What could be blocking this Unitas 6428?? (VIDEO)

[ign03]

I recently bought a new watch (sold last year) with a NOS Unitas 6428 movement in it. The owner mentioned that the watch was fully wound but didn’t run. The first thing I did when I receive it was to release the tension of the mainspring, wind it again and check if something happened. Nothing. However, I realized that when the watch is fully wound, if I turn a bit more the crown (just a quarter of a turn until it blocks because the mainspring is already coiled) and keep it in that position, the train of wheels seems to unblock and the watch starts running. When I release the tension from the crown the watch stops again.

Yesterday I had a bit of time and I decided to disassemble it to try to find the issue. I removed the escapement, crown & ratched  wheels, barrel, mainspring, and the train of wheels except for the center wheel because I was not able to remove the canon pinion (not with my canon pinion remover nor the presto tool). I inspected every part, cleaned them and assembled it again and tested the free running of the train of wheels, balance, pallet fork, jewel holes, etc. only to find that the issue still persists.

VIDEO: 

 

 

Now I’m thinking that the issue could be in the keyless works or perhaps a too tight canon pinion that somehow causes a blockage in the movement. But, if that’s the case, why does everything unblock once I turn the last bit on the crown? Could a tight canon pinion cause this? If not, does someone have any idea about what could it be? I wanted to think this through before trying to remove the canon pinion by force with some hand removing tools or tweezers (also, advice appreciated), but I can’t think of anything that makes sense.

Thanks!!

[grsnovi]

38 minutes ago, ign03 said:

I’m thinking that the issue could be in the keyless works

I didn't watch your video. In your description you talk about servicing the train but you mention nothing about the keyless works. Since you seem to get results with the crown, I would suspect something between the stem and keyless components.

[Randy55]

I think that you may have to get that canon pinion and center wheel off in order to know.

I'm thinking that there is a rust/ seizing condition going on that is stopping power from moving through the train unless you use excessive force ( via the crown ).

Also verify that your barrel cap is on completely, and not riding against the plate.

 

Edited June 21, 2022 by Randy55

[Saldog]

When winding, the crown/stem doesn't engage the cannon pinion. If setting the watch is high effort, the cannon pinion is too tight, but if it is normal, it is not that. My guess is that what you are doing with winding is changing the alignment of the barrel arbor such that it supplies power to the center wheel without pushing it out of alignment or binding with it. I would bet it is barrel arbor end shake/wobble that is the culprit here. Possibly center wheel pivots/bushes alternatively. But misalignment will prevent the gears from meshing together correctly and cause binding.

[Klassiker]

Remove the balance with the mainspring fully wound. Does the pallet fork flick back and forth enthusistically If you unlock it? If it does, your problem is in the balance assembly, if not, it's in the train.

Let the power down again. Take out the pallet fork. Does the escape wheel spin as soon as you try to wind the mainspring? If not, take out the train wheels one by one working back to the barrel to find the blockage.

[nickelsilver]

A tight canon pinion will not impede the running. Putting additional pressure on the crown at full wind adds a lot of additional power- like, a lot, so no big surprise if it sort of runs when doing that. Klassiker has laid out the correct basic checks, only thing I would add is the pallet fork should snap back and forth cleanly with just 1/4 (or less) turn of wind on the barrel.

 

I've seen NOS movements that had the original oil so gummed up it took multiple cleanings through a professional machine with full pegging of the jewels each time to finally get it to run correctly. Just a little gumming of oil at the pallet fork hole jewels will completely stop a watch from running. Normally these aren't oiled, but I see gummed up oil there so often I always peg those holes.

[Nucejoe]

I bet you didn't check end shakes on all arbours.

A ballance with faulty pivot may seem to be turning freely when you shake the watch,  by puf of air or when forced through the crown,  yet fail to oscilate by the torque watch supplies. 

Check if the roller table rubs on fork horns or barrel lid rubs on its bridge. 

Good luck pal.

[canthus]

Have a look at 'Chronoglide' on YouTube.  He covers many of these checks and their effects on the running of a movement. Live streams are a bit pedestrian but edited versions cover the salient points.