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Seiko 7T42 Service Walkthrough


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I received this really nice Seiko 7T42-6A00 to service and the description was that the timer (yes, this particular 7Txx model has a timer also) was not working. After first inspection, actually I noticed that it had some more issues, among which the quickdate that was not working.

I made a video presentation of this watch: 

 

I decided to strip down completely the movement since it apparently had never being serviced. A movement swap was just not an option...

Opening the case no sign of damage was visible, although I did notice some very fine white dust, probably some acid liquid that had dried out. Removing the movement from the case, and inspecting it, showed indeed traces of dried up acid:

 

seiko_7t42_021.jpg

seiko_7t42_007.jpg

seiko_7t42_016.jpg

Edited by GeorgeClarkson
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A closer inspection showed a pretty common damage on the top plate of this series of Seiko Quartz movements:

The tip of the plastic top that covers the chronograph start/stop switch lever was broken. Interestingly, the missing part was nowhere to be found inside the case.

seiko_7t42_019.jpg

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Most impressive.  I've not yet even considered tackling a quartz movement and this one appears especially intimidating.  I'm anxiously awaiting your update.

Very pretty watch too BTW.

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7 hours ago, ro63rto said:

Looking good George.
Don't know many people that would tackle a 7t movement.

Can't wait for the next set.

Thanks ro63rto, I mostly appreciate that. This is the reason I do tackle them: nobody does, they usually swap the movement, but this is not watchmaking at all, only a commercial decision. And honestly, even if these watches are made mostly of plastic, they do have a soul of their own, and it would be a real pity just to have them sitting in a drawer with a leaking battery slowly eating them away.

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Great job and and a good looking watch. to bad there is so much plastic? 

What did you do about the missing plastic part?

Does the chronograph movement work without it? 

Edited by rogart63
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1 minute ago, rogart63 said:

Great job and and a good looking watch. to bad there is so much plastic? 

What did you do about the missing plastic part?

Does the chronograph movement work without it? 

The 7Txx series of chronographs from Seiko are basically all made 90% plastic, rogart63. As per the missing/broken part, I will replace the entire plate since I have still a couple of 7T32 movements that have identical structure.

As per the chronograph, it does work even with that broken off tip, but the switch lever could be misplaced if you'd were to press the pusher too hard.

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Hats off to you sir, WELL DONE! I have two 7T32's on the bench right now, one is complete and running, but no case or brace, the other I got in a pile of misc, thought just in case I needed parts. Those appear to be 'hot' items, since I have not been able to locate a inexpensive case to transplant running mov't to. Anyway if I have problems, your service will help! THANKS!

Dave

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Here it goes with the rebuilding of the Seiko 7T42 quartz movement... And let's start with the basics: the base plate!

I started refitting the rotor stators, the 2 golden switch pusher levers and the center wheel and pinion.

seiko_7t42__001.jpg

Edited by GeorgeClarkson
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