Seiko 7A38 - by the numbers

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Forum Home > Parts Info, Tech Tips and Tinkering > The 'crush' caused by the back.

Rob Benham
Member
Posts: 281

On one of the more erm, colourful ebay seller's watches, the inside of the back is shown.  It clearly has rotational scoring, some of it quite deep.  This focused some of my thoughts.

Since the Tachy ring is free to rotate until the back is on, and indeed the entire mechanism is held down as the back goes on, I suddenly realized my liking for the flat back gasket might not be such a good idea.  Is there a very specific 'crush'  or positioning of the writing on the back to indicate the correct position?



January 10, 2014 at 4:12 AM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14137

Rob. I've never actually tried to measure the gap between the top +ve side of the battery and a fully screwed-down case-back.

I'd suspect that it could possibly be measured in 'Engineers Blue', but I can assure you there's no 'crush' involved.

Couple of things I need to correct you on:

1) The Tachymeter spacer ring is only free to rotate until the dial / movement is put back into the case.

2) The movement is held in position by the crown / stem (to a greater extent) - without the case-back fitted.


Again, I've never torqued a case-back when tightening one down - you do it by instinctive feel (as tight as you can, basically) .... 

Without taking the risk of overdoing it and the case-back tool slipping out of the locating notches and gouging the case-back.

But always with the correct flat hard rubber gasket, either p/n FH3180B0A and FH3181B01 in place (on Seiko 7A38's at least).


January 10, 2014 at 12:22 PM Flag Quote & Reply

Seiko7A38
Site Owner
Posts: 14137

On one of the more erm, colourful ebay seller's watches, the inside of the back is shown ....


Assuming you are referring to a Seiko 7Axx (and not something else), perhaps you could share the eBay item # with us. :|

Perhaps we can suggest the cause of the 'rotational scoring, some of it quite deep'.

January 10, 2014 at 12:32 PM Flag Quote & Reply

Rob Benham
Member
Posts: 281

I did in fact look before posting but the photo, fairly unusual in that it showed the inside of the back, does not seem to be there. 

It was one of the Mainstream 7A** but with so many "This listing was ended by the seller because there was an error in the listing." and other excuses, it is sometimes difficult to know if one was dreaming. :roll:

The scoring in the surface was at two different radii and probably spanned 30 degrees.  It's hard to imagine just what cut the metal, but it wasn't the battery.  A screw left too high?  But even then, it's hard believe its head could inflict that cut.   I suppose someone could have left something in it!

The very fact they showed the inside seems to be a declaration of honesty.  But who knows, it might be that again they really didn't want to sell it.

January 10, 2014 at 4:59 PM Flag Quote & Reply

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