Arc start question: Miller Synchrowave 250 vs Lincoln Precision TIG 275

I just finished a 2 day TIG class - my first time welding. We welded small (maybe 14 gauge) stainless plates. I used a Miller Synchrowave

250, but near the end of the class I switched to a Lincoln Precision TIG 275. The HF arc start on the Lincoln seemed MUCH cleaner than the MIller. The Miller would wander and buzz a bit until I got the current up to the right level, after which the arc was OK. The Lincoln started with a nice tight small arc right from the start. I was probably at 60-80 amps for these welds. Is this difference a real one, or was the Miller operating abnormally?

I was looking at buying an inverter, not one as large as those in the class. The drift I get here is that Miller seems to be preferred for TIG and was leaning to Miller Maxstar 150 or Thermal Arc 185 (not sure about needing aluminum), but this arc start difference makes me pause. If the Synchrowave was not misbehaving, would a Maxstar or Thermal Arc start the arc more like the Lincoln?

Reply to
lens
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I would suspect the high frequency unit on the Syncrowave needs the points cleaned and regapped.

Try cold scratching your tungsten each time before you hit the foot pedal. It usually helps a lot with arc starts.

I have a Maxstar 200DX and love it. It is DC only but does everything I have needed for a portable machine. I have a Syncrowave 250DX for my main machine.

The Thermal arc is a very good machine, but if you don't need AC then buy a Maxstar 200SD or 200DX. The Maxstar 200's can run from any AC power from 80 to 500 volts, single or 3-phase.

Inverters use a very different high frequency arc start. It is called Capacitor Discharge high freq, and is more like a photo flash is design than the high freq transformer and spark gap used in transformer based welders. I have had my Maxstar 200DX for 5.5 years and it is still going strong.

Reply to
Ernie Leimkuhler

There was a field upgrade kit issued for the Synchro 250 a number a years ago to improve the low current arc stability. It converted the current sampling circuitry from a sampling resistor to a Hall effect device. The unit you were practicing with may not have had this upgrade installed. I've been told it makes a big difference in low current operation. I bought the kit for mine but haven't installed it yet. I bought the upgrade because my controller board failed and the older Syncrowave boards were no longer supported by Miller. While I was waiting for the upgrade kit to arrive I was able to troubleshoot my board and fix it. It turned out to be the op-amp at the feedback summing junction that had died. The kit was pretty pricey if I remember correctly - seemed like close to $500. Looks like significant work to install it so I decided to wait until my board fails again. That was six years ago. I rarely weld less than 16 gage and the unit works fine as is. If you're considering buying a used Synchrowave 250, I'd make sure the upgrade has been installed or negotiate the price, because a failure on the old controller is going to be expensive to fix unless you're handy with electronics. (The schematic is included in the owner's manual.)

Reply to
Terry Mayhugh

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