4R36 Hair spring, odd problem.

[Bimroy]

A friend of mine stopped by today with a problem with his watch.  It was a brand new Seiko aviators watch.  A smart  looking watch with an E6b calculator on the Bezel. He'd picked it up in Asia.  It was "keeping random time"  as he complained.  

On to the vibragraph and it had an amplitude of 140 and a beat error of 1.8. Nasty for a new watch, but the amazing thing was,  it was actually still running within 60 sec per day. 

Off with the back and straight away I could see that the spring curb pins had rotated nearly 90 degrees and the Hair spring was looking very distorted!  The curb pins on this movement appear a cheap looking brass attachment fitted into a fork type arrangement on the regulator arm.  After a bit if manipulation,  I figured that it was history,  as the curb pins kept snapping back  to the 90deg position.  Perhaps a manufacturer error or a botched assembly.  Shame as Seiko really are usually  a good product. 

Everything  looked fairly familiar to the earlier movements.   So after a rummage in the junk  parts box I came up with a 7S26 assembly, balance cock and all.  The curb pins on this are the typical riveted in kind.

A good clean up and the appropriate tiny dot of oil on the end stone and it fitted straight in.  Watch is now  clattering away with excellent numbers,  just like a brand  new one...

So what's the rub on the changes to the regular arm?  Cheaper?  Better? 

 

 

[autowind]

Seiko would do well to remember the old adage "If it ain't broke don't fix it.)  If they have altered it as a cost saving measure what would be the saving?  a millionth of a penny?  If everyone of this model has the same problem and all are returned under guarantee that will be mighty expensive for Seiko.  One of the main requirements of a regulator is that it does not move under any normal conditions and in the case of Rolex,  even under abnormal conditions, as it does not have a regulator but is free sprung.

[jdm]

2 hours ago, Bimroy said:

The curb pins on this movement appear a cheap looking brass attachment fitted into a fork type arrangement on the regulator arm.

That's actually the Seiko version of Etachron, newer than the fixed regulator pin, and is generally considered a progress. Long thread and great discussion:

 

Edited May 23, 2016 by jdm

[Bimroy]

Thanks for  the replies,  I've been having a close inspection of the offending parts,  and there is no way that I can get the curb pins to remain in the correct position,  they seem to by  spring effect of the forked regulating arm,  rotate back to close to  90deg position.  

 

 

[jdm]

Regulator arm fork a little lose? You could try closing it a little, but it's a delicate affair.

Attached tech sheet with indications how to remove balance from cock in case you need (incorrectly titled "how to remove balance staff") 

Seiko 7S36C - Technical Guide.pdf