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P3, date won't turn off unless you use the magnet

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dodger1954

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P3, date won't turn off unless you use the magnet

Post25 Aug 2018, 23:47

Hi Gang,

I recently acquired a goldfilled Pulsar P3 watch on eBay, and while I didn't really expect that it might work, it actually DOES work, and keeps perfect time! However, it has ONE annoying problem, which I have not been able to figure out: whenever you press the left button to display the date, and then release the button, afterwards the date display STAYS on, and will not turn off, unless and until you wave the magnet around on the backside of the watch, at or near the 'hours' indentation, on the watch's caseback. Is this due to a stuck reed, as I have read about in others' posts? And, if so, what can I do, to remedy the situation? The watch DOES work really well, apart from the date display staying on perpetually, and I suppose I could just use it as is, as long as I'm careful to never press the date button.. ;-) .

Also;...other than the problem with the date, the watch does have some condition issues, which, although they're not all that serious (at least, to me), I wondered if they could be addressed: for one thing, the red lens, which is in pretty decent shape otherwise, is missing the 'Pulsar' logo, that these watches would usually have (however, the lens doesn't look like it ever had a logo on it...?), and I'm wondering where another lens could be found, and how hard it is, to replace it?

Additionally, as you can tell from the picture, one of the links of the bracelet is missing its' top-cap piece, and I was thinking that I might just remove that one damaged link entirely, but, I couldn't figure out how to disconnect it. I did manage to disconnect the upper end, towards the watch case, but I couldn't figure out how to disconnect the other end. It looks sort of like a large, beefy springbar, but I could not get it to compress to remove it, so, I'm not at all sure if that's how it's done...?

Thanks in advance, for any help or advice that you guys can offer. I'd always wanted a Pulsar, and specifically a P3, as I think they're so futuristic-looking, and even though this one definitely has some condition issues, I'd be perfectly happy with it as it is (especially for the price I paid for it, which was only $100!), if I can at least figure out why the date display won't turn off.. :bang:

Thanks,
Dodger
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767Geoff

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 03:54

The reed switch is not releasing.

The wave of the second magnet is strong enough to release the reed switch.

So, some options from easy to harder:

- Reposition the reed switch away from the push button magnet. To do this try putting a spacer between the offending push button magnet and movement. A thin metal shim.

- reposition the reed switch away from the offending push button magnet without breaking the reed switch by moving it slightly.

- Replace the magnet inside the push button with a weaker one.

The upshot is the push button magnet is too strong now for the reed switch because the reed switch return to an open state is weaker.

I would try inserting a thin metal shim between the module and the push button magnet.

Cheers, Geoff
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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 05:27

Is it possibly the button itself that is sticking in the on position? Peter
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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 06:02

To Geoff:
Thank you very much for your reply, it is greatly appreciated! While I have tons of red LED watches, this is my first Pulsar (well, I bought a silver one a couple of years ago, but it didn't work, so I resold it, for parts or repair), and as such, I really didn't have much of a clue as to how they work. So, when you mentioned the internal magnet, I'm embarrassed to say that I didn't know that it HAD an internal magnet, or magnets, nor would I have any idea as to how to access it, to replace it. So, I wonder how I would go about accessing it, or where to find another magnet, if I did successfully get it open? I think maybe, finding somebody who actually knows what they're doing, might be a better way to go, rather than risking destroying it, myself? But, then, I don't know anyone who does that type of repair, or how much it would cost...?

To Peter:
No, the button doesn't appear to get stuck, and is actually quite "springy". It pushes in and retracts with ease, and seems to come back out all the way, too, whenever you release it. Do you think it would do any good, to spray a spritz of electronic-contact spray into or around the button, either on the outside or the inside of the watch, to see if that helps? Or, do you think it might be harmful, to do so?


Thanks very much,
Charles
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767Geoff

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 06:50

The buttons are soldered sealed inside the case. That is the button/magnet is inserted, then a spring is inserted. This is then sealed in the case by a thin metal plate. This limits the movement of the button in its chamber. Over time the magnets lose their magnetism. Dirt can enter this chamber via the exterior button case interface. Dirt cannot penetrate the case as this chamber is sealed from within with solder and the metal plate.

A weakening magnet would make it difficult to engage the reed switch.

Therefore it is the reed switch which is at fault, ie: it has become sensitive over time. So opening the back of the case and inserting a thin metal shim to: a) move the module away from the button/magnet and therefore the reed switch from the magnet and b) to reduce the magnets strength.

This would be my first attempt at a repair.

At the factory it was a balance and finesse to which reed and magnet would work correctly. Over time the precise magic drifts as in your case.

Geoff
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767Geoff

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 07:00

Also,

Try introducing (spraying) isopropyl alcohol Into the external button case interface. Then work the utton while introducing the alcohol into it. The shape of the button is such that dirt may not be letting it release fully. The magnet is attached to the base of the button and floats in the chambe with the button.

The shape is that if a flange. Dirt may work it’s way between t(e flange and the button.

Do this with the case back in place.

Contact solvent like DeOxit gold and etc. Won’t make a bit of difference as there is no electrical contact when the button is depressed. It is simply deforming the internal reed switch encased in a glass tube (think relay) which completes a timing circuit for display.

Look up “reed switch and magnets”.

See this b6 oldpulsars:

http://oldpulsars.brinkster.net/phpBB2/ ... c.php?t=58

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 07:14

Hi Geoff,

Thank you for all of your replies and your help, you've been really great with the descriptions of the inner working of Pulsars, and I really appreciate it :) .
Now, I can't wait to give it a try with a shim, to see if that takes some of the pressure off of the magnet set-up, and hopefully make it work properly. But, as to the shim, does it necessarily have to be a metal shim, or would a thin piece of plastic work, as well? I've used a thin piece of plastic, before, to put a shim between the watch case and module of other red LED watches, to try and get the module's contacts just a bit closer to the buttons, but, I've never tried to put a shim in a Pulsar, before. Anyway, I'll also try spraying some isopropyl alcohol into and around the button, to see if that helps at all. So, thanks again, and I'll let you guys know how it goes :) .

Cheers,
Charles
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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 07:29

What you have is technically known as a "latching" reed switch. While it could be a defect in the reed itself, this is highly unlikely.
A too-strong button magnet is the most probable cause, and it is easily remedied. Time Computer's solution was the installation of a small piece of mu-metal (pronounced "mew") over the inside of the flat button plate. Mu-metal is a special nickel-iron alloy with low magnetic permeability, and so "shields" the reed switch from some of the button magnet's field...effectively weakening the magnet without actually changing it's field strength (note: ordinary metal foils will do little to nothing). Time Computer referred to these as "high-mu shunts", and they are typically 3x5 mm in size. The amount of shielding effect can be adjusted and fine-tuned by changing the position of the shunt on the button plate (it can also be trimmed to smaller size, if necessary; the metal is only about .1mm, about .004 inch, thick). A cyanoacrylate adhesive is the fastest and simplest means of fixing the shunt in place.
BTW, NEVER remove a button from a case unless it is severely cosmetically damaged, or immovably jammed...they are extremely difficult to re-install properly (in 16 years of doing repairs on Pulsar, Hamilton, and Omega watches, I have had to do this only three times).
Since you are in the United States, I could send you a couple pieces for a few dollars.
I'm pretty sure I can help you with the damaged bracelet link, too.
Last edited by bruce wegmann on 28 Aug 2018, 23:38, edited 1 time in total.
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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 08:21

Hi Bruce,

Okay, I tried Geoff's suggestions about trying to wedge a thin piece of metal between the module and the watch case, and there was simply NO way to accomplish it without removing the module entirely, and I was afraid to try it (I assume you have to remove those two small screws, to get the module out, right?). Also, spritzing isopropyl alcohol into and around the button had no effect, either...in fact, the more I tried to get it to work right, the worse...MUCH worse...that the situation got, because the watch suddenly stopped working, at ALL! So, in a panic, I took the back off the watch yet again, and removed and reinstalled the batteries, and it suddenly, thankfully, decided to work again...whew!! Of course, the left button still stays "on", when you push it and release it, the same as before ;) .

Anyway, as it turns out, the thin piece of metal I was trying to wedge into it, probably wouldn't have done any good, after all, since it needs to be the high-mu metal, right? Well, then, I'm glad I hadn't had the nerve to try and remove the module completely, trying in vain to shim it up with any ordinary piece of metal. And, I'm also VERY glad that I didn't mess up the watch completely, while I was trying these do-it-yourself attempts. But, all that aside...Bruce, rather that having you send me some bits of mu-metal, and risking me ending up totally destroying the watch in my efforts, would you be interested in giving it a try, to see if you could fix the problem? If so, I'd gladly send it to you for repair, and then you might also be able to replace that damaged bracelet link (or two?), if you happen to have a couple of extra links laying around. Obviously, as the watch already has significant wear to the bracelet, even a couple of previously-used but functional links would be greatly appreciated! Or, as it is right now, with the number of links it has in it, the watch fits my wrist perfectly, so even ONE link, replacing that broken one, would be fantastic! Anyway, do you think you would be interested in taking on this poor old, badly-mistreated Pulsar?


Thanks very much,
Charles Jenkins
Shalimar, FL
850-651-3272
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bruce wegmann

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 09:19

Short answer...yes. I will call you Sunday afternoon (allowing for what must be a two or three-hour time difference). I have all the correct parts and tools to do the repair.
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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 14:30

Hi Bruce,

Hey, that would be really terrific, thank you so much! I'm so happy to get this baby fixed, as I'd always wanted my own Pulsar P3, and now I've got one...I've got lots and lots of other red LED watches of all kinds, but not a (working) P3 until now. and I think this Pulsar is destined to become one of my favorites, for daily wear :) .
Ohh, and yes, we're on Central Time, here in the Florida Panhandle, so it's two hours' difference. But, please feel free to call anytime, as I'm here pretty much all the time.

Cheers,
Charles :)
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767Geoff

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Re: P3, date won't turn off unless you use the magnet

Post26 Aug 2018, 17:19

Well the expert has waded in! (Bruce) :Hi:

Mu metal of course, certainly not plastic. Plastic will not reduce the strength of the magnet. It wont take much to do it and the module will have to be removed to do this.

:?:
Bruce, a question, why would the magnet become stronger over the last 40 years and not weaker? Surely this watch didn’t leave the factory this way.

I too have only removed the button once, had to to release it from a jammed and dirty position. Fortunately it worked correctly after the repair

Cheers, Geoff
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Re: P3, date won't turn off unless you use the magnet

Post29 Aug 2018, 00:34

Exposure to a strong external magnetic field can either weaken, or strengthen, a button magnet, depending on the field orientation of the applied magnetic force. I have successfully re-strengthened buttons with a rare-earth magnet. Button magnets were made of AlNICo5, a mix of aluminum-nickel-iron-cobalt powdered metal, heated and compressed (sintered) to shape, then magnetized. They were the strongest permanent magnets we knew how to make, at the time, but had relatively low coercive-field strength value.
Engineering definition:

Coercive field strength Hc describes the force that is necessary to completely demagnetise a magnet. Simply said: the higher this number is, the better a magnet retains its magnetism when exposed to an opposing magnetic field.
There are differences between the coercive field strength bHc of flux density and the coercive field strength jHc of polarisation. If a magnet is exposed to a demagnetising field strength of bHc, the magnetic flux density in the magnet disappears. The magnet itself is still magnetic, but the flux density that the magnet generated is contrarily exactly the same size as the flux density of the demagnetised field, so that the two cancel each other out. The magnet only loses its magnetic polarisation, and thus its total magnetism, by a demagnetising field strength of jHc.

Neodymium-boron-iron (rare-earth) magnets typically have field strengths many times higher than necessary to re-polarize AlNICo magnets. The trick is to get the field orientation and polarity right...usually takes a bit of experimentation; the reeds are polarity and orientation sensitive.

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