Looking at buying a used Lincoln 350 mp mig welder. Own 2 of them just like it already and love them, imo best machines available for light fab-general welding repair work. Havent ran into or had any problems with mine whatsoever. Found another one that seems to be priced right. My question is what to look for in a used mig welding machine other than if it turns on and welds and overall appearance.  From what im told these machines do not have a built in hour meter. They are not your typical mig welder, they have more than just your on/off button and current and wfs knobs. Have heard that some places run into bad or failed circuit boards with these type of machines.

here a link to lincolns website

http://www.lincolnelectric.com/en-us/equipment/mig-Welders/Pages/power-mig.aspx

Didnt know if anyone has run into something like this. Any info or advice would be greatly appreciated, thank you