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oldpulsars · Posted: Tue Jan 29, 2008 9:46 am Post subject: What's in those Pulsar buttons?

The first button assembly was invented by John Bergey. The early Pulsar button assembly unutilized a Placovar (Cobalt-Platinum) magnet. Placovar was a company trade name for the magnets used in the button assembly. Placovar was a product that came from the Military Division of HMW and developed and patented by Marlin S. Walmer. These small powerful cylindrical magnets produced an average of 1.300 gauss and were pressed into the button vertically, or perpendicular to the reed switch. These small powerful magnets were also used in Hamilton's fiirst electric watch. The large stock of magnets (left over from the electric watch project) played a big part in the Pulsar watch project.

As stock of the CoPl magnets dwindled and precious metals increased a new and improved button assembly invented by Arthur O?Connor using a Samarium-Cobalt magnet replaced the early button design. Using an epoxy to fasten the magnet to the spring clip in the horizontal position, there was no longer a need to press the magnet into the button. This was a much more economical assembly as well as the cost savings of the magnets. Both button assemblies used a Million Cycle Havar spring.

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Greg Ratcliff · Posted: Mon Mar 03, 2008 11:22 am Post subject:

The newer magnets may have been less expensive and more practical but ,we ran into alot of button repairs because the magnets would become detached from the spring. I guess the epoxy wasn't made for the pushing of the buttons every day. Or if you accidentally dropped the watch 1 or both would become detached. After this happened you had to replace the buttons for the watch to work properly. Greg R.

oldpulsars · Posted: Tue Mar 04, 2008 9:42 am Post subject:

Thanks Greg . . . for those unfamiliar, Greg worked at the Pulsar Service Center owned and operated by his father, Eddie Ratcliff.

The Service Center was created to honor their warranty program after Time Computer closed. Ratcliff was the Service Manager at Time Computer at the time of closing so Ratcliff was a natural to take on the challenge.

I am working on a section on the OldPulsar.com website that will provide more details of the Service Center as it played an important part in the history of the Pulsar.
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oldpulsars · Posted: Wed Mar 05, 2008 5:09 pm Post subject:

Another interesting fact about the original Platinum-Cobalt magnets was revealed just last month. Thousands of these small cylindrical magnets were already an "Off-the-Shelf" item at Hamilton. The first electric watch used them as part of their analog movement. Those that know the history of the Hamilton Electric know the watch nearly bankrupt the company due to warranty repairs for problems with the 500-501 movements.

In the late 60's, when button discussion came up for the Hamilton Prototype (co-developed with Electro/Data) the costly magnets suddenly had a place to go. It's anyone's guess how the button would have been designed if Hamilton didn't have such a huge investment sitting in inventory.

Only when Time Computer could see an end to the stock of the Platinum-Cobalt magnets was a less costly magnet developed. The magnet-reed button concept gave a unique definition to the Pulsar unparalleled by any other digital timepiece! It's clear to me this concept contributed to the huge success.
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Greg Ratcliff · Posted: Sun Mar 09, 2008 2:11 pm Post subject:

Probably the nicest thing with the plat-cobalt magnet was you could adjust the magnetism of the button with a magnetiser/ demagnetiser. The newer magnets you can't or you will detach the magnet from the spring. I guess that's why there were 4 different colors of reed switches. We had to put the right set of reed switches in modules to go with the buttons magnetism for the watch to work perfectly. Greg Ratcliff

pulsar3 · Level 5 Joined: 07 Mar 2008 Posts: 113

I have several Pulsar watches with push buttons- i.e. a Classic, a green and red men's dress. Now that I have several to compare things to, I noticed that some of the buttons have more of a "springy" feel to them than others, while some you have to push down a little more or a little less- although they all work fine. What accounts for the differences- would it be the springs? the magnets?

hdled · Moderator Joined: 26 Jun 2007 Posts: 51 Location: USA

Looking at the illustration above, you see that the reed switch is comprised of two overlapping metal blades located inside a glass tube filled with an inert gas. The blades come together to complete a circuit when exposed to a magnetic field.

While these magnets were machined to be very close in physical size, it didn't take Pulsar long to determine that they did not all produce the same amount of magnetic strength (gauss). Depending on the model, Pulsar tested and assigned each magnet into two or more categories of magnetic strength. Reed switches were then manufactured to coincide with the different levels of magnetic strength. The switches can be identified by the color code painted on the end.

This did not mean that every reed switch engaged at exactly the same distance of pusher travel. There were small differences from one watch to the other. Like you said in your question, "some you have to push down a little more or a little less- although they all work fine." And that is the point. Pulsar knew that they weren't all going to be exactly alike, but they would all fall within an acceptable range.

pulsar3 · Level 5 Joined: 07 Mar 2008 Posts: 113

Thanks- that clears things up!

Handy · Level 3 Joined: 05 Aug 2007 Posts: 22 Location: England

A fascinating thread.
I have never seen the later type buttons and was wondering what models they were used in?
Sorry to revive such an old thread but I feel that it is an important one.
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Ian G1DRP

oldpulsars · Posted: Mon Jul 05, 2010 2:55 pm Post subject:

From all indications, they ran out of the V.1 magnets sometime in 1976. You'll find the Version II buttons in the later P4 and Men's Dress models.

Thousands of new watch cases were destroyed by a hammer and nail-set at the Radcliff Service Center in the late 80's. In an effort to find a way to make money from something that nobody wanted at the time, buttons were punched out of cases with the V.1 magnets to recover a few bucks from the platinum in the magnets. I have personally seen hundreds of these cases.
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Handy · Level 3 Joined: 05 Aug 2007 Posts: 22 Location: England

That explains why I've never seen the later type. I am only interested in the P2, P3 and Sport models.
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Ian G1DRP