Omega Cal. 680 Balance Replacement & 620 Compatibility

In an act of great hubris, I decided I would buy and service an old Ladymatic to give to my wife. In cleaning the balance assembly, I completely demolished the hairspring. Turns out the parts being so small has consequences beyond just being hard to handle. In this case, I had dipped the balance assembly into a petri dish of hexane. I lifted it out with the balance wheel on bottom, and the surface tension of the hexane caught the wheel. I should have stopped and flipped it over under the hexane, but I didn't. When the balance wheel broke the surface tension, it flung itself up and over the cock, landing upside down on top of it, and the hairspring looked for all the world like a tiny version of one of the many short-lived slinkies I had when i was a kid. Ha! After about a half hour of trying desperately to rescue it, I finally destroyed the spring beyond all repair.

So there's my cautionary tale for anyone thinking about working on their first Ladymatic. 😀

Anyway, I've spent days considering my options, which seem pretty simple. I can either get a NOS balance complete and put that on my existing balance staff, or I can replace the entire balance assembly with one from a donor movement. Given my track record handling the tiny balance so far, and the fact that I have never removed or replaced a balance complete, this (the tiniest movement of it's kind on the planet in the early 60s, I read) is probably not the place to start. So I'm shopping for either a complete balance assembly, or a donor movement.

People selling complete balance assemblies seem to think they're made of solid gold. I don't get that, because every "working" movement comes with one, along with a bucket of other spare parts, and generally can be had for less than just the balance assembly.

That leaves the donor movement route. I have read (though have had trouble confirming) that the 680/681 movements are in the 620 family, and that any 620-family balance assembly will fit in a 680. That (I believe) includes calibers 620, 630, 670, 671, 672, 680, and 681. While it would be great to have a 680/681 with all it's matching spare parts, the 620s seem to be plentiful and cheap, and my priority at this point is to not sink a ton more money into this boondoggle while still getting the watch running reasonably well.

So I have two questions... 1. Am I missing any options? I'm still really new at this. and 2. Are my assumptions about the compatibility or balance assemblies between those calibers correct?

Thanks so much for your help!

I think i have a Balance wheel with hairspring attached in my parts. Where Are you located?

I'm in Redlands, CA. You must have one heck of a parts collection! 😀

Ha! It hurts to learn lessons this way, but it's not a mistake I intend to make again! 😀

I'm bookmarking this resource. I really did search pretty hard for something like it, and found some really old websites, but somehow missed this one. Thank you!

I had forgotten about this, but if "the device rearranges the matter of the universe to its state 13 seconds prior, but it preserves the memories, injuries, and consciousness of the person who pushed the button," as I read just now on Reddit...I might get my hairspring back with it, but I'd probably still have the 40 or so gray hairs it gave me once I realized my mistake! Ha!

Unfortunately i‘m in Europe. It wouldn‘t make sense to send such a Part such a Long distance.

Indeed. I'll be in eu
Thanks for considering it! I'll keep an eye out for one closer to home once I've had some time to practice attaching and removing the collet from the balance staff...something I've yet to attempt, and plan to on some larger practice balances in a few old Chinese movements I have before I try it on anything that matters.

Thank you for checking!

Just to close the loop on this one, I ended up buying a decent 620 movement to harvest the balance from. I assumed the entire balance assembly would be the same, but of course, it wasn't. The cock on the 680 has a cutout for the rotor and the one from the 620 does not, so I ended up having to transfer the balance spring and wheel, which ended up not being a big deal.

Nearing the end, I was being exceedingly careful, considering the time and energy I had invested in this. So you can imagine how grossed out I was when the lyre from the incabloc setting flopped out onto the plate when I opened it to put the chaton in! Ha!

I don't have a microscope, so I have to double up on loupes to see the extra tiny, and I was amazed to discover that the bloc hinge is machined to allow you to insert one side of the hinge then tip the other in to reinstall it. God, that was fidgety.
Anyway, it's all back together and has been running well, looking pretty good on the timegrapher, and the automatic works is functioning well, so I'm pretty pleased.
A number of lessons learned, especially that at my skill level, I should stay far, far away from these tiny movements with automatic and date complications! Ha! But the wife really likes it!

I Hope you wife appreciates the struggle 😄 Respect! I also almost lost my mind working on an ladymatic. I broke of the incabloc Setting on the Balance bridge. I had to completely dissaseble the Balance to install a new spring…

Oh man...the worst!

She definitely appreciates it...she offered encouragement all along the way. Ha! In retrospect, I should definitely have fixed up the Movado Museum watch with the Zenith movement I got her before digging into this one. That watch doesn't even have a second hand! 😀