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Seiko 7005a


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Hi all, this is a question born of distraction and I’m sure it’ll get me some interesting replies. ?

is it just me or does anyone else have a problem lining up the escape wheel with the B&T bridge?  I’ve taken apart and (mostly) reassembled 6138’s and 6139’s and not had much issue. I thought, naively, that the 7005a would be a straightforward strip and rebuild to practice on but I’m continually stumped!  When I’ve finally got the escape properly seated, the rest of the gears refuse to move. Maybe I have too much time on my hands. 

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1 hour ago, LonglineOjoe said:

Hi all, this is a question born of distraction and I’m sure it’ll get me some interesting replies. ?

is it just me or does anyone else have a problem lining up the escape wheel with the B&T bridge?  I’ve taken apart and (mostly) reassembled 6138’s and 6139’s and not had much issue. I thought, naively, that the 7005a would be a straightforward strip and rebuild to practice on but I’m continually stumped!  When I’ve finally got the escape properly seated, the rest of the gears refuse to move. Maybe I have too much time on my hands. 

maybe the jewel is cracked. Never had any issues like this on any seiko 7xxx movements.

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I would add the gears in one at a time to see which one is jamming the gear train. 

The mainspring can also bind. Check for wear. And as above inspect all jewels.

This should be easy after a 6138 rebuild!

Good Luck.

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The seiko 7 series are usually straight forward.  Assemble it bit by bit testing at each stage, Barrel, the train, check. escapement wheel, check. fork/pallet, check action with one turn on the spring is it snappy  if so add the balance.  the thing is check the freedom of rotation at each stage.   You might find the attached sheet handy

Seiko 7005A.pdf

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    • I would go for the dearer spring. You won't need to remove the spring from the carrier ring and then use a mainspring winder to get it into the barrel, for a start. Also that spring is closer to the needed dimensions, especially the length. The length plays a part in the mainsprings strength. If you double the length you will half the force (strength) of the spring and vice-versa. A spring with 20 mm less length would be about 7% shorter, so technically would be 7% more strength, but I find halving this number is closer to real-world findings, so the spring would be about 3 to 4% more strength/force. On a mainspring that ideally kicks out 300 degrees of amplitude, a 3% increase in amplitude would be 309 degrees. Increasing or decreasing the length of the mainspring will affect the power reserve to a greater or lesser degree. It depends how much shorter or longer it is.
    • I recently bought this but not on ebay. I figured if I want something Japanese I better check Japanese auction sites since these don't seem to pop up on ebay. I paid 83 € plus shipping & taxes. I think it was pretty reasonable for a complete set in good condition.
    • Did you take the friction pinion off the large driving wheel and grease it? Although, now that I think about it, that shouldn't have any effect on the free running of the train if the friction pinion isn't interacting withe minute wheel/setting wheel...
    • I did in fact use Rodico to get the spring into general position and "hold" it there while I used a fine oiler to make subtle positional adjustments.
    • The two measurements of particular importance wound be the height and the strength,  the length would obviously correspond with the increase/reduction of half mm of barrel diameter. There is a big difference in price considering that the more expensive one is the shortest. The longer one might be ok ? But then it is taking up more room in the barrel, might it effect the unwinding ? I wouldn't have thought so for just that small amount.  Ideally a pro might reduce the longer one to suit. But there is some information that might help, do you have the one that was fitted to measure up, though not necessarily the right one.
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