The Seagull ST3600 Low amplitude performance problem (Unitas 6498)

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When working with this movement for illustrating the lessons in my Watch Repair Course, I have perhaps stripped it down and re-assembled it some 5 or 10 times in the past month.

The last time I did this was during the Live stream and once it was assembled the watch gave a very low amplitude. I did not show this in the stream as it was then past 10pm and I had dinner waiting for me, but when I came back to the movement the following morning, sure enough it was running with very poor performance.

The performance picked up just as soon as I slightly loosened the balance cock screw and so this led me to believe that the balance staff had no end to end play (called end-shake).

My initial thought was that, this being a clone movement, maybe it was fitted with different sized end-stones. I had removed both incabloc settings during the live show and so, I wondered if I had replaced them wrongly – as you can see, they look identical – but sometimes you do get them with slightly different thicknesses and, 1/100th of a millimetre can make a big difference. In this situation, replacing the incabloc settings the wrong way round can cause exactly the symptoms I was observing.

After checking that it was not an even simpler problem – like a rogue hair lodged in the balance spring or the like, I took out the incabloc settings and swapped them around.

Confusingly, this did not resolve the problem. In fact, the watch movement was running with just the same low amplitude performance.

Again, loosening the screw resolved the issue and so, yes it is definitely an end-shake issue.

I removed the balance and took a closer look and noticed a small dot in the lower main plate where the balance cock sits.

Once little trick some watch repairers will do in order to make fine adjustments to the balance end-shake will be to make a bump in the metal where the balance cock sits in order to lift the balance cock very slightly upwards and allow the balance staff more play.

This practice is frowned upon by many watch repairers but other watch repairers who try to keep repair costs down for their customers will have no problem with it – the purpose of this video is not to open a discussion about wether this is good practice or not, but I was fairly surprised as this movement was brand new when I purchased it and had never even been installed into a watch case.

I have another of these movements and so I thought I would take a look and see if that had the same issue, and sure enough – yes, a small dot where the balance cock sits indicating that the Chinese manufacturer for this Seagull movement makes it common practice to make fine adjustments of this sort.

The purpose of this video is to point out this issue. I am sure that after removing and re-fitting the balance assembly several times, I had flattened the dot made by the manufacturer to a point where I had reversed their adjustment.

A simple case of making a fresh dot with my screwdriver, allowed the balance to be lifted up and now the movement is running like a champ again.

On the whole, these Chinese clone movements are very good, especially for the money you pay for them. However, they do not come without their quirks, and this is one of them.

I hope you found that information useful

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