My 1st Completed Practice Project (ETA 2390)

[Pauly]

I bought a load of old Accurist ETA movements on eBay for practice (all reported not working in listing) 4 of them are ETA 2390 with small variations (different balance settings).

These arrived yesterday morning. A couple of them run at least for a few minutes, but I decided to tackle the 'worst' one first, I figured it would be easier to see if I had made a difference. (It wouldn't 'start' at all despite being fully wound).

It had a fair bit of corrosion and was pretty dirty. Photos show a summary of strip down and cleaning. I manually cleaned in a small jar with horosolve, removing corrosion as best I could with pegwood and fibreglass pen, the end result is far from perfect but a massive improvement on how it started, and joy of joys, on reinstallation of the balance it started running! I got quite emotional!

I did a reasonably thorough job, relubricating as I went through reassembly, only 'shortcuts' were that I removed the barrel lid and checked spring for damage, but didn't remove it, and I didn't tackle disassembly of the balance as it seemed too much too soon (really should since this doesn't have a shock setting so balance disassembly is required to clean and lubricate top setting) I gave it a brief go, but after failing to get at the tiny screw on the stud after several attempts, I had fears of ever being able to get it back together if I did manage to get it apart.

Anyway, on timegrapher the initial readings on a full wind were amplitude of around 240 and beat error of 1.5ms, rate anywhere between -3 and +20 depending on position, so not brilliant, but I'm happy enough given it is a scrap movement that didn't run at all yesterday. I cannibalised one of the other 2390s from the lot for its hands (this one was missing a minute hand) and reinstalled the dial so I could pop it on my desk under a glass to let it run for a couple of days and check its rundown and timekeeping over a longer period. With the experience gained on this one, hopefully I can get the 'nicer' ones from the lot working a bit better!

[jdm]

Very good, congratulations.

After getting a watch running, in all positions for a time near to the expected power reserve, the next step is to use a timegrapher or equivalent application to see how it runs.

And if you want to look it better try an ammonia based solution. You won't need any cleaning machine or ultrasonic.

Edited May 31, 2020 by jdm

[Pauly]

45 minutes ago, jdm said:

Very good, congratulations.

After getting a watch running, in all positions for a time near to the expected power reserve, the next step is to use a timegrapher or equivalent application to see how it runs.

And if you want to look it better try an ammonia based solution. You won't need any cleaning machine or ultrasonic.

Thanks, I'm really new to this, but so far finding it a lot of fun and therapeutic. Does the ammonia based solution remove the corrosion somewhat? Would you do that as well as (after?) cleaning in horosolve or naphtha? Or instead of?

I will see how the power reserve is and report back, only finished rebuilding around 6 hours ago so will run it in a few positions this week. Beyond that, not sure how much more effort I will spend on this one for now regarding timing and such. It seems 'out of balance'? and for the moment, adjusting that on this fixed stud balance is beyond my confidence to tackle. I may come back to it one day as it would be a good candidate to practice tackling that specific issue on when I feel up to it!

The other 3 2390s in the lot all have nicer finishing to the movement (a sort of rose gold colour) and have shock settings on the balance, and movable studs, so if I do try and build up a watch with the case that was in the lot too, I'll probably use one of those rather than this one.

The case is weird, also accurist, just base metal plated and with very strange lugs, the like of which I've not seen before, and the case construction is 3 parts, so the dial actually sits between the crystal and midcase on a lip, so you would need to install the movement from the dial side into it. I did briefly try putting this movement in there but the stem hole in the case was slightly too small to allow the stem to pass into the case fully so abandoned it for now.

[jdm]

13 hours ago, Pauly said:

Thanks, I'm really new to this, but so far finding it a lot of fun and therapeutic. Does the ammonia based solution remove the corrosion somewhat? Would you do that as well as (after?) cleaning in horosolve or naphtha? Or instead of?

Use ammonia and rins with naptha or even better petroleum ether. Ammonia cleans up tarnish on brass and gold. Corrosion once has eaten material can only be repaired with lapping, There are easy techniques producing high-end effects, these are good to learn to develop a feel for materials and handling.

13 hours ago, Pauly said:

 Beyond that, not sure how much more effort I will spend on this one for now regarding timing and such

It's not about timing, it's about "how correctly it runs". On a petrol engine you could tell by sound if a cylinder is not firing, but on watch it's not to easy judge by look and sounds alone. You want a regular pattern, sufficient amplitude, and and acceptable positional error. Only after that is all good then you move to correcting beat error and timing. The timegrapher is an unreplace itool once you work and even just service mechanical movements.

[Pauly]

I let it run in a few positions, power reserve is around 36 hours in all of them, which is a little low vs the documented specs for a 2390. I will strip it and rebuild it again, having stripped and rebuilt another 2 of these 2390s now this week, (both of which run longer) I think the train on this one wasn't quite as free as the other 2 so I will recheck all the wheels for damage and end shake.

I have a weird behaviour on the timegrapher on one of those other 2 I've rebuilt. I'll see if I can track it down, otherwise I'll be back looking for advice!

[Jon]

@Pauly It's great breathing life back into something that look and feels dead, so well done on getting her running again!

You might find changing the mainspring will reap rewards with the amplitude, but also, for the sake of a tenner, you'll save a lot of bother trying to track down faults which was the mainspring all along! 240 amplitude is not such a good start point, as faults might start showing themselves, when it was the mainspring all the time.

Nice to see you got her going again!

[Pauly]

Thanks, it has been really satisfying, I had 4 of these arrive in a joblot from eBay last Saturday, and I've now rebuilt 3 of them, it has been kind of an addiction! the 4th one has given up its balance and a shock setting spring to the cause of the other 3 so it's not going to make it sadly, all the other 3 now run to some degree or another though (See my other thread on timing weirdness on one of them!). I do have the going barrel from the 4th one that I could swap in as a test to see if it makes much difference but I think it is likely I just over oiled this (only 2nd watch I had tried a rebuild on outside of the practical bit of Mark's course) or missed something during rebuild, and it was really filthy  and corroded when I started on it. Like I said, with the experience of the other 2 behind me now, I think this one was a bit stiffer to turn the train... The other 2 would literally spin the train under the puff of a dust blower... The barrel is an easy swap so I will try that first. It's really not worth buying a mainspring for it. This, 5 other movements and a case only cost me £12 all in for something to practice on. I will do my best on the 3 I have and build the best running one into the case when I'm done, I've done a trial build in the case now and it looks pretty neat!

[jdm]

Seems to me you are doing very good with your pragmatic approach. Thanks for sharing and best of luck!