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10BPAC or 10BPA, 10CBAC, 10BPAD mainspring needed

I have an L4 Bulova 23C and a L6 Bulova 23B, both with 10BPAC movement.
I want them serviced, but my 'service-guy' always wants to replace the mainspring when serviced.
Since the 10BPAC is an Bulova inhouse movement, spare parts are really difficult to find in Europe. (Holland).
I understood on this forum that 10 BPA, 10CBAC, 10BPAD can be used.
If you have one (or two), they come in a barrel, or you know where to find one, this would be really really helpfull !
Thank you in advance, Sybren

Reverend Rob's picture
Reverend Rob
Panel Member
Posted March 1, 2019 - 5:55pm

Automatic mainsprings should be replaced during service, generally speaking. One of the reasons for this is that the spring must be removed from the barrel to be cleaned properly. Depending on the end result, (and the quality and age of the watch) manual springs might be ok. (Textbook and repair depot says all mainsprings will be replaced.) The difference is the automatic mainspring is not anchored to the inside of the barrel and is designed to slip with a specially designed bridle. 

In the case of these sealed barrels, the barrel complete was usually replaced during service, and Bulova was not the only company that did this. 

There is a lack of spec available for the spring, so it must be measured and then a suitable one substituted. The sealed barrel can be opened and then closed without issue by a competent watchmaker. If I find one, I will measure it, but this may take some time. The watchmaker should be able to do this for you with no issues.

SybrenAnne's picture
Posted March 2, 2019 - 6:45am

Tnx for the info Rob !