Service: Longines Advocate 9LT (25.17ABC)

This is a beautiful Longines Advocate watch. It’s in excellent condition apart from a scratch on the dial. It looks like somebody slipped while trying to lift the hands. It’s a real shame, but it happens, though I wouldn’t want it to happen with any of my watches. Or even worse, on a watch I’m working on that isn’t mine.

The serial number dates this watch to 1953. If you’d like to date your own Longines, you can try this Longines Year Identifier.

The movement is the Longines 9LT. It’s a movement with an indirect subsecond. I’ll come back to what that means later. This particular one is a 25.17ABC with a monometallic balance. There’s not much to find about this movement, except for the standard info.

This Longines Art Deco needed a service. The power reserve was way down from what it used to be, and it sometimes suddenly stopped.

Disassembly

Make sure to remove any power from the mainspring and lift the balance and the pallets.

Be careful because the pallet cock in these particular movements doesn’t have 1 but 2 jewel holes.

Remove the hour wheel and the cannon pinion on the other side of the movement.

As I said before, this movement has an indirect subsecond. In this case, that means that the 4th wheel isn’t the seconds wheel.

Instead, this movement has a pinion with a long pivot to attach the subsecond hand.

The 3rd wheel drives this pinion, and the pallet cock covers it. That’s why it has two jewel holes instead of 1.

Lift the train wheel bridge and then remove the wheels (escape wheel, 4th wheel, 3rd wheel, and seconds pinion.

The barrel bridge covers the center wheel.

Usually, you’d remove the ratchet wheel and the crown wheel. However, in this movement, the crown wheel is secured by three small screws from below. The click-spring is on the back of the barrel bridge as well.

Remove the ratchet wheel and then lift the barrel bridge.

Lift the center wheel and remove the main barrel.

Flip the movement to the other side. Start with removing the set lever spring.

Then remove the rest of the motion work and the keyless works.

Clean all the parts in the watch cleaning machine. I use L&R #566 cleaner and L&R #3 rinsing solution.

While the parts were being cleaned, I polished the crystal. You can read this article if you like to know how to polish a watch crystal.

Assembly

Start with placing back the wheel train and the main barrel. Remember that the barrel bridge covers the center wheel, but it needs to be under the wheel train bridge as well.

Lubricate the bearing jewels of the wheel train bridge with Moebius 9010 or similar.

Remember to fit the crown wheel first (from the back) and reinstall the barrel bridge. Fit the ratchet wheel.

Lubricate the center wheel with Moebius HP1300 or similar.

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

Lubricate the shaft of the center wheel with Moebius 9501 or similar before you fit the cannon pinion. Use the same grease for the keyless works as well.

Lubricate the bearing jewels (except for the one for the pallets) with Moebius 9010 or similar.

Turn the movement around and reinstall the second’s pinion (remember to check if the spring is on the right side).

Reinstall the pallets. Be careful because the pallet cock covers both the pallets and the second’s pinion. Keep testing while you gently push down the pallet cock a little at a time. Lubricate the pallet’s exit stone with Moebius 9415.

Reinstall the balance and enjoy watching the movement come back alive.

I like to keep the movement running like this to see if it runs steadily and to test what the power reserve is.

The 9LT kept running for 45 hours, so that’s not bad at all.

I fitted the hour wheel and a washer (that was missing) and re-cased the movement with the dial and hands.

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Do you have a Longines Advocate or a similar Longines Art Deco Watch? Let me know in the comments below.