If an 18000 balance complete were installed instead of the intended 19800 ? ... (Seiko 6216A)

[Rory]

So, I’ve just received a lovely 6216-9000 to get back in shape ... symptom reported by previous owner (flipper, with no knowledge of its service history) was of losing something like 5 min per hour (!).

However, I thought I’d lucked out when I popped it on the timegrapher - good accuracy (after minor dialling in), decent beat - but noticed that it was auto-detecting at 18000. The 6216A movement is supposed to run at 19800.  I manually set to 19800 and the grapher wouldn’t even provide a reading.

Observing the dial over the space of 5 minutes confirmed the movement is losing a ton of time, as reported by the previous owner.

So, this got me wondering ... if somewhere in this watch’s history someone replaced the balance complete with one from one of it’s 18000 rated cousins (in the 62 movement series) ... wouldn’t that be a prime contender for the cause of the very poor performance?  I’m mid teardown so other issues may present themselves, but the auto detect on my Wishi 1900 got me wondering, so wanted to get your view on this.

Cheers - Rory

Note on 62 series : https://www.watch-wiki.net/index.php?title=Seiko_6200

[Repivot]

The difference between 19800 and 18000 is 1800 beats per hour. That is the difference of 360 seconds or -6 minutes an hour (based on a 18000bph standard) or about -5 minutes 25-30 seconds (based on a 19800bph standard). So you theory that the wrong balance complete was used is very likely. I suspect if a 19800 balance complete was installed you issue would resolve. Let us know how it goes.

[Nucejoe]

I am glad Repivots has already done the calculations. 

In case a new oscilator is expensive, you might want to consider speeding up this one.

Regs

Joe

 

[Rory]

I could have fainted, but Cousins actually have the balance complete in stock - so I should have an update later in the week.  I had to triple check it was the right part - delighted.

Assuming this is the cause, it’s been an interesting “note to self”.  Anything new to you and running consistently off-pace in the region of multiple minutes per hour - double check the actual and expected vph.

Many thanks for the arithmetic - blaming my 2 year old for not thinking of doing that immediately  

[JohnR725]

This problem comes up with other watches Rolex and Omega for instance. There are several watches from each of these companies where the base movement may run at one frequency others will run at other frequencies. Especially with Rolex unscrupulous sellers will put just about anything in the get the watch out the door claiming it running and not really pay attention to how well it's running.

The simplistic of all of this is the balance wheel oscillated at its natural frequency with its hairspring of course the timing machine will pick this up you can regulated absolutely perfectly and If the gear train ratio doesn't match your screwed.

[Rory]

Some progress - new balance complete arrived this afternoon. Photo attached of the pair, with the correct one sitting out pre-installation - with jewel impulse.

Happily, the timegrapher immediately autodetected 19,800 off the new part.  

Strip down, cleaning and inspection lies ahead. An uneasy feeling remains - what else did ‘they’ get wrong?  I’ve been picking up some key parts (NOS) here and there just in case.

Regards - Rory

[Rory]

On 2/22/2021 at 5:59 PM, Repivot said:

The difference between 19800 and 18000 is 1800 beats per hour. That is the difference of 360 seconds or -6 minutes an hour (based on a 18000bph standard) or about -5 minutes 25-30 seconds (based on a 19800bph standard). So you theory that the wrong balance complete was used is very likely. I suspect if a 19800 balance complete was installed you issue would resolve. Let us know how it goes.

Can you share your working for how 1800vph difference ends up as 360s?   Many thanks - Rory

[spectre6000]

19800 bph/18000 bph = 1.1

1.1 * 60 m/h = 66

6 minutes fast.

[Repivot]

In an 18000bph watch, there are 5 beats per second. So 1800 ÷ 5 = 360.        360 seconds = 6 minutes

In a 19800bph watch there are 5.5 beats per second. So 1800 ÷ 5.5 = 327.27.         327 seconds = 5 minutes, 25.5ish seconds.

To be clear we are measuring beats per hour (bph) not vibrations per hour (vph). My understanding is a vibration is full oscillation of the balance one way then the other. Beats are just one way or tick.

It looks to be running slow on the timing machine, but also looks by the position of the regulator you have plenty of room to regulate it faster.

I hope it all works out.

Edited March 12, 2021 by Repivot