WatchUSeek Watch Forums banner

Teardown: HMT Sona

9K views 26 replies 11 participants last post by  tony1951 
#1 ·
I've taken apart my HMT Sona and taken some photos - if you are interested.

Review: HMT Sona | Watch Guy

For the money it costs, a great watch!
 
#2 ·
The movement in the Sona is common to most if not all hand wound HMT'S . I find them to be very robust and see lots of watches which have not been used for ages, spring to life with a simple cleaning/service.

Thanks for the tear down. The close up pictures are awesome.


Sent from my iPad using Tapatalk
 
#5 ·
The movement in the Sona is common to most if not all hand wound HMT'S . I find them to be very robust and see lots of watches which have not been used for ages, spring to life with a simple cleaning/service.
Thanks for the tear down. The close up pictures are awesome.

Sent from my iPad using Tapatalk
Well, HMT is producing only one hand winded men's calibre as far as I now. It is a licensed Citizen, and is very robust and reliable as its ancestor. Good that in XXI century one can catch such a beauties on ebay any time !
wilderbeest - try to use the screw from Seiko 7009 if you have one, it will fit as far as I remember
 
#3 ·
Very interesting, thank you.

And I agree, cool close-ups. That one focused on the pinion on the escapement wheel is great.
 
#4 ·
Great photos! Too bad about the barrel screw. Whit a nice little movement that is inside. It gives me a new appreciation of my little Janata (thanks to Fateh, in fact!)
 
#8 ·
Nice pics and story! Just a tip: if your camera has a manual white balance preset (most do), put it in the custom preset and snap a photo of a white piece of paper under the same lighting. It will adjust the white balance correctly so you don't get the yellow overcast. This is easy to do and removes the color cast from lighting.
 
#14 ·
Ouuch!!!

After taking my new pilot watch apart to clean it (I found debris in it coming from the stem tube where there seemed to be some filler) I STUPIDLY managed to drop the movement about 30 cm onto my desk while the stem was fitted........ I was adjusting the hour hand to stop it touching the lume dots and it just slipped.

The stem hit the desk first and snapped off inside the watch.

I have removed the stub, but now have to track down a stem that will fit.

I should have left it alone.

Does anyone have a spare from a scrap watch?
 
#15 ·
Ouuch!!!

After taking my new pilot watch apart to clean it (I found debris in it coming from the stem tube where there seemed to be some filler) I STUPIDLY managed to drop the movement about 30 cm onto my desk while the stem was fitted........ I was adjusting the hour hand to stop it touching the lume dots and it just slipped.

The stem hit the desk first and snapped off inside the watch.

I have removed the stub, but now have to track down a stem that will fit.

I should have left it alone.

Does anyone have a spare from a scrap watch?
Not to worry, I got a winding stem from an HMT Janata - that will probably fit.

Shall I just ship it with the bumper when I do the hands?

Christian
 
#17 ·
My grandfather was an amateur watch-repairer, and I wish I had gotten into watches while he was still alive so I could fix my own stuff like you guys.

I recently got an HMT Jayanth (thanks Fateh!) that was working for 3 days until I tried to re-set the watch and pull the tiny crown. Long story short, my finger slipped and I think I pulled a little too rough, because now the dial moves when I turn the crown. And while the hands move, it feels like the crown loses traction at some point during a full rotation and spins freely for a few turns, before "grabbing on" again. The watch will run for about 20 seconds at a time before stopping. HMT is my first foray into mechanical watches so I don't know what's going on.

Trying to decide if this is worth servicing, since I have two sterling Janatas that work wonderfully and a Sona on the way.
 
#20 ·
It could also be a screw on back like this:



If that is the case, you can get a tool to grab it in those little detents around the edge and twist it off. The tool is not expensive, but if the back has not been screwed very tightly you might be able to turn it with a pin or even a fingernail.
 
#21 ·
This is brilliant information. Thank you. And yes, the caseback is exactly like the picture above. My Sona (which arrived today) and my newer-model Janata have snap-on casebacks, while the older Janata and the Jayanth (which has the crown problem) have screw-down ones. As I type this, the Jayanth is running. I have no idea how or why, but it's running just fine. It was fully wound when the problem occurred a few days ago, and I haven't tried to re-set it since. I picked it up today and swayed it back and forth like you typically do to start an automatic and it began ticking. It has continued for several hours.
 
#22 · (Edited)
If you wind the crown in the opposite way to normal, and then wind normally, the problem may disappear if the stem is properly seated when you pull it out as if to set the time. If it comes right out of the watch when you do that, then you will need to open the case and press that small button I was talking about as you gently press the stem back into the watch. Rotate the stem slightly as you insert it to make sure it is fitting in properly.

Please let us know how you get on. I am interested in this case.

Cartoon Clip art Illustration Graphics Line art
 
#24 ·
Hello everyone i signed up to this forum because i need some help. I bought an HMT sona and it is beautiful. When i opened it i wound it until i felt resistance and wore it but i noticed it was continuously stopping. I tried checking what caused this and sometimes movement (such as walking) or even just putting my hand down on the table would stop it. The would stop only until i noticed it and moved my hand. I tried swaying it a bit to make it tick but even in some cases it would stop a few seconds later. There are no instructions so i need some help on how to use the watch and i wonder if anything is normal right now. So far i swayed it and have laid it down on my table and it has been ticking for 5 minutes but then it stopped again, touching it provoke movement. What do i do?
 
#25 ·
No special instructions here - normally, you wind it, you wear it, it tells the time ;-)

If it stops, there is something wrong - and I can't tell what it is from what you tell me. Could be all sorts of things - worn out pivots, wonky wheels, worn-out mainspring, dirt, ... it needs looking at I'm afraid.

Unfortunately, the value of the watch doesn't really justify bringing it to a watchmaker. Shaking his/her hand would be more expensive than the value of the watch ;-)

Maybe a good project for your first venture into the world of watch repair?
 
#26 · (Edited)
Okay. I opened the Jayanth today. My dad has tools so I asked him to help. Anyway, with the Jayanth open, the entire movement seems to rotate when I try to turn the crown. If I pull the crown out, as if to set the watch, I can see nothing untoward happen, but the same phenomenon happens that I was describing before.

Also, one of my Janatas (the "new" one) is not broken or anything, but the crown is VERY sluggish when I try to wind it. It feels to me that it needs some lubrication, but I wanted to check here first. Maybe something is wound too tight?

Can you use "3 in 1" oil for a watch or does the oil need to be thinner?
 
#27 · (Edited)
There should be a plastic or metal movement ring in the watch to hold the movement still in the case.

Watch Circle Metal


This photo taken through my loupe with my phone shows the white plastic ring inside the case of my HMT Pilot (ignore the red arrow - that was for something in another thread). It isn't a great picture surrounded by the ring of the eye loupe, but you can see the crown on the left and the rim of the watch case with the white spacer ring and the movement in the centre.

If your Jayanth is an old one, it may have a metal spacer ring - I don't know, but without a ring to support the movement, I think the whole watch and the dial might move when you wound the crown. I am guessing your Jayanth has no support if it is moving as you say.

DO NOT use 3 in 1 oil in your watch. It is very prone to dry out and form a kind of stiff gum. I used it to wipe over shotguns in the past after they ahd been out in the rain on the farm and they ended up covered in a kind of soft varnish. This is the very last thing you want in a watch.

Some watches have stiffer winders than others. If you really fear it is dry, apply a tiny amount of watch oil to the winding mechanism, - but be warned - you are far more likely to harm the watch performance by putting oil in it unless you have learned about the pitfalls. Over oiling a watch is the worst thing you can do, so avoid it.

If it is a new watch, I would say you should leave it alone. It will be as it should be, most likely.

Let us know how you get on with the jayanth. If it has no movement ring and if you can't get one for it, there is some kind of paste that can be moulded to make a new one. It cures and sets and I saw something about it on here a week or so ago.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top