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 ’50s. Also, the crystal was in very bad shape. So is the case and the bezel but unfortunately I can’t do anything about that. Let’s take a look at it.
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.
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.
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.
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.
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.
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.
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.
The wheels and the train wheel bridge are next.
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.
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.
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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