No, the Miyota 90S5 is not a drop-in replacement for the Seiko NH35. Don't even think about trying it.

I'd also suggest that a watch you "truly like" should not be the first watch you open for tinkering.

 

On its second NH35 in how many years...and why are you seeking to replace a serviceable movement?
This is watchmaking...we tend to repair movements here and replace only as a last recourse.

Regards,
BG

 

I use the Armida as a beater and don't feel the $130 for a service is worth it. I could have a new nh35 put in for under $90. I did purchase one of the recommended books from the sticky above. After reading up a little more maybe I will try to tackle the service myself. The Armida is my cheapest automatic, and the one I would least feel guilty of messing up. I had a russian watch that I had sent back to Russia for a $50 service. That guy did a great job, but he only works on russian watches. I just have to stop knocking the Armida off the night stand, dresser, bathroom counter, etc. I'm using a Casio Oceanus now and I hate to have to look to the manual to do anything with it. Plus the lume is non-existent. I do work on my cars, house, and electronics so the mechanical aspects of working on the watch interest me.

 

A "brand new" NH35 should be serviced before installing in a watch...no way of knowing how long since manufactured and the factory servicing tolerances are just about as broad as their manufacturing tolerances. What is your definition of "accurate time". (I have a stopped watch that is correct twice a day).

Regards,
BG

 

Seiko and Miyota movements and cases/dials are not cross-compatible. Figure out a different plan.

 

... It is no longer keeping accurate time ...

As what the others have already mentioned, switching to a totally different movement is not so easy. things that needs to be considered:

• will the movement fit the case
• can the movement be secured properly in the case; else it will be shifting about and pulling out the stem to set time would stress the dial/movement connectors
• will the spacer ring fit the new movement
• will the dial feet fit onto the new movement
• will the old hands fit onto the new movement
• can the case back close securely if the new movement is too thick
• the stem needs to be cut to length

If the movement is no longer keeping accurate time, it's possible to regulate the watch by tweaking the balance wheel ("stud carrier"). There are quite a few good youtube videos that describes the process (search "regulate automatic watch NH35". There are inexpensive apps ("timegrapher") that run on mobile phones that helps u time the tweaking.

I have a 20yr old Seiko watch using 7S26 movement that slowed down. I just tweaked the balance wheel to make it go faster. So far so good. I know it has to be serviced but I lack the skills and equipment, oils to do so. Probably replacing the whole movement would be fastest thing for me.

 

Why do you think it's not keeping time? Or how much is it varying by?

 

To regulate the balance could be a good excuse to open up the watch for the first time. But be extremely careful around the balance; that hairspring could be damaged easily. Without a timegrapher, you still can make your watch highly accurate by making very small adjustments over several days. If you're going to tinker with watches, this is a good first skill to acquire.

If your watch is otherwise running ok and undamaged, I'd leave the movement in place.

 

If you want to start tinkering just order the correct movement based on winding crown position and do the swap yourself. The hardest part is setting the hands. If you ask me, I would not try to regulate the movement without having a timegrapher. Pay attention to the color of the movement spacer in the watch ie grey or black and if the replacement movement you purchase has the same color then fine otherwise you will need to swap over the spacer to the new movement. Lots of YT videos to watch. I would highly recommend good optics that have long eye relief, I use a 7x Optivisor and I have two one at home and one in my workshop, I find them invaluable. Since tweezers are your fingers when it comes to watches a nice pair of Dumont tweezers cannot be beat And last but certainly not least are these two inexpensive items, Rodico and a gasket greasing tool will both earn their keep IMO. YMMY of course.

 

Thanks for all the replies, and now to answer some questions posed. The watch is running at least 50 seconds slow. I need to reset every few days, where I want to reset once a month. Once I get my watch repair book delivered, I will try to regulate it myself. I have the old movement as well, in case I break something. I appreciate the tool advice as well. You can NEVER have too many tools.
I think this idea of watch repairing will join my other depreciating assets hobbies, such as RC aircraft, kites, G scale trains, knife making (love that forged in fire show), candle making, soap making.

 

Thanks for all the replies, and now to answer some questions posed. The watch is running at least 50 seconds slow. I need to reset every few days, where I want to reset once a month. Once I get my watch repair book delivered, I will try to regulate it myself.

50 seconds per day is likely to be within that movement's range of regulation. There have been times when I was aiming for a change of 10spd but moved the arm too far and got close to 50spd instead.

 

Don't get into soap making or candle making. The professionals do it better and your wife will always complain about the smell or the texture of them.

 

One of my goals in my soon to start retirement is to buy a propane forge and a triphammer, also an electroplating rig for my automotive hobby.

 

I like the Armida very much and I want to return it to my wrist. But I also want to have it be at least +- 10 secs. If I can't regulate the NH35 movement, I'd like to replace it with something more accurate.

 

Your desire for ±10spd coincides with my own personal standard for Seiko movements. I expect my Swiss movements to run within ±5spd.

Two of my five NH38A movements were accurate to within 1spd when averaged over the most recent week I wore them. Two of the others have been running within ±10spd. The one NH38A that averaged slightly worse than ±10spd for its most recent week of wear had been running within ±5spd, and I'll be re-regulating it unless it returns to ±10spd.

It is considerably easier and less expensive to regulate a Seiko NH3x than to replace it. Regulating it is several orders of magnitude easier than replacing it with an incompatible movement.

 

Serviced and not otherwise abused or neglected, the NH35 should easily be -10/+10 spd.
The key is "serviced" and as mentioned above, do not expect that "new" means "serviced".
Regards, BG

 

After reading a couple of books about watchmaking and repair, I've decided this is one hobby that is not for my nervous fingers. I might get a timegrapher to maybe regulate this watch, but other than that, I wont even think about messing with movements with their intricate and very tiny, tiny, tiny parts.