Help With Tissot

[Outatime]

Hello friends!

 

New to the forum and new to watch collecting in general.  Maybe some of you will have an answer to my question.  I received a 1967 Tissot Seastar in pieces the other day.  By pieces i mean the movement, case, glass, and two screws.  After putting everything back together I am finding that the movement is losing time.  After a good wind and letting sit it keeps great time for about an hour then the movement starts losing time and ends at a half an hour behind compared to my other watches.  The funny thing is, it keeps great time after it loses that initial half hour.  Any ideas or suggestions to why this is happening?  

 

Some observations to help:

 

-The movement is a Tissot 782-1 Unadjusted 17 jewel manual wind

 

-I am noticing that  when i wind it balance wheel speeds up greatly compared to when it sits for a few hours

 

 

Thanks for your help.

[swordfish]

If it runs slowly during the first hour or two, and then at a proper rate for about 20 hours or so, check to see if the hands are slipping (relative to their posts) or dragging across part of the dial.

[rogart63]

Slipping mainspring? or the cannon pinion? But my guess is the mainspring? Try winding it up but not to the bitter end. What happens then?

[Outatime]

Thanks for the replies,

 

Swordfish, it does not run slowly for the first hour, it keeps time for the first hour or so then starts to slow to approx. 30 min behind my other watches and remains at that rate.

 

Rogart63, refer to the third line in my post to answer your question.

 

Thanks for your help.