The day of reckoning has come – Cousins came back to me to tell me that the unlocking date spring they had supplied was correct. The manufacturer had substituted the original spring for a different construction! No wonder did I think it was the wrong part – it looks completely different. So now I can put together Dave’s Zenith!
The good news is that there must have been a reason that the spring broke in the first place, and that the substitution will get rid of that problem. If you read this because you are servicing a Zenith calibre 400, replace the spring as a preventive measure.
Here you can see the new spring in place – it assures a very swift date change at midnight.
Finally, I can put the bottom plate assembly back together.
The dial and hands go on – the bottom dial still needs the hand perfectly aligned – it doesn’t point right at the “12”.
As the crystal is scratched, I ordered a new sapphire crystal and gasket.
Case cleaned, and the new crystal fitted.
The case back gets a new gasket as well.
Movement cased. You can see that the chronograph hour dial hand now sits straight at 12.
Time for a bath … All is well.
Finally, the watch is back together and all is done. Chronographs are notoriously complicated, and this one adds the 10 bps high-speed movement on top. I haven’t kept exact records, but I’m guessing I have put at least 12 hours work into the job, if not more. But I’m very happy with the result, and it was well worth the time.
After 21 years, this El Primero has a new lease of life!