The Orient Emperor sent me a really nice old 7009 that was running very fast. I quickly spotted the trouble and was dismayed because the hairspring was bent quite badly. I don't know if this was the work of a hack, an accident or something else, but it was bad.
I had another balance assembly that looked like it was good but it wouldn't run properly in this watch. I discovered that the top pinion or balance staff pivot was worn to about half it's length
So I figured I would have a go at the original and bent spring.
With the assembly out of the watch, I could see where the offending bend was. While struggling to hold my loupe and the balance cock in one hand; I used my #2 tweezers and reshaped the bent part to what I hoped was the right shape.
Lucky first time around! Upon putting the balance back in the watch, it started right up. Unfortunately, it stopped when I screwed the bridge screw down tight.
I remembered some advice and pics that Randall had posted about adjusting end shake and I tried it out. Two attempts later and the watch is ticking along happy as a clam...the first 'divot' I made was not close enough to the staff.
Thanks for encouraging me Doc and thanks for the advice you've freely given so far
..dared to mess with hairsprings yet! Can you please explain about the 'divot' a bit more please - is that like a kink in the spring?