Valjoux 7750 mainspring

Deggsy1969 · Apr 5, 2026

Good afternoon everybody, hope your all having a fantastic Easter break.

I’m servicing a Valjoux (not eta) 7750 in a Breitling Chronomat 81.950 (known as the plane Jane due to no branding) and have a few questions I cannot find definitive answers to on the internet orFacebook groups, so hope it’s ok to lump them all together here as one post.

1. The balance is not etachron, (instead it’s a simple stud fixing) but all references I am finding on the internet say that the balance for val and eta 7750 are compatible? I’m now wondering if the movement is a fake, or were the val 7750 balances non-etachron? Also the barrel parts are differently coloured (barrel nickel, cap is golden). Not sure if this is correct or not.

2. I’d like to install a new mainspring. Cousins seem to change specs on a monthly basis possibly to use available stock. My question: is there a definitive spec (dimensions) for the val7750 mainspring?

3. There is an option to procure a mainspring and barrel complete. Are these fit to install from blister pack, or do I need to strip it down, clean and apply braking grease to barrel wall?

4. Finally, if it’s correct that the val balance is not etachron and the movement is genuine, are there any other parts which differ? In particular I’m thinking about the balance jewels which under worst case scenario for me could become 😞

Thanks in advance for any help you can provide
Kind regards. Darren

Archer · Apr 5, 2026

D Deggsy1969
1. The balance is not etachron, (instead it’s a simple stud fixing) but all references I am finding on the internet say that the balance for val and eta 7750 are compatible? I’m now wondering if the movement is a fake, or were the val 7750 balances non-etachron? Also the barrel parts are differently coloured (barrel nickel, cap is golden). Not sure if this is correct or not.

The old Valjoux versions didn't use ETACHRON, at least I've never seen one that did. The balances are not the same obviously, since the stud is completely different on the two designs. An ETACHRON stud will not fit on the movement.

The colour of the barrel is just a function of it being plated or not. I've seen both.

D Deggsy1969
2. I’d like to install a new mainspring. Cousins seem to change specs on a monthly basis possibly to use available stock. My question: is there a definitive spec (dimensions) for the val7750 mainspring?

I would just order by caliber rather than size.

D Deggsy1969
3. There is an option to procure a mainspring and barrel complete. Are these fit to install from blister pack, or do I need to strip it down, clean and apply braking grease to barrel wall?

When using a barrel complete, the only thing you need to do is apply some 9104 to the spot where the barrel arbor meets the barrel drum or cover (so oil each side). There's no need to take anything apart.

D Deggsy1969
4. Finally, if it’s correct that the val balance is not etachron and the movement is genuine, are there any other parts which differ? In particular I’m thinking about the balance jewels which under worst case scenario for me could become 😞

You will find some small differences, but nothing significant. So for example the lock, 2 functions might look very different (crude) compared to the modern movements. I've never looked into the balance jewel differences, but there are charts out there that will tell you what you need.

Deggsy1969 · Apr 5, 2026

Archer
The old Valjoux versions didn't use ETACHRON, at least I've never seen one that did. The balances are not the same obviously, since the stud is completely different on the two designs. An ETACHRON stud will not fit on the movement.

The colour of the barrel is just a function of it being plated or not. I've seen both.

I would just order by caliber rather than size.

When using a barrel complete, the only thing you need to do is apply some 9104 to the spot where the barrel arbor meets the barrel drum or cover (so oil each side). There's no need to take anything apart.

You will find some small differences, but nothing significant. So for example the lock, 2 functions might look very different (crude) compared to the modern movements. I've never looked into the balance jewel differences, but there are charts out there that will tell you what you need.

Hi, thanks for the fast reply .. I’m very grateful for your prompt and informative response as ever. Definitely in the right place for help here, thank you. I’m relieved that the movement seems to be genuine. Thank you again! - and have a great Easter !!!🐣

Valjoux 7750 mainspring

Deggsy1969

Archer

Deggsy1969

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