Hi I have bought a second-hand Clarke 135TE Turbo. I have done some rudimentary maintenance; cleaned it, new tip, new shroud, adjusted wire tension. I'm new to all this. I have been practising on 1.5 mm mild-steel sheet using CO2. The welder has two switches labeled 1-2 and Min-Max respectively. Following advice in the manual I have set these to 2 and Min with wire-speed set to 6. This seems to get me close to the sizzling bacon sound but there seems to be no penetration - the weld just seems to sit on top of the sheet, I do not get the equal-sized bulges top and bottom as illustrated in the tutorial (https://www.mig-welding.co.uk/power-setting/mini-sectioned-welds.jpg). I have tried playing with the wire speed, welding speed and height of the shroud above the work. I seem to be able to get bigger beads but still no penetration. I have tried setting the second switch to Max. On a couple of occasions this has resulted in some penetration but I have found it very easy to blow holes. Any advice please?