Welding Tips and Tricks

i just bought a used Eutecarc 24-40 Buzzbox with a 'Voltage Stabilizer' for Tig welding. paid 400 with a full tall bottle of argon and a tall bottle of oxy and Acy thrown in for good measure.. The manual is unreadable since it got rained on..ok !st question.. what is the purpose of the adjustable spark gap inside the unit.. should it be set to?.. right now its at .006 and it seems to be ok (i think).. This unit is a scratch start with the only adjustment on the tig box being a knob that simply says Low and High.. i was tol by someone that that knob controlled 'Arc Force; or Ve.. can anybody tell me what is arc force.. can u have it at minimal amps (25 a in this case) and still have max arc force.. should the spark gap be increased for beginners like me.. will this welder do aluminum... im also told that without proof of ownership i cannot get my bottles refilled.. any help on this welder would be REALLY appreciated .. it also came with 10 of the pink cups of various sizes and about 30 lbs of 6011 and 6013 should i have spent my money on a modern unit or iis this thing workable.. ive tried welding some stainless and i keep burning the electrode.. right now the electrode is positive and the unit kinda looks like it was designed to stay positive..in that the connections on front of the volt stab box look like they wernt intended to be switched..

DC TIG should be electrode negative, or you will destroy tungsten.

The spark-gap is part of a HFAC system, so it should be able to weld aluminum. The High-Low knob is probably AC arc balance. .006" is about right... the Miller 250DXs I use at work call for .008", with a tolerance I don't recall.

Talk to your welding supply about the bottles. I've refilled/exchanged bottles without any proof of ownership.

If you get it working right, you probably got a good deal.

Steve

thanks steve i really appreciate the help.. what is arc balance.. and have u ever seen a welder like mine?.. it says made in the usa but it has tio be 40 yrs old at least.. i tyrie contacting the company and apprantly they no longer make welders just consumables now.. i should just play with the adjustment knob and see what happens but it would help if i knew what the hell i was doing when i turned the knob to and fro...do the sparking contacts need servicing like cleaning or whatever.. ya know its kinda strange to see that spark action going on inside the box.. makes me almost think theres something wrong like a loose connection.. can a pedal be wired i on a unit like this... is a pedal a must for aluminum... so if i was to weld aluminum how do i know its switched to A'C im sorry for asking dumb questions again i should just try it and see what happens .. i think...i wish i had a damn manual for it i tried to post a pic of it but the forum says its too big.. and i dont know how to make it fit..

Everything I've found about that welder says it's a 250A AC-only unit, so you won't be TIGing steel with it, but should be great for Al with that high-freq box.

Arc Balance, if that is, in fact, what the knob is, controls how much of the AC "wave" is positive vs. negative. The more negative, the greater the heat on the material (and less on the tungsten) for penetration. The more positive, the greater the "cleaning" action (breaking of the oxides on the aluminum), and more heat on the tungsten.

BTW, that will be a "sine-wave" machine, so you're pretty much limited to pure tungsten for it. Someone will surely correct me if I'm wrong.

Is there any info on the HF box?

If you set your camera to it's lowest resolution, you should be able to post the pics.

Steve S.

Hi, now that you've got the welder and you also have HF for ally, you could just add a set of diodes and an inductor in the form of an add on black box to the welder output to make the output DC....not hard to do as long as you invest in a set of diodes at least bigger than the max amp of the outfit, and around 100 volts too, with a heatsink to match..

As you already have AC with HF (high frequency) you most probably have a gas flow before and after circuit for tigging, can't see why they would give you AC with HF if it didn't have any provision for gas control, but if not you will have to have the gas valve on the handpiece which is not too much of a problem.

On one of the other welding forums they have an add on SCR circuit with foot pedal control to give you variable amp control at the foot pedal, which is also a low voltage for safety......I can't post the circuit without the permissio of the originator, but I'll ask and see what he says.......it was his brainchild and work to get it to a final solution, even if it was a part development of another posters idea.....at very worst you could go onto the other welding forum and browse the thread and just pick the brains etc without ruffling any feathers.......the circuit is not design protected per se, but acknowledgement of the poster is more ethical.

The SCR circuit, which is actually a heavy duty dimmer switch type circuit, is quite a common circuit, the biggy is in the foot pedal which in the circuit I mentioned is low voltage for safety, and that is the beauty of the posters idea.'

All SCR circuits for dimmer type controls have a potentiometer which is at full mains potential of 240 volts etc, so bringing the pot out (on a long cable) and putting it into a foot pedal is not a wise idea seening as how the foot pedal and especially the cable are subject to lots of banging about and could give you a "hot foot" if it develops a short circuit....LOL ....not very funny.
Ian.

Billbong,

a SCR (silicon controlled rectifier) is a one shot electronic switch. When you trigger the gate, it allows current to flow from the cathode to anode and it will remain in the 'on' state, until the power is removed or the voltage on the anode is at the same potential as the cathode. Remember there will be a voltage drop of .7volt when crossing a semiconductor junction, so another means of achieving the same potential must be employed.

Typically, the 'off' state is achieved by placing a capacitor and a resistor across the anode and cathode. The resistor is designed to slow the rate at which the capacitor charges up to full potential. When the capacitor reaches full charge, the anode and cathode will be at the same potential and the SCR will shut off.

The gate is triggered 'on' continuously at what ever rate that you desire, in order to control the current flow, while the capacitor and resistor across the anode/cathode are constantly turning 'off' the SCR. This is a basic chopper circuit.

This same circuit is used as a 'Watchdog timer' with the gate being triggered thru an opto-isolater from a computer. Watchdog timers are used to disable the current from a device when the computer is turned off. In this way, the electronic device will not function without computer control.

SCRs can handle a substantial amount of current but their 'on/off' switch times are relatively slow for most high speed circuitry.

MOSfets (Metal Oxide Semiconductor Field Effect Transistors) switch very fast but cannot handle high current, so they are paralleled in a circuit to handle more current. MOSfets are also very static sensitive and relatively easy to damage from voltage spikes.

The best device on the block is the IGBT (Insulated Gate Bipolar Transistor) which can handle high current and switch fast. All of the above devices are used to control the current (flow of electrons). This is the definition of electronics.

Hi, the circuit on the other forum I refered to has 2 SCR's, and switches at the mains frequency of 50/60 Hertz.

It's already been made and tested and by all accounts works well by itself, the foot pedal development went a step further and added the low voltage safety aspect to it.

This circuit was designed to control the welding primary circuit, and as such will handle the primary currents of 240 volts at 10 to 15 amps, so switching for the 50/60 cycle rate should not be a problem.

The overcoming of problem of the low voltage foot control just made the whole package feasible.

I recently bought an SCR type controller on a board the size of 1/2 a credit card, and it is rated at 3,800 watts......which at the 240 volt level will handle 15 amps, probably the max, so rating it at just over half this and you could go to 10 amps continuous.

The cost, on Ebay was $10, post free from China......that's dirt cheap for an infinately variable current controller to handle the load a welder primary circuit would draw.

The main attraction is that it will be able to infinately variably control the welder current for tigging and enable the useage of a foot pedal.

In the welder mentioned before at post #1, he already has HF, which is the hard bit to add, so current control and a set of diodes gives the whole package for AC/DC tigging on ally and steel.....just add gas control to the handle.

It would not take too much imagination to further add an electronic gas control valve with a timer delay circuit to allow post gas control for the Argon.
Ian.

Hi, just thought about the IGBT device you last mentioned....this is a totally different application, whereby in an inverter circuit you MUST switch the current/voltage on/off at a very fast rate which SCR's cannot do.

The inverter circuit does away with the transnformer of old, and relies on the ability of the IGBT to switch the power on and off very fast to maintain the required output, totally different to an SCR circuit that merely maintains a set mark/space ratio to the incoming 50/60 Hertz wave form.

The SCR circuit does not sense the load ( it is predetermined by the setting of the mark/space on/óff ratio) like the inverter curcuit does, which is turning the power off and on many times, after it has been rectified to DC for the control circuit, and adds or subtracts power as the output draws it......a very tricky balancing act.

This is like switching the light switch on and off very fast to control the brightness of your bedside table lamp....LOL.....it can be done, but you need fast reflexes.

Practically all power supplies are now inverter type, and hardly any, if any, have mains handling power transformers per se, they do have small transformers, but only as part of the initial control circuitry....the main power load is straight through in a series of small very fast steps up to the power level output as predetermined.

When an inverter circuit power supply malfunctions, it becomes an instant throw away item, mainly due to the dedicated function (not available over the counter) IC's that handle the power control, whereas in the old transformer power supplies, the most likely cause of failure was a blown rectifier or diode array, and more often than not the fuse.

The irony is, an inverter power supply that will handle 240 volts at 30 amps (rated at half) cost mega bucks, whereas an SCR circuit doing the same cost only $10.

The reason the Inverters are so popular is because they're light, compact and cost initially less to make.......they also are able to use the production lines and components used in printed circuit board production, whereas a transformer requires a machine shop to produce the frame and core windings etc.
Ian.