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Bulova Accutron


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After repairing 2 Accutrons recently, I've developed a facination for them. So far I have a 218, 219 and 224. I have some questions concerning Accutrons. 

I sometimes see on ebay a suffix like N2, N3, N4.... What does the "N" number signify? Is it a model number?

Why is the price range so huge? I see some for below $100 and some for $3000.

I know that the 214 was the first model produced. What was the last?

I've seen some Accutrons that were not tuning fork movements. Did Bulova continue using the name Accutron for quartz watches?

And lastly, do we have any Accutron experts among our distinguished members? 

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Hi there HectorLooi, here is some dating info for Bulova from 50s through to 2000s 

For Bulova watches created in 1950 or later, the manufacturer switched to a two-digit alpha-numeric code system. These codes are usually found on the backcase, but some can be found on the inside movement near the set-screw.[4]

The first digit of the code corresponds to the decade. The second digit of the code corresponds to the specific year.

The decade codes are as follows:

1950s: L

1960s: M

1970s: N

1980s: P

1990s: T

2000s: A

The second digit of the code matches the ending digit of the year in which the watch was manufactured. When "0" is used, the end of the year was a "0" (1950, 1960, 1970, and so on). When "1" is used, the end date of the year was a "1" (1951, 1961, 1971, and so on). This pattern continues for digits "0" through "9."

For example, a Bulova watch marked with "N2" was manufactured in 1972. A Bulova watch marked with "T8" was manufactured in 1998.The original Spaceview was not intended for sale at all – it was a demonstrator model, whose purpose was to appear in ads and in store display windows. The Spaceview showed off not only the forward gliding motion of the seconds hand, but also the distinctive green baseplate and contrasting copper coils for the tuning fork, as well as the transistor essential to the operation of the watch.

They usually are priced on rarity, condition, and case material, box and papers etc. hence the huge price range. Bulova released an Accutron collection with quartz movements in 1976. One year later, the tuning fork Accutron production was stopped once and for all after more than 5 million pieces were sold. That year marked also the end of Bulova’s golden age.The last 214's were made in 1977. During the 17 years that tuning fork watches were made they were the most accurate production timepieces on the Earth, and in space.

Edited by Graziano
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Thanks Graziano. That was very informative. 

Have you serviced any tuning fork watches before? Would you kindly share your experience? 

As for Nucejoe's request for a service walk through, I would be too embarrassed at this moment to post one. I was just stumbling around  clueless. Maybe after a few more Accutron repairs, I may dare post one.

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https://youtu.be/ADpzwTdNvyY

https://youtu.be/whjzesnM3hQ

https://youtu.be/8bS2IDEBxBk

https://youtu.be/5n791JAVpv0

Hi HectorLooi please watch these videos they will help you understand phasing and just how delicate the pawls and indexing wheels are which I have no doubt you already know .I don't know if you have seen these videos but they are just like sitting in school .From what I can remember (hahahaha) ,I fixed a work colleagues  1975 214 asymmetrical tv case 2 years ago and it is still running within 3 seconds a year ,but I did not phase the watch ,from what I could see it was ok the when power was applied so I left it .Mind you it took me six months to get his watch back to him. I was being so careful not too lose or damage this watch .He had the original box ,paperwork and receipt ,I wanted to buy it there and then but to no avail ,Dam............. Buy the way you do need a microscope as even a 10x loupe is not enough as mentioned in the video.

hope this helps

Graziano

Edited by Graziano
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Thanks Graziano. I've watched of them before. But if you notice, when it came to the part when he set up the Accutron test meter to do phasing, the video was abruptly cut out ( end of Part 3). The video then continues with the casing up and finishing of the watch.

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42 minutes ago, HectorLooi said:

Thanks Graziano. I've watched of them before. But if you notice, when it came to the part when he set up the Accutron test meter to do phasing, the video was abruptly cut out ( end of Part 3). The video then continues with the casing up and finishing of the watch.

Yes I have seen that .Do you have the service manuals ,I think I was very fortunate the one i repaired , 

Accutron214ServiceManual.pdf accutron_service_manual_series_218.pdf

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Thanks. I already have the manuals for the 214, 218 and 224.

I was lucky too. My 224 had a hum but the hands were not moving. I cleaned and oiled the movement and phased it according to the manual. Then the index wheel started turning. I have been wearing it for the past week but it runs a bit fast. I may tweak the pcb to improve the timing at s later date.

My 218 was dead. I first tested the coils and found thst they were ok. I then desoldered the components, intending to replace the transistor. But I discovered that the leads of the components were spot welded to each other, then soldered to terminal posts on the coil assembly.

Anyway, I tested the transistor and it appeared ok. So I resoldered it to the coil assembly and the fork started humming this time. I haven't cased it up yet as the caseback is missing and have to fabricate a cell strap for it.

Now I'm hooked. I'm searching for an affordable 214 ( non working ) to try fixing it.

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I just fitted the battery strap that I made this afternoon. I'm surprised at how well it fits. This is purely by luck ( or Divine guidance) 20210715_225518.thumb.jpg.df8c165c171e799a7ebdcc7ae8079c0a.jpgas I didn't do any measurements at all.

It was made with just the dental tools I had in my office.

Probably can't make another one like it.

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  • 1 month later...

Since my last post, I worked on two 214s and a 218. I managed to revive one of the 214s and the 218.

218s are easier to phase than 214s. They can run on 1.55V silver oxide batteries without any problems. But 214s are another story. When a silver oxide battery is used in a 214, the watch runs crazy fast. We're talking about several hours per day. Rephasing it to run on 1.55V is a real pain. I think I've figured it out but I better get more experience before I disclose anything more.

Watch this space....

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As I understand it some 214 have an overall lighter fork than others, these are the ones that simply have too much amplitude and no amount of adjustment will correct it. I have used the special batteries (accucell), and they do work, but seem to have a shorter working life and iffy shelf life.

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On 7/12/2021 at 6:57 PM, HectorLooi said:

I've seen some Accutrons that were not tuning fork movements. Did Bulova continue using the name Accutron for quartz watches?

I think it might help to have a definition of what the word means which is not tuning fork watch but this ACCUTRON stands for  “ACCUracy through ElecTRONic". Or basically it's a nifty word that sells watches whether it has a tuning fork or not.

then for phasing are using the instructions in the book or the instructions at the website below? the reason I point this out the website below tells how to phase the watch for silver cells. 

http://members.iinet.net.au/~fotoplot/accphs.htm

 

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6 hours ago, JohnR725 said:

then for phasing are using the instructions in the book or the instructions at the website below? the reason I point this out the website below tells how to phase the watch for silver cells. 

http://members.iinet.net.au/~fotoplot/accphs.htm

 

I was following the instructions from the website, but I didn't have the variable power supply. I used an Accucell battery as the low voltage reference and a fresh silver oxide battery as the high voltage reference. 

The fresh silver oxide battery generates such a high amplitude that the index wheel tends to click 2 teeth each cycle, making the watch run crazy fast. Under a digital microscope with 90X magnification and a frame rate of 30fps, the movement of the index jewel appears as a blurry block. The width of the blurry block seen is the amplitude plus the width of the jewel.

The secret to phasing a 214 is getting the amplitude down to a level that it advances only 1 tooth each cycle. And that's the hard part.

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1 hour ago, HectorLooi said:

fresh silver oxide battery as the high voltage reference

I have a theory for you? Something that they don't explain in the phasing you can make this work but you going to have to take the meter out of which you're going to have to do the phasing without a meter then you should build get it to work.

My interpretation of what they're saying is that basically a phase like a normal tuning fork watch then you'd tested at the higher voltages and if necessary tweak it just a little to get the index rate where it's supposed to be. But you can't use a silver cell with the meter or any meter for the most part when you're doing this. The problem is you drop the voltage across the meter so with that fresh silver cell at 1.6 V. Dropping voltage across the meter when you take the meter out of it you now have a higher voltage and if you didn't phase for a higher voltage that's where you going to have an issue. That may be why they tell you take it as high as you can because at higher voltage at the watch is probably much closer to the silver cell voltage.

This is simplistic of what I said above is when you're doing the phasing or verifying the phasing of the higher voltage put the battery in the watch with no meter and then adjust so it runs up the correct rate that it should be fine.

 

 

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20210829_232126.thumb.jpg.74b7911c653202156320e349b3d236f5.jpg

This is my latest acquisition. All cleaned up and lubricated. It still runs about a minute fast per day. I'm not sure if it's a phasing problem or the oscillating frequency is off. I'll probably test it with my frequency meter to find out.

Is there any timing machine that can be used to regulae an Accutron other than a Vibrograf? I don't think I'd want to repair/ restore a Vibrograf and go through the hassle of using paper tracings.

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7 minutes ago, HectorLooi said:

Is there any timing machine that can be used to regulae an Accutron other than a Vibrograf? I don't think I'd want to repair/ restore a Vibrograf and go through the hassle of using paper tracings.

ask your question in the watch repair tools section?  the reason for this is I think one of the software-based machines that's currently out there can do this I just can't remember which one kind of.

then when they were more common there were actually quite a few machines that would do them. Of course the problem is finding the older machines even more problematic to find them running. I know for instance witschi used to have a machine or several probably I have an ancient machine around here somewhere that does them.

 

 

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7 hours ago, HectorLooi said:

Is there any timing machine that can be used to regulae an Accutron other than a Vibrograf? I don't think I'd want to repair/ restore a Vibrograf and go through the hassle of using paper tracings

Search for Vibrograf M80, no paper. I bought a working one for £75 and a broken one for £35 (will get round to fixing it eventually!) 

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On 8/27/2021 at 2:52 AM, HectorLooi said:

Since my last post, I worked on two 214s and a 218. I managed to revive one of the 214s and the 218.

218s are easier to phase than 214s. They can run on 1.55V silver oxide batteries without any problems. But 214s are another story. When a silver oxide battery is used in a 214, the watch runs crazy fast. We're talking about several hours per day. Rephasing it to run on 1.55V is a real pain. I think I've figured it out but I better get more experience before I disclose anything more.

Watch this space....

Are you thinking of dropping the dropping the battery's voltage down 0.2V to 1.35V? I've not worked on any Accutrons but I have modified a couple of Omega f300s (ESA 9162/4). I put the project to one side as I wanted to focus on mechanical watches a couple of years ago. I haven't sold the watches on as they technically aren't original but if you're interested I can let you know what I did, plus what I think might be an even better solution? You probably have the same thing in mind as me but the picture shows how awkward a job it could be - soldering without damaging the surrounding 50 year old circuit was the trick part!

19921132359358.thumb.jpg.12d9bc2c06dff64ede5eb14d25699deb.jpg

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2 minutes ago, HectorLooi said:

Is that a Schottky diode? I've taken apart an Accucell battery and it looks like there is a bidirectional Schottky diode in series to the battery. I think a bidirectional diode is used to confuse anyone trying to reverse engineer the Accucell. 

Spot on! The one I used is RB520CM-30T2R after trying some others, I didn't need to worry about it being bidirectional. The package is a SOD-923 which is just about small enough not to be noticed, but it was pretty nerve-racking soldering it as too much heat will melt the plastic on the module. The fix works perfectly on one Omega but the other one is a bit slow to start - it might be an unrelated problem. Even the dodgy Omega keeps time to under 3 s/day after a few months running.

I think the Schottky could be replaced with a resistor but it might depend on how much current each watch draws and that could change with the condition of each watch?

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https://www.ebay.com.sg/itm/BULOVA-Accutron-Automatic-Watch-Swiss-Made-Sapphire-Crystal-100m-All-Stainless-/234164475111?mkcid=16&mkevt=1&_trksid=p2349624.m2548.l6249&mkrid=705-154756-20017-0

This is what I mean. Bulova did use the name Accutron for watches that were not using tuning fork technology. 

I just got a 10 watch lot labelled as Accutrons. All of them were quartz. 

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  • 10 months later...
On 8/30/2021 at 7:57 AM, Plato said:

Spot on! The one I used is RB520CM-30T2R after trying some others, I didn't need to worry about it being bidirectional. The package is a SOD-923 which is just about small enough not to be noticed, but it was pretty nerve-racking soldering it as too much heat will melt the plastic on the module. The fix works perfectly on one Omega but the other one is a bit slow to start - it might be an unrelated problem. Even the dodgy Omega keeps time to under 3 s/day after a few months running.

I think the Schottky could be replaced with a resistor but it might depend on how much current each watch draws and that could change with the condition of each watch?

Hi all!

I'm new to the forum, but have a few used Accutrons (214, 218) I Picked up in the 80s (before Mercury cells went away) and some recent 218s that came with silver oxide cells - some within original accuracy spec and others not.

I've heard of Accucells and people installing schottky diodes in their watches (which seems like the better approach) but never thought much about it till recently.

I'm a retired electrical engineer and remember that one of the benefits of schottky diodes was lower forward voltage drop and .2 volts was an often mentioned number. However, what that drop actually is depends on the particular diode temperature and the actual forward curent. For an Accutron, it's 8 to 10 microamps. And for the diode part number you are using:

https://www.digikey.com/en/products/detail/rohm-semiconductor/RB520CM-30T2R/5955710

the typical forward drop in that curent range is:

  25C   .15 volts                                             -25C  .24 volts                                               75C  .06 volts                                               31C   .14 volts estimated  (skin temp)

The numbers will all be about .02 volts lower at 8 microamps drain.

It makes me wonder if a resistor (small axial, or SMT) wouldn't be a better choice. With a 1.55 volt cell, a 21.5K 1% metal film resistor will provide a voltage range (including current extremes and resistor tolerance) of 1.333 to 1.379 with lower sensitivity to off wrist temperature swings. The one concern that comes to mind is the initial circuit drain when the battery is first connected - and the related consideration for 218 versions that break the battery circuit when hacked.

I'm guessing the coils could be modeled as resistors and capacitors as their ESRs (plus knowing the transistor specs) to estimate initial current and 21.5K voltage drop. It's a possible issue the diode wouldn't have.

Any thoughts?

 

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Hi @PSquared, welcome to WRT.

I tried the Accucell before and I'm not really a fan. Because of the extra thickness occupied by the Schotty diode, a thinner cell had to be used, resulting in reduced battery life. I only managed to get about 6 - 7 months out of it and at the cost of the Accucell, it's just not worth it. 

Most Accutrons can be phased to use a silver oxide cell, save for some really hyperactive forks. 

I'm sure @JohnR725 will chime in soon and elaborate more on this matter. 

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