[cas3]

yoyodyne said it all right there. The old machines have a lot of off the shelf components. the simple parts that might fail are common electrical parts available from many sources. modern machines are designed so that when a circuit board, or anything else, fails, its a specific part only available from the manufacture, for big money. My old Millermatic 35 mig welder needed a contact switch a few years ago. Miller said it was not available, ( buy a new welder?) . Its a contact switch, the concept has not changed in about 80 years. Your air compressor has one, your furnace has one, and they are on ebay, old us made units for about 35 bucks. I found one the correct amp rating, but i had to change the terminal ends. For the most part, the big parts, like transformers are way over built, and usually dont fail