Under the Loupe/Installing a Piezzo Alarm Crystal
On occasion, a watch will come in for repair with a broken piezo crystal, causing the electronic alarm to no longer function. In the majority of cases, the piezo is glued to the inner surface of the watch's caseback.
Removing the Old Piezo
If the piezo crystal is visibly cracked or shattered, it must be removed. Soak the caseback in acetone, or a similar solvent, for several hours and the old piezo crystal should come loose. It may require a bit of prodding with screwdriver or stout sewing needle. If the caseback is painted on the outside, apply solvent to the inside of the caseback only, re-applying as necessary.
The glue bond can also be broken by applying heat or by freezing. When applying heat, however, make certain not to discolour or alter the temper of the caseback.
Applying the New Piezo
Install the new piezo with a two part epoxy, or similar bonding agent. If the piezo is not in close contact with the metal of the caseback, the alarm will not chime correctly. To ensure a close fit, and therefore a strong chime, set the caseback on a firm, flat surface and apply pressure on the piezo for 24 hours.