Help with ETA movements please

[Deggsie]

Hello. I am trying to source a hair spring (does not need to be balance complete) for an ETA 2408. Could you please advise if the hairspring on an ETA 2390 is compatible, and for my own future reference, how do I find such information please? Kind regards, Deggsie

 

 

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[HSL]

The hairspring often are matched by what they call vibrations, so the first you should look so it vibrates/oscillates at the same frequency. Next you have to match the diameter of the spring with the diameter of the balance Wheel. If they are the samme then it might work.  next you look at the balance staff, If these are the same the chances for success has increased enourmously since the collar on the hairspring will sitt tight on the balance staff.
At RANFFT you can find the most except the diamater of the balance Wheel.
http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&2&2uswk&ETA_2390

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&2&2uswk&ETA_2408

Edited March 27, 2019 by HSL

[Deggsie]

Thank you for your reply. It seems it will be taking quite a chance to buy the eta 2390 spring in the hope all the criteria match when I receive it. I think I will hold on an wait for the eta 2408 to come along on eBay. I might be lucky - no hurry. Thanks again, Deggsie


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[Nucejoe]

Compatable , a HS out of eta2390 fits on 2408, streigtht away also the space to accomodate the guest is readily available in the new surroundings, the main problem remains, the new  HS and BW team should vibrate to the design beat together, For instance to 18000 beat/ hr. That is how many loud beats we or timegrapher hears per hour.   At this point you are dealing with the length of the HS. The longer the length the longer the period.. To get the beat you need for time keeping of the watch, the only alteration at our disposal is to shorten the HS preferably in increments to approach and not pass by the 18000 beat/ hr vibration. Shortened too much, you need another HS to start all over.

You can vibrate balance wheel- HS outside the movement on a tool specially made for this purpose or vibrate inside your movement.

If the new HS is already too short, it should go back on 2390. You have just lost a bit of the factory poising. 

Regards

 

 

 

[HSL]

1 hour ago, Deggsie said:

Thank you for your reply. It seems it will be taking quite a chance to buy the eta 2390 spring in the hope all the criteria match when I receive it. I think I will hold on an wait for the eta 2408 to come along on eBay. I might be lucky - no hurry. Thanks again, Deggsie 

If you decide to wait Otto Frei has sometimes good tips and trix in how to choose things and in this case they have written a couple lines about it on their page, Reading is Always a good past time.
http://www.ofrei.com/page820.html

[noirrac1j]

I'm guessing the part you're looking for is the incabloc and not the  KIF? The part number for Incabloc ETA balance wheel with flat hairspring is 721.

When I put this part number into Bestfit, this is what I get for possible replacements:

MATSYS says only difference between  2390 and 2408 is that Rolex/Tudor uses same balance assembly (2402) with KIF shock protection for its 21Jewel version.

[Deggsie]

Hello all. This forum never ceases to amaze me by the way people are so willing to help out. Thank you so much for all of your very useful replies. It certainly helps to know that the ETA2390 HS will be a ‘direct’ donor part into the ETA2408. whilst I appreciate what NuceJoe is explaining about needing to set the length to establish the correct vibration period, it seems in this case that the HS will not require further adjustment? Is that correct?

And to clarify, yes the BW has Inca shock system. [emoji846]

Many thanks again!!

Kind regards, Deggsie


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[noirrac1j]

2 hours ago, Deggsie said:

. whilst I appreciate what NuceJoe is explaining about needing to set the length to establish the correct vibration period, it seems in this case that the HS will not require further adjustment? Is that correct?

And to clarify, yes the BW has Inca shock system.

Many thanks again!!

Kind regards, Deggsie
 

I don't think you'll need to adjust the hairspring.

J

[Nucejoe]

Worked as best as I could have dreamed. We get this balance out of the way and hear about a proceedure to vibrate HS. 

Regards joe