ETA 7750 Oscillator bearing.

[Len33]

Good evening, everyone and, hopefully, you are all well.

I have successfully stripped, cleaned, and reassembled an ETA 7750 automatic chronograph. It has superb time keeping abilities now, as shown  on my timegrapher, in four positions. Ok, that's lovely. 

Now, to the nitty gritty.

I bought a new bearing to replace the sloppy old one and, no matter how I try, the new bearing just will not go into the oscillating weight.

It is a friction fit type, not the one that uses the Bergeon tool.

Also, I got the bearing from Cousins, not China.

Now, I am wondering if there is a difference between an ETA 7750 watch and  Valjoux 7750.

If there is, that may be the answer because I just cannot keep trying to line this bearing up with the oscillating weight and tapping away at it because, to use a technicle term, 'something will go for a Burton'!

So, has anyone got any idea about how to complete this task?

I have watched Mark's video and that does not help.

I have tried warming the oscillating weight first, but it cools faster than the tax man helping himself to my earnings!

Okey-dokey, over to you.

Thanks for reading this and all the best.

Len.

 

 

 

[jdm]

2 minutes ago, Len33 said:

If there is, that may be the answer because I just cannot keep trying to line this bearing up with the oscillating weight and tapping away at it because, to use a technicle term, 'something will go for a Burton'!

Can you measure bearing and hole. A decent digital caliper will be enough. 

[Len33]

Good evening, JDM.

Thank you for your suggestion.

Yes I did try to do that and, although it was very difficult, I do think that there was gnats whisker larger with the new bearing.

That is why I am wondering about the two models.

Regards.

Len.

 

[HSL]

Yes they might be even totaly different in construction. I took a picture so you easier can see what I mean.
Newer ETA 7750 is locked in place by a shim and need a special tool.
Old Valjoux 7750 is press fitted.
These boths systems have different diameters on the bearing hole on the oscillating weight too.
So the Valjoux is smaller and will not stay in the newer oscillators hole.
The ETA has a larger diameter and will not go into the Valjoux ocillators hole.
Hope this helps.

[Len33]

Thank you for this information, it helps very much.

If I have understood this correctly, it would seem that I have an ETA  7500 bearing and, for some reason, a Valjoux 7500 weight.

The bearing that I got from Cousins will not press into the weight.

The one that I removed, did.

The watch I have, is definitely a 17 jewel ETA 7500.

In your picture, the bearing on the right looks like the one I removed from 

the oscillating weight and the one on the left looks like the one I got from Cousins.

Anyway, "thanks" again for your post.

Len.

 

 

[HSL]

If you have the 17 Jewel you have the right oscillating weight. Since ETA took over the production they had the old equipment and drawings too. So, just looking at your oscillating weight you can see it is missing the shallow groove for the locking shim which is on the 25 jewel one.  The 17 jewel version of the 7750 is the one to the right in my picture.

The pressfitt bearing is like 2 tens of a milimeter smaller in diameter. 
Easiest way to determine if you got the right bearing is to meassure the hole you got on the oscillating weight and on the small flange on the bearing. If you look at your last picture it is the small bit peaking up you see on the bearing to the right.
If the part you got isn't completely circular but got four straight edges on the flange like it looks to be on the bearing to the left in your picture, then you for sure know it is the wrong bearing, that one is for the 25 Jewel one.

[Len33]

1 hour ago, HSL said:

If you have the 17 Jewel you have the right oscillating weight. Since ETA took over the production they had the old equipment and drawings too. So, just looking at your oscillating weight you can see it is missing the shallow groove for the locking shim which is on the 25 jewel one.  The 17 jewel version of the 7750 is the one to the right in my picture.

The pressfitt bearing is like 2 tens of a milimeter smaller in diameter. 
Easiest way to determine if you got the right bearing is to meassure the hole you got on the oscillating weight and on the small flange on the bearing. If you look at your last picture it is the small bit peaking up you see on the bearing to the right.
If the part you got isn't completely circular but got four straight edges on the flange like it looks to be on the bearing to the left in your picture, then you for sure know it is the wrong bearing, that one is for the 25 Jewel one.

The new bearing that I have from Cousins, has indeed got the four flat bits that you mention. 

Incidentally, the bearing on the right of my pictures is the old one.

So that confirms I have the wrong bearing.

I have searched the internet for the press fit one (No flat bits) and, so far, I have drawn a blank.