HI I have been having issues with my welder for a while now with the wire speed changing during welding after about 10 minutes use so i got the welder out today and started using it to fully diagnose the issue anyway after about 10 minutes welding I had to keep dialling down the wire speed until eventually its now on the minimum wire speed setting of 1 to get a decent weld. essentially the motor is speeding up and now runs way to fast - as I change the power settings it changes wire speed appropriately but is too fast across the range.. if i turn the dial slowly to around 5 it will suddenly slow right down for a fraction of movement then speed back up as if its a potentiometer issue in the switch? I have taken the casing off and also noticed that the transformer is surprisingly rusty? I store it in the outside shed but its dry and always covered which surprised me as its around 6 years old is it the case that I will need a new switch and pcb board? I am wondering if its worth it tbh looking at the transformer?