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Seiko M421 alarm spring contact

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Dave Matthews

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Seiko M421 alarm spring contact

Post21 Dec 2015, 03:48

Hi folks,

Bit of a long shot! I've just acquired a really nice M421 which runs well but the spring contact for the alarm is missing. I've tried searching online for a replacement (Part number 4246 028) but no luck. Does anyone happen to know of a place where I might be able to get one, please? I am in the UK but no problem acquiring one from overseas if necessary.

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Many thanks!

Dave
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767Geoff

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Re: Seiko M421 alarm spring contact

Post21 Dec 2015, 05:06

Pull the spring out of a narrow spring bar, cut to size and voila!

Did that in my 421.

;-)
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Dave Matthews

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Re: Seiko M421 alarm spring contact

Post24 Dec 2015, 04:01

Thanks, Geoff! Sounds like the best way to go!

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Dave
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Dave Matthews

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Re: Seiko M421 alarm spring contact

Post02 Jan 2016, 19:05

Hi folks,

I've tried Geoff's suggestion of using a spring from a springbar and it nearly works! I am getting sound from the alarm now but only very intermittently. The piezo-electric element on the inside of the caseback appears to be OK but is it possible for them to undergo some sort of breakdown without any visible deterioration?

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Dave
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Kasper

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Re: Seiko M421 alarm spring contact

Post02 Jan 2016, 21:06

clean the plate with a stiff brush :-D
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Dave Matthews

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Re: Seiko M421 alarm spring contact

Post02 Jan 2016, 22:04

Thanks, Kasper!

I tried that but it didn't help, unfortunately. However I've done a bit more experimentation now and it seems as though pressing the caseback into place is what is preventing the alarm from sounding?!! If I detach it but then hold it gently in place, so that the spring is brushing against the piezo plate, the alarm sounds! :scratch:

So I wondered whether the action of compressing the spring when the caseback is properly clamped down is causing the spring to contact against the metal module cover and perhaps that has the effect of muting the alarm. So I've packed a little bit of BluTack around the spring to prevent it from touch anything other than the piezo plate. But still no alarm sound when the caseback is clamped down. So basically the "looser" the contact between the spring and the piezeo, the more likely the alarm is to sound. Very very odd!

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Dave
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Adam

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Re: Seiko M421 alarm spring contact

Post02 Jan 2016, 22:10

try cutting a smaller length spring and stretching it till you get sound

regards

Adam
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nick0123

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Re: Seiko M421 alarm spring contact

Post03 Jan 2016, 08:38

Some watches come with a sticker (the better ones with a die-cut piece of thin plastic) that covers most of the module apart from the spring and maybe one or two other components.

If your watch is meant to have one of these, and doesn't, it could be unintentionally grounding (or whatever the reverse is) when you press the caseback on.

Check with someone who has the same watch who could confirm if you've meant to have an extra piece of plastic or not.
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Dave Matthews

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Re: Seiko M421 alarm spring contact

Post03 Jan 2016, 19:01

Adam wrote:try cutting a smaller length spring and stretching it till you get sound

regards

Adam


That seems to have done the trick! I am puzzled, though, as to why this should work! Many thanks for the suggestion! :-D

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Dave
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767Geoff

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Re: Seiko M421 alarm spring contact

Post03 Jan 2016, 20:42

Too much spring will simply fold over horizontally. This places the piezo on the case back under compression when the case is snapped closed or screwed in place. At the correct length it simply is compressed vertically back into its retaining hole providing a connection only, with out a compression force. It is the compression that prevents the peizo from vibrating fully.

Another term for the peizo is 'bender'. Preventing the bender from bending will subdue the sound it can produce.

Cheers, Geoff.
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Dave Matthews

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Re: Seiko M421 alarm spring contact

Post03 Jan 2016, 22:45

Ah, thanks, Geoff - that makes sense - though I never realised that piezos would be that "sensitive". Useful lesson learned there! :-D

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