Tommy Ku Timepiece

Unlike mechanical timepieces which depends on the balance wheel to regulate the rate of it's ticking, a quartz movement used quartz crystals which ticks accurately at a much higher frequency.

This is an innocent looking quartz with brutalist numerals. I got it because I liked the angled sides of its lugs.

That watch runs with a fresh battery. The movement itself looks clean too.

I noticed a missing screw at one corner of the movement. It doesn't seem structural, as the movement is held onto the case by the case screws, so I omitted it.

Once I've cleaned the watch I was content to see this nice looking watch on my wrist. However, a few days later I realized the watch was running ery fast unlike normal quartz watch at a +4s per day rate.

On early quartz watches, there are regulating mechanisms such as the trimmer condenser, with a slight turn one can adjust the movement to run plus or minus a few seconds. 4 seconds is within such limit so that what I did, turning the trimmer condenser at anticlockwise direction.

I didn't know which direction or how much I should turn, but the rate difference caused by the adjustment would tell me.

To my surprise, no change observed on the next day, still +4 s/d. I turned the screw more in anticlockwise direction.

Still no change.

Tracing the wiring connecting to the trimmer condenser I realized it's connected to the socket where a screw was missing. Using a multimeter I see that the contact between the wire and the pillar below is open, and it became closed once I screwed a replacement screw in.

The trimmer condenser probably is running in parallel as the rest of the circuit to add capacitance, which would regular the quartz crystal's vibration but if it's circuit is open, it's as if the trimmer condenser doesn't exist, thus causing the crystal to run fast. Reconnecting it to the circuit should now make it's adjustment effective.

As I had expected, the watch runs +2 s/d after putting a screw back. I adjusted the trimmer condenser further and reached a -0.5 s/d per day, within spec of ±15 s/m, well good enough for me, and much better than +4 s/d anyways.

So there you go. A quartz watch may be running and appear to be in good condition. Who'd have thought a missing screw would throw away the rate by that much? You do after having read this! Now, be careful out there.