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Ascanio

Bulova 5ap stops tightening the balance cock

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Hi!

Since long I did try to bring this tiny movement back to life:

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&2&2uswk&Bulova_5AP

I got two other movements for parts and I had to refit a balance wheel with his own cock from another movement

The problem I am having is that if I tight the screw of the cock, the balance wheel stops.

If I loose the screw and push up the cock from the mainplete, the balance wheels starts spinning itself for a several minutes, until the gravity pushes down the cock, then pushing it up it again from mainplate makes it spinning again.

I did try to lube but it appears it mate things worse and not better.

Any suggestion about what problem I may be facing?

Thank you!

 

 

 

 

 

 

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Did you remove the cap stones on the balance and fully clean out the old oil?

If not the old oil could be gumming up the new oil.

Have you checked the pivots of the balance for wear?

Checked the jewels for any cracks?

Does the anchor snap cleanly from side to side if you nudge it with an oiler with the balance removed?

 

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If the cap jewels are seated correctly and you have not transposed them then the balance is not aligned correctly. Rule of thumb DON'T FALSE ANYTHING. By any chance when you removed the balance cock for cleaning was there a shim between the cock bridge and plate. Sometimes if a new balance staff is changed and it is bit tight a cheats way is to put a thin shim under the cock.

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Thank you for the answers!

11 hours ago, Tmuir said:

Did you remove the cap stones on the balance and fully clean out the old oil?

If not the old oil could be gumming up the new oil.

The bottom one yes and appears clean, i have oiled properly it now. Not the top one because I would need to remove the balance wheel to unscrew from bottom, the regulator is not boot type, I am afraid I will never mount it again, it's too tiny piece for my skills.

11 hours ago, Tmuir said:

Have you checked the pivots of the balance for wear?

Checked the jewels for any cracks?

Does the anchor snap cleanly from side to side if you nudge it with an oiler with the balance removed?

All these tests are passing fine, in my opinion.

I made a round of cleaning in ultrasonic for balance wheel and bridge, trying to better oiling, I will see if any change tomorrow.

10 hours ago, clockboy said:

If the cap jewels are seated correctly and you have not transposed them then the balance is not aligned correctly. Rule of thumb DON'T FALSE ANYTHING. By any chance when you removed the balance cock for cleaning was there a shim between the cock bridge and plate. Sometimes if a new balance staff is changed and it is bit tight a cheats way is to put a thin shim under the cock.

No shim originally found... I will eventually consider one or two hour wheel shim/spacers eventually, if that woudl still make a difference.

Thanks again! I'll try to make good use of your suggestions, this movement means a lot to me.

Ascanio

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I'm so frustrated... after cleaning and oiling the bottom cap jewel and the upper jewel it works much worse, anchor snaps when rotating the wheel manually but it does not swing on its own any more :( I used 9010 oil. I will just try to oil the pivots a bit more and make sure all is properly aligned... this tiny movement drives me crazy.

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If you didn't clean the balance jewels introducing fresh oil could dislodge the old gummed up oil and make things worse.

I'm afraid you you wont make much progress without cleaning the balance jewels.

Assuming you have checked that all jewels are clean and balance pivots are not bent bu the problem still persists,... I would check the endshake of the balance. A watch this old may have had the balance staff replaced and the replacement may not have been an exact fit. On most watches you can adjust the endshake a bit by pushing the jewel housing in the mainplate up or down a bit (using a staking set). Note that this may change the interface between roller jewel and pallet fork so this needs to be considered.

On larger mens watches you can sometimes get a screwdriver between the hairspring coils to remove the jewels but on these smaller ladies watches its not so easy.

Good luck

Anilv

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Your original description reminded me of a recent problem I had with a different movement.  I switched screws.......The head on the screw holding the pallet cock turned out to look the same, but had a minutely thicker head.  This caught the balance and stopped it.  I felt really silly but it was a very rewarding fix!

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