of work is good in the winter, for days when I really don't feel like going anywhere.

Mike


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## Starlight Tools

Somewhere in the bowels of the shop, there is a Hughes Aircraft High Frequency unit that I picked up with the intention of setting up my old Miller 225A Thunderbolt AC welder.  Plugs into 110V power and then the leads to the welder go through it, but that never came to happen and have since upgraded that machine to a dedicated TIG machine, a Miller Synchowave 200.  

Tried the Miller Dynasty 300 at night school, that is one sweeeeeet machine!

Oh well, the HF unit is here and available if anybody wants to make an offer on it.

Walter


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## bcall2043

I had a HF for a short while. A buddy of mine and I  tried to hook it to an old buzz box and managed to blow all the ground faults in the nearby kitchen. Gave it away and found a bargain, an old Airco TIG welder with the needed stuff built in. 

Benny
In middle Tennessee, USA


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## DanLins

About 7 or 8 years ago I had that identical Century HF start unit. I retrofitted my old Montgomery Ward AC/DC stick unit with one of these kits: http://www.tigdepot.net/products2.php?categoryID=67

That worked good enough to get me hooked, and from there I moved on to a Miller Syncrowave 300, which was a monster, and now I have a Miller Tigrunner 250. 

Bottom line, from my perspective, is that the unit gave good performance given what it actually did. I had no foot pedal current control, but sometimes you make do with what you have.

I ended up selling it on eBay for $120 or so....


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## Hawkeye

I finally got around to trying the HF function last weekend, without hooking up to a welder. I hadn't even done that much until now. Nice to see it arc at about 3/16". Now I need to make a couple of adapters to connect the torch to the HF output.

I'll try it with my little AC welder first, then the inverter. I'll run it through the current detector and set it up for Off, Startup and Continuous. After I get all that going, it will be hard not to go hunting for a bigger AC welder. Proof that winter is here.


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## Rbeckett

Hawkeye, I have a straight sine wave machine and the HF is set to continous when I am welding aluminum.  It's a miller Econotig I got back around 2006 and it is old tech at best.  I doesn't have much in the way of bells or whistles but I can work pretty consistently with 3/16 and push ot for 1/4 with a little preheat and luck.  Thicker stuff I use my Miller  210 Mig with a 3035 spool gun and call it good.  So sine wave just needs the HF to keep the arc going when the wave is passing through the zero voltage section of the wave.  Works great and is tough as nails due to being transformer technology.  Have a great day
Bob


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## Hawkeye

Thanks, Bob. That's pretty much what I was thinking. Play around with thin aluminum, just enough to see if I'm getting anywhere. Then it's pretty easy to pick up an old tombstone or something cheap to go thicker. My TIG torch is only rated for 125 amps anyway, so I'll do some learning before I try to move up.


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## Rbeckett

Hawkeye. I would avoid very thin Alli as a learning or test plate.  It is actually more difficult to control the puddle and burn through especially if you dont have a foot pedal.  I recomend starting to practice on around 1/8 material, that will give you time to see and react to the puddle before it sags and falls through.  A good starting amperage is generally 1 amp per .001 material thickness and keep your material meticously clean including your filler rods.  Miller has a great TIG book, about 14 chapters in all that you can download for free from the miller electric site.  Well worth the read if you have a little spare time.  Good luck and let us know how you did.
Bob


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## Starlight Tools

Mike

The Miller TIG Handbook is a great resource.  

http://www.millerwelds.com/resources/TIGhandbook/

Having just gone through "welding upgrade classes" I had that, the Modern Welding Textbook and any of the the info from Lincoln I could download plus the handouts from the instructor to compare.  Miller was the most comprehensive, Lincoln was more about Miller bashing and why Lincoln is better than MIller.

Definitely start with 1/8" plate.  Start by puddling.  There is a fine line between penetration and plop! so watch your puddle closely.  I found that I was getting really nice beads, but that my penetration was not quite deep enough, if you watch the puddle, you will see it start to slump and flatten out when you get proper penetration.  On flat plate, you do not want to see any protrusion through the back of the plate.

The trickiest joint that I found was the butt joint, again I got really good beads, but only was getting about 50% penetration on 1/8" plate until I caught onto the puddle.  If you hold the torch there just a bit longer, you can actually see the puddle start to flatten out, at that point dip in your filler rod to cool the puddle and advance your torch a little bit to get the next point.  You should have full penetration and actually have a small bump on the bottom of the plate.  Be careful as you move along the plate as the whole plate is heating up, the slump point gets quicker.  Oh and only takes a split second after the slump point to get to the "plop" point when the whole mess just falls onto the floor.

Lap joints, Tee joints and corner joints are fairly easy to control.

Aluminium can not be welded without a filler rod!  Unlike steel where you can melt the two together (autogenous) and get a really nice weld without filler, not so with Aluminium.  Also rod choice is fairly important.   ER5356 is the one that will be used for most of your welding on the common alloys like 6061-T6 or 7075T-53.  The other rod, and the one that was available at the local welding shop was ER4043.  this is good for 2014-T6 and 6061-T4.  I found this puzzling as I have never run into 6061-T4, only the T6 temper is around.  OH and if you plan on Anodizing the aluminium after welding, then ER5356 is the rod that has to be used.

If you get into TIG welding on steel, the filler rod used for oxy-acetylene welding is different than the one used for TIG.

Walter


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## Starlight Tools

Oh forgot to mention, Methyl Hydrate was the solution of choice at the school for cleaning rods and Aluminium before welding.  Any rods not used withing 30 minutes had to be recleaned.

When I worked at a fabricating plant as a young pup, (we manufactured vacuum cleaners for fish) there was a lot of Aluminium welding and all the castings and weldments were tacked together then soaked in this huge vat of "acid" before going to "Missy Tiggy" to be welded up.  

Walter


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## Hawkeye

All good advice. The problem at this point is that my AC supply is just a little 70 amp unit. I'll be able to get a bit of technique going, but I won't try to weld anything I'm going to use. Once I see that I'm starting to get it, I'll hunt up a bigger transformer.

I do have a supply of TIG rods, but no aluminum yet, other than a roll of aly MIG wire. Thanks for the tips. I hadn't heard about the wood alcohol for cleaning. I've got lots of that. Will Scotchbright work for pre-cleaning?

I finally got a couple of adapters turned today to plug the torch into the HF unit. I'll pick up the last connector I need tomorrow and maybe try it out in the afternoon. Hope I don't forget to turn on the argon. :huh:

Thanks for the expertise.


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## Starlight Tools

Mike

Stainless Steel Wire brush, kept sacredly preserved for use only when welding Aluminium is "industry standard" not sure on scotchbrite, never used it. A grinder with an aluminium grind stone, flap type abrasive mop disc or belt sander works as well.

The methods of cleaning Aluminium are

mechanical, ie; brush, sand, grind 

or 

chemical, Methyl Hydrate or Acetone

Walter

EDIT:  these are both highly flamable substances, do your cleaning and keep any wet rags way outside the welding zone!


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## Hawkeye

I managed to dabble a bit today. As you can imagine, there's not much you can do with a 70 amp buzz-box. Especially when you do everything wrong. Quick rub with emery, wipe it down with the methanol (paper towel outside to the trash right away), set the argon to 20 cfh, clamp the 1/8" aluminum to the steel welding table with the ground clamp (steals heat like crazy).

The HF unit had a bit of trouble getting it started cold. By the time it lit up, my 10 seconds of gas flow had probably run out (it's complicated - don't worry about it). That likely explains the black mark. I didn't wipe down the piece of aluminum MIG wire I was trying as filler.

Still, it actually took in the filler. Not much penetration, but that comes as no surprise to anyone. I consider it a roaring success. It shows me that a decent-sized sine-wave welder and proper prep will let me learn to weld aluminum.



I checked the local on-line ads. There are a couple of Forneys - one for $250, one for $80, and a tombstone for $150. Some of the Forneys used aluminum cable sockets, so I'm not sure I want to go there. It could cost more than the purchase price to restore. I'll see what comes up in the next few weeks. Maybe someone gets a new welder for Christmas and wants to make room for it. :biggrin:


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## Rbeckett

Hawkeye.
Thats definately a two thumbs up initial weld.  I have been following your thread and know you are going the right way.  As you progress you will want a tombstone or similar type machine if you can find one within your budget.  Craiglist may yeild some good candidates like you said from folks looking for a little more room.   You can do a fair bit of practice at 70 amps, so enjoy and keep us up on your progress.  Good luck and have a Merry Christmas.
Bob


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## ShawnR

Hawkeye, are you still using your Century HF box? I have just acquired one and am having trouble. I am thinking I have a problem in it but it does produce great arc. I can not get anything like what you have there as a sample weld. I was wondering if you could check a resistance on a winding for me...? I will touch base with you in a pm too. Thanks


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## Hawkeye

After my house fire, they threw away my AC welder, so I can't try any aluminum welding for awhile. The HF was stored in the shed, so it survived. What parts do you need resistance readings for? I don't know how soon I can get to it, but I can try.


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