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Discussion Starter #1 (Edited)
So, after being forced to "work" from home during quarantine and finding much time to do research, I decided to fix this watch myself.

Opened it up, took it apart, found out that the rubber seals for the chrono pushers have hardened over the years. These disintegrated into tiny little pieces within the pusher assembly.
Scraped them off and soaked the pusher buttons, springs, c-clips in lighter fluid, then wiped them clean.

Now on to the movement. No sign of acid leak, Anti-magnetic backplate was in pristine condition, circuit block had absolutely no damage. All good.
Removed the circuit block spacer and found out that all 3 of the lever actuators for the chrono had pitting and corrosion build up which fused it on to the mainplate.
Failure of the seals allowed moisture to creep in and do its work over the 37 years of this watch's existence. Thankfully the rotor stators and coil blocks were unaffected.

Took apart the mechanical movement and dabbed the rusted levers with WD40, then carefully peeled off the fused actuators one-by-one.
Mainplate was then cleaned off of all corrosion residue. Especially the tiny little 1mm pegs where the levers attach to pivot (this took microscopic scraping without a microscope!).
Sourced out a beaten up 7A48 for parts, and replaced the lever actuators.

Now everything works as it should. Just waiting on some Moebius, crystal, rubber seals, and the almost impossible to find Seiko S-6 oil in the mail and this should be complete.
All in all this was a thoroughly satisfying learning experience since I have never done anything like this before.

badly rusted actuators (sorry for blurry photo)
449188


blackened, heavily pitted levers
449189
 

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Nice little project! Those levers really took a beating over the years it seems.

Sent from my SM-G973F using Tapatalk
 

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Great stuff.

Shout out if you get stuck. That main bridge can be a massive PITA to fit sometimes.

Well done on finding the S-6. This was definitely not essential as you have the same results with HP1300.
 

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Hats off to you for this effort! Particularly as your first tinker. I have a 7a28-7040 with a sometimes-stuck 9 o'clock 30-second subdial (if I wear the watch for an hour or so it frees up, if it's cold it just stutters - suspecting some gummed oil). I haven't had the courage to dig into it yet as the main bridge scares me off and everything else works perfectly. Perhaps you've inspired me, though....
 

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Hats off to you for this effort! Particularly as your first tinker. I have a 7a28-7040 with a sometimes-stuck 9 o'clock 30-second subdial (if I wear the watch for an hour or so it frees up, if it's cold it just stutters - suspecting some gummed oil). I haven't had the courage to dig into it yet as the main bridge scares me off and everything else works perfectly. Perhaps you've inspired me, though....
7a28 is a great movement to work on but definitely only work on your own 7A28-7040 if you are competent as these have become extremely valuable. Find a cheap Gold 7a28-7029 and practice on that.

A service would get yours running like new.
 

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Discussion Starter #6
Yeah I have a 7A48 I am practicing on right now. It is intimidating so I'm taking my time with it. I have heard of the movement's notoriety.
 
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