# UHF vs. Pescisionist movements



## tmathes

The title sort of says it all, except for the high speed chrono function, are they fundamentally the same movement? Some Precisionists are just plain 3 handers so I'm a bit confused on the full differences of the movements.


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## Tomas472

As more folks with various Precisionist and UHF 262 kHz movements get braver and actually look at their movements, we will know very little about them.

My Bulova Military 96B239 UHF 262 kHz watch has been opened and carefully inspected. It appears to carry one of the four Precisionist movements I am aware of, the 8102 movement, which I assume to be an 8102.10 since it appears to be a 10.5 ligne size. (The other three are the BA101.10 and the P102.12 the P112.10 movements.)

I do not know for certain that is the movement number, but the ONLY markings visible on the back of the movement are "8102" "JAPAN" "PUSH" (with a tiny arrow) and "BULOVA EIGHT JEWELS" ... This is inspecting at 150 power.

Bulova appears very closed mouth about the movements, and very few others have posted useful information about them.

Maybe we can get something going in this forum, eh?









(I have pics of the other markings, too, should anyone wants to see them.)


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## BenchGuy

tmathes said:


> The title sort of says it all, except for the high speed chrono function, are they fundamentally the same movement? Some Precisionists are just plain 3 handers so I'm a bit confused on the full differences of the movements.


Are you questioning differences in accuracy, durability, or interchangeability of parts? Regards, BG


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## tmathes

BenchGuy said:


> Are you questioning differences in accuracy, durability, or interchangeability of parts? Regards, BG


Differences in the movements themselves, if there's a fundamental difference in the movement mechanics or the circuit block, quartz timing circuit, etc..

For example, is the movement in the 3 hander Precisionists the same as the 3 hander in the Accutron II or does the A/II use a newer, 'improved' circuit, improved quartz crystal, or is it the same movement just with a new name. Just idle curiosity.


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## odd_and_vintage_fan

I believe the main differences had to do with the quartz crystal and the logic applied to the microchip. Someone on IIRC the Affordables forum did a tear-down of a Precisionist movement. It was a mostly stock quartz movement with a different quartz crystal and a tacked-on larger battery holder.

From what I recall, the Precisionist moved the seconds hand 16 times per second. The Accutron II cut this down to 8 times per second to save battery. The UHF three-hander cuts this further, but I don't recall the number. FWIW, I could see the "ticks" when I tried one on. IIRC, each version used a quartz crystal that vibrated a little slower to save power as well, slightly dropping accuracy.

The chrono version of the UHF has a small running seconds that ticks once per second, but the chrono second hand sweeps.


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## Tomas472

odd_and_vintage_fan said:


> I believe the main differences had to do with the quartz crystal and the logic applied to the microchip. Someone on IIRC the Affordables forum did a tear-down of a Precisionist movement. It was a mostly stock quartz movement with a different quartz crystal and a tacked-on larger battery holder.The movement mechanicals are very similar to an "ordinary" quartz except for the gear reduction ratios being different to account for the faster step rate compared with the "average" quartz that steps one-per-minute or the "two-hand" quartz that often step once every ten seconds.​
> From what I recall, the Precisionist moved the seconds hand 16 times per second. The Accutron II cut this down to 8 times per second to save battery. The UHF three-hander cuts this further, but I don't recall the number. FWIW, I could see the "ticks" when I tried one on. IIRC, each version used a quartz crystal that vibrated a little slower to save power as well, slightly dropping accuracy.The watches sold as "Precisionist" "Accutron II" or "262 kHz" all step 16 times per second (960 per minute). All three also have a three-fingered crystal that vibrates at 262,144 Hz.​
> The chrono version of the UHF has a small running seconds that ticks once per second, but the chrono second hand sweeps.


Once again, here is a quick video of my Bulova Military 262 kHz (96B230) watch​


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## odd_and_vintage_fan

Fixed that for me, thanks!


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## BenchGuy

Folks might find this an interesting read: Precisionist Materials and Bulova's History - How the Bulova Precisionist Works

Regards, BG


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## tmathes

BenchGuy said:


> Folks might find this an interesting read: Precisionist Materials and Bulova's History - How the Bulova Precisionist Works
> 
> Regards, BG


From pg. 3 of the above article:
*
Bulova engineers tackled the problem of temperature fluctuation by adding temperature regulation to the Precisionist's circuitry.

*I thought there was no temperature compensation in these movements.


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## Samantha

Interesting, thanks BG!
Samantha


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## Tomas472

tmathes said:


> From pg. 3 of the above article:
> *
> Bulova engineers tackled the problem of temperature fluctuation by adding temperature regulation to the Precisionist's circuitry.
> 
> *I thought there was no temperature compensation in these movements.


I've heard people claim that there is temperature compensation and others claim that there is no temperature compensation, and since neither side can claim to have "inside information" and can provide no documentation, design specs, drawings, or even movement numbers, I discount them all.

If anyone wandering by here knows for sure and can provide backup for their knowledge, I'd like to see it.

If anyone here can even just get a list of movements and their specs I'd really, really like to see it.

Until we actually have some valid source materials, though, most of this info appears to be simply pulled out of, uh, "the air"...

*Anyone have a contact at Bulova or one of the Repair Centers???* (Don't ask me: Bulova won't even acknowledge that I contacted them.)


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## BenchGuy

tmathes said:


> From pg. 3 of the above article:
> *
> Bulova engineers tackled the problem of temperature fluctuation by adding temperature regulation to the Precisionist's circuitry.
> 
> *I thought there was no temperature compensation in these movements.


This is what Bulova has to say about that:
Precisionist
Precisionist

Author also correlates quartz frequency to output "beats" per second. This is a function of circuitry design and not directly related to quartz rate (ie. you don't plug a 262144Hz quartz into a 32768 circuit to go 1 step to 16 steps per second).

Still an interesting read in that it gives an overview of the relation of frequency to accuracy in watchmaking. Not all of Mr. Cunningham's information is entirely correct...depending upon interpretation. If you consider that the quartz unit is part of the circuit...and it is designed to "compensate" within a certain temperature range (by virtue of 3-prong and tortional qualities)...then it is designed to compensate for temperature. Note that Bulova does not go into great detail in explaining their design. Most folks observe that accuracy is better when the watch is worn than when off the wrist...haven't seen anyone post results of a credible study however.

That said...good reading on your part. And perhaps not extremely precise writing on author's part (writing precisely and concisely is an uncommon skill...would that I were possessed of it).

Regards, 
BG


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## Tomas472

BenchGuy said:


> This is what Bulova has to say about that:
> Precisionist
> Precisionist
> 
> Author also correlates quartz frequency to output "beats" per second. This is a function of circuitry design and not directly related to quartz rate (ie. you don't plug a 262144Hz quartz into a 32768 circuit to go 1 step to 16 steps per second).
> The electronics are obviously different since it forms a resonant circuit with the quartz crystal, then reduces the frequency in a number of stages, halving it each time, until it reaches 8Hz instead of the .5Hz driving the rotor of the more common 1-step-per-second quartz movement.
> 
> Each full (square wave) cycle drives the rotor one full rotation in two half-rotation steps.
> 
> The "beats per second" shown by the second hand is based on dividing the oscillator frequency by two a fixed number of times AND by the gear train following the rotor having the proper reduction to turn the 480RPM of the rotor to the 1RPM of the second hand.
> 
> Since the rotor of the Precisionist or 262 kHz movement is rotating at 480RPM instead of 30RPM the gear train leading to the second hand obviously has a different reduction, or the second hand would be whipping 'round at 16RPM. (The gear reduction for the minute and hour hands are the same as in any other 12-hour watch since they are based on the 1RPM of the second hand.)​
> Still an interesting read in that it gives an overview of the relation of frequency to accuracy in watchmaking. Not all of Mr. Cunningham's information is entirely correct...depending upon interpretation. If you consider that the quartz unit is part of the circuit...and it is designed to "compensate" within a certain temperature range (by virtue of 3-prong and tortional qualities)...then it is designed to compensate for temperature. Note that Bulova does not go into great detail in explaining their design. Most folks observe that accuracy is better when the watch is worn than when off the wrist...haven't seen anyone post results of a credible study however.
> 
> That said...good reading on your part. And perhaps not extremely precise writing on author's part (writing precisely and concisely is an uncommon skill...would that I were possessed of it).
> My problem with his writing is he is writing professionally on a technical matter and as such I expect him to be accurate. That is, in fact, the most important part of a technical writer's job: Accuracy.
> 
> ​Disclaimer: I spent a portion of my engineering career as a technical writer, producing step-by-step manuals to guide technicians in the performance of their jobs. Not once was I ever able to say "that's close enough" or "I don't know" or "no one will catch that error."
> 
> When one writes on a technical subject, accuracy is simply a requirement, not an optional extra. Either one knows what they are writing about or they do not. there is no middle ground. ***​
> Regards,
> BG


* Just for a laugh, here is some of the tech writing I did, long before I retired... 313 layer, Bell System Practices.


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## BenchGuy

Tomas: Thanks for the in-depth illumination...I don't believe you've covered any new ground for me, though.

With respect to this observation: 

When one writes on a technical subject, accuracy is simply a requirement, not an optional extra. Either one knows what they are writing about or they do not. there is no middle ground. **

*Something about glass houses and stones comes to mind...or possibly sin and throwing the first stone...and possibly some of Einsteins work (among others)? Some of the mankind's most remarkable discoveries are buried among inaccuracies.

Should you decide to further evaluate the specifics of the Precisionist calibers, I'm sure we would be interested in your methods, results and conclusions.

Best regards, BG


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## sixtysix

Does any body know if citizen sells replacement movements for these?


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## tmathes

sixtysix said:


> Does any body know if citizen sells replacement movements for these?


Very, very likely not. I think this movement is unique to Bulova, I don't even see anything like it in the Citizen-branded line. I do not believe Citizen sells movements under that name, they market them under the Miyota brand name.

I perused the Mityota web page, they have some movements that appear similar to the UHF chronos in terms of functions but they spec +/- 15 seconds for the movement. So far these high-frequency quartz movements seem to be a Bulova exclusive for now. To get a replacement my wager is you'll have to send it back to Bulova or if there are independent Bulova/Citizen authorized repair stations maybe they could get them.

Unlike auto or appliance part availability, watch parts appear to be very protected by the manufacturers (Rolex is one of the worst offenders with Swatch group following closely behind). If a car or appliance maker did this there would be a big blow-back over it.


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## constellation90

There a few ways to achieve thermocompensation in a quartz watch...

High frequency crystal 
Digital Count Adjustment 
Forced constant frequency
Dual Quartz

So to me the UHF and the Precisionist both operating at approx 262khz should run in the first category, and maybe the second. But the question is if it's a HEQ? Well to me that's though to decide as most people will say a HEQ is a quartz that's +/- 20 Secs a year. But in reality I think there is more to consider like movement finishing and materials, where the Precisionist falls short. 
So maybe watches like a Bulova is more of a HAQ?


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## Blarpie

Still seems like a gimmick to me. What are folks using this watch for that they need that type of precision? Given that more steps per second is going to wear down a battery faster, I wish they'd have kept it at 1/second and simply use the larger battery to power the watch longer.

An insanely accurate quartz watch is not what most people want. A quartz watch that doesn't need to have the battery replaced every couple of years is exactly what most people want!


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## moneysworth

tmathes said:


> Very, very likely not. I think this movement is unique to Bulova, I don't even see anything like it in the Citizen-branded line. I do not believe Citizen sells movements under that name, they market them under the Miyota brand name.
> 
> I perused the Mityota web page, they have some movements that appear similar to the UHF chronos in terms of functions but they spec +/- 15 seconds for the movement. So far these high-frequency quartz movements seem to be a Bulova exclusive for now. To get a replacement my wager is you'll have to send it back to Bulova or if there are independent Bulova/Citizen authorized repair stations maybe they could get them.


Unfortunately, while I thought that Bulova and Citizen were not mixing technologies. Some digging I've been doing lately may prove otherwise. The link to the article article below seems to be written by someone who has a lot of knowledge on the subject. It is well written. The last paragraph is quite sad.

The Accutron Revolution - Accuracy Through Electronics 1960-1977


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## Calibrel

Blarpie said:


> Still seems like a gimmick to me. What are folks using this watch for that they need that type of precision? Given that more steps per second is going to wear down a battery faster, I wish they'd have kept it at 1/second and simply use the larger battery to power the watch longer.
> 
> An insanely accurate quartz watch is not what most people want. A quartz watch that doesn't need to have the battery replaced every couple of years is exactly what most people want!


Zombie thread alert:
IMO, your statements are fairly myopic.

I think _most _people really don't care about watches or horology in general, so why bother at all, correct? I mean, who really needs a radio controlled watch anyways now that every one has cell phones? Why bother making mechanicals since quartz, who wants that? Who really needs a 200M capable diver, or a slide-rule bezel, or a moonphase complication, or 1K gauss resistant movement, or a tidegraph/altimeter/barometer/blah blah blah...

Honestly, how much of an inconvenience is it to have a battery changed once every couple of _years. _Most people simply don't care. And we can easily play the game from "the other sides" for everything ("why bother with X, who wants that?")


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## GUTuna

The zombie thread rises again. Actually, I used this thread in research when I was purchasing the Bulova "Archive Series" Reboot of the Chronograph C "Stars and Stripes". This is marketed as using the UHF movement. When I opened it, it says it has the Bulova 8136 movement. No jewels. Small seconds ticks one beat/sec. The chronograph hand move much more smoothly. Chronograph also has a 1/10 sec wheel.


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## DaveK12

Where'd the jewels go?


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## tayloreuph

Only 12 moving parts...


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## Nietzsche_Darko

Sorry to revive this thread but I think I have some answers after a recent conversation with Bulova. While I can't confirm whether the watch is thermo-compensated or not, there's some interesting information about the different movements within the Precisionist collection. Hope this helps:

Precisionist movements were introduced in 2010 (3 hand calendar) and 2012 (chronograph). They were marketed as 'The world's most accurate watches with a continuously sweeping second hand'. The accuracy comes from the very high frequency, 262kHZ, of the 3 prong quartz crystal. 
The special 3 pronged quartz crystal vibrates at an incredible frequency of 262kHz, a frequency 8 times greater than standard quartz watches. The greater frequency leads to a more accurate watch.

Precisionist Movements (watches) are accurate to 5 seconds a month, versus 15 to 20 seconds a month for standard quartz watches.

Precisionist Movements also feature a continuously sweeping second hand that beats 16 times a second. Nearly fluid. This feature is UNIQUE to Precisionist movements/ watches.

Bulova has introduced three additional high frequency 262kHz movements. In 2014 (3 eye chronograph), 2016 (CURV chronograph), and 2017 CURV sub sweep). They have the same frequency and accuracy as the two previous high frequency movements (in Precisionist), HOWEVER, they do not have the continuously sweeping second hands.


Starting in 2014, with the introduction of the third high frequency movement, it was decided to place all watches featuring the 262kHz movements into a collection called UHF, Ultra High Frequency. Precisionist was included.
Bulova Accutron II was created in 2014. It used two movements. One from Precisionist (the 3 hand calendar introduced in 2010) and the 3 eye chrono introduced in 2014. We marketed the use of UHF movements in this brand (collection).

In 2016 we dropped the use of UHF, and started to use the term 'HPQ' 'High Performance Quartz'. HPQ, however, is not used in marketing the product, I do not believe.

We have 5 movements that feature 262kHz frequency with 5 second a month accuracy.


2010. Precisionist 3 Hand calendar. Also features a continuously sweeping second hand.
 2012. Precisionist Chronograph. Also features a continuously sweeping second hand.
2014. 3 eye chronograph.
2016. CURV chronograph
 2017. CURV sub sweep.


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## tmathes

Curve sub sweep? Which one is that, the "Ladies" Curv line I assume? If they dropped the 'bling' in that line I'd bet they could easily sell to men since they're a reasonable sized case.

As for the Precisionist line, they dropped a couple of models last week on the US web site, they were the 'smaller' models (under 45mm). They were also the most tame looking of the line up too.

The entire line up has shrunk it seems, not only are the Precisionist line culled but the entire Accutron II line up is gone. Glad I snagged them when I did.


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## Nova Gentleman

I can only assume that the Accutron II and Precisionist models simply don't sell as well as everything else they make. 

Too bad however there are still deals out there to be had on these...


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## tmathes

Nova Gentleman said:


> I can only assume that the Accutron II and Precisionist models simply don't sell as well as everything else they make.
> 
> Too bad however there are still deals out there to be had on these...


The Precisionist would benefit from a smaller case size and less garish styling.

Regarding the Accutron II, dunno what happened there. The watches were attractive and sized right. My only gripe was the dials were too "flat" looking, nothing was interesting in terms of texture on them except for one cushion case version.


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## ross2187

So they've dropped the UHF labeling? No one my Lunar Pilot says High Performance Quartz on the back, I thought I got a fake!


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## jlind

*Zombie Warning*


Nietzsche_Darko said:


> Sorry to revive this thread but I think I have some answers after a recent conversation with Bulova. While I can't confirm whether the watch is thermo-compensated or not, there's some interesting information about the different movements within the Precisionist collection. Hope this helps:
> 
> _"Precisionist movements were introduced in 2010 (3 hand calendar) and 2012 (chronograph). They were marketed as 'The world's most accurate watches with a __continuously sweeping second hand'. The accuracy comes from the very high frequency, 262kHZ, of the 3 prong quartz crystal. _
> _The special 3 pronged quartz crystal vibrates at an incredible frequency of 262kHz, a frequency 8 times greater than standard quartz watches. The greater frequency leads to a more accurate watch.
> 
> Precisionist Movements (watches) are accurate to 5 seconds a month, versus 15 to 20 seconds a month for standard quartz watches.
> 
> Precisionist Movements also feature a continuously sweeping second hand that beats 16 times a second. Nearly fluid. This feature is UNIQUE to Precisionist movements/ watches.
> 
> Bulova has introduced three additional high frequency 262kHz movements. In 2014 (3 eye chronograph), 2016 (CURV chronograph), and 2017 CURV sub sweep). They have the same frequency and accuracy as the two previous high frequency movements (in Precisionist), HOWEVER, they do not have the continuously sweeping second hands.
> 
> Starting in 2014, with the introduction of the third high frequency movement, it was decided to place all watches featuring the 262kHz movements into a collection called UHF, Ultra High Frequency. Precisionist was included.
> Bulova Accutron II was created in 2014. It used two movements. One from Precisionist (the 3 hand calendar introduced in 2010) and the 3 eye chrono introduced in 2014. We marketed the use of UHF movements in this brand (collection).
> 
> In 2016 we dropped the use of UHF, and started to use the term 'HPQ' 'High Performance Quartz'. HPQ, however, is not used in marketing the product, I do not believe.
> 
> We have 5 movements that feature 262kHz frequency with 5 second a month accuracy.
> 
> 2010. Precisionist 3 Hand calendar. Also features a continuously sweeping second hand.
> 2012. Precisionist Chronograph. Also features a continuously sweeping second hand.
> 2014. 3 eye chronograph.
> 2016. CURV chronograph
> 2017. CURV sub sweep."_


After doing some researching of my own, I've found the five movement calibers referenced in the conversation with Bulova

*P102* with P102.10 and P102.12 revisions: 2010 8-jewel 3-hand. Powered by a 3V CR2016 Lithium. I believe this is the same movement used in the Alpha Spaceview even though it's marked "BA101.10" on the dial side. I've concluded the photo showing an 8102 is actually this movement. This movement is in every one of the 3-hand Accutron II and Precisionist I own and I believe it's used in the ladies Precisionist models with central seconds, other than the CURV which have sub-seconds.

Battery and insulator have been removed - they would cover the entire movement if present. Photo from Caliber Corner









*P123* with no known revisions: 2012 16-jewel 4-eye 1/1000th second, 12 hour max elapsed time chronograph. Powered by a 3V CR2016 Lithium. Fourth crown on side opposite the other three switches function between timekeeping and chronograph stopwatch. It's the only one of the three chrono movements with 1/1000th second precision measuring elapsed time.

Photo by Ricky from Caveman's Watch Forum









*8136* with no known revisions: 2014 0-jewel 3-eye, 1/20th second, 60 minute max elapsed time chronograph. Powered by a 1.55V 395 Silver Oxide. Operates intuitively like nearly all other quartz chronographs. It's a derivative of the Miyota 6S20 32kHz movement with the beat rate cranked up to 262kHz and regulated by the Precisionist triple-tine crystal. This would explain it being the odd one out among the five with no jewels. The 8136 is used in their Apollo 15 Lunar Pilot chronograph.

Photo from Caliber Corner









*8137* with no known revisions: 2016 11-jewel 3-eye, 1/2 second, 12 hour max elapsed time chronograph. Powered by a 1.55V 395 Silver Oxide. Operates intuitively like nearly all other quartz chronographs. Why the elapsed time precision is only a half-second mystifies me. Used in all the CURV branded men's chronographs and has no central seconds hand; seconds subdial is also used for elapsed time seconds.

Photo from Caliber Corner









*8138* with no known revisions: 2017 6-jewel 2-hand with sub-seconds in a smaller ladies size. Powered by a 1.55V 395 Silver Oxide. Used in all the CURV branded ladies watches.

Photos of ref # 98R240 from Rakuten Japan
















Notes:

Bulova advertises 1-year life for the 395 battery in the 8136 and 8137 chronographs using it. Expected life in the 8138 is unknown but probably isn't much longer. Expected life of the 3V Lithium in the P102 is advertised at 2 years but I've been getting a couple months over 3 years in them. The P123 chronograph is about 2 years, which would be expected with some chronographs. Chronograph battery life will vary greatly depending on how much the stopwatch function is used.
Using a 1.55V SR927SW / 395 / 399 cell with only 54 mAh (Energizer specs; 84 mWh) with a 1 yr. anticipated life in two of the chronos is disappointing. Much shorter than I would want. A SR43SW / 386 / 301 with 127 mAh (Energizer specs; 197 mWh), over twice the energy, would be much more desirable. Better yet, going back to the CR2016 with 90-100 mAh at twice the voltage, giving 270-300 mWh energy would have roughly three times the energy.
The CURV case and crystal shape precludes using a central seconds hand, hence the seconds subdial for the 8138 and reuse of the seconds subdial for the stopwatch seconds function on the 8137. While this might be acceptable on the ladies 2-hand with sub-seconds, a chronograph with no central seconds, reduced to 1/2 second precision is an absurd compromise of functionality for sheer fashion. If central seconds isn't possible, even on the men's CURV, then make it a time/date instead of a crippled chronograph.
Why Bulova feels compelled to cover the battery on the display backs with the tuning fork logo has me mystified. Was able to deduce they're 395 cells from various photos that piece together enough of an SR927SW on them to conclusively conclude that's what's under the label.


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## tayloreuph

jlind said:


> *Zombie Warning*
> 
> After doing some researching of my own, I've found the five movement calibers referenced in the conversation with Bulova
> 
> *P102* with P102.10 and P102.12 revisions: 2010 8-jewel 3-hand. Powered by a 3V CR2016 Lithium. I believe this is the same movement used in the Alpha Spaceview even though it's marked "BA101.10" on the dial side. I've concluded the photo showing an 8102 is actually this movement. This movement is in every one of the 3-hand Accutron II and Precisionist I own and I believe it's used in the ladies Precisionist models with central seconds, other than the CURV which have sub-seconds.
> 
> Battery and insulator have been removed - they would cover the entire movement if present. Photo from Caliber Corner
> View attachment 15434915
> 
> 
> *P123* with no known revisions: 2012 16-jewel 4-eye 1/1000th second, 12 hour max elapsed time chronograph. Powered by a 3V CR2016 Lithium. Fourth crown on side opposite the other three switches function between timekeeping and chronograph stopwatch. It's the only one of the three chrono movements with 1/1000th second precision measuring elapsed time.
> 
> Photo by Ricky from Caveman's Watch Forum
> View attachment 15434978
> 
> 
> *8136* with no known revisions: 2014 0-jewel 3-eye, 1/20th second, 60 minute max elapsed time chronograph. Powered by a 1.55V 395 Silver Oxide. Operates intuitively like nearly all other quartz chronographs. It's a derivative of the Miyota 6S20 32kHz movement with the beat rate cranked up to 262kHz and regulated by the Precisionist triple-tine crystal. This would explain it being the odd one out among the five with no jewels. The 8136 is used in their Apollo 15 Lunar Pilot chronograph.
> 
> Photo from Caliber Corner
> View attachment 15434991
> 
> 
> *8137* with no known revisions: 2016 11-jewel 3-eye, 1/2 second, 12 hour max elapsed time chronograph. Powered by a 1.55V 395 Silver Oxide. Operates intuitively like nearly all other quartz chronographs. Why the elapsed time precision is only a half-second mystifies me. Used in all the CURV branded men's chronographs and has no central seconds hand; seconds subdial is also used for elapsed time seconds.
> 
> Photo from Caliber Corner
> View attachment 15435003
> 
> 
> *8138* with no known revisions: 2017 6-jewel 2-hand with sub-seconds in a smaller ladies size. Powered by a 1.55V 395 Silver Oxide. Used in all the CURV branded ladies watches.
> 
> Photos of ref # 98R240 from Rakuten Japan
> View attachment 15435006
> View attachment 15435030
> 
> 
> Notes:
> 
> Bulova advertises 1-year life for the 395 battery in the 8136 and 8137 chronographs using it. Expected life in the 8138 is unknown but probably isn't much longer. Expected life of the 3V Lithium in the P102 is advertised at 2 years but I've been getting a couple months over 3 years in them. The P123 chronograph is about 2 years, which would be expected with some chronographs. Chronograph battery life will vary greatly depending on how much the stopwatch function is used.
> Using a 1.55V SR927SW / 395 / 399 cell with only 54 mAh (Energizer specs; 84 mWh) with a 1 yr. anticipated life in two of the chronos is disappointing. Much shorter than I would want. A SR43SW / 386 / 301 with 127 mAh (Energizer specs; 197 mWh), over twice the energy, would be much more desirable. Better yet, going back to the CR2016 with 90-100 mAh at twice the voltage, giving 270-300 mWh energy would have roughly three times the energy.
> The CURV case and crystal shape precludes using a central seconds hand, hence the seconds subdial for the 8138 and reuse of the seconds subdial for the stopwatch seconds function on the 8137. While this might be acceptable on the ladies 2-hand with sub-seconds, a chronograph with no central seconds, reduced to 1/2 second precision is an absurd compromise of functionality for sheer fashion. If central seconds isn't possible, even on the men's CURV, then make it a time/date instead of a crippled chronograph.
> Why Bulova feels compelled to cover the battery on the display backs with the tuning fork logo has me mystified. Was able to deduce they're 395 cells from various photos that piece together enough of an SR927SW on them to conclusively conclude that's what's under the label.


Do you happen to know the movement dimensions? I wonder if you could swap to a more standard dial/case configuration? Like... maybe... the new Accutron Legacy series?

Sent from my iPhone using Tapatalk


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## jlind

tayloreuph said:


> Do you happen to know the movement dimensions? I wonder if you could swap to a more standard dial/case configuration? Like... maybe... the new Accutron Legacy series?
> 
> Sent from my iPhone using Tapatalk


You're not the first to ask this question. Bulova keeps the movement dimensions necessary for stem, case, dial and hands a closely guarded secret. None of them are available from a typical source for replacements (e.g. Ofrei, Esslinger, etc.). You'd have to acquire a watch with the movement and reverse engineer it's dimensions, a risky endeavor to accomplish with the necessary precision. The only one on which there would be low risk data is the 8136, which was derived from the 32kHz Miyota 6S20, and you could use Miyota's 6S20 data sheet. That means you could probably put an 8136 into a Citizen or Bulova chrono made for a 6S20. Problem would be acquiring the 8136 movement. Bulova and Miyota won't sell you one.

I very seriously doubt you could successfully adapt an Accutron Legacy for any of these Precisionist movements. All of the Accutron Legacy models have crowns/stems, dials, hands and cases (with the spacers) dimensioned for the Sellita SW200-1. You could put an ETA 2824-2 in an Accutron Legacy as they're identical in form, fit and function, and that's about it (an ETA 2892A2 wouldn't fit). There's no such thing as "standard" or "generic" movement dimensions except in a family of movements by the same manufacturer, and even then there's often a difference in one or more of the dimensions (e.g. ETA 2824-2 vs 2834-2 vs 2804-2). Basically, a watch is designed for a specific movement caliber and that's it. Folks were asking about swapping in a Seiko 4R36 into an older Seiko with a 7S26 or 7S36 to give it hand wind and hacking. Nope. Close, but cannot be done. IIRC, the first big deal breaker is the distance between movement top (side on which the dial mounts) and stem, and it went on from there.

I had a custom watch assembled after separately procuring the case with crown, dial, date wheel, hands, and movement. It was a nightmare. The case had to be designed for the specific movement caliber. Dial had to be the correct diameter for the case and chapter ring, with its feet designed for the specific movement. Date wheel had to be correct diameter for dial date window and the dial numbers the correct size for it. The dimensions list is nearly endless, all down to 1/100th millimeter to make it all fit and work when you're done. Took me over a year to find everything in the color and style I wanted. The master watchmaker rolled his eyes when I handed it to him . . . until I walked through all the parts with him . . . and he warned me in advance any fitment problem would bring the job to a dead halt. Had to trim the needle tip of the seconds hand by about a half millimeter. Knew that before he started as I knew it was likely too long - not a problem as that's occasionally done with generic replacement hands.


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## GregorAmbroz

Interesting reading - especially while I am waiting for my Precisionist to arrive. I did stumble upon something that is written in @jlind post - AFAIK there have been many 7S26 to NH36 movement upgrades done in SKX modding communities and it's supposed to be pretty much straight forward. Haven't done it myself though.


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## jlind

GregorAmbroz said:


> Interesting reading - especially while I am waiting for my Precisionist to arrive. I did stumble upon something that is written in @jlind post - AFAIK there have been many 7S26 to NH36 movement upgrades done in SKX modding communities and it's supposed to be pretty much straight forward. Haven't done it myself though.


No, it's not. Major issue number one is the crown and stem. Stem isn't interchangeable and the crown is not made to be removed from a 7S26/7S36 stem. Quite problematic for screw-down crowns that must be matched to the case and threaded stem tube. Second potential issue in many of the 7S26 watches is taller height of the 4R3x center pinion which can hit the underside of the crystal in some watches. In other words, they're not a drop-in replacement. You could, with enough work, make just about any movement work in any watch case, provided it's smaller than the watch case. The key phrase is _"with enough work"_. At some point, the amount of work required, and the cost of it, isn't worth what you have after it's finished.


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