Service: Eterna Dress Watch with In-house 905 Movement

This is an Eterna dress watch that found its way onto my workbench. The serial number is 2892981 which places this watch in 1941.

The movement is the Eterna 905 movement. Bestfit tells me that it’s interchangeable with the ETA 825.

The two-tone dial is still in good shape, but the hands are a mismatched pair of non-original ones.

Last but not least, it doesn’t run at all. So, here we go.

Disassembly

Remove all power from the mainspring before you start working on the movement. In this case, it’s extra important since the watch is fully wound. The mainspring didn’t have a chance to transfer its power because it was a non-runner.

Move the click away from the ratchet wheel while slowly letting the crown slip between your thumb and index finger. I like to use a cocktail stick because the wood is hard enough to move the click, but it’s soft enough not to leave any marks.

Remove the balance and the pallet fork with the pallet cock and store them somewhere safe.

When I checked the moving wheel train from the side, I noticed that the 3rd wheel was very wobbly. I always write my findings down to investigate or sort it out later.

Lift the cannon pinion on the dial side of the movement. It’s easier to do it now than with the wheel-train bridge removed. You won’t be able to lift the center wheel with the cannon pinion in place.

Lift the wheel-train bridge and remove the crown wheel and the ratchet wheel. This will make it easier to lift the center wheel.

The crown wheel screw is left-handed although it’s not marked as such so be careful.

Lift the center wheel, third wheel, fourth wheel, and escape wheel. I noticed that the 3rd wheel was wobbly because of a bent top pivot so I ordered a new one.

Disassemble the click and the click spring and lift the barrel bridge.

Take out the barrel.

Flip the movement around to work on the bottom plate.

Remove the motion works and the keyless works. You can see that the minute wheel is corroded. I ordered a new one because it caused friction with the set lever spring.

Pre-clean the pivot holes and bearing jewels with some peg wood. Don’t forget to remove the bottom balance end stone to clean it separately.

During the inspection of the mainspring, I noticed that it’s probably still the original mainspring. At least, it’s an old one because it’s a blue type without the S-curve.

Clean all the parts in the watch cleaning machine.

Assembly

Fit the barrel (with the new mainspring), the escape wheel, the fourth wheel, the (new) third wheel, and the center wheel.

Install the wheel train bridge.

Install the barrel bridge, the crown wheel, and the ratchet wheel. Don’t forget the bushing for the crown wheel.

The wheel train spins freely without any friction, and the third wheel isn’t wobbly anymore.

Turn the movement around and fit the motion works and the keyless works.

Flip the movement to the top plate and reinstall the pallets.

Wind the watch a couple of times to check the pallet fork. If the wheel train spins freely, the pallet fork snaps to the other position with the lightest touch.

Place the balance in position, and the movement should come alive. It might need a little flick to jumpstart it.

Sadly, the movement doesn’t keep accurate time. It’s all over the place.

The movement does run, and it has a decent amplitude in the dial-down position. However, it runs much too fast.

In the dial-up position, the timekeeping is horrible.

The wheel train spins freely, and the pallet fork snaps with the lightest touch. That means that the problem is with the balance.

If you look closely, you’ll see that the hairspring is kinked to the left of the regulator and the distance between the windings on the left are smaller than those on the right. I guess that someone tried to move the regulator while the regulator pins were too tight. That caused a kink and distorted the whole hairspring.

The balance complete for the Eterna 905 and ETA 825 are obsolete, and I can’t find any on eBay. That means that the hairspring has to be manually manipulated.

Unfortunately, this is way beyond my skills, so I don’t feel comfortable doing that. Especially without a safety net in the form of a new balance complete.

This one has to be repaired by an experienced pro. It sucks but that’s just how it is.

---

Do you also have fits of crying because of problems with the balance or hairspring? Let me know in the comments below.