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LCD Polarizers

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albertofenini

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LCD Polarizers

Post24 Nov 2012, 18:43

ciao a tutti,
I have received the polarizers that I have ordered few days ago @ 3Dlens.
I was about to replace them on a old C359, following Ade51 example in this thread :
http://www.newdwf.com/viewtopic.php?f=64&t=5661
but I have some problems.

Please, help me in understanding what I'm doing wrong.
This is a picture of the module with the actual LCD, very faint.

IMG01603_SMALL.jpg

In the next picture, a polarizer is on top, and yes, it gets a little better but not
as better as in Ade51 situation.

IMG01604_SMALL.jpg

Anyway, I have cut a piece of the polarizer as in this picture :

IMG01605_SMALL.jpg


There are two protective films, that must be removed.
Under one of the protective film, the polarizer is self adhesive.

first question : both films must be removed ?

I have removed both, but it turns out the if I lay onto the LCD the adhesive side
of the polarizer which makes sense, is the wrong side of the polarizer and all I
get is a very very dark LCD.

Same thing if I put the polarizer UNDER the Lcd rather then OVER.

Waht I'm doing wrong ????
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Ade51

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Re: LCD Polarizers

Post24 Nov 2012, 19:44

Hi Alberto, first thing try rotating the polariser to see if you get better looking digits at a different angle. I'm sure Kasper and some of the others may help shortly but you may just have the polariser at the wrong angle which is turning the screen black.
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albertofenini

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Re: LCD Polarizers

Post24 Nov 2012, 20:32

Thanks Ade51,
that's what I did, I rotated the filter of 90° and discovered that the adesive was now on the correct side.
So I cut another strip, and put on the LCD, however, the result is not better that before I replaced the polarizer
if you compare it with a good one. See pics but keep reading becasue I went further :
IMG01610_SMALL.jpg

IMG01611_SMALL.jpg

since the result was not wat I expcted, I treid to remove the added polirazer and
by doing so, also the old came way, which is good thing :
IMG01612_SMALL.jpg

keep reading what happened next .
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albertofenini

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Re: LCD Polarizers

Post24 Nov 2012, 20:41

having had the chance to peel the old ones off without breaking the lcd,
I cleaned and replaced with both front and back new polarizer, since I think
this the way it should be done.

IMG01613_SMALL.jpg


However, even if the polarizers have been cut in a way that the thickness of the lcd
is not impacting on the zebra strip, I'm not able to get a good contact as before.

Moreover, when the module is inserted back in the housing, probably because of the
top polarizer, the lcd is probably pressed to much and start showing non correctly and
faint anyway.

IMG01614_SMALL.jpg


However, I had a third module (one is good and I'm not going to touch it,
the second one is the one I have been working on) with a display that have had
the orginal polarizers removed before I had the watch.

In this case I have only added the front polarizer, but I can see a good contrast
only at a certain angle.

IMG01616_SMALL.jpg


So, for now it seems very complicated and the result not worth, but I'm sure I'm doing something
wrong ......

thansk for help, take care Alberto
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Kasper

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Re: LCD Polarizers

Post24 Nov 2012, 21:58

you cannot win them all :-D

i always start with the top polarizer cause thats the one getting the first uv in the watch. But as you can see below..it,s not always the polarizer. It,s also possible that there
is a problem with the lcd self.

here i wanted darker digits and another background.
i cut another (gold) background, then got rid of the top polarizer and noticed that it didn't make that much difference, so i also changed the back polarizer but still no avail.

then i checked the lcd and now you can easy see that there is a problem with the lcd itself...don't ask me why. I think that the polarizer burned in the glassplate :?: :!: from lying in the sun.

Image

Image

and don't forget, polarizers have to be in an angle of 90 degrees of each other to have the best effect!
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albertofenini

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Re: LCD Polarizers

Post24 Nov 2012, 22:13

Thanks for the tip Kasper,
Do you mean that in both cases the LCD could have just faded out ?
I'll do more test, I didn't take in consideration that top and bottom must be in opposition of 90 degrees ....
Is going to be a long night ....
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Kasper

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Re: LCD Polarizers

Post24 Nov 2012, 22:31

i'm not there yet but it,s possible that the liquid crystals don't have enough voltage to get black enough!!

Twisted nematic displays contain liquid crystals that twist and untwist at varying degrees to allow light to pass through. When no voltage is applied to a TN liquid crystal cell, polarized light passes through the 90-degrees twisted LC layer. In proportion to the voltage applied, the liquid crystals untwist changing the polarization and blocking the light's path. By properly adjusting the level of the voltage almost any gray level or transmission can be achieved.


the part in red is important :-D
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albertofenini

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Re: LCD Polarizers

Post24 Nov 2012, 23:47

Yes, it could be, but not on two units, or at least not so often,
battery is new, and both the zebra strip and the lcd contacts are
clean.
What chances I have to find some NOS lcd for thse modules ?
take care Alberto
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Ade51

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Re: LCD Polarizers

Post27 Nov 2012, 00:14

Hi Alberto, oh dear I'm sure you have done the same that I did. Perhaps I was just very lucky that by adding a new polariser film this fixed the faint LCD digits straight away. I also took both sides of the film off the polariser.
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cobra007

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Re: LCD Polarizers

Post27 Nov 2012, 13:14

albertofenini wrote:Yes, it could be, but not on two units, or at least not so often,
battery is new, and both the zebra strip and the lcd contacts are
clean.
What chances I have to find some NOS lcd for thse modules ?
take care Alberto


There may also be a problem with the chip on the circuit board. I had a look at a watch some years ago with a faint display and it appeared that the drawn battery current was much higher than what it should be. You could measure this current, it shouldn't be much more than 1uA and certainly not in the order of 100uA.

Michel

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