Hello,
I am from Italy and apologies for my bad english.
I just purchased a massive Grindig Concert Boy (it is a 209 I guess).
It works, but I cannot tune it. The knob doesn't work, I opened tha back of my radio and I see there is a (cotton?) thread that ends with a small spring that is loose. And this thread is linked with the tuning knob.
There are 2 tuning knobs, and both don't work, one is for the general tuning, the second is for fine tuning.
There are 2 loose threads, one with the small spring that is connected to the main knob. the other thread is without spring.
Any help?
Thank you,
regards,
Carlo

Try replacing the thread with a rubber band or the belt from an old record player? These can be fixed if you're resourceful.
N9ZAS.

Don't know if this untimely posting will do you any good, but if you still have the unit, you need to get a copy of the Service Manual for it. It should include instructions for Dial Cord 'stringing' of replacement. [the information was pasted in a lot of vintage equipment. The generic dial cord is especially made for the purpose, any other attempt with improper cording will not function very long; and you get to do it all over again. There are exacting turns ratio between the various shafts/pullies, and sundry connected device [such as a dial pointer], if you don't do it right, your pointer may move in the wrong direction, or at the wrong rate of travel.