Omega R17.8 beat error question

[frenchie]

Hello everyone,

I got lucky in an antique store and bought an Omega watch with a nice R17.8 movement (reference: http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&&2uswk&Omega_R17_8)

The watch was covered in green gunk, smelled like shoe polish, and I had to take a gamble on it without seeing the movement (the case has weird clamps to keep it shut (I'll post pics when I'm done)). It would only run for a few seconds when wounds a turn or so. I made my concerns very clear to the seller (largely emphasizing the amount of grime on the case and what it might mean for the insides), made a lowball offer that was promptly accepted... weird

 

Anyways...

the movement had a lot of dried sticky oil in it but after a disassembly and cleaning, it started right up. On the timegrapher, the amplitude is in the 200-230 range, (a little low), the beat error is 3.5ms. The rest of the readings are fine (2 exactly parallel lines), either gaining a few or loosing a few seconds depending on the position. The beat error surprised me a bit so I took out the balance and the pallet fork to check the position of the roller jewel between the banking pins (thank you Mark for the great video on beat error) but it is smack in the middle, not even a tidbit on one side or the other, in the centered middle. I double checked the pivots and jewels on the balance but I see nothing out of alignment (I thought maybe a pivot was bent on the balance staff, but not that I can see). I checked the jewel holes for the balance, all clean (cleaned them 3 times). I cannot see any grime on the hairspring and I don't see it catching on anything when it's running.

 

I'm at a loss as to how to proceed next, and what to check. Any helps and advice is greatly appreciated!! Thanks

 

 

[matabog]

Choose! Either you want to see the impulse jewel in the middle of the banking pins, or you want to see a single line on the timegrapher  Try minimizing the beat error on the timegrapher, then see where the impulse pin is.

 

I believe, but I don't know for sure (just thinking out loud here...), maybe if somehow the pallets had an offset (having all the angles right but somehow shifted...) then you had a beat error even if you had the impulse jewel in the middle of the banking pins. 

 

[jdm]

Maybe a next step could be instead replacing the MS as that would probably improve amplitude?

I think that if the pattern is regular, and positional error is small, one can live with beat error on a salvaged vintage mov.t.

Edited June 2, 2016 by jdm

[JohnR725]

For Omega they used to use a different numbering system your number is under the old system. Then the new system can get confusing unless we have a picture or more details about your watch. I've attached a PDF parts list for the 300 which I think is the base caliber. To get an ideal the confusing numbers in the meaning here's a link.

http://www.ranfft.de/cgi-bin/bidfun-db.cgi?10&ranfft&0&2uswk&Omega_300

Then for the lift angle it depends upon which watch you have. All of them are listed as 21,600 beats but the lift angle is either 52 or 54° depending upon which one you have. Because they're so close together it's not going to matter a new timing machine very much.

2368_Omega 300.pdf

[oldhippy]

You need to start at the basic what's wrong with the watch first.  I would demagnetize the whole watch and then check.

[rodabod]

I've witnessed beat error increase o some watches when the amplitude is reduced, either due to a hardly wound, or weak mainspring. I'd make sure that the mainspring is good, and I presume you check that the gear train runs smoothly while the pallets were removed and mainspring wound down.

Edited June 4, 2016 by rodabod

[frenchie]

26 minutes ago, rodabod said:

I've witnessed beat error increase o some watches when the amplitude is reduced, either due to a hardly wound, or weak mainspring. I'd make sure that the mainspring is good, and I presume you check that the gear train runs smoothly while the pallets were removed and mainspring wound down.

Order new mainspring, can't hurt...

On 6/2/2016 at 6:42 AM, oldhippy said:

You need to start at the basic what's wrong with the watch first.  I would demagnetize the whole watch and then check.

I forgot to say that I demagnetized as a first step in any cleaning I do   I did it again but no change...

[JohnR725]

On 6/1/2016 at 5:13 PM, frenchie said:

On the timegrapher, the amplitude is in the 200-230 range, (a little low)

One of the problems with in particular the Chinese timing machines is if the amplitude is abnormally low a timing machine will pick up the wrong part of the waveform give you a visual amplitude much higher than what it actually is. Then yes when the amplitude is low the beat error visually increases which is why you normally never deal with beat error until you get amplitude up to something decent.

This is where visually looking at the watch does the amplitude look like what the timing machine is indicating? I saw this once on a pocket watch a friend was showing me amplitude looked great on the timing machine but to me the balance wheel was barely moving. Timing machine is not always right if it cannot pick up a nice clean signal and then sometimes misinterprets what it picks up anyway.