There are a few things that you can do, to aid in deciding what to do. Wind the 3 mainsprings until the key will not turn any further. If two can be fully wound, and the third “snaps” and cannot be fully wound, then you have a broken mainspring. This problem can be easily solved. Here’s how you do it:
1- The hands are held on by a nut. Remove the nut and the hands.
2- Turn the clock face down and remove the four screws holding the movement in the case.
3- Turn the movement FRONT side up. Make sure you know which spring is broken. Identify it.
4- Picture # 1. The arrow points at a screw. Remove it.
5- Picture # 2. Remove the screw (see arrow) on the broken spring.
6- Picture # 3. Remove the “finger” (see arrow), and remove the ratchet wheel from the arbor (see arrow).
7- Picture # 4. Ratchet wheel removed.
8- Picture # 5. Grip barrel arbor with pliers, and lift upward as shown. Remove it.
9- Picture # 6. Barrel can now be slid out of place laterally, as shown.
10- Picture #7. Turn the barrel over. Look for a number (as circled). That is a part #. Using the part #, order a new one for a Hermle 340.020.
11- A replacement barrel, complete with mainspring, can be ordered from many suppliers. Butterworth being one of them.
12- Once you have your new barrel, using the 7 pictures enclosed, reverse the process, and you’re done. By the time you ship the clock, pay for a repair, pay the return freight, your clock isn’t worth repair. Do it the way I’ve shown, cheap like borscht!
