Seiko 6309A / Balance wheel oscillates very fast

[BlueHarp]

Hi,

I've got an old Seiko 5 (1976 or 1986) equipped with a 6309A movement. The seller indicated that it started, then stopped within a few seconds.

I disassembled, cleaned and reassembled the movement, but the balance wheel does not start unless I help it, and then it oscillates at a speed rate wich is at least twice the normal speed.

Could that be a question of magnetisation? Here are a few pictures.

[Neverenoughwatches]

15 minutes ago, BlueHarp said:

oscillates at a speed rate wich is at least twice the normal speed.

What do you mean by twice the normal speed ? Are you using a timegrapher? 

Sometimes we have to understand what you're trying to say before we can answer.

Twice the normal rate would be a fairly standard 2.5hz oscillator, oscillating at 5hz, making it 24 hours a day fast which wouldn't be possible.

[BlueHarp]

Sorry for not being clear enough. I realized that the balance wheel was oscillating too quickly. So I compared the Seiko with the watch I wear everyday, and I could see that the second hand of the Seiko is moving far more quicky than the one of my watch.

[HectorLooi]

Do you have a timegrapher? 

Most common cause for a watch running fast is a magnetized hairspring. Try demagnetizing the whole watch.

The next most common cause is a sticky hairspring, where the coils of the hairspring are stuck to each other, usually due to grease getting onto the coils. Remove the balance cock and degrease it in lighter fluid/ naptha/benzine/one-dip/etc

Thirdly, the hairspring is distorted. Usually caused by dropping the watch or rough handling of the balance cock. Check under magnification whether the gaps between the coils of the hairspring are evenly spaced when it is back in the movement at rest. Check that the hairspring is level and flat and not touching the hairspring stud.

Hope this helps.

 

[BlueHarp]

14 minutes ago, HectorLooi said:

The next most common cause is a sticky hairspring, where the coils of the hairspring are stuck to each other, usually due to grease getting onto the coils. Remove the balance cock and degrease it in lighter fluid/ naptha/benzine/one-dip/etc

That was it! I examined carefully the hairspring and I noticed a very tiny "thickness" at some point. I was kind of dirt which could be removed easily. Now the oscillations of the balance wheel look far better, and a comparison with my personal watch shows that the Seiko runs smoothly.

Thank you so much