synchronar resurrection

[clockace]

moving along on this project. i had problems getting the back to fit down all the way, as the 80mAH cells are thicker. even with the gel removed down to the pc board it was not quite enough. i think one problem was the interconnect strip is on the pc side. i should have had it welded on so it was on the top. i suppose i could unsolder the wires and turn it over, but i had enough of that. what i did was use my foredom motor with a burr and remove some of the lexan inside the back where the cells were touching. the thickness at the cell recess is about .045". i removed about .015 in the area of the solder tabs. now it fits down fully. the watch is running great, keeping good time. i have located a place in ca. that sells weldon #16 in a 1.5oz tube which is used for gluing lexan. it is syrupy thickness and should do the job. does anyone have any idea how long the nmhi cells are good for? the nicads that were in it began leaking after 5-6 yrs. that is why i opened it and took them out yrs ago. when i get it done i will post some photos if i can figure out how to do that. suggestions? peter

[767Geoff]

Seriously, good for you. I just purchased a mark III sunwatch and Synchronar Mark III and hope I can get them working also.

The NiMH batteries according to Howard Riehl should last the 30 years or so and are not as subject to the memory effect and overcharging that the older NiCd batteries were.

See Howards response to my query along the same lines, concerning my just assembled Synchronar Mark IV by Howard this spring:

http://dwf.nu/viewtopic.php?t=2634

Cheers, Geoff

[Synchroserious]

The older Nicads were not themselves prone to leak.It is a great mis diagnosis to say that was the problem.If i didn't know any better i would tend to think that was the problem to.However the greater majority of Synchronar/Sunwatches that ever developed any corrosion or leaky batteries inside was the result of 1 or more of the following reasons.
(A) Bad mix of potting (B)Potting material found to react with epoxy glue on 3m electrical tape while curring, causing electrical shorts and hence the batteries to then over vent or Leak.(C) Poor main seal or seal at plug area.D) Defective Lexan mold that caused small cracks to form and permit water and or other invasion.(E) chemical reactions between dissimilar metals and silicones failure to block water and Ion diffusion that formed a white cloud.
Bottom line is the old Nicads DID NOT LEAK or vent to any damaging degree on their own unless overloaded.Overcharging was never a factor in causing them to leak.
With all that said some batteries were just plain better than others even though it was the same manufacturer and yes a small percentage of them were defective or became defective on their very own.

All of the possible problems above are avoided now with better sealed non toxic NIMH batteries,good Lexan with metal plate at the bottom,great permanent seal and a non Silicone potting material.

I can't say how long the New NIMH batteries will last.Logic tells us since some of the older Synchronars with Nicads go 10,20,30 years or more we should get similar or better results.As for predicting how long the NIMH batteries will last in an opened up and self repaired module that is a mystery in itself.

[rewolf]

Nice summing-up of possible causes of battery corrosion. I read it with great interest, though I don't even have a Synchronar. Thanks, Howard

[clockace]

thanks howard & rewolf. i guess some cells are better than others as you said. it is possible that the lexan seal leaked in sea water on my watch. it has been many years, but if i remember right it was after i had a swimming session in the pacific at san diego that i noticed problems. not only did i see corrosion on the cells thru the back, but also a small blemish in front of about one half of the led area. it partly obscurrs the lower half of the display. not enough to blank it out, but a haze is there. it looks like a separation of the gel right inside the lexan front. unless you turn on the display, you can't even see it. anyway, it did have a problem at one time. i am just happy to be able to use it again. looking forward to receiving my new bracelet sometime this week. it just does not look right on a leather strap. peter