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Pre-service was fine but Post-service watch doesn't run in vertical positions

GuyMontag
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GuyMontag Super WRT Addict

GuyMontag

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This is a 1970 Bulova 10COAC movement that was running when I received it. The  timegrapher mostly looked good pre-service but showed about a 60 degree drop in amplitude in vertical positions:

DU: +3  295 amplitude, 1 ms BE
DD: +6   290 amplitude, 1.2 ms BE
CD: -6   230 amplitude, 1.2 ms BE
CU: -1   225 amplitude, 1.8 ms BE

I didn’t see anything during inspection that was an obvious cause for the positional deviations (no cracked jewels, all pivots looked good, etc). In fact, it was sold as NOS in the original box and looked really clean with none of the usual dried up oils. As I was installing the balance after servicing I dropped the balance and it bent the hairspring to the point where I don’t have the skills to fix it. I did have a spare donor movement (in parts) and took the balance complete from that.

The issue I am having is that now the watch stops when in vertical positions. Originally it looked like the impulse jewel was stuck on top of the pallet fork so I moved the stud arm to center it but it looks like the impulse jewel is still “riding high” and while it runs in dial down, as soon as I move it to a vertical position it will stop, sometimes with the impulse jewel overbanked. The pivots on the donor balance look fine. I haven’t tried running it yet with the train side balance jewel installed but I’ve never had this kind of an issue at this point in the service in the past without the jewel installed.

Any thoughts on what I should check next?
 

 

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Marc Distinguished Member

Marc

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Posted
14 hours ago, GuyMontag said:

I haven’t tried running it yet with the train side balance jewel installed

Try installing them and see what happens

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