Seiko 7s36 - No good turn goes unpunished...

[hofnerpres]

After many years of never seeing a 7s36 three came along at once. All Pro Bono family watches which were in good nick and in danger of being thrown away. The first two were amusing and gave little trouble. I admire their simplicity and good balance design. The dumbed down balance jewel shock spring design takes some practice to manipulate but can be mastered. Sharp tweezers and thin pegwood in the other hand works - the more ingenious approach is to take a toothpick - and flat one end -  use a 1.5 mm drill to create a concave hollow shape on that end. Lower carefully and trap the pesky spring - then twist it into place. Half the time it worked. Don't use 2mm pegwood - it's too hard and slippery - the slightly ragged bamboo of the toothpick helps to grip the flimsy metal. 

Watch No3 was cursed. Poor amplitude after re-assembly especially DD. Mmm. Tried all the usual free running checks  - the pallet fork looked a bit lazy in one direction so I cursed myself for trying to cheap out by re-using the main spring. New spring - better but 140/190 deg consistent amplitude. Check it all again. The only thing I didn't like was the balance spring did not look central. Removed it from the cock and yes - not a nice final curve and not perfectly central. I hate reshaping but have got better over the years however it's dangerous work and there was a £7 pattern part on the internet... It came and apart from the stud attachment with the groove in the wrong place it looked reasonable. . So now 250 deg DD - Armageddon 140 deg DU . This clearly suggested the drive system was good and the problem lay with the balance. Yes the spring was flat and not rubbing when inverted.  Got everything under the microscope and had a good look the especially check the balance cock jewel was not at fault. A few hours adjusting and  reshaping failed to change matters. Tell friend to buy a new watch - these 7s36s can still be had for £100. He is reluctant. Two sleeps later we strip it right down again and find a huge lint ball at the top of the escape wheel. Hurrah - problem solved ? NO - Still runs horribly DU. Enough - Move onto a spare NH36 with a battered balance spring and spend a character building afternoon getting this straightened out. The task is really aggravated by the fact that the spring is hard pressed onto the arbor and clearly not meant to be removed - you are forced to work with the balance wheel on top and getting in the way. I liked the Etachron type fixings but sad my ETA style adjustment tool is too small to fit. They turn easily enough with a home made mini spanner.

We win - first try - 250 deg and just 17 secs variation DU to PD - Good enough for a beater.

So - What have we learnt ?

1. If the balance spring is not happy and central don't rush to blame the rest of the watch for strange amplitudes. 

2. Cheap pattern parts can waste hours.

3. With new NH36 movements with manual winding and hacking available for less than £40 why are you bothering ?

4. The watches that drive you crazy will force your skills to improve.

5. Golf is not always the most frustrating pass time..

Still think this was mostly my blundering fault and the watch was not cursed ? As I tidied my tools away there was a faint click from my wrist - the new crystal spontaneously split. I laughed so hard....