Welding Tips and Tricks

I have an old (circa 1990) Presto-weld MIG 130 that only has a few hours on it but no manual. The machine is in perfect condition and my LWS said they'd be glad to sell me a new one, but that it is a really good, tough machine. I have contacted ESAB who bought LTEC and they didn't even have the courtesy to respond. Does anyone by chance know what the voltage ranges are or even better, have the manual!?

In order to get in the ballpark I've calibrated the wire feed as per Jody's suggestions. It is then a matter of calculating the required feed according to the material thickness and tweaking the voltage until it "sounds" right. This is all good, but I'd like to have specific information for this machine if possible.

Thanks for any help!

If it didn't come with a chart inside the door or on the side then the manual probably doesn't give any specifics either. Everlast mig welders don't come with a chart and their explanation as to the reason why is total BS.

ESAB has a "contact us" page at http://www.esabna.com/us/en/support/contact/

I found this manual
http://www.esabna.com/eu/literature/arc ... 007453.pdf

Maybe you can glean facts about your machine from there? It's prest-o-lite, not presto-weld...

Thank you Artie. That page is what I tried before but got no response.

That machine looks to be a fair bit different from mine, but again, thank you for trying!

Not sure I understand. Trying to determine the correct weld settings? Use the Miller App. Or you are saying there is no scaled display of voltage? If not just use a meter or get real fancy and install a little DVM in the case. And everyone uses the 6 second trick on wire feed, just to many variables between machines/feeders for anything else really.

DLewis0289 wrote:Or you are saying there is no scaled display of voltage?

Yep, That's what I was saying. I just have A-K.

Knowing the voltage is just the means to an end though. I don't need another quest! No DVM permanently installed for me!! All I want is a chart that translates the Miller calculator into the starting settings based on material, thickness, and joint type.

The six-second thing is what I meant when I said I calibrated the feed settings. When I used that on a sample, I got the right sound and off I went. Unfortunately, the bead didn't have proper penetration. I know what adjustments to make - that's not the problem. Me and Jethro can cipher with the best of them (naught by naught is naught...), but I'd rather skip all of that. I just want to weld stuff !!!

glassTransition wrote:

DLewis0289 wrote:Or you are saying there is no scaled display of voltage?

Yep, That's what I was saying. I just have A-K.

Knowing the voltage is just the means to an end though. I don't need another quest! No DVM permanently installed for me!! All I want is a chart that translates the Miller calculator into the starting settings based on material, thickness, and joint type.

The six-second thing is what I meant when I said I calibrated the feed settings. When I used that on a sample, I got the right sound and off I went. Unfortunately, the bead didn't have proper penetration. I know what adjustments to make - that's not the problem. Me and Jethro can cipher with the best of them (naught by naught is naught...), but I'd rather skip all of that. I just want to weld stuff !!!

Determining the voltage of each setting is straightforward. Open the feed-roller clamp so you're not feeding, and put a DC voltmeter between the supply lead to the feed roller and the ground. If your VM doesn't have auto polarity sense, pay attention to the + and -, of course. For each volt setting A-K, squeeze and hold the trigger and let it stabilize. Write the number beside the letter on the dial with a permanent marker. Your machine is a "constant voltage" source, and depending on quality will remain within anywhere from 0.1 volt to 1.0 volt of your marked setting when under load. This will give you starting points for the Miller App mentioned before. Assume at first that your machine is dead on the written voltages you've just measured, and (since you've already calibrated the wire speed) experiment. Excess spatter is a sign your "loaded" voltage is "much" lower than your calibrated open-circuit voltage. Expect most machines to stay pretty damn close to your measured voltage when loaded; It's the cheaper Chinese stuff that varies a lot under load.

Don't bother trying to measure voltage under load, as there are way too many variables affecting the reading for the average voltmeter to keep up with... You would need an "averaging" feature to avoid erratic readings, and an automated process that keeps advance rate and stick-out constant.

Steve S

Man that's to simple! Why didn't I ever think of that.

Thank you Steve, that's very helpful. I'll give it a shot.

Have you ever used a o'scope or averaging to figure out how much droop there is under load? I'm wondering if there is a rule-of-thumb adjustment that could be made from the unloaded measurements.

glassTransition wrote:Thank you Steve, that's very helpful. I'll give it a shot.

Have you ever used a o'scope or averaging to figure out how much droop there is under load? I'm wondering if there is a rule-of-thumb adjustment that could be made from the unloaded measurements.

I have not. The Miller app assumes a modern Miller machine, like the 252, that is very stable. Most average quality and above machines will likely remain within 100 mV of the set voltage under load. It's only the low-end machines that will drift significantly.

Generally speaking, anything the Miller app says should work great in the 1G/1F/2F positions, and this is where to judge your machine's accuracy. As I mentioned before, an excess of spatter (this usually indicates too much wire speed for the voltage) for a known wire feed speed tells you your "under load" voltage is more than 500 mV below the no-load condition. This circumstance makes a second problem, as the load will vary with your stick-out. The varying load will affect the voltage, which will affect the load... A vicious cycle that can cause "operator induced oscillation", further magnifying the problem.

You also have, as you stated, a 130A machine, so you're going to be using it near it's limits for many things. This also will magnify the problem, if you have one.

You may also have an average to exceptionally stable machine. I know nothing about your brand. In your stead, I would do extensive experimentation to understand it's properties, but you lack the luxury of experience, so I'd suggest the drill I mentioned earlier and experiment from there.

Good luck, and keep us posted. Pictures of your welds will help when you're unsure of your results or concerned about possible issues.

Steve S

I should have added:

If the machine is of decent quality, the 130A is not it's limit, but rather the point where the duty cycle falls below 40%.
This machine "may" be capable of 175A for short periods.

Steve S

I finally got around to trying to measure the voltage with a DVM. Whatever the circuitry inside the welder, it was not responding to the high impedance load of the meter. I got a reading of around 20 VDC no matter where the knob was set. I could try to measure it under actual conditions, but am afraid of frying the meter without proper filtering. And I have no idea what sort of filter would be needed.

To the folks that suggested this measurement, have you actually successfully done it? Did you just use a garden variety meter?

Thanks for any help!

It may take two people. One to run the gun and the other to use the meter. Read it at the lugs on the machine as the other guy welds.