The Ultra-Chron were fitted with calibre 340 and was Longines entry to the High beat race of the late 1960’s. This watch is fitted with a 341 that also features a date mechanism. The serial number says this watch is from 1968. It’s in very good condition, but is not running. I’m suspecting that the mainspring is broken.
Movement is a bit dirty, but very nice.
The 340 series have nice movements, but I don’t see the need of a loose oscillating weight washed and bush.
I remove the autowinder mechanism.
Here you can see the inside of the autowinder mechanism.
The movement without the autowinder mechanism.
Movement out of the case and I’m about to remove the hands and dial.
Dial and hands removed and you can see the date mechanism. Nice construction that has a very snappy date change.
Date mechanism cover plate removed revealing more of the date mechanism.
I start taking the base movement apart.
Here you can see the gear train layout.
Movement almost taken apart.
Hmm is that an invitation to open the barrel?
As suspected the mainspring is broken.
All the parts cleaned and ready to be put back together.
The cap jewels are tiny.
I fit a mainspring that is close to the original: 0.95 x .15 x 340 x 11.2
Movement looks so much nicer when clean.
I put the setting/ winding mechanism back in place.
I put the autowinder mechanism back together.
Date mechanism back together.
Movement back in the case looking very nice!
The mainspring was spot on and I’m happy with the performance of the 36.000 beat pr hour movement.
I now fit the oscillating weight.
Watch in fantastic original condition.
The 37mm case is almost too large for my wrist, but still feels very nice.