millermatic 250 problem

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i have a millermatic 250 acting up. it acts like voltage is WAY too high. i put a new liner in and no effect. u can hear gas at gun when trigger is pulled and guage fluctuates when upull trigger. arc looks and sounds like a stick welder on very high when trying to arc,makes big puddle . cannot adjust anyway to make normal "sizzling' sound to weld. any suggestions. thanks
Reply:Sounds like you have lost control of the welder out put.Which millermatic 250 do you have, there are three versions.these suggestions are based on the older plain mm250.With a volt/ohm meter. test the voltage control pot on the front panel.Make sure it reads correctly. Could be a 1k ohm pot. Also look for 10 volts DC on the out side terminals. Follow the wires to the pcb and make sure they are good.Then find the voltage feed back wires to the pcb. wires 43 and 44. rc3- 11 & 12.Must have correct control and feedback for the pcb to work correctly.Pcb must also have the correct and all power inputs.Look at the simple stuff first. If you can't figure it out, you may have to take it in.
Reply:when we have a machine act like that at work, it usually winds up with a new board in it.
Reply:I agree. But i like to check the other stuff first. You sure would hate to replace a $500 or more pcb and then find out it was just a bad pot or a broken wire.
Reply:I replaced the board in my 250 earlier this year. Total cost was a little under $400.MillerMatic 212, Lincoln Precision TIG 225, Hypertherm 45XP
Reply:Any chance your tip is not isolated from nozzle and grounding out when welding.
Reply:is it possible you have contaminated gas? did the welder act up out of nowhere, or did it coincidentally start when you changed gas bottles?
Reply:I have a Memcomatic 250 doing the same thing... I was welding seams on a steel barge with .045 er70s-6 and a 75/25 mix with no issues for hundreds of feet of welds... I even pulled off that job to finish building my sawhorse i-beam stands and it welded the 3/8" and 1/4" beautifully. I then went back to welding the barge and when adjusting the machine to the previous settings it starting acting like the voltage was too high and also caused extensive porosity... As I jump off the barge and onto the weld table with a scrap piece of material 1/8'' or 10 gauge roughly, I could not manage to get it welding properly again. I took the covers off the sides and used the air line to blow the dust out of it... I changed the welder plug and cleaned the contacts. Checked the gun (Bernard Qgun) looks brand new inside still... Nothing has worked yet. Any suggestions before I take it in with my Plasma cutter - Miller Spectrum 500 (turns on but won't arc or light up at all)????? Thanks for any inputRanger Welding Inc.24 Hr In-House/Mobile Welding & Sandblasting13 Holland Dr #3Bolton, OntarioL7E 1G4647-519-7638