# Accuracy and stability of rate of El Primero movement



## heb (Feb 24, 2006)

Hello,

The new models have reintroduced sanity to this good brand. But, is the movement as good in terms of subject criteria as say, an ETA 7750?

I'd like to hear from some longer term owners and users of the brand's chronographs.

TIA,
heb


----------



## Rickr23 (May 29, 2008)

The current movements are no different than previous EPs. Other than adding some feature, like the Striking 10th, to the EP.

Do you have any subjective criteria in mind? I have some objective criteria that makes the EP better than the VJ7750: thinner, your don't have to press the chrono pushers so hard. In one of my VJ7751 watches, the chrono seconds hand doesn't reset to zero anymore but to 1.5 seconds and it keeps moving further the more I use the chrono. All my EPs are more accurate than any of my 7750s. Subjectively, the EP looks better to me in finishing and construction.


----------



## heb (Feb 24, 2006)

Hello Rickr23,
This is admittedly an extreme example, but my MIDO 7750 chronograph has shown these values over the last three respective months (calculated over the entire 30 day period): +4.3s/d; +4.2s/d; +4.1s/d. Accurate and VERY Stable. Can a Zenith match it, within reason?

heb



Rickr23 said:


> The current movements are no different than previous EPs. Other than adding some feature, like the Striking 10th, to the EP.
> 
> Do you have any subjective criteria in mind? I have some objective criteria that makes the EP better than the VJ7750: thinner, your don't have to press the chrono pushers so hard. In one of my VJ7751 watches, the chrono seconds hand doesn't reset to zero anymore but to 1.5 seconds and it keeps moving further the more I use the chrono. All my EPs are more accurate than any of my 7750s. Subjectively, the EP looks better to me in finishing and construction.


----------



## Ray916MN (Feb 11, 2006)

The variation between various movements in terms of accuracy and stability mostly comes down to production and assembly tolerances/skill. I'm not sure blanket statements can be made with respect to accuracy and stability. The EP should generally (there are an awful lot of modified and fettled 7750s out there which should be very very good performers) theoretically be more accurate and stable than a 7750, but when it comes to the performance of individual movements nothing is assured. 

Personal experience is really not a good indicator either as it is unlikely that any owner could ever have enough watches to have a statistically accurate representative sample. I've got well over a dozen automatic chronographs including several 7750, and EP based ones, but I would never think that my experiences represented much other than my personal opinion.

If you want to get a watch which performs well, start with buying a watch with a good movement and have a skilled watchmaker clean it and adjust it. You'll be amazed at how well a good watchmaker can make even a relatively unsophisticated movement work. I have no proof, but I believe, some of the performance superiority of watches from different makers is more due to their fettling and assembly of standard movements as opposed to changes they make to standard movements.


----------



## Rickr23 (May 29, 2008)

In my experience with my 5 EPs they are very accurate and stable. I believe that almost all current EP models are chronometers. Moreover, you could take you Zenith to an AD to have it further regulated, I assume for free. Not sure if that still applies now, it was mentioned it previous manuals.


----------



## Hartmut Richter (Feb 13, 2006)

Forget about "monthly rates". What is generally considered important is the daily rates (difference in rate between now and 24 hours later). And what is much more important is the difference between the daily rates. The daily rate just shows how well regulated the watch is. The difference(s) between daily rates shows how well the watch has been serviced but also the general quality of the movement. A cheap pin lever movement without jewelling will never make it to a maximum difference between daily rates of less than 5 seconds (if that).

After my El Primero was last serviced, I monitored the daily rates over a period of 3-4 months. The watch ran ca. +1 second/day fast. The lowest was ±0 seconds/day, the maximum was 2.5 seconds/day. This makes a maximum deviation between daily rates of 2.5 seconds. Around that time, "ArmbandUhren" tested four modern chronographs, one each by JLC, Patek and IWV, the three being pitted against a Rolex Daytona (and don't ask *me *why this was more of a three vs. one rather than an all against all test! :roll. Much was made of the fact that the Daytona gained nerly ±0 over two weeks whereas the others gained ca. 1 second/day so that at the end of the test period the Rolex was at near enough the setting it had before whereas the others were 15-20 seconds fast. Not a single word about the fact that the greatest difference between daily rates was 4 seconds/day for the Rolex - but only 3 s/d for the Patek and the JLC (the IWC was somewhat worse in most categories). And my EP managed 2.5 s/d *over several months!* Show me the Valjoux 7750 that can better that.

Don't get me wrong: although I don't own one, I think quite highly of the Valjoux 7750. A movement that has been around for as long as it has, that is as rugged as it is and can achieve chronometric accuracy must be a good movement. But better than the EP? Not a chance!

If an expert (i.e. watchmaker's) opinion should be required on this matter, I usually direct those desiring it to the following review (comparison between movements at the bottom):

Rolex Caliber 3135 - Still worthy of the crown after all these years?

Hartmut Richter


----------



## Horlosjebedonderd (Oct 13, 2006)

Hi all

My Tag Heuer Monza with the Cal 36 (el Primero) movement was so accurate over a one year period that it gained less than 60 seconds during that time! Nowadays it will gain more or less 30 seconds over a period of a few months. 

I have recently started selling off my Valjoux 7750 movement watches because the "stopwatch" function is just not adequate. First of all - and this applies to the el Primero movement as well - measuring minutes in 30 minute units on a small little dial is not ideal. Here the different Lemania movements that use a central minute hand provide a far better option. My biggest problem with the Valjoux 7750/1 movement however is that, if you were to stop and start the chrono without resetting it to zero over an extended period of a few hours, the hour hand (of the chrono) becomes "confused". It creeps forward, so that, after a while you do not know any longer if you are nearing the completion of an hour or half of an hour. I have observed this in all my Valjoux 7750/1 movements. This may however not be true for the Muhle Glashutte MU9408 (their version of the Valjoux 7750 movement) as they have made certain improvements to it. I am however not sure if my observation about MU9408 is correct. 

The hour hand of the el Primero chrono does not creep.

Albert Kotze


----------



## heb (Feb 24, 2006)

Thanks to all. Good discussion.

heb


----------

