What kind of potting material to use and best way to reseal?

[calabash]

Hello. I am new to the forum and would appreciate any answers any member can offer to the questions I pose below. I have successfully opened a Mark I module and wired in 2 new Varta V80H batteries. It works well now; keeps time and charges the new cells fine.

My issues are that I don't know what kind of gel would be suitable to refill the module with or what type of adhesive is best for resealing the case. I would like to wear the watch, but I am not going to attempt to sell it, treat it roughly, or put it underwater so a perfect seal is not necessary.

I would like for the seal to look reasonably nice, so I want to avoid adhesives that would cloud the module case. I just want to do something that is in the spirit of the original design and any suggestions from experienced persons would be appreciated.

Thanks!

[Synchroserious]

Hello Calabash, WTTF
It is very difficult to re-pot the module thouroughly.It requires a vacuum chamber for degassing a silicone or polyurethane poymer after sealing the watch permanently and leaving a hole in it for entry of gel under vacuum.In other words it is a big project with no guranteed results.The other thing is these different gel options out there do not come in a tube and most manufacturers want 1 Gal or 55 Gal minimum order.You have to mix it yourself,degass,pour and....___....all in 20 minnutes before it starts to cure


Now if you just want to fill the bottom area and leave the solar cell area without gel or with the old gel intact there may be a dielectric electronics type silicone in a tube you can pour on the bottom around the voids but bubbles will happen.These bubbles might not be as much an eyesore as compared to a bubble stuck between the solar cell and the Lexan top.


A good RTV clear silicone could do a good job of temporarily sealing things but you may have to inpect the seal for repair every few months.


If you don't plan on getting it wet much and everything works, your already jellin fine. Seal it up

Not sure how i was branded wizard here but i still have professional hands on experience.

[bruce wegmann]

Get yourself a tube of PermaTex 65AR Flowable Silicone Windshield and Glass Sealer. It has the viscosity of warm honey, is water-clear, and is designed to flow into and seal leaks around glass surfaces [believe me, this stuff sticks like crazy to plastic and metal as well, as long as the surfaces are clean]. I use it to re-pot replacement quartz crystals on Time Computer modules, and the result is indistinguishable from the original. It comes out of the tube bubble-free, and if you fill a 5cc syringe, you can let whatever bubbles that might form rise to the top, force them out of the syringe, and get a bubble-free volume of sealant into the case. It dries in an hour, cures fully in 24. If you can't find it locally, PM me, and I'll arrange to get you a tube [it's $7-8, not a big investment].

[Synchroserious]

However Windshield sealent does not stick well to Lexan plastic,it also has a chemical in it that can damage the Lexan,leaving a white cloud.Whatever you do make sure you have spare parts if it does not work out.As for using it inside near electronics and or batteries it is not made for that and is not an electronic potting/encapsulating gel compound by any stretch.The idea is to have future accsess to all parts so you do not want a potting gel that sticks hard to everything inside.


Just trying to keep you on the right track.

[retroleds]

there may be a dielectric electronics type silicone in a tube you can pour on the bottom around the voids but bubbles will happen.

I think Howard meant a non-dielectric: dielectric means it conducts electricity, it would short things out. On that subject, I'll weigh in that silicone of any type is a bad choice - that vinegery smell is acetic acid(same stuff that makes vinegar sour). It is harmful to fine electronics, but fine for sealing up big wires on appliances and such. If you are curious, put a big blob in the corner of a small glass jar, seal it and stick in the 'fridge....you will be amazed at the amount of condensate that appears.

[Synchroserious]

I meant a silicone with "dielectric strength" qualities that are non conductive.When considering the electrical properties of a potting compound for electronics one of the first things you look at are it's dielectric strength(arc resistance and dielectric constant) as well as volume and surface resistivity qualities.

[calabash]

I appreciate all of the information very much! I always thought dielectric meant it would not not conduct, so I looked it up:

Dictionary.com Unabridged (v 1.1) - Cite This Source - Share This
di·e·lec·tric
–noun
1. a nonconducting substance; insulator.[/b]

Anyway, regardless of nomenclature, we're on the same page. Again, thanks for the info!

[bruce wegmann]

By their very nature, silicone compounds tend to be highly dielectric [there may be some conductive formulations around, but they are a tiny minority]. Remember, we're only talking about insulating against three or four volts here, not kilovolts. If you go to either the Dow/Corning or GE sites, you will find pages of silicone compounds, grouped by properties and common applications. I would be astonished if among them you could not find one with characteristics exactly matching the original compound. Flowable silicone was used on the Time Computer modules with no damage to the electronics; it seems like it would certainly be worth a try here. It has worked well for me.

[Synchroserious]

Bruce. I am sure Time Computer or whom ever used the Dow Corning/G.E recomended silicones for electronics and not windshield sealent for a reason.If it were all that simple they(permetex) or someone would market it as for such use.I agree most all Silicone does inhearently have great electrical insulating properties but that does not mean it will not react with various metal surfaces while influenced with a magnetic field . It probably is just fine to cover a Quartz Crystal with the stuff Bruce mentioned but not for covering everything inside as a transparent gel.

MasterBond has this tube called SIL 711,I read they have a clear tranparent version.Maybe calabash or someone can get some of that in a sample order.

I really don't have answers yet myself on how to reseal and somewhat re-fill the inside with gel on old Synchronars.That practice was just never done,not even by RWR or staff.If any thing went wrong the person got a new module,not an opened up and fixed back together one.

[Synchroserious]

Or maybe one of the EP series from MasterBond that comes in a syringe?Remember both part A and B must be clear.Have good glass transition strength etc.

[bruce wegmann]

Obviously, whether we're talking about vintage Pulsars or old Synchronars, we are dealing with problems and modes of failure the original manufacturers never had to deal with, because it took more years for the problems to develop than the company lasted. So, we are forced to deal with kinds of repairs that the factory never had to face [I call this field of vintage LED repairs "geriatric horology"; human beings are no different...when people usually died before fourty, you didn't see diseases typically suffered by seventy-year-olds]. In that respect, we are in uncharted territory, making it up as we go along...future generations of collectors will face even more and tougher challenges.

[Synchroserious]

Well said Bruce but remember we're talking about a company that was around for 5-7 years versus one 37 years plus of poitting electronic watches.I could tell someone not to waste time on certain things,only to try to save someone from learning the hard way like my father had to do 10.20.30 years ago.Face it some silicones and polyurethanes are toxic while curring and can even cause electrical shorts with the 3M epoxy coated insulating fiberglass battery tape becoming conductive while the Silicone is in curring state.Been there done that bought the T-shirt and sold it at a garrage sale.

[bruce wegmann]

I say again, given the improvements in materials technology over the last 30 years [the batteries in these watches are a perfect example; much better batteries out there now, and cheap], there must be something not just as good as, but superior to, the original potting compounds, and available now. Just need to find it...time for some serious and dedicated research and experimentation by someone...I will stick to the Pulsars, myself, though.

[Synchroserious]

Well Bruce you are someone qualified for the Pulsar chat.I use the highest technology potting material available and yes it is expensive.If folks want to experiment with gel types to re- fill Vintage Synchronars I am still here to help on that as best i can.

[Synchroserious]

So Bruce you say there are much better Pulsar batteries out there than the ones made long ago? really? they last 30% longer now?

[Synchroserious]

Just in case anyone is still mis informed the batteries used in a Synchronar were always far supperior to any cheap batteries used in others.That is why several Synchronars made in the early seventies still work with thier original batteries.Since Nickel is now considered a bad thing in batteries NIMH batteries are used by the same manufacturer that made the 30+ year potential batteries.

[bruce wegmann]

Modern batteries now embody technology that neither your father nor all the Time Computer engineers could have dreamed of in the 70s; nickel-metal-hydride and lithium-ion, for example. Today's 357 cell has about three-quarters of the storage capacity of the old 355, in slightly less than half the volume...that means they last only three-quarters as long, but their ENERGY DENSITY [that is, the amount of power stored in a given volume]is 30% higher. If we could only convince someone to start making the 355-size cell again, we would get about 30% greater total lifetime per cell. I have no doubt that future improvements will make today's cutting-edge technology look crude and primitive [and I mean everything...metals, CNC fabrication techniques, semiconductors, you-name-it], but for the time being, we can only work with what we have. To return to the original topic; there are now dozens of encapsulants specifically formulated for the electronics industry...one or two must surely have the right characteristics for your application.

[Synchroserious]

Well my previous post I meant since cadmium is considered a toxic thing,not nickel my father switched to NIMH 5 years ago and there still is not anything better for a Synchronars charging circuit.Only Phil Bowler was using and promoting sub standard quality batteries in a Synchronar,not the inventor.

[retroleds]

I stand corrected on the dielectric vs. insulating terminology. I agree with Howard - the silicone conducts electricity while wet, and sometimes for several days afterwards. Take a working module, squeeze some silicone around the two wires, and you will have a dead module for at least 3 days. Securing them with it away from the wires is fine. And most silicones also have a fair amount of shrinkage while curing which seems like it would induce a lot of stress on the parts. Potting gels are still sold for a reason.

Something Howard and I have argued over, is whether or not the batteries are SAFE to seal up - Howard says they are. I, and some of the manufacturers say they are not.

So many answer and questions - this must be a good topic.

I took the middle road on the unpotted modules I bought off Howard about a year ago - small dots of silicone to hold the solar cell,module and batteries from shifting about(allowed to cure for a few days) and an extremely thin line of clear urethane caulk for the seal. I have no plans to swim with, shower with or pressure cook my Synchronars.

BTW: NiCads are still sold - they can withstand more charge cycles than either LI or NiH batteries before not holding a charge. But the other two are much lighter(laptops),smaller for their capacity and better for the planet.

[Synchroserious]

The thing to also avoid in gels,silicones or poyurethanes is PLASTISIZERS.It may take years but eventually this ingredient can breakdown the lexan forming small cracks.