Service: Eterna Dress Watch with In-house 520U Movement

 In Watchmaking

This week an Eterna dress watch that’s part of a batch from Poland.

The movement is the Eterna 520U with 15 jewels and a hidden ratchet wheel and crown wheel. It’s Eterna’s first caliber for gent’s watches. The serial number dates this watch to 1952.

This watch did run but it was a mystery when it was last serviced. The crown was bent and the crown action between the two positions was sluggish.

Disassembly

As always, it’s important to remove all power from the mainspring. Because of the design, the click is located underneath the barrel bridge so you’ll have to reach through the hole with a cocktail stick or a watchmaker’s pick to move the click away from the ratchet wheel.

Slowly let the crown slip between your thumb and index finger or you may damage the mainspring.

Eterna dress watch with Eterna 520U movement

Talking about the crown…Here you can see that the crown is crooked. I ordered a new one in the US.

Remove the balance and the pallet fork with the pallet cock and store them somewhere away from harm and dust.

Turn the movement around and lift the cannon pinion.

Eterna dress watch with Eterna 520U movement

Balance and pallet fork removed. The red arrow points to the access point for the click.

The escape wheel bridge and the wheel-train bridge are two separate parts in this particular watch. Lift both to gain access to the wheel train.

Eterna dress watch with Eterna 520U movement

The escape wheel bridge and the wheel-train bridge removed.

At this point, it’s difficult to lift the center wheel because it’s underneath the barrel bridge and the ratchet wheel. It’s safest to begin with the center wheel because then you can lift the wheels straight up without having to wiggle them from underneath the next wheel.

The barrel bridge is divided into two separate parts as well. One for the ratchet wheel and the click and one for the crown wheel. Remove both so you can lift the wheel train, starting with the center wheel.

Eterna dress watch with Eterna 520U movement

Both parts of the barrel bridge from below. Make sure to disassemble these parts further. The crown wheel uses a regular screw.

Remove the barrel to complete the top plate.

Eterna dress watch with Eterna 520U movement

The top plate empty, apart from the set lever screw. Note the dirt around the barrel arbor hole. It’s a good idea to remove dirt like that with a peg wood or cocktail stick before you clean it in the watch cleaning machine.

Flip the movement around to start with the bottom plate.

Eterna dress watch with Eterna 520U movement

The bottom plate with a broken set lever spring.

As you can see, the set lever spring is broken. The broken part is in between the cover plate and the return bar spring. This caused the sluggish feeling of the crown between the positions. I ordered a new one.

Remove the set lever spring (and the broken part) and lift the minute wheel, the setting wheel, and the intermediate wheel. Then, lift the return bar spring and the return bar.

Flip the movement around to remove the set lever screw and lift the set lever from the bottom plate.

Eterna dress watch with Eterna 520U movement

The bottom plate completely empty.

Pre-clean as much as you can with a peg wood. The bearing jewels, the pallet stones and the pallet fork crown need some extra attention.

Clean all the parts in the watch cleaning machine.

Assembly

Always begin with the set lever and its screw. It’s a fiddly job so it’s easier without any extra parts installed.

Fit the barrel. Place the escape wheel, fourth wheel, third wheel, and center wheel in position.

Eterna dress watch with Eterna 520U movement

The barrel and the wheel train installed.

Reinstall the escape wheel bridge and the wheel-train bridge. Make sure to keep testing the wheel train while you’re installing these bridges. Everything should spin freely.

Eterna dress watch with Eterna 520U movement

The escape wheel bridge and the wheel-train bridge installed.

Reassemble both barrel bridge parts. Place the one with the crown wheel in position and screw it down.

Install the ratchet wheel on top of the barrel arbor and place the barrel bridge part over it. You’ll need to wiggle the ratchet wheel because the click and the crown wheel have to fall into place.

Eterna dress watch with Eterna 520U movement

The ratchet wheel. the crown wheel, and both parts of the barrel bridge installed.

Turn the movement around to begin work on the bottom plate.

Place the clutch wheel and the winding pinion in position and install the winding stem. Fit the return bar and the return spring, the setting wheel and the intermediate wheel. Make sure that the setting wheel has the rounded part at the bottom.

Lubricate the bearing jewel for the third wheel and fit the minute wheel.

Place the (new) set lever spring in position and screw it down.

Eterna dress watch with Eterna 520U movement

The bottom plate completely reassembled with a new set lever spring.

Turn the movement around to install the pallet fork and the pallet cock. Test the wheel train by giving the crown a few turns. The pallet fork should snap to the other position with the lightest touch.

Install the balance and if it doesn’s start to move on its own, give the movement holder with the movement a small flick.

Now, it’s time to clean the shock protection system which is the Eterna-U device in this case. This is almost the same as with an Incabloc.

Unhook the spring and lift the endpiece and the jewel hole. Clean them with Onedip or similar, lubricate them and reinstall them.

Fit the hour wheel and the washer and fit the dial and the hands. Blow the dial and the inside of the crystal clean with the dust blower.

I always place a lint-free tissue for watchmakers on top of the casing cushion and place the movement with the dial on top of that. Slide the case with the crystal over the dial and the movement and carefully turn everything upside down while holding the case and the casing cushion. Now you can reinstall the winding stem and secure the casing screws.

Eterna dress watch with Eterna 520U movement

What do you think of this Eterna? Do you have one in your collection? Let me know in the comments below.

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