Wristwatch restoration, servicing and repair

Posts Tagged ‘Sinn’

Sinn 103 Flieger (Valjoux Cal. 7750)…

An iconic pilot’s chronograph on the blog this time, a Sinn 103 Flieger. Although this is the first Sinn to feature on the blog, I’m sure the name will be recognised by many watch enthusiasts.

(Click pictures to enlarge)

The company ‘Helmut Sinn Spezialuhren’ was founded in Frankfurt in 1961 by flight instructor and pilot Helmut Sinn. Specialising in navigation cockpit clocks and pilot chronographs, the timepieces were manufactured in Switzerland and were offered to customers directly rather than via a dealer network which saved on costs, resulting in a lower retail price. The business model worked well and the company grew steadily over subsequent decades.

In 1994 Helmut Sinn (then aged 78) sold the company to certified engineer and former IWC employee Lothar Schmidt who re-structured the entire company, expanded the model range, introduced a dealer network, and moved a lot of the manufacturing in-house. The company achieved many technological firsts based mainly around material hardening for the watch cases and magnetic resistance. Pictured below are a few of their other models; the U1, EZM4, 142, and the T1.

The 103 is a stalwart of the Sinn line-up and has been in production since the early 1980’s. Exact records detailing specific model changes weren’t kept before Lothar Schmidt took over so it’s hard to be sure, but the watch in this post is most likely one of the earlier models.

It arrived in a reasonably sorry looking state, the lume had deteriorated throughout and the watch showed signs of water ingress which is never an encouraging start. With the caseback removed, the cause of the problem was immediately apparent… the caseback gasket had a big gap in it!

Perhaps the last watchmaker didn’t have the right size in stock and cut the largest gasket he had with a “Well, it will be 15/16th’s more waterproof then with no gasket at all” idea? –  not recommended.

Even though the moisture had taken its toll on the lume, the movement was surprisingly unaffected. The only parts showing tarnish were the steel parts of the bearing race in the winding rotor which was cleaned to preserve the Sinn branded rotor, and the cannon pinion which was replaced.

The calibre in this watch is the Valjoux cal. 7750 and though I’ve serviced many, this is the first cal. 7750 powered watch that I’ve written about on the blog.

Having been in constant production since 1974 the cal. 7750 is still the automatic chronograph calibre of choice for many brands. Many manufacturers enhance and/or decorate the calibre and then give it their own model number (i.e., Breitling cal. 13, IWC cal. 79350) but the base calibre is often recognisable by the subdial layout; running seconds at 9, minute counter at 12 and hour counter at 6.

There is an alternative version of the calibre, the cal. 7753, with the subdials placed in the 3,6 and 9 positions. Despite being a more traditional layout the 7753 seems to be used much less than the 7750 for some reason, production numbers perhaps? An example of a cal. 7753 powered watch that springs to my mind is the Montblanc Timewalker Chronograph.

Ok, back on topic…. With the movement serviced it was on to the cosmetic part of the job – obviously the most pressing issue being the lume. Re-luming numerals directly onto the surface of a dial is a tricky business and best left to a lume specialist, so on this occasion the dial and hands were sent out for the work to be completed while I was servicing the movement.

When the dial and hands returned, the case was cleaned and the crystal polished, the watch was rebuilt and a new caseback gasket fitted – without the gap this time. 😉

The Sinn 103 is still in production in a range of case materials, and the full range of Sinn models can be seen on their website: http://www.sinn.de/en/

Rich.

** Many thanks to David Lloyd for letting me feature his watch on the blog and to James Hyman for his excellent re-luming work. **