Repair + Service: Omega calibre 620

The Omega calibre 620 is a fairly small movement – just 17.5mm diameter, 2.5mm high and hand winding without a date. With that sort of size, it’s meant to go into elegant, small wrist watches like this one. Neil sent it in as it’s not keeping good time, and I’m sure there will be a reason for that!

A very neat looking little movement.

The movement is way too fast, with a feeble amplitude and a big beat error. This could just be dirt, or something worse.

When taking apart the movement, I notice that the hairspring lightly touches the balance cock. That explains the timegrapher image – so I will have to reshape the hairspring a bit to make it fit properly. Not an easy task on a movement that small.

On the bottom plate, the set lever spring has broken off, and the missing bit is nowhere to be seen. Not a big deal, as I can get hold of a new one.

Everything ready for the cleaning machine.

The spare parts have arrived, and I start off with the new mainspring.

Just in case you didn’t know how much 17.5mm are 😉

Now that looks better. Having adjusted the beat error and beat rate, I get a much better timegrapher image.

The broken set lever spring (left) and the new one (right).

The bottom plate ready for the dial.

A truly classic Omega.

14 thoughts on “Repair + Service: Omega calibre 620

  1. Hi!
    Could You tell me is there a big difference between cal 620 and 625?
    I mean if, and if the answer is yes – then which parts od cal 625 can be used as spare for cal 620.

  2. I loved your blog – it was like watching open heart surgery but on a watch ! I’ve always found the inner workings of a watch fascinating and a great mystery. Thank you Christian for keeping these beautiful timepieces of the past functioning in a modern era.
    Best wishes,

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