On the input board there are two relais near together. If everything is oke these relais comming up after 0,5 sec after switch on the machine. If not check the capacitors near the both relais.
Send it to a repair shop. Lincoln Invertecs, like most recent inverter welders, are not easy to work on, unless you are a well trained electronics tec. I have got lucky sometimes and fixed them but I have also sent a good few to silicon heaven. If you do not understand what a pre-charge circuit is, then put the covers back on.
Dave