Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > 7A28 - Help after Battery Change

SuperJ
Member
Posts: 11

Hi,

Had my battery changed today (local Seiko dealer), and unfortunately, only the Chrono function works (all 3 hands).

The Hour/Minute and Second hand do not move at all.

Is it possible that the battery should be cycled again, or do I have a major problem here?


January 24, 2018 at 9:14 AM Flag Quote & Reply

Rob Benham
Member
Posts: 280

Firstly, did it function correctly recently?  i.e. did the dealer assist in its demise?


If you look at the seconds dial at 6 o'clock, can you see the hand twitch with the seconds pulse?  You may need a loupe to see this minute movement.

January 25, 2018 at 6:11 AM Flag Quote & Reply

SuperJ
Member
Posts: 11

Yes, the second hand is stuck at 2 seconds past 60 and is trying to move (pulse every second), but it seems stuck.


January 26, 2018 at 8:24 AM Flag Quote & Reply

Rob Benham
Member
Posts: 280

That does make one inclined to think it's mechanical, which of course would be the best option though I suppose there's a chance the battery is down as of new.  It is possible to read the on load voltage from the middle of the 3 little test points - the only ones with 3 in a row.  The top one (with the battery to the right) should show pulses of about .7 v - they are square waves if you're posh and have a scope. 

I have had some success in coaxing the wheels round while under power.  It may just be the lube is a bit dry and the break in operations while the battery was changed left it at the worst sticky spot.  Anyway, try that first.  If it proves the pudding, then clean and lube is in order anyway.

A bendy plastic toothpick on the teeth is best to avoid damage.  On one I had, that exact fault, I coaxed the wheel round with battery out and circuit removed - and suddenly a blue blob came into view.  It was hard, like brass corrosion, yet bright blue.  I have a needle in a handle ground to a curved chisel shape - best tool I've made - and GENTLY coaxed the blob off.  It took a while - vacuuming the bits out with a pipette and rubber tube.  Lubed top and bottom and perfect ever since. 

If it's not mechanical, then cleaning the coil/printed circuit contacts might help but as you know, one wrong touch an the coil's finished.  I've just spent an hour or so trying to repair one.  Tried before and failed and this is going to be no different, I fear.  Inner coil winding was O/C as well.  Looks a lot like willful damage. 


January 27, 2018 at 10:36 PM Flag Quote & Reply

gk2121

Posts: 6

I was trying to post a new thread but it would not let me.  But this is the exact crisis I'm in right now!  SuperJ, did you get your watch's time running again?  If so, what was the solution?  I guess I might as well post my issue:


I'm having a mild heart attack over here! I just received a 7270 a couple days ago and was working perfectly. I noticed there were a couple small smudges on the dial so opened her up today to clean. I am not 100% positive, but pretty sure that when I removed the crown to take out the movement the seconds dial (6pm) stopped working. I didn't think much of it and figured that maybe taking the crown out stopped the time keeping. So I went about my business and cleaned up the insides with some rodico.

After cleaning I decided to take off the back plate and battery terminal cover (7 total screws removed) to make sure there was no rust or anything around the movement parts. After verifying that it looked good I reassembled everything. After getting the crown back in my heart sank when the seconds didn't start ticking.

I immediately tried the chronograph but it is working fine. It did need the hands reset which I was able to do with the crown out 1 click and pushing the corresponding buttons. Then the chrono worked totally fine. I let it run for 5+ min and had no issues. But the time keeping still does not work! Please tell me this is normal and a simple fix!!

October 9, 2019 at 4:26 PM Flag Quote & Reply

gk2121

Posts: 6

Alright, I have the issue narrowed down to the crown.  When I take the movement out of the case and then reinsert the crown, the time keeping works just fine.  But, when I put the movement back in the case and reinsert the crown, time keeping doesn't work.  Sounds to me like the crown isn't long enough to make contact with whatever part tells the watch to start ticking.  Is there a part in the movement that I need to slightly move?  Or is there a way to slightly lengthen the crown stem?  It looks like there is threads on the stem but I don't want to put much pressure on it since it seems very fragile.

October 9, 2019 at 7:42 PM Flag Quote & Reply

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