Eterna 1500K Rotor Removal (an oily mess)

G___ · Mar 8, 2026

Hello,

Does anyone have experience removing a rotor or winding assembly complete from an Eterna 1500K family of movements?

It appears that a 3-pronged tool would turn a locking ring to free the rotor. Asking before I go and try to bodge this (disclaimer, I'm a bottom-feeding hack) and muck the movement.

Also, shame on whomever "oiled" this watch. Did they just fill it from the back side with a couple quarts and call it good? I'm still cleaning the oil off the inside of the case after trip # 2 through the ultra sonic; not to mention having to de-oil the damn hands.

Thanks and regards,

Archer · Mar 8, 2026

My guess is that once you remove the automatic assembly from the movement, you will find three screws on the underside that you can undo to remove the rotor.

If not, then you may have to rotate that ring…

ErichKeane · Mar 8, 2026

The shape of the inside of that ring looks very much like some sort of cam-locking system. I'd put money on rotating it counter-clockwise unlocking the rotor.

That said Archer is likely ALSO right in that those 3 pins in the center section are probably the bottoms of screws, and how you do different diassembly (bearing + rotor + pivot instead of just bearing + rotor), and is probably 'just as good' of a disassembly.

G___ · Mar 9, 2026

Archer
My guess is that once you remove the automatic assembly from the movement, you will find three screws on the underside that you can undo to remove the rotor.

If not, then you may have to rotate that ring…

Thanks, I was pondering that as the other option .

G___ · Mar 9, 2026

ErichKeane
The shape of the inside of that ring looks very much like some sort of cam-locking system. I'd put money on rotating it counter-clockwise unlocking the rotor.

That was my thought, looks too intentional and clever.

Will need to determine the best way to turn it (2 or 3 old screwdrivers rotated as one?).

G___ · Mar 22, 2026

As I (and @ErichKeane) suspect, the ring is a cam locking system with a bushing and 7 tiny ball bearings underneath (blued steel). A stout screw driver in one of the slots facilitated the unlocking.

However, trying to reassemble (it isn't up for a full service, yet) has been maddening. I assume Eterna made a proper 3 pronged tool to maintain and even downward and rotational pressure. Without that, the cam ring wants to walk out of its location and then ball bearings get everywhere. I gave up after attempt #6 and after 2 of the ball bearings joined the Swiss Space Program (eff). Will reattempt and change the approach.

Got the dial, hands, and other bits cleaned of the green slime oil, however.

Archer · Mar 22, 2026

Yes that’s the problem. The three screws removed from the underside of the automatic bridge would have removed the rotor, but turning that key has disassembled the bearing, which is not a normal part of a service.

I would start by removing the rest from the bridge so you can properly support the inner race of the bearing as you assemble it. You may have to create a stepped support to ensure that the various parts are at the correct heights as you put it back together. You will also have to make some sort of tool, as these locking rings are much easier to remove than to install.

There are commercially made tools for the locking rings that hold the bearings in various rotors, such as the 2892 and 7750. But it would be pure luck if they have the right diameter and spacing for this job. The movement does resemble a 2892 though, so if you can provide some dimensions of the tool you would need, I can check it against the tools I have to see if it might be close.

G___ · Mar 22, 2026

Archer
Yes that’s the problem. The three screws removed from the underside of the automatic bridge would have removed the rotor, but turning that key has disassembled the bearing, which is not a normal part of a service.

I would start by removing the rest from the bridge so you can properly support the inner race of the bearing as you assemble it. You may have to create a stepped support to ensure that the various parts are at the correct heights as you put it back together. You will also have to make some sort of tool, as these locking rings are much easier to remove than to install.

There are commercially made tools for the locking rings that hold the bearings in various rotors, such as the 2892 and 7750. But it would be pure luck if they have the right diameter and spacing for this job. The movement does resemble a 2892 though, so if you can provide some dimensions of the tool you would need, I can check it against the tools I have to see if it might be close.

As always, many thanks Al.
Will let you know about dimensions if I can't sort it.