WS 6: Repairing a Caliber PUW 910: Old and new Coil
Here you can see the plastic spacer better. Why is this so interesting? First, I did not see them and started cursing when trying to replace the new coil, it just would not fit. Only a look under the stereoscope revealed those tiny transparent spacers. And second, it was another artistic job to pull them out without damaging the coil. If you think that is easy, just imagine, the tips of the tweezers 5 (the finest) are huge, almost too huge. A toothpick also seemed to be too big. And I imagined, any force applied could just take me back to the shop... and I remember that the sales person "One or two?" and wished I had bought two...
On the contact of the old coil right, you can see that one contact is still ok. The upper contact is however gone. I had also scratched a bit on the gold layer to see how deep the corrosion penetrated. While doing this I realized that the fiberglass had expanded and on the outer right end, you can clearly see that the contact has become disconnected from the board. Could be humidity, battery fluid, age. The old coil's head seemed to be made of an older compound called "Pertinax". If you disassembled old radios as a boy, you will remember that very typical smell of that older brown material that was used then (until early 70ies). The new coil's contact end is made of a more modern fiberglass and you can see both wire ends soldered to the contacts as it should be.
Now did this new coil do the job? Nope, the movement would not start at all, not even a tiny bit like some watches some time start to tick and stop and if you look closely with a loupe then you see the second hand vibrating at the same location. But this watch had no second hand, making it of course more difficult to check whether the movement was running or not. But quartz movements with no second hands normally advance the minute hand every 20 or 15 or 10 seconds, this really depends on the manufacturer.
So what to do? It was not the battery contact, it was not the coil. The circuit had looked ok, but I did not have a circuit tester that could have given an conclusive answer. I also tried to use my Bergeon crystal pen (basically a pen-like instrument that has two contact claws that allow you to bypass a crystal on a circuit). If the movement starts working after you bypassed the crystal with your crystal tool, then you know the original crystal on the board was defect and did not oscillate anymore. Soon I realized, the Bergeon tool must have been from the early 70ies, when quartz movements were still huge, this PUW910 from the 80ies had a far too small crystal. Thus I decided to try to buy a spare circuit for the PUW910. After being able to buy the battery contact and the coil, I started to believe in my luck and thought spare circuits would be readily available about everywhere.
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