Watch beat all over the place - help

[ThePadd]

I have been hunting through Mark Lovic's videos trying to find a cure, maybe someone on here can help me.

I have been making watches for a little while now. Usually buying in the parts from a small number of suppliers then assembling them for friends/family, but sold a few too.

My own watch, which started the whole thing off is still my favourite, but I have some upgrades in mind that will probably mean building a whole new watch.

However, much as I love it, it is currently driving me mad. I bought a Timegrapher for myself for my birthday, and while another watch I have built has a lovely clean beat and runs easily under a second a day, my daily wearer has a horrible beat. I can adjust the beat, regulate it fine, but it doesn't have a clean beat, it runs fine for a few seconds, then jumps all over the place, then runs fine for a few seconds, then goes all over the place. You wouldn't know it to watch it, but the Timegrapher shows how bad it is. Of course, as far as keeping time, its minus 1s one day, minus 7 the next. WTF!

Here's the watch and Timegrapher plot, so you can see what I'm talking about.
http://imgur.com/0Tk2FDz
http://imgur.com/nkWdbSa

By the way the movement is a Seagull ST2130.

Thanks

[me32dc]

For the best results, take the movement out of the case to measure it.
Does the result change with position? To me it looks like something is touching something, be it the hairspring touching itself or the balance cock, or a hair/fibre touching a wheel at regular intervals. From that timing machine screen I wouldn't say the beat wasn't all over the place, but more that something is interfering with the regular motion of the balance wheel.

[Thewatchbloke]

The beat is fine, something is interfering with the rythm at regular intervals. Do the usual checks, the hairspring is flat and centred, it's not catching on anything, there's no stray fibres or particles anywhere near the escapement or balance. If it's happening every minute check the seconds hand isn't catching the minute one, or check there's nothing stuck in the teeth of the the centre wheel.

[Webwatchmaker]

That's a pretty poor amplitude.
Have you demagnetised it ?
You will get case echo and should test it out of it's case.
How regular is the reading drop off ? You can then figure if something is intermittently touching something else.
Hands or hands on glass for example.

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