Diagnosis a ETA 2836-2 (balance speed change)

[richiesgr]

Hi,

I've received a tissot seastar using an ETA 2836-2 before service there was no reading on time grapher the watch is running but the time grapher was unable to evaluate the beat.

I've made the service and reassembled but the problem is the same the time grapher cannot pick a beat.

When I see the balance I remark that it's accelerate and slow down and repeat this again and again it's really visible with clear eyes.

I've inspected all the pieces every wheel pivots and jewels plus the hairspring seems perfectly concentric. 

Do you've any idea what can be the cause ?

it's a very nice watch

[Kalanag]

Measure the repeating time of the speed change and you will know which wheel is compromised. It‘s most likely either the escape wheel (about two seconds for one rotation) or the fourth wheel (one rotation per minute).

Edited August 24, 2022 by Kalanag

[richiesgr]

Thanks a lot I'll check this 

[richiesgr]

Hi

I've disassemble and re-assemble the movement again. This time the balance is almost dead I post a short video 

what do you think of the hairspring seem to have a problem ? 

I can't post video so here is a youtube link

[Kalanag]

For me it looks as if the balance is not running freely.

Let the mainspring down again, remove the pallet fork and test just the balance by agitating it with a blower.

[richiesgr]

Thanks for your help on this 

Indeed the hairspring was tangled but not all the time.

When I've disassembled the balance from the bridge I could see the hairspring tangled.

For the record I've tried to repair the hairspring and failed miserably. But I'm lucky because complete balance from china for 2836 are really cheap so I ordered a new one

[JohnR725]

On 8/24/2022 at 5:00 AM, richiesgr said:

ETA 2836-2 before service there was no reading on time grapher the watch is running but the time grapher was unable to evaluate the beat.

I've made the service and reassembled but the problem is the same the time grapher cannot pick a beat.

usually best if you can determine what the problem is before cleaning as cleaning usually doesn't fix problems.  sometimes cleaning will fix the problem if it's because the watch basically is it running because it desperately needs to be cleaned but usually if there's a problem it's best to figure out what the problem is and try to fix the problem before you do a cleaning.

On 8/24/2022 at 5:00 AM, richiesgr said:

hairspring seems perfectly concentric.

hairsprings are tricky things to look at. One of the key things is they have to be flat they can't be touching the balance that would cause issues Be touching the balance bridge more issues basically can't be touching anything and not supposed to touch. Often times that is really hard to see.

2 hours ago, richiesgr said:

hairspring was tangled but not all the time

it be nice to see a picture of your tangled hairspring and why is it not tangled all the time?

 

[Nucejoe]

The symptoms you describe are. 

1-Timegrapher can not identify the beat.

2- Oscilator's speed changes.

This points to intermitant sticking of the hairspring. 

A slow- mo   best reveals intermitant sticking.

 

[watchweasol]

Hi did you demagnetise the watch at all ?