Seiko 7T62 repair--anybody taken one of these apart?

[LittleWatchShop]

A friend of a friend sent this to me for a battery replacement.  Simple enough, no?  Well, I discovered the alarm function did not work.  On further inspection I find this damaged coil.  How could that have happened???  It is a long way from the battery.

Anyway, I think I can fix the coil, but have never disassembled one of these.  Once the plate screws are removed, there are clamps on the side that latch to the plastic movement.  I am worried that once unclipped, all manner of movable parts will go flying.  Dunno.

Anybody serviced one of these?

[jdm]

31 minutes ago, LittleWatchShop said:

On further inspection I find this damaged coil.  How could that have happened???  It is a long way from the battery.

But it's close to the edge, maybe someone had removed it to clean under the crystal,  or the like. And coil wire can also break due to shock.

 

31 minutes ago, LittleWatchShop said:

Anybody serviced one of these?

If you can fix the coil removing the least stuff possible, that would be great. In any case just enter the mov.t number in the search box top right to be presented with the collective knowledge about it.

[LittleWatchShop]

Gonna try to fix it in situ.  Will report back.

[watchweasol]

Hi just in case you need them 

7630_Seiko 7T62A, 7T92A, 7T94A Part 1 of 3 (4).pdf 7632_Seiko 7T62A, 7T92A, 7T94A Part 3 of 3 (5).pdf 7631_Seiko 7T62A, 7T92A, 7T94A Part 2 of 3 (3).pdf

[LittleWatchShop]

This is great.  Looks like I can remove the circuit board  cover plate without much fear.  Then I can get to the coil. Thanks!

[watchweasol]

Your Welcome     good luck

[LittleWatchShop]

This is great.  Looks like I can remove the circuit board  cover plate without much fear.  Then I can get to the coil. Thanks!

[LittleWatchShop]

Fixed.  Had to unwind a couple of strands.  There were two breaks.  Twist and solder.  Did not try to clean up the mess...just made it ohmic.

The watch is working.  This was quite tiring to do!

[xyzzy]

You got the coil out without removing the plastic main bridge?  I didn't think you could do that.  One of the coil holes is on a post that protrudes from the base into the bridge.

The movement spacer ring is sandwiched between the movement and the dial, and the dial feet are not held with screws, just friction.  So handling the movement by the spacer can force the dial off into the hands and scratch it.  I haven't found a movement holder that does a decent job of holding these, especially with the dial ring on so the hands can be set.

[LittleWatchShop]

4 hours ago, xyzzy said:

You got the coil out without removing the plastic main bridge?  I didn't think you could do that.  One of the coil holes is on a post that protrudes from the base into the bridge.

The movement spacer ring is sandwiched between the movement and the dial, and the dial feet are not held with screws, just friction.  So handling the movement by the spacer can force the dial off into the hands and scratch it.  I haven't found a movement holder that does a decent job of holding these, especially with the dial ring on so the hands can be set.

It was tricky. I used a traditional Bergeon style holder. It camped securely to the plastic spacer ring. After removing the screws holding the ckt board, using two hands with pegwood in one, tweezer in the other, I lifted an removed each end off their respective posts. 

[LittleWatchShop]

1 hour ago, LittleWatchShop said:

It was tricky.

In retrospect, not sure how I got away with this...prolly a little luck on my side.  At the end of the day,  the movement was essentially non-functional.  Could not make it any worse.

[xyzzy]

I took a look at broken a 7T92 movement I had, which should be about the same as a 7T62.  The small coils are close to the edge and held down by a "peninsula" of the bridge.  So maybe it's possible to bend this enough to get them off?  The larger coils have the posts closer to the center and this wouldn't work.

But still, you must have bent the bridge quite a bit to get the coil off. You can see in this picture I'm bending the bridge up and there still isn't clearance to get the coil off the post.  The gap above the post needs to be maybe 5x-10x larger than it is for the coil end (center metal part) to be able to fit.  I'm surprised it didn't break.  Would have been a lot safer to take the bridge off.

[LittleWatchShop]

13 minutes ago, xyzzy said:

The small coils are close to the edge and held down by a "peninsula" of the bridge.  So maybe it's possible to bend this enough to get them off?  The larger coils have the posts closer to the center and this wouldn't work.

Probably correct.  The alarm coil is the closest to the perimeter (or is at the perimeter) and is also the smallest coil.

I have done a teardown and rebuild of a quartz movement before and it was not fun.  Did not take the time to figure out (even with the docs) what had to be removed and then refitted with the plate removed.  So, given that I had a backup plan I took the shortcut and it worked.

I take no credit nor assert that it was a brilliant plan executed flawlessly.

[xyzzy]

Maybe I should keep this a secret?  While these have a reputation as impossible or very hard to service, the reality is the design allows for disassembly and reassembly and it's quite easy.  Yes, there are a bunch of little wheels, but they all drop into place and the pivots all want to go into the right spot on their own as the bridge it put on.