Quartz movement repair modify

Quartz movements are common in a lot of analog clocks. They are quadratic small boxes that house the mechanism that drives the clock. 

In short they consist of a circuit board with a quartz crystal, a lavet type motor with a coil and cogs to move the hands. Alarm clock movements also has a buzzer and an extra set of cogs to activate the buzzer.

The motor is driven by both negative and positive pulses and the driving cog turns counter clockwise.

The alarm activating cog closes the connection between the negative side of the buzzer and ground by allowing connection tabs to reach pads on the circuit board. The alarm turns silent after about an hour when the cog lifts the connecting tabs.

General advice on repairing 

Opening the movement is done by pulling some plastic tabs on the sides apart.

Some cogs might fall out when it is opened. this is normal. Pay som attention to the cog placements. The movement is divided into cog layers. Do not worry, it might look complex at first but they cogs are quite ready easy to refit. if you are unsure take some photos during the disassembly.

Be very careful with the coil wires that are connected to the circuit board. If they get lose you will have to re-solder them. Avoid breaking the wires.

If you plan to work in the movement more than once then consider de-soldering the wires from the circuit board and then put some more wear resistant cables in between and solder these to the circuit board. Then use tape to secure the thinner and thicker wire junctions directly on the coil.

If you break the coil wire anyway then you might have to rewind the coil. This is possible and you can use some steel wire as an axle for the coil and some plastic parts like those in soap pumps to construction axle to pick up the wire from the coil.

Beware. Make sure you have two very straight axles that turns without resistance so the coil winding goes smooth. Avoid breaking the wire. If you do anyway then you can tie the wires together and then solder on the knots. The problem though is that each break and tie will result in increased resistance.  Also make sure that you rewind the wire evenly over the whole coil.

I succeed to rewind the coil but with three breaks and the resistance in it went too high, about 240 ohms compared to another with only 195 ohms and as a result the current was not enough to turn the clock.