Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Hand alignment out by half second

Christian
Member
Posts: 16

Hello, as this is my first post I introduce myself. I'm Chris, a german guy located in Rome and have recently begun to collect some 7AX8s, despite my vow to NOT buy quartz watches any more, but I just can't resist the charm and solid build quality of the 7AX8 series.

So this is my problem: after having partly dismantled and cleaned a 7a28-703b with a stuck minute counter hand, it came back to life, but disconcertingly both the second and minute chrono hands were misaligned by half a second. It's not a non-hitting-the-markers-spot-on problem, they are consistently out by half a second. I didn't touch them at all, so how come? I tried to nudge the hands with a tooth pick, but they would just jump forward by one second, not permitting intermediate adjustments. Does this have something to do with the stepper motors and residual magnetism? Shall I try to pull out the crown and leave it for some time to let any residual magnetism dissipate?

Is there a way to adjust the hands in intermediate positions without taking them off?

Thank you very much!

Chris.


February 27, 2016 at 2:48 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 12380

Chris.

You say that you 'partly dismantled' it, (in your efforts to sort out a stuck minute counter hand). Did that include removing any of the chronograph bridges and the intermediate gears ? If so, it's possible that you replaced one of them a gear tooth out. I've done it myself a couple of times - on one occasion I remember, on a work colleague's 7A48-7000. The only answer is to pull the hand(s) and carefully re-set it on the mark. Edit: I found the thread I wrote up: http://www.seiko7a38.com/apps/forums/topics/show/8569376 - and quote:


Originally posted by myself on January 27, 2013 at 5:45 PM


You'll notice the 30 minute and sweep second hands are slightly off their marks. That's simply because I'd left them on the ends of their spindles while I was messing about with their bridges, so I might be an odd tooth out, either way. I'll re-fit them properly later.



February 27, 2016 at 4:11 AM Flag Quote & Reply

Christian
Member
Posts: 16

Hi Paul, yes, in order to gain access to the minutes counter bridge the chrono second hand bridge must first be removed. Still learning much stuff and understood that it's just a problem of meshing teeth! And thinking of it, maybe it's easier to work on the gears instead of prying hands off? Besides, working on the same problem on a 7a38 6020 I screwed the bridge on, not noticing (aargh) that it wasn't completely set and the bearing of the main gear popped out. I pushed it back into place but as soon as I tightened the screws some friction built up and the final result is that the minute counter hand is still stuck. Nudging the hand with a tooth pick it would only move backward! I must strip it down again to have a deeper look and see if the problem is similar to yours or else I might need a new bridge. :(

Chris

February 28, 2016 at 4:43 AM Flag Quote & Reply

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