My trusty Siemens master clock, after some years of service without any trouble, it needed repair. The electromagnet coil that charges the weight, it is triggered by contacts that got dirty over time. So I cleaned all well with contact cleaner and some ultrafine abrasive paper.
With these little repairs complete, the clock showed another issue. It just stopped after some random time, and that is no good for a Master Clock. Generally speaking, pendulum clocks that stop oscillation randomly are difficult to fix. It may be dirt in some gears or bearings, it may be incorrect adjustment of the escape wheel, it may be some local disturbance.
Fortunately, the full clockworks can be removed without touching the Invar pendulum.
There are connectors at the top, well large in size, and with some silk spun wire.
Upon closer inspection, one of the main gears, which also drives the minute hand, showed issues. It is not fixed in position, but moved in and out. How can it be? When it gets out too far, there won’t be any reliable force transmitted to the pendulum, so it will eventually stop.
There is a washer, brass, on the back side of the movement, and this is supposed to hold the axle in a fixed position, while allowing it to spin freely.
Somehow, this washer had worn out. So I just rotated it.
Giving the clockworks a good clean and oil (only special clock oil made for medium-heavy clocks supposed to be used!), but without a full disassembly.
Now it is ticking away again, and showing the time, day and night.