Replacement Reed Switches?

[abem]

Greetings,

I recently bought a P4 (Big Time) and found that the bottom (time) reed switch had been tinkered with in such a way that made it very touchy. In an effort to fix it, I managed to rectify the touchiness problem by rendering it permanantly broken (not surprisingly).

So, I was wondering about replacement reed switches. I believe that I'm looking for switches that are open by default and for the P4, they look like they need to be about 7mm long and 1mm in diameter.

My first guess was to take a look at the switches offered by Hamlin, since I had read somewhere that they made the originals for Hamilton. Hamlin's reed switch product guide is available online at the link below:
http://www.hamlin.com/specSheets/AN110A ... _Guide.pdf

They make an "Ultra Small" switch that's 7mm long with the product code: MITI-3V1 which would seem to fit the bill. These little guys are available from DigiKey for less than a buck and a half a piece:
http://search.digikey.com/scripts/DkSea ... e=HE516-ND

Does anyone know if these will work or what models of reed switches are preferred replacements for each of the Pulsar module types?

Any tips on reed switch replacement would be highly appreciated.

Thanks,

-abe.

[bruce wegmann]

Your best bet is to salvage a reed switch from a dead module. The P4s use the same switches as the Dress and Ladies' Pulsars [and of course, a switch from a dead P4 module will work fine, too]. There are wheelbarrows-full of dead modules out there, so finding one that way should not be a problem. I've never heard of Hamlin, so the interchangeablility with the original Pulsar parts is problematical, at best. Believe it or not, the company that made the switches for Time Computer all those years ago is still in business, and will still make parts to the original specifications [you have to know EXACTLY what to ask for, though, and they have minimun purchase restrictions on special orders...the one good bit of news is, the modern parts are vastly superior to the ones they made 35 years ago]. All their new production goes into medical devices [implanted pacemakers and such], so they HAVE to be good! Anyway, try a transplanted switch first...if a few other people are interested, maybe we could pool our orders and meet the minimum purchase requirement...PM me if interested.

[abem]

Bruce,

What company manufactured the reed switches for the P4 modules? I read that Hamlin made the switches for the original Electrodata / Hamilton prototypes and without anything else to go on, I assumed that they made the switches for the later modules as well:
http://www.xs4all.nl/~doensen/k1.html

If at all possible, I'd like to try to find a source of reed switches other than old dead modules both from an expense point of view and also from a reliability point of view. The reed switch that I broke on my P4 was extremely brittle and all it took was a slight force on the leads to fracture the glass enclosure. I was hoping that new ones would be more reliable and perhaps a little less fragile.

Digi-Key is the only supplier that I could find that has the Hamlin part (MITI-3V1) listed and they are backordered until the end of January 2010, so if you know of another reed switch manufacturer that makes something comparable, that would be worth trying.

Another company called Hermetic Switch Inc. offers a couple of switches that would seem to fit the bill. They are available in sizes between 4 and 10mm in length:
http://www.hermeticswitch.com/reedswitc ... ature.html
http://www.hermeticswitch.com/StockReed.asp

If you or anyone else knows the precise specs on the reed switches for the different modules, then please chime in since that information would be really useful in finding replacements.

Other than dimensions, I'd think that we'd have to match the magnetic sensitivity (in ampere turns?), resistance (ohms) and make sure that the switches are closed by default. I'm guessing that we probably don't need to worry about carrying or breakdown voltage and things of that nature since it's not a high power application. If someone knows what the sensitivity of the original switches is, I'm guessing that that is probably the most critical parameter to match. The ranges listed on the spec sheets look kind of rough, so we might have to just order a couple of switches and try 'em out. I'm not an electrical engineer, so these are all guesses.

On Ed's site, it says that for reed switch replacements "We stock 5 different strength reed switches(new) to cover the 4 types used originally (men's watches), and to accommodate weak magnet situations." It's not entirely clear whether those are old or new switches, however. Ed?
http://www.retroleds.com/Part%20and%20Repairs.htm

I'd like to try ordering a couple of new standard reed switches and If we strike out with those, then it would be worth looking into doing a special order. That's a very innovative idea. Ed notes that due to the weak button magnet issue, having the original reed switches may not suffice to entirely solve the problem.

-abe.

[bruce wegmann]

Hermetic Switch is the original manufacturer, so I would just forget about Hamlin [whoever they are]. As far as matching to the magnetic strengths of the buttons...a salvaged, vintage switch is still the best way to go [I have done dozens of such replacements, with no problems]. 99% of the problems show up on the demand switches [they are, after all, used a hundred times or more frequently than the setting ones]. If your need is really desperate, PM me, and I'll go through my wheelbarrow of deceased modules [I'm sure I can find something to get you up and running again]. BTW, all reed switches on the Pulsar watches are NO [normally open]. Finally, weak button magnets can be strengthened using a modern N-B-I magnet; the trick is to get the field polarity and orientation correct [but that is a topic for another thread...].

[rewolf]

... Hamlin [whoever they are]....

Hamlin used to be a (or even THE) leader in reed switch (and reed relais) technology and manufacturing - at least in the past, dunno about now.

[abem]

Bruce,

Thanks much for the offer of helping with replacement switches. I think that what I'm going to do is to attempt to order and try out a selection of new switches (from Hermetic Switch) and then report back results.

If I strike out, I'll be sending you a private message for help, but wouldn't it be nice to find a source of almost unlimited numbers of cheap, reliable, workable switches!

-abe.

[bruce wegmann]

If you're going to order anything from Hermetic switch, wouldn't it be more reasonable to order exactly what you know will work, rather than a Whitman's Sampler of switches? In fact, I can virtually guarantee you that the standard Hermetic parts won't work in a Pulsar watch; their magnet suseptability is the wrong value [remember, the original parts were made to non-standard specifications]. So, even if they will physically fit into the module, they just won't operate properly. If the special order isn't an option, you're going to be vastly better off doing the replacement with a transplanted vintage switch, and there is certainly no shortage of those [Ed, back me up here! Let's save this fellow from a lot of unproductive effort...].

[abem]

Bruce,

Hmmm... that is disappointing news. Are the non-standard switches more or less sensitive to magnetic fields than the standard switches? Any idea of the magnetic sensitivity of the non-standard switches in ampere-turns?

I did write to the Hermetic Switch people to see what they would say on the off-chance that there are some old-timers around who might still remember something about the switches used in the Pulsar / Hamilton modules. I also asked what the minimum size is for a special order to get an idea if that's even a possibility or not. I'll let you know if I find out anything.

-abe.

[bruce wegmann]

Oh, there are definitely people still there who remember making parts for "those strange-looking watches". I was told the President of the company [at the time I called] still had a Pulsar watch sitting in his desk. I got as far as having them send me a few samples for evaluation [so I can tell you, with authority, that the ones they make now are vastly better than the ones they made for Time Computer], but at the time, I couldn't come anywhere near affording their minumum parts order [at least a hundred per switch type]. You may get a bit luckier than I did, and get a better quote. If you do, let me know... But I have to say, I have proposed a combined group order in the past, and gotten NO response, so the grave-robbing of parts continues... Finally, I doubt that writing to them will accomplish much. I made all my inquires by phone, and I probably talked to half a dozen people before I had any worthwhile conversations. The Pulsar switches operate at lower-than-standard field strengths [I guess permanent-magnet techology has improved a LOT since the 70s].

[rewolf]

abem,
Digikey alone has 800 reed switches, according ot their search function: http://search.digikey.com/scripts/DkSearch/dksus.dll?Cat=1114199&k=reed%20switch.
Farnell is another big supplier.

There must be some modern replacement that fits at least mechanically - magnetic parameters/sensitivity are of course another story. But reed switches are so cheap that it could be worth a try. Not everbody has a pile of Pulsar modules at home to salvage from.

What's the reqired size of the Pulsar reed switch (length and diameter of the glass tube)? Normally open or normally closed? Maybe I even have somthing in the lab that fits.

[bruce wegmann]

Hey, guys, I think we're veering off the track here! All this talk of alternate suppliers and maybe finding something in a drawer somewhere that'll "fit" seems silly to me, especially when the original manufacturer is still out there! I don't know about the rest of you, but when I repair a module, I keep it as original as possible...that normally means vintage parts. We're fantastically lucky that the switches...really, the most vulnerable parts on the module...are still available from the original maker; I would consider a module repaired with a modern Hermetic part to be still fully original. Sure, Hermetic charges four or five bucks apiece, but that's a small price to pay to maintain the collectible integrity of the watch. Work with me here! There's a lot of Pulsar collectors on this Forum, and I'm sure quite a few wouldn't mind having a few spares around [or even need them now]. Let me know how many you need; if the number gets reasonably close to 100, I'll send the order in, and we can start putting correct parts back in these watches [as if there aren't enough bodge-jobs out there already!]. I'm ready when you are...

[abem]

Bruce has a good point. Although I'd prefer a working module with non original parts to a non-working one, I'd much rather stay as close to original as possible since that does appear to be a real option (which can't be said for displays, ICs etc). This is actually rather cool - the possibility of returning some number of dead Pulsars to life with almost original but improved parts instead of just cannibalizing the dwindling number of existing modules. From a historic preservation standpoint as well as as a purely selfish Pulsar mongering standpoint, that's a good thing, right? If this turns out to be a real option, I'm in for 25 switches. Anyone else?

[bruce wegmann]

Outstanding! I could use 15 or 20 myself...so we're nearly halfway there, already! Let's get this together and do it sooner rather than later.