can any one give me some tips on a sealy 150/5 welder ,doesnt seem to be working right.when welding it sounds like pop pop pop pop even on the highest setting,it starts to smell and the wire feed stops working .ive had it to a shop to be repaired and all they did was put a new earth clamp on it and charged me £50 bl***y quid any ideas(well they say theve checked it over as well :?