protecting DSM LCD life

[635 nm.]

Can someone tell me if it is better to let devices from the early 1970's that use DSM LCDs to operate even though they are in dry storage? Or should they only be powered up when being used or every 4 months or so? I have one of the early LCD watches that still has a good display and a calculator that has the first LCD for consumer use (or so I have read) and want to keep the displays working as long as possible.
Thank's To All,
Richard

[leddwatch]

I asked Greg Zanoni to ask his Dad this question, his father invented the things, so he should know !! Here is the reply:

We are not sure if it is better to keep the watch running or not to preserve the display.

So there we go, the answer is a definate....... maybe.....

[635 nm.]

Thanks for the answer. I repair old transistor radios & vintage electronics and there is a similar question about operating those devices. I personally like to run them at least twice a year to keep the electrolytic caps formed. Of course it may not make any difference, but it's a good reason to play with them.
Regards,
Richard.

[rewolf]

...I personally like to run them at least twice a year to keep the electrolytic caps formed. Of course it may not make any difference, but it's a good reason to play with them....

For electrolytic caps, this is a good idea. For DSMs, I don't know. However, my DSM is the only watch I don't keep in operation all the time.

[635 nm.]

Here is my new DSM life extension plan. I keep the devices in a three ply poyethelyne bag that I filled with nitrogen. Then power them up twice a year or so. I stored a Technics Quad receiver from 1979 until this year with that method and it looked and worked like new.

[rewolf]

This plan could work
Is the nitrogen free of moisture (silica gel)?
Low temperatures will also help to stop whatever chemical process could make the LC decay.
Also very bad is UV light. Early field effect LCDs had UV filters, that's why they appear yellow.
So keep it in a dark cool dry place.
Unfortunately, I like to see my watches from time to time :wink:

[635 nm.]

One of the plys in the plastic is a light barrier, I came across a small cylinder of dry nitrogen that I use for stuff like this. That is the big draw back, having to unpack everything to power them up and check them out.

[rewolf]

I see you considered everything to preserve this watch for the 22nd century (at least) :wink:

[AlmightyTallest]

I like to wear my Optel watches, so for me I try to keep them from conditions that are too cold or hot, and avoid constant direct exposure of the display to sunlight.

Also, I coated the watch crystals in PSC Anti Scratch cold dip. http://www.watchpolishing.com/antiscratch.htm

Mr. Zannoni told me personally not to be afraid of wearing these watches. They are rugged and he has the parts to keep them running for a lifetime. So I wear mine almost every day.

[leddwatch]

These are all good tips but slightly off topic, the peculiarity of the DSM display is that it was very un-reliable even when brand new, Ive seen them where the crystal starts to degrade. I know we cant get an answer from the inventor either way because Ive tried, but I would also like to know whether leaving batteries in or out is good for the DSM display itself, wiping the plastic or glass screen with anti-scratch wont help it and I think thats what 635nm is requesting when he started the thread. Anyone know the answer?

[AlmightyTallest]

Hmmm. I don't know then, other than to coat the crystal with a UV protective coating and avoid sunlight to help protect the liquid crystal from degradation.

Sometimes these watches just seem to die even after not having their battery in for years and being stored and cared for properly.

[retroleds]

I'm thinging it doesn't make any difference to the screen if you run it, since the electrical action isn't what makes them degrade to blackness, air infiltration between the glass matrix layers is. Usual considerations of crystals aging from being ran and trying to keep capacitors healthy thru occasional usage. The LCD screens that go slightly "rainbow" or tan, but still work - some of those just have a degraded polorizing layer over the display glass(under the actual crystal). The late '60 were the infancy of polorized plastics...you can get much better polorizing film today to replace that stuff. A good photography store or Zantech will have this - most is .010-.015" thick.(.2-.3mm) If you slip off the plastic polorizing layer your display will "disappear" while running, lay it back down, it reappears, magically. 8) El cheap LCD displays are another source of fresh polorizing film....the cheapest stuff of today is probably much better than the premium crap of 1975. :?

To quote Zanoni's Digital Watch Repair Manual," The display consistes of two pieces of glass, coated with a transparent conductive coating and sealed together. It is then filled with the lquid crystal and plugged. Polorized light is required to see the effect of the voltage on the liquid. Therefore, polarizers are adhered to both sides of the display".

[leddwatch]

LOL, Ed you have done a wonderful job of telling us about field effect LCDs but we are talking about DSM, there aint no plastic polarising layer here my friend, wrong thread!

[retroleds]

My bad!! The leakage/discoloration is caused from the same effect - leakage. You are right that DSM has no polarizer....I guess I jumped threads

[MR_LED_&_LCD]

Hello, AlmightyTallest
It means we can buy parts from Mr Zanoni? I would like to buy some DSM displays. Do you know if he sells it?

[rewolf]

Actually it's Greg Zanoni, Louis Zanoni's son, ebay ID ztv99.
He's been selling quite a lot of DSM watches in the last 2 years.

[MR_LED_&_LCD]

Thank you.
In fact, I've met Greg some months ago.
I've asked him about selling parts, with no response.
I guess it sell only (entire) watches :( .
It's a pity, as I have a NOS Opticom I (Jules Jurgensen) with problems on the display (after two decades of storage the liquid crystal disappeared from some display areas!).

[azimuth_pl]

I asked Greg the same question and he replied without hesitation.
Approx. 250$ for a new DSM display and service.
He has a stock of NOS parts.

[MR_LED_&_LCD]

Hello Piotr.
It's me, Rogerio, from Brazil.
I've obtained a good display from a non-working DSM watch and I've solved this problem partially.
As it fades sometimes, I think there is some electronic problem in the circuit. It will need a little more care.
Thank you.

[azimuth_pl]

hi Rogerio,
you were the lucky bidder with the OptcomI in box :)
was it working?
could you share your comments on removing the display?
I have a BWC DSM working but in need of work and I have an identical working oval module with damaged TNE display. I'm thinking of swapping the DSM display to the working TNE module.
any suggestions will be appreciated.

PS. the DSM goes blank with 2, 4, 6 digits at the end. Greg told me that this might be a short somewhere in the display, not the IC.

[MR_LED_&_LCD]

Hi Piotr,
Sorry for the late response.
Yes, I’ve bought that watch!

The picture was poor - so, it was a great surprise to receive a watch in NOS cosmetic condition (but with some problems!)

The display was almost completely dry – with liquid material in few areas only – but enough to allow see the watch was working.
I’ve obtained another display not exactly in good condition: some indium oxide conductive pads were corroded due a battery leakage, so, some segments were not flashing. I’ve repaired those pads with carbon conductive ink and what a surprise: all the segments are flashing now!

To remove the display from OPTEL modules is easy: there is a stainless steel frame above the display. Slide it to one of the sides.

Another problem: the divider chain IC (that little IC) was in troubles: it was generating a pulse every ½ second, not every 1 second. I’ve replaced this IC and this problem was solved too.

The last problem is the display fade sometimes. I think there is some mechanical problem (oxidation in the contacts) at the crown mechanism (I’m going to use a contact cleaner to see what happen).

[azimuth_pl]

hi again,

I'm stuffed with other projects so I have left the DSM's for one xmas evening.
I'm aware of the steel frame on the display but later I guess you have to use silver epoxy to stick the display to the module? right?
at least that's how the Nepro DSM watches are made.

do you think the TNE and DSM displays can easily be swapped?

and is the IC easy to remove with standard soldering?

best
Piotr