Restoration: Zentra Watch

 In Watchmaking

This Zentra watch ran too fast and sometimes stopped. The movement is an FHF 70 and I’d date this watch to be from the late 50’s. Also, the crystal was in a very bad shape. So is the case and the bezel but unfortunately I can’t do anything about that. I decided to take a look at it.

Zentra watch

You can’t miss the sorry condition of the crystal. It hides a beautiful dial underneath

Disassembly

I remove the crown and the remaining case screw. Then I remove the bezel with the crystal and afterward I remove the hands and dial.

Zentra

The FHF 70 movement. It’s missing the upper right case screw as well

Zentra watch

The dial side of the FHF 70. I noticed that the set lever spring is broken so I’ll have to fit a new one

First, I remove any power from the mainspring. To do that I hold the click away from the ratchet wheel whilst letting the crown slowly turn between my thumb and index finger. After that, I remove the balance and the pallets.

Zentra watch

Balance and pallets removed

Flip to the dial side. I remove the set lever spring (broken) and afterward I continued with taking out the motion works and the keyless works. This is important because normally, you can’t pull the center wheel without having removed the cannon pinion.

Zentra watch

Dial side all cleared. I forgot the endstone for the balance so I removed that after I took the picture

 

Flip back to the other side and lift the ratchet wheel and the crown wheel with its shim. After that, I can pull the barrel bridge.

Zentra watch

Ratchet wheel, crown wheel, and barrel bridge removed

Then I take off the train wheel bridge to expose the train wheel. I noticed that the bearing jewels are gummed up and there was some dirt between the escape wheel and the fourth wheel. That was probably the reason of the Zentra watch running too fast (lower amplitude=faster rate) and why it sometimes stopped running.

Zentra watch

Train wheel and main barrel

Then I lifted the wheels and the main barrel. I clean most of the grime and dirt with a peg wood, with extra attention to the jewel holes (both sides). I put everything in the watch cleaning machine for 6 minutes per bath and another 6 minutes to dry.

Assembly

It comes out squeaky clean and I immediately start with putting the main barrel back. Before I do so I lubricated the mainspring with some Moebius 8200 and the barrel arbors with some HP1300.

Zentra watch

Just out of the watch cleaning machine with the barrel fitted again

The wheels and the train wheel bridge are next.

Zentra watch

Train wheel with the train wheel bridge securely in place

Then it’s time to fit the barrel bridge, ratchet wheel and the crown wheel with its shim. I lubricate the shim a tiny bit with HP1300.

Zentra watch

Barrel bridge, crown wheel and ratchet wheel fitted again

Now it’s time to flip it back to the dial side and fit the motion works and the keyless works again. I had a set lever spring for an FHF 70 in good condition so I fitted that. I had to turn on the light because it was getting dark, excuse me.

Zentra

Dial side all reassembled except for the hour wheel and the washer

Turn the movement back around to fit the pallets and the pallet cock and the balance. Afterward, I immediately cased the movement and fitted a new crystal. It runs great again and didn’t stop running anymore. The end result is at the top of this article. Apart from the chrome loss and wear of the case and bezel, I believe this Zentra watch is lovely.

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Jeanôt de Graaf