Question for those who work on Vintage Timex watches:
I've restored several Timex pieces from the late '60s to the late '70s. The technique I learned (from Internet posts and tutorials) say to simply loosen the dial-side balance pivot by unscrewing it 1/2 turn prior to cleaning the entire movement in an ultrasonic cleaner. This method contradicts the official Timex service manuals, which state that the balance should be removed, cleaned separately and reinstalled. Thus preventing the hairspring form being damaged in the ultrasonic cleaner.
My experience is this:
Leaving the balance in place (slightly loosened) is much easier and will work on the standard movements used in the '70s (M24/25, M32/33, M104, etc.)
Attempting the same method on movements from the '50s and '60s (M22, M29, etc) will result in a kinked hairspring that is damn near impossible to un-kink.
So my question is this:
What do you experienced Timex restoration experts recommend? Leave the balance/hairspring in the movement for cleaning, or take it out to soak in a separate jar?
Is the potential for hairspring damage greater when removing/reinstalling the balance - in comparison to leaving it in place?
I've messed up a couple of vintage movements that I really wish I hadn't. I don't want to make those mistakes again.
Thanks for any insights!