EEVblog #920 - World's First Transistor Watch!

[EEVblog]

The Bulova Accutron Spaceview 214, the world's first transistorised
watch!
Space age technology from the 1960's, the world's most accurate watch at the time using a 360Hz tuning fork mechanism. Used by NASA on many space missions including Apollo 11.
See it operate at 1000fps!
All the info: http://members.iinet.net.au/~fotoplot/acc.htm

[MK14]

Thanks I enjoyed that. I'm amazed that it had 8,100 turns in those tiny coil, and that it had ONLY a single transistor, as the non-passive components. Not even a single IC there.
2 seconds per day accuracy, is pretty remarkable for a non-quartz time piece.

They were very impressive at the time they were popular (ignore the pun). But since they have been available until now, that DOES not mean you can guess my age. I was somewhat fascinated by them, and I agree, the sound was really something as well. The smoothness of the second hand movement was fun to watch.
Thanks for doing the video in such a comprehensive way. Seeing the back of it again (I'm NOT 100% sure it was that exact make etc, but it seems that it was), has brought back memories. Also taking the effort to record the sound, reasonably well, was a nice touch.
Seeing the 1,000 frame per second, was interesting seeing the tuning fork oscillate like that.

The purely mechanical watches of that time era, were pretty ropey by today's standards. What with forgetting to wind them (although some had weights which auto wound the springs), very poor time accuracy (in later ones, forgetting to advance the date at the start of the month, as this was not automatic) and an amazing lack of reliability. Some people would have like half a dozen (broken, but too expensive to bin) mechanical watches in their bedside cabinet, because they would tend to break every 6 months or so.

I think they were VERY expensive. I'm guessing, but maybe £500/$750 or maybe more (or less), in today's money. The battery life seems impressive as well, although I'm not clear exactly how long it lasts.

[EEVblog]

I think they were VERY expensive. I'm guessing, but maybe £500/$750 or maybe more (or less), in today's money. The battery life seems impressive as well, although I'm not clear exactly how long it lasts.

Yeah, US$1000 in today's money I believe.

[jnissen]

This is really cool! I had no idea that tuning forks were ever used in wristwatches. Fascinating stuff to consider this was developed in the early 60's. I really liked the slow motion showing the actual mechanical movement of the tuning fork. Good job.

[MK14]

I think they were VERY expensive. I'm guessing, but maybe £500/$750 or maybe more (or less), in today's money. The battery life seems impressive as well, although I'm not clear exactly how long it lasts.

Yeah, US$1000 in today's money I believe.

I suppose it is sort of equivalent to having the latest Iphone 7 or similar, so $1,000 is not so ridiculous. Many people (including me), get rather lost without an accurate time piece. By the sound of it, it was like the watches that were to come out some fifteen to twenty years later (quartz=accuracy + LCD=long battery life, since early LED ones had a potentially poor battery life and having to press the button to turn the Leds on for a second or so, was a pain at the time, I would think).

[EEVblog]

By the sound of it, it was like the watches that were to come out some fifteen to twenty years later (quartz=accuracy + LCD=long battery life, since early LED ones had a potentially poor battery life and having to press the button to turn the Leds on for a second or so, was a pain at the time, I would think).

Yes, it owned the market for something like 10 years, nothing else could touch it.

[MK14]

By the sound of it, it was like the watches that were to come out some fifteen to twenty years later (quartz=accuracy + LCD=long battery life, since early LED ones had a potentially poor battery life and having to press the button to turn the Leds on for a second or so, was a pain at the time, I would think).

Yes, it owned the market for something like 10 years, nothing else could touch it.

10 years is a very good run, and they would still make smashingly nice watches, even today.
It is a clever combination of electronics and mechanical engineering.

Because motors tend to use a hundred or more milli amps, if not amps, solenoids tend to use amps, and relays are often around 150 ma's, but can be lower or higher. How they get it to use such a tiny amount of power is also impressive.
Presumably it uses about 10 micro amps (guessing 100ma/hour battery capacity and 1 year life, battery life info via an internet search).

So about a 10,000th of what a (100ma) relay coil would use. I guess the 8,100 turns in the coil helps, and it only needs a relatively tiny movement to keep going (resonance), so the current scales down. Still amazing.
Also the current may only be needed for tiny fractions of a second, so it may be a couple hundred micro amps, but only for 5% of the time, or something like that. So 10 micro amps, is the AVERAGE.

EDIT: tl;dr
It would be interesting to connect a scope up to it, and see the current that it uses, and its waveform, over time. Is it discrete pulses of consumption or a more continuous affair ?
Any capacitors across the supply would make it a lot harder to measure (a quick look again at the circuit diagram in the video, seems to show that the capacitor is NOT decoupling across the battery, so it should be ok). I guess these watches are so valuable, tiny and delicate, it is difficult to sort out.
Your video shows how difficult it is to open them as well, ideally needing a special tool and great care and training (on how to open those watches).

[nctnico]

I wouldn't be surprised that movement of the tuning fork circulates some of the energy around so it may use even less energy than you'd expect when just driving a solenoid.

[MK14]

I wouldn't be surprised that movement of the tuning fork circulates some of the energy around so it may use even less energy than you'd expect when just driving a solenoid.

Well one of the pages, found by following Dave's original link in the OP post, has a fair amount of technical details, explaining how it works.

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

It does seem to say that it is "off" a fair amount of the time (using little power), but through the use of the feedback coil(s), the transistor turns on and regulates the thing, as it oscillates. Amazing for just a single transistor, and very clever because transistors were incredibly expensive, in the early days of those watches being produced. So if it had, had twenty transistors, it would have probably been considerably more expensive, and maybe too big to easily fit in a watch.

It also would probably have used too much current. they could of just about put more transistors into an IC for it. But in the early 1960's IC's were in their very early days and would have been prohibitively expensive (I think).

The linked to article does say it was a significant/major job to develop it, like it ended up.

Extract:

The Electronics

While it is relatively simple, it is neverthless interesting how the electronics driving the Accutron works. The electronic circuit combined with the tuning fork forms a a servo system . Each of the iron cups of the tuning fork has a little magnet inside it, surrounded by a coil. The fork provides the resonant or tuned part of the circuit while the electronics provides a sustaining circuit and feedback control from the fork, which is created by induction by the fork into the feedback coil.

Power from the battery flows through the transistor, and then through both of the driving coils. One of the coils (the one which is attached to the plate holding the transistor and its components) also has a secondary coil built into it. When the fork springs one way, this secondary coil provides a feedback voltage which causes the transistor to almost stop the flow of current in the driving coils, and stop driving the fork. When the fork springs back the other way, this feedback coil generates a "reverse" voltage, which causes the transistor to allow current to flow in the driving coils again. The fluctuating current in the driving coils produces a varying magnetic field, which alternately attracts and repels the tuning fork magnets. Thus it keeps on vibrating. The system is self-regulating. If the watch receives a jolt which adds to the fork vibration, the circuit automatically reduces power to the fork until it reaches the normal amplitude of vibration. The reverse is also true. While I said it is simple, it took quite a lot of work to develop the electronics to vibrate the tuning fork at the right amplitude, and yet work at such a low current that a battery would last at least a year.

[Tim T]

Nice blog.

Bulova date codes are
1950's: L
1960's: M
1970's: N

So Dave's watch M9 = 1969.


This is one example where it would be better not to take it apart. The case and movement could be easily damaged if handled by a novice without the correct tools and training. No offense intended... watch repair is a hobby of mine and while comfortable disassembling/reassembling a typical 17 jewel mechanical movement I will not touch an Accutron.

tim

[rollatorwieltje]

The index wheel on this thing is less than 3mm in diameter and has 320 teeth. I wonder how they mass produced that. Even with a microscope the teeth are barely visible.

[TheSteve]

I want one! It would look great next to my 1991 Motorola Pager Watch.

[Fungus]

How long does the battery last?

[Fungus]

Your video shows how difficult it is to open them as well, ideally needing a special tool and great care and training (on how to open those watches).

I dunno about "training" but yeah, it's a special tool to unscrew the back. You can get one on eBay for <$5.

eg. http://www.ebay.com/itm/232019738190

[G7PSK]

In the late 60's early 70's I was an apprentice watchmaker. I can remember one of those being brought in for repair, as a lowly minion I was not even allowed to touch it that and the service was reserved for the boss. Around 1967 Seiko introduced the quartz watch which as I remember it was advertised as being accurate to 3 seconds in a million years, I always wondered who would ever be able to claim on that.

The second hand on the Bulova  watch dose move in steps it has to due to the way the mechanism works, it is just so small and so fast a step that it looks smooth to the human eye, the first quartz watches were the same but soon got reduced to one second movements due to power requirements. Some of the very early watches had a rechargeable battery in the back and were recharged with what looked like a converted torch, the front lens of the torch was removed and a clip like device was screwed into the bulb holder. The clip thing had a single resistor inside to limit the charge current and the watch batteries were around 30mm dia and 2 to 3 mm thick and I think some type of Ni-cad. 

[MK14]

Your video shows how difficult it is to open them as well, ideally needing a special tool and great care and training (on how to open those watches).

I dunno about "training" but yeah, it's a special tool to unscrew the back. You can get one on eBay for <$5.

eg. http://www.ebay.com/itm/232019738190

As Dave explains in the video, and from reading sources about this watch myself, in response to the video. They seem to explain that opening this watch (even to ONLY change the battery), needs *training*, so that you can avoid damaging the delicate and very rare/expensive collectors watches.
Apparently opening the back, is only the first part of the problem in repairing the watch and/or changing the battery.

The "training" can probably be done by reading up on how to service these watches (including simply changing the batteries), and maybe watching any applicable youtube videos, if available. Especially if you are already into electronic item repair.

[G7PSK]

You also need very fine mechanical skills to repair these watches, they still have gear wheels and an escapement device the only difference between these and clockwork watches is the driving force.

[Fungus]

Your video shows how difficult it is to open them as well, ideally needing a special tool and great care and training (on how to open those watches).

it's a special tool to unscrew the back. You can get one on eBay for <$5.

As Dave explains in the video, and from reading sources about this watch myself, in response to the video. They seem to explain that opening this watch (even to ONLY change the battery), needs *training*, so that you can avoid damaging the delicate and very rare/expensive collectors watches.

Apparently opening the back, is only the first part of the problem in repairing the watch and/or changing the battery.

Yeah, I wasn't talking about repairing it or taking the innards out. The claim was that simply taking the back off is difficult. It isn't.

[MK14]

Yeah, I wasn't talking about repairing it or taking the innards out. The claim was that simply taking the back off is difficult. It isn't.

But if you need a special tool, which most people don't have. Then I'd consider that not so easy to open, then.

If Dave with all his impressive electronic tools, equipment and skills, can't open it, without purchasing a special tool. Then I'd consider it far from easy, even to open the back up.

It might be all too easy to somewhat badly scratch the watch (especially the back), if you don't even know how to take the back off properly. So if it is worth a large amount of money (rare collectors watch) and still in relatively scratch free condition. You could do hundreds of dollars worth of damage, just by clumsily taking the back off.
I DON'T know that for certain, but that is the impression that I got from watching Dave's description of the situation and my own experiences, of trying to open difficult watch backs.

[Fungus]

Yeah, I wasn't talking about repairing it or taking the innards out. The claim was that simply taking the back off is difficult. It isn't.

But if you need a special tool, which most people don't have. Then I'd consider that not so easy to open, then.

If Dave with all his impressive electronic tools, equipment and skills, can't open it, without purchasing a special tool. Then I'd consider it far from easy, even to open the back up.

It's not like it's welded shut though, or needs a special waterproof gunk to close it back up again or something like that.

The astro-computer teardown linked to at the end of the video. THAT was "difficult to open".

Needs a special $5 spanner? Not in the "difficult" category. Not really.

[rollatorwieltje]

Even with that tool it's a pain to do it. When it hasn't been opened for a long time quite often the back case will be extremely stuck. It's even worse on this watch as it has a separate battery slot. The proper tool has the exact dimensions so it's less likely to slip. It's best to replace the gasket as well when you open it.

There's also nothing interesting to see, you still can't take the movement out and the rear doesn't show much anyway. You'll have to disassemble the movement to look at the gear train. I highly recommend you don't do that without experience.

[MK14]

It's not like it's welded shut though, or needs a special waterproof gunk to close it back up again or something like that.

The astro-computer teardown linked to at the end of the video. THAT was "difficult to open".

Needs a special $5 spanner? Not in the "difficult" category. Not really.

We are not really disagreeing here (just having different perceptions of how difficult something is). It is somewhat arbitrary, what people consider to be difficult and easy. For ME, I would definitely consider that difficult and best left alone. I don't like having to go out and buy special tools for things, when I have a fairly comprehensive set of screwdrivers etc, already available to hand.

I somewhat recently tried replacing the battery, on my fairly cheap, "normal" digital watch. It has ridiculously tiny screws, one of which I managed to drop/lose permanently, and had great difficulty opening it.

It then had this horrible metal flimsy clamp thing, which I couldn't easily see how to get it to open, and out of frustration, managed to bend it (and/or snap plastic bits of it or something) and make it fall out (in a way it was probably NOT suppose to).

As a result the alarm sounds/beeper is almost 100% bust and I ended up leaving the old battery in it. When it eventually fully runs out (maybe a 10 year lithium battery), I will probably scrap the watch and use another one or buy another one. I have had the watch a long time, and I think it is already on the (if I remember correctly) second or third battery (previous attempts were successful at changing the battery I think), and it is partly worn, so it is not a problem, scraping it.

You also need very fine mechanical skills to repair these watches, they still have gear wheels and an escapement device the only difference between these and clockwork watches is the driving force.

This I think is the main reason why it is recommended not to open one, unless you are ready for them.

[Fungus]

I don't like having to go out and buy special tools for things, when I have a fairly comprehensive set of screwdrivers etc, already available to hand.

But ... you already went out and bought some special-purpose screwdrivers? 

[amyk]

Obligatory service manual link: http://www.timetrafficker.com/about/watch-care/pdf/accutron-214-service-manual.pdf

You also need very fine mechanical skills to repair these watches, they still have gear wheels and an escapement device the only difference between these and clockwork watches is the driving force.

Unlike typical mechanical watches which are relatively robust, the index wheel in these is extremely fragile and easily damaged (and also quite expensive.) The teeth are approximately 10um high.

[MK14]

I don't like having to go out and buy special tools for things, when I have a fairly comprehensive set of screwdrivers etc, already available to hand.

But ... you already went out and bought some special-purpose screwdrivers? 

Compared to many households, I agree. We typically have many things most house holds don't have, such as oscilloscopes and MCU test boards, etc etc.

I suppose if you had an old version of that tuning fork watch, did not realize how valuable they were, and it was already broken and/or somewhat badly scratched. You could probably buy that ebay tool, and open it up.
But as others have said/implied, that is probably not a good idea. It is better to either let someone with the skills and experience of dealing with those watches, handle it. Or train yourself up, using available resources.