Overhaul Procedure – Omega Seamaster 300 (Omega 1120)

Up today is a fairly straightforward overhaul of an Omega Seamaster 300 with an Omega 1120 movement. An 1120 movement is basically a glorified ETA 2892. There are a few differences that Omega made, but nothing major. The ETA 2892 is a great workhorse of a movement which doesn’t always get a lot of love, but it’s a solid caliber.

Here is the watch in question.

I put the watch on the timing machine to see what we are dealing with. As you can see it’s not running well even at full wind.

I then unscrew the caseback so that we can begin dismantling.

Next, I remove the automatic block.

The hands & dial are then ready to be removed.

With the dial and hands removed I expose the calendar, winding and setting work.

I then remove the dial side work.

Then the movement side is ready to be tackled.

Once I remove the barrel bridge you can see how dirty it is under there.

Once dismantled, the watch is ready to be put through the cleaning machine.

Once cleaned, the movement is ready to be assembled.

First, a new mainspring is installed in the barrel.

I then assemble the underside of the barrel bridge. With the cover off.

With the cover on.

The barrel and the gear train are installed.

Then the bridges.

Next, the pallet fork & bridge.

Then the balance is put in place.

I can now initially check the time-keeping. With no adjustments yet, we can see that the service rectified the amplitude and time-keeping results. The beat error is a little off, but that can be adjusted. A good reason why regulating a watch when it needs service is not a viable option.

Now that the watch is running well, the winding and setting work is installed.

The rest of the calendar work is then put in place.

Dial and hands are put on.

Once cased the automatic work is assembled.

Then installed.

The watch is now ready for testing.

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