Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > Another 7A38-7000, with the opposite fault!

Rob Benham
Member
Posts: 281

This time, the clock goes, but the tachy does not.  I opened it last night, but really didn't start until 07:00 this morning.  Unheard of for me.

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http://www.ebay.com/itm/400660616219?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649

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I rushed at this because I needed the movement, but almost at once, I didn't as the fault was fixed on another one.  I regreted paying so much for it despite that rusty movement from Florida fetching so much, but when it arrived form ameri*pawn it was very well wrapped and the case was better than I'd feared.  (much better underneath than my other gold one.)  The band is scrap, and there's an inscription, so now I've got to make the best of a bad job.

Again, it's astonishingly clean around the pusher switches.   I swapped the coils, but also found the accumulated minutes just chattered upon test mode.  It seems this has two separate faults and I found a minute blob of HARD blue stuff between two teeth of a wheel driving the a-mins.  I managed to make a tiny chisel and cut this out to some degree.  It now runs but will obviously need to be done properly.  The sweep second hand never budges, despite the gear train being smooth.  The hand does turn when wheels turned.

Circuit swap again, but this time I do fear the worst.  Nowt' else I can think to do. 

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In haste. Supposed to be working on doors.


February 12, 2014 at 4:04 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

Great.  ameri*pawn called me back after a PM to them.  I just asked if they 'could work with me on this'  and they say they will.  Calling me tomorrow as they're in a snowstorm now.

February 12, 2014 at 5:13 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

One of two or three faults on this movement is a defective coil.  Two point six ohms.  I thought it was okay, but I can see a wire sticking out at the opposite end to the contacts.  When I first checked it, it didn't show any continuity for a moment and then did.  I assumed it was just me not getting the probes onto the contacts.  Now I know it is intermittant - the scourge of electronic bod's fault-finding.  Any one know where I can lay hands on one?

February 15, 2014 at 10:44 PM Flag Quote & Reply

GeorgeClarkson
Member
Posts: 508
You could try at cousins.co.uk, or search for a 7Axx on ebay that comes at a cheap price and simply swap the coil
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My personal Blog: www.onlyvintagewatches.com/blog

February 16, 2014 at 4:33 AM Flag Quote & Reply

Rob Benham
Member
Posts: 281

I found a lot of coils generally, but not one for mine.  I should have said two point-six k of course. 

I spent an age last night trying to join the wires.  If I'd had my microscope I feel I might just have done it.  Eventually one end fell off and it was all over.

I would like to get the part in the US if possible - by the time I've paid for it and shipping from the UK I'd be part way to an old banger for spares. 

February 16, 2014 at 4:54 PM Flag Quote & Reply

GeorgeClarkson
Member
Posts: 508

That would be better, indeed... Source an old battered 7Axx, all coils are basically the same.

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My personal Blog: www.onlyvintagewatches.com/blog

February 17, 2014 at 2:35 AM Flag Quote & Reply

donwatch
Member
Posts: 568

Rob, I have a couple of 7a coils I can send you ---so you can complete your trouble shooting.  :)

February 17, 2014 at 12:05 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

My dear fellow!  That would be fantastic.  After two hours last night the only ones I found were with cousins and they will only send to the address tied to the card.  Please see my message.

February 17, 2014 at 3:57 PM Flag Quote & Reply

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