Quartz Watch Running at Twice Speed

[MattWatch]

Hi All,

I've just obtained an old Seiko Quartz Diver (5h26 7a19).

The watch turned up without a battery so I popped a (correct) new battery in, the watch now works but is running at twice speed. So for every 1 minute it'll actually gain 2 minutes.

It isn't the 'ticktick pause ticktick' you'd get from a dying battery, its literally running at twice the speed it should.

Does anyone have any idea what might cause such strange behaviour on a quartz watch?

I thought quartz watches were supposed to be easy/reliable - I seem to have nothing but problems with them!!

Cheers

Matt

[watchweasol]

Hi  The quartz watch runs at 32,768 Hz and via the circuit board divides down to 1sec pulses which drive the stepper motor, As the mechanics depend on the rotor stepping I would suggest that you have a faulty circuit board. With an ocilloscope you may be able to determine the pulses being delivered via the coil to the rotor and the gear train

The rear section of the attaced document explains the theory of the quartz watch and will give you an understanding of its workings.    cheers.

Witschi Training Course.pdf

[MattWatch]

Thanks very much for the informative response sir.

Well, I have to say, that's a drag! Are we talking a new board (or complete movement, if I can find one), or is it possibly fixable?

[HectorLooi]

Just last week my mentor told me about a watch he was servicing having this same problem.

He found that it was due to an extremely loose cannon pinion. Every time the stepper motor ticked, the momentum of the wheels carries it forward. He solved it by tightening the cannon pinion. 

Check if the hands seem abnormally loose when you are setting the time. If they are, you might have a similar problem. 

[xyzzy]

Does this movement have an adjustment? Could need that is way out.

If you have an oscilloscope you can check the crystal frequency.  Should be 32.768kHz.  It's possible for quartz crystals to resonate at an overtone of the desired frequency.  Or it could be broken.  Or maybe the trimmer capacitor is bad.

If not the crystal, then possibly something with the rotor?

The divide by 32k circuit is part of the IC.  It being damaged on such a way as to still work but be a divide by 16k just doesn't seem realistic.

[MattWatch]

Hi All,

I always like to try and close threads off in case someone ever finds this looking to solve a similar problem.

Following the above I decided to let the watch sit and run for a day or so. It hadn't been used in a while, I believe, so I hoped by letting it run for a while it may be some miracle correct itself. And guess what? It did! 

As I type the watch is running perfectly. Will wear it for a few days to make sure, but as it stands we're looking good.

Thanks again for all the replies and assistance.

[Tomm]

Hello

I have similar problem , whith an vintage LCD , runs at twice speed on my hand , but at normal speed on the table , I think , have a relationship with the temperature , .