Bulova 10CSC Automatic goes ‘BZIK!’

[WpgRob]

Hi! Has anyone here had an automatic watch that quickly loses power? My 1954 Bulova 10CSC runs ok for a while, then seemingly at random makes a ‘bzik’ noise and then stops within 2 hours. The watch was serviced by a local jeweller some 8 years ago (before I got hooked by Mark’s videos), but I haven’t worn it much because it’s unreliable.

The 10CSC movement includes several clutches and clicks, which complicates reverse engineering to troubleshoot. The rapid release occurs too fast to see. Slow motion mode on an iPhone camera does not seem to have a fast enough frame rate to catch the culprit. A clue is the sudden release happens when more power is added to the mainspring either from the rotor or from the crown, and usually under some tension after roughly 20 winds of the crown. Some of the clutches and clicks are likely there to prevent power release back through the rotor by spinning it, but that’s not an issue on this watch. I’m guessing the cause of the power release might be a worn inner barrel wall, worn mainspring end, wrong braking grease, or a worn click or clutch. 
 

- Has anyone here encountered and solved this issue?
- How can we know when a part on an old watch is too worn to function?
- Am I stuck with replacing parts one by one until it holds power?

Thanks in advance,

Rob in Winnipeg 

 

[HectorLooi]

I have a couple of Russian watches that do that too. If I wind the watch by hand up to a certain point I'll hear a "whirr" and lose power.

This is caused by the automatic mainspring slipping. The funny thing is, it happened only after I serviced it and used a strong braking grease.

I haven't had time to regrease the mainsprings but my theory is that the braking grease holds the bridle to the barrel wall until the force is enough to overcome the friction + adhesive force of the grease and cause a major slippage. Something like tectonic plates causing an earthquake.

[RichardHarris123]

Automatic mainsprings are made to slip as the rota is constantly winding them. I would suspect a faulty spring or braking grease if slipping too early though. 

[WpgRob]

Thanks, guys. I’ll check the mainspring

Cheers!

[MarioJ]

There's only a few ways to lose power instantly as you described. It sounds like the mainspring is doing its job, winding up and working for a few hours. You said it happens so fast your camera cannot catch it so I assume something is happening externally for you to record. I would check the winding wheels, crown wheel, there engagements, and make sure all the teeth are there. (I had a chipped tooth on a Longines barrel drive me ABSOLUTELY CRAZY once trying to figure out why it kept stopping.) The other thing you said was while winding it happens, check the click and click spring. It doesnt take much for these parts to not function 100%. 

As to your questions: I would start with process of elimination.  I'm working on the same movement you have, the entire autowinding mechanism comes off with three screws. You said it didn't matter If it was automatically wound or hand wound. You had the same problem so I imagine you're gonna find the problem on the movement but seperating them will verify that. Best of luck my friend. The answer is there, inside this tiny little machine, you just have to find it and that's the fun of it, solving the problem.

Mario