How flip clocks work

Old fashioned digital flip clocks display digits on flip-down leaves. The mechanisms are described in this page.

Summary

An animation of how a split-flap display works

The earliest form of digital clock displayed the digits (and possibly days or the week and months), each split into top and bottom halves on adjacent leaves in a pack as in this animation. These are brought into Restart Parties from time to time as cherished legacy items, or treasured finds from a car boot sale or similar. They were electromechanical devices with ingenious mechanisms which it helps to understand in any repair situation.

Safety

Old mains powered devoces may have worn or perished insulation on the mains lead, creatng a shock or fire hazard. In the oldest devices, the design may be inerently insafe, for example with no earth connection to exposed metal parts.

The Timepiece

Older clocks normally have a mains-driven synchronous motor, locked to the frequence of the AC mains supply, which is guaranteed to be stable over a 24 hour period (though it may vary slightly over the course of a day). In a very old example, if there are concerns over its safety or if the coil appears to be open circuit, this website describes various options.

If the motor isn't turning even though the coil is definitely not open circuit, then the motor spindle or gears may need cleaning and lubrication.