Herre's a good for ya.
I have a sister that knows every thing as long as your doing it wrong.. she's 75 and a lifetime sewer.
she has two machines. according to her there both thread bound and have been for years.
ok 1st one a 1960 viking Husky, very cool machine, yet it was thread bound plus oil stuck. hair dryer fix. she about died seeing that trick LOL.
#2 a pfaff 2222E ( same as a 2221) walking foot and needle up machine. clean no thread anywhere, but stuck like a BIG dog.. finally get the covers off a good 2 hours later, finding nothing causing a problem.
I do see what looks like a electro magnet / servo. so be very careful, dealing miss no it all.. cause for sure I'll break something and this is a Hi $$$$ machine. so working with white gloves and in a vacuum chamber.
I see a red lever next to the presser foot lever ( wth ? ) ( no manual) ok the red one engages the walking foot
now what makes thing a needle up machine ? ah ha that servo. which does nothing more than drop a pin into the hand wheel to stop it in needle up positron
now what controls this ?? so plug in back in, take a chance on touching buttons and levers. no buttons do anything , red lever doesn't either .
BUTT O dang lookie there . Hmmm mover the silver lever up (presser foot) and oh gee the servo unlocks the handwheel and the machine turns as free as a brand new top.
Those germans are so smart !! when you stop sewing. the needle maybe down, lift the presser foot, this sends a signal ? power to the servo and it drops that pin down, then the motor rolls the machine untill that pin fall into a hole in the handwheel and lock it in the up postion.
she has had both those since new and has no Idea what nice machines both of those are. believe me she keeps them very clean and she knows how to sew !! Those are the only machines she has had in her lifetime.
right now goodwill is full of machines just like those.. as k her to make sure someone gets them and they do not good to goodwill when she dies or sold for pennys