Regulating an ETA 2873

[spazthecat]

Hi,

I've got an old ETA 2873 that I picked up cheap and was going to clean it and use it in a future build. I've taken it apart and cleaned it twice and I still can't get the darn thing regulated properly. Upon tear down, I didn't see any broken gear teeth and the main spring looks to be in good shape. So, I'm leaning towards it being a problem with the balance/hairspring.

The problem I'm having is that I can get it in beat properly at 21600 but it's always too slow. By a lot. Like 2-4 minutes per day.

I'm using the iPhone app Kello for timing it (I know, but I don't do enough movement services to warrant spending the money on a proper piece of equipment and Kello has worked reasonably well on the other two movements I rebuilt) and sometimes I'll get a good reading using it but most of the time I get a "signal unstable" reading and the waveform displayed in Kello is very irregular.

Any suggestions for next steps in troubleshooting this?

Thanks,

Andy

 

[ado213]

If you could post your Kello readings in "Dial Up" and "Dial down" positions first I may be able to help. Alternatively the usual suspects:-
Mangnetized
Cracked jewel
Barrel arbour play
Loose pallet jewel
Over oiled
Incorrect oil
weak mainspring (how's the power reserve?)
Worn train pivots
Dry cannon pinion
Burred gear teeth
Bent pinions

To check most of these fairly simply remove the pallet fork and balance, wind the watch, listen to the run down. It should be nice and evenly toned and free. it should also run down to no power left in the mainspring. If this is fine move onto you escapement and balance.

The balance assembly:- Clean the balance wheel and hairspring with "one dip" this should eliminate the problem of oil on the hairspring if there is any on it?.

Look at the balance running, does the hairspring flex and breath evenly about its axis, is it flat, is it touching the terminal stud? does it bounce open and close?. These are not easy to tell without good vision or a scope but a 10X loupe would help.

On running, check the pallets are clearing the escape wheel evenly and smoothly, pallets on this should be oiled only with mobious 941 oil.

If this is Ok look at the balance/hairspring. Remove the complete balance and invert so you looking at the impulse jewel, make sure the staff is located in the cock jewel. Look closely using a loupe to see if the coils are even in spacing and concentric to the staff. Look closely at the flatness of the hairspring and balance wheel to the cock. If your balance tilts to one side this will misshape the hairspring once you place it back in the movement.

Check the shape and Arc of the terminal curve from the stud end to hairspring. With the cock and assembly out of the watch and inverted, move the regulator backwards and forwards in its arc of movement, if it pulls or moves the hairspring, the arc is incorrectly formed.

I could go on and on here, but I guess you have enough to work with now, hope this helps!

 

[spazthecat]

Thanks for taking the time to type all of that out. I really do appreciate it. I have some time this weekend and I'll go through the steps you've outlined. Power reserve seems OK. I gave a full wind at about 8pm last night and 24 hours later it's still ticking. I'll check it again in the morning and see if it's still running. I did, however, notice this evening that the balance wheel will slow down then speed back up if I watch it long enough. Not a huge slow down, but noticeable to the naked eye. I can't say it was doing that yesterday after a full wind up.

Kello output is as follows.

Dial up:

Dial down:

Thanks again,

Andy

 

[ado213]

The reason I asked for dial up and dial down readings is that if these are not with 5- 10 seconds in the DU and DD positions you will never accurately time this watch in, Your reading dial down is "unstable" which means its too random a reading for Kello to make any sense off.

Have you checked the top pivot on the balance staff ?, I have a suspicion this is damaged?.

 

[spazthecat]

Hi,

I'll take a closer look at the balance staff this weekend. But the pivet that inserts into the main plate looks ok to me. Also, I mixed up the dial up and dial down Kello readings above. So, based on that, I should focus on the bottom pivot, correct?

I did remove the balance and pallet fork. Once wound up, it runs down completely with a nice even whirring sound.


Sent from my iPad using Tapatalk

 

[ado213]

Just a word on Kello, I have personally never used this so I have no experience as to its accuracy, I have heard its not that good, and it may be that you are getting false reading??. Sounds like the gear train is free and functional, so lets move on to the escapement. If you can get amplitude readings off this it would help considerably.

Check each step one by one, replace the components, then run again and see if there's any difference in its functionality, if you do all the steps then reassemble you will miss the opportunity to isolate the fault.

Firstly, check the pallet jewels are fixed firmly into the pallet fork, I have known one of these to be loose in the fork. do not lubricate the pallet fork pinions, if you already have, clean them off thoroughly and replace, do not lubricate the pallet jewels (yet).

Re- run the movement and take your readings, no change, go to the balance jewels.

remove the balance ( check both staff pivots) remove both jewels and thoroughly clean both the chatons and the cap jewels themselves. I dont know what oil your using on these but it should be mobius 9010, if you dont have it dont lube these at the moment. If you do have it lube the end cap jewels only, as a rough rule of thumb, you should apply a drop of oil approximately one third of the diameter of the cap jewel and in the centre of the cap jewel. these should be really clean, pegwood both the chatons and end stones, then rinse off. make sure there is no residue of dirt or old oil left inside. Make sure both staff pivots are cleaned also. It is also worth checking the impulse jewel whilst the balance is out, again I have known these to be loose in there fixing, so check for stability of the jewel and clean off thoroughly.

RE- assmble and take your readings again.

Lets see how we go from there?

 

[spazthecat]

Yeah, I think Kello is hit or miss. There's a thread about building a microphone for use with a timing software program. I'm in the process of building that as it seems that it is more accurate than Kello.

The pivots of the balance staff look OK to me. It's kind of hard to see them both without removing it from the hairspring. But, I don't want to remove it unless absolutely necessary.

I hit a little roadblock, this morning. I had taken the cap jewel off the balance to clean it and when I was putting it back together, the retainer spring must have sprung somewhere. I thought I dropped it into the movement. So, I disassembled movement and still can't find it.

Soooo, I'll have to see if I can find one on eBay or more likely locate another movement that I can use for parts.

Thanks for all of your advice.

--Andy

 

[ado213]

Easy done, slippery little suckers those shock springs!!. Keep going with it, you'll crack it eventually. Just look at this as a learning curve which wev'e all had to go through.