The movement was soon fully stripped ready for a trip through the cleaning machine. With the circuit block removed you can see the coil, hacking lever and top bridge.Ī bit farther in and the train’s exposed. Turning the movement over work can start on the circuit side. It’s only when the calendar side is stripped the differences are seen. Under the day ring the similarities to the 6309 are remarkable. Underneath the dial this could be a 6309 if it weren’t for the wider canon pinion and hour wheel. The hands in particular do tend to suffer from corrosion on these tunas. You will not see a nicer example of dial and handset than this one, both have turned a beautiful creamy colour and both are amazingly preserved. The best method to undo the battery clip is to fully undo the screw farthest away from the coil then the clip just swings out of the way allowing the battery to be replaced, there’s really no need to undo the other one! This happens when a screwdriver slips out of the bottom screw nearest to the coil and punctures it severing the fine wire thats wrapped around the armature. One of the most common faults with these movements that will actually stop the watch (and the 7546/8 ones) is a dead coil, and these coils tend to be killed at battery change time. With the back off we can see the calibre 7549a movement which was developed from the 6309 platform. The batteries were rated for 3 years so with a production date of March 1978 you had six months warning of when the battery should need changing – no excuses!Ī shot of the shroud removed in preparation for undoing the caseback. You can see on this one there is a dot stamped in the third quarter area of 1980 (before the 81). This was designed to indicate when the first battery change was due so you could address it in plenty of time without the risk of the watch stopping during a dive. As well as the production date there is a ring of years around the perimeter of the caseback. The 300m divers utilise a two piece case (unlike the 600m line) and there’s quite a bit of information on the caseback. Excuse all the reflections but these are buggers to photograph on the bench because of the domed crystal! This one came in for a movement service and a crystal change as it had acquired a non standard AR coated one at some point. These were the first quartz divers to be seen from Seiko. It’s not hard to see how this watch earned the nickname ‘Tuna can”! The watch featured is a very early production 300m 7549-7010 from March 1978 and was released simultaneously with the 600m 7549-7009 ‘Professional’ titanium divers line. This means that the crystal cant blow out as atmospheric pressure drops in a decompression chamber as it’s physically restrained by a locking ring. With a 600m depth rating, the 6159 dispenses with a helium release valve in part due to very consistent and tight manufacturing tolerances, but also due to the one piece case and screw down crystal retaining system. It included several industry firsts, the first titanium case, the L-shaped single crystal gasket and of course the ceramic-coated titanium shroud. Although the Japanese are famous for taking a design and applying their interpretation to it, the shrouded diver owed nothing to anyone, it was a truly unique design. This watch came into being due to Seiko seeking to find a solution to the complaints from professional divers about watch failures at depth. Seikos shrouded diver line started way back in in 1975 with the introduction of the Seiko 6159-7010 Professional.
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