Weld power pot

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Anyone have issues with theirs? Around 75 amps, in low and mid range alike, my machine goes nuts. Wondering if it's the pot, or something indicative of a bigger problem. Powcon 300st (my favorite)Miller Goldstar 600ssLincoln Idealarc 400/400Miller 12vs2 LN25'sMiller Deltaweld 302Miller Bobcat 250 G EFIMiller Bobcat 225d Plus (Dropped a valve, up soon)Everlast 255ext (ordering soon!)
Reply:First the powcon operates in the audible frequency range. You will hear everything the switching circuits do. The scale on the front should be 0 to 100% of range selected. So 75 is 75% of range setting. If you use a large diameter rod and low amp setting the inverter will not like it and may produce an extra squeal. Evan new inverters will squeal if used this way. And they use ultrasonic switching (10khz and higher) So try a smaller rod. Check the current rating on the rod being used,Then do the math to estimate the correct machine setting. If you machine has a V/A switch, set it to A and have some one read the actual amps while you weld.
Reply:3/32 7018 should operate 65-100 amps easy. 75% of 10-100 is about 77.5 amps. The rod burns at 70% on that range and 80%. Just not 75%. The equivalent amp setting on the medium range does the same thing. I guess I just need to take the ****er apart and figure out how they control the output via the pot. Whether they parallel Xfrmrs and caps, then series them or whatever they do with the scr's... I'm also a controls and electronics guy. I was just wondering if anyone had similar problems.Powcon 300st (my favorite)Miller Goldstar 600ssLincoln Idealarc 400/400Miller 12vs2 LN25'sMiller Deltaweld 302Miller Bobcat 250 G EFIMiller Bobcat 225d Plus (Dropped a valve, up soon)Everlast 255ext (ordering soon!)
Reply:I changed the pot on mine. It seemed to have a dead spot in it. Just a common pot, nothing special. I think it was 5K ohms.