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HP 320LX - very dim screen

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wmundstock Page Icon Posted 2023-01-19 6:17 PM
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dl1av - 2023-01-19 5:58 PM

I suppose the layer to scratch on is the upper layer of the matrix. Else it would not be sensitive enough. So no chance to seperate the top layer.

Stefan


Agreed, and it seems to be attached to a harder glassy surface. You can see that part in the picture I posted (upper part).
Next time I take it off I will take more pictures.

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dl1av - 2023-01-19 5:58 PM

I understood you wanted to look for a new polarizer? Did you reassemble it without it?

Stefan


I just put the one that was there back and reassembled. Did not completely close it, just moved the LCD back to its position. The flat cables are very thin, don't want to risk braking one. I will let it be until I get a new film.

I was able to find a number of films on our "local ebay". I learned that there are different types of polarizers. The Modern LCD polarizers are different, meant to be used with color LCD with lots of brightness.

Folks use a different one for things like Gameboy which are grayscale - just like the HP 320. In general, those are glued to the LCD screen with adhesive rather than just placed in front it.

I have not found any information on how the original polarizer was in the HP, but I will guess it was glued like the other grayscale LCD's I saw. I was able to see air bubbles, like some parts of the film were touching the front panel, other parts weren't.

I ordered a piece with twice the size I need to try out. Wish me luck!
My biggest fear is to damage the flat cables, if one of those break, it will be the end.
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dl1av Page Icon Posted 2023-01-19 7:00 PM
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I ordered a piece with twice the size I need to try out. Wish me luck!
My biggest fear is to damage the flat cables, if one of those break, it will be the end.


This would be my biggest fear throughout the whole process. I damaged some displays that way before, when the foil with the laminated copper tapes get older and looses flexibility it is sometimes easy to break.

Good luck with your orders and please come back when you have results

Stefan
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Citgo Page Icon Posted 2023-01-19 7:25 PM
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some polarizing filters have a self-adhesive backing. but you need a clean room for something like that. I didn't stick the film on the Gameboy. try that first. To loosen something on the LCD, it's best to use a heat gun, otherwise the foils can break.
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wmundstock Page Icon Posted 2023-01-19 8:48 PM
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Citgo - 2023-01-19 7:25 PM

some polarizing filters have a self-adhesive backing. but you need a clean room for something like that. I didn't stick the film on the Gameboy. try that first. To loosen something on the LCD, it's best to use a heat gun, otherwise the foils can break.


The filter I bought have self-adhesive. I think it must be glued because there is a small gap between the screen and the touch plate.
I believe that the touch matrix should not touch the display, that was causing some bubbles which made the screen look bad, so gluing it with the adhesive should resolve that.

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Citgo Page Icon Posted 2023-01-19 9:11 PM
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Yes that should help.
I'm excited how ot works
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wmundstock Page Icon Posted 2023-01-25 5:35 PM
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Ok fellows... I am almost throwing the towel.

I tried 2 different sources of polarizer film, none seem to work. Screen is too dark as always.
From my reading, this is a reflective LCD display where as all polarizers found in the market are for transreflective (that need clearer display or backlight).

I can't find any supplier that sells something like that. Even the Gameboy films, they require a backligt mod to work - don't think this is practical on this case.

I will try to look a bit further, but I don't think I will find anything that will fix it. That is sad.
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torch Page Icon Posted 2023-01-25 5:43 PM
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wmundstock - 2023-01-25 10:35 AM

I can't find any supplier that sells something like that. Even the Gameboy films, they require a backligt mod to work - don't think this is practical on this case.


I have no experience with any of this - but just had an idea - is there a film that would work with a front light to light up the screen that way? At least it could be readable, even though having a front light would be annoying?
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dl1av Page Icon Posted 2023-01-25 6:20 PM
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wmundstock - 2023-01-25 6:35 PM

Ok fellows... I am almost throwing the towel.

I tried 2 different sources of polarizer film, none seem to work. Screen is too dark as always.


But you showed us the effect of a glass polarizer before? The effect there was nice and clear and something to work with? There must be some kind of plastic polarizer in the market so that you don't need to use real glass :)

These displays are transflective. You can judge by the way ist reacts on direct sunlight (or neon office light): If it is the better readable the more ambient light you throw on it then it ist transflective.
The light goes through the display ("trans") and gets reflected by the reflective coating ("flective") that sits below all other display parts.
The more light you throw at it the better gets the readability. Backlight is only necessary if the ambient light is not sufficient.

The digits itself (or dots or pixels) are indifferent to light and don't reflect anything. Therefore they are black.

In the dark old ages they tried a different approach first: the so called "scattering-LCD". The digits were the ones to reflect and they appeared to be white in front of a black (non-reflective) bottom layer. There had to be external light in the right angle to view anything on them (and they were really slow, you could watch the segments flipping).

This was simply the wrong way to use liquid crystals (which were discovered 50 years before) and quickly these things got forgotten around 1971. There were only LED displays in all sizes for a few years and around 1977 some clever guy invented the transflective TN-LCD like we know it from every pocket-calculator since then.

But back to the topic: Try a polarizer from a one dollar calculator to get a quick test result. If that proofs to be working you can try to get one from an old defective notebook and cut it to size.

Stefan

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wmundstock Page Icon Posted 2023-01-25 6:43 PM
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It is most readable when
1. I throw a lot of light - except that it creates a bit more reflex. A office spotlight with a LED lamp works ok.
2. If I turn the lights off and then turn on the device light (this is good as it generates zero reflex).

I will see if I can salvage the filter from an old calculator.

That effect with the glass filter:
I think it was better than average because it had a lot of light and because the glass itself is more translucent than the plastic films.


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stingraze Page Icon Posted 2023-01-26 1:45 AM
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Never tried it, but this product may help.

It's $39.00, and there might be a few different options.
I see lots of mods for WonderSwan portable gaming device with mod to make very dim color screens to LCD and with backlight...
I think a video of 200LX polarizer sheet replacement may help you.

Product on Amazon.com:


(Japanese video but)
200LX polarizer film replacement video:


Video 2:



Edited by stingraze 2023-01-26 1:45 AM
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wmundstock Page Icon Posted 2023-01-26 1:27 PM
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I believe the films I purchased are similar to the one used on the 200LX on that video. You turn it and one side makes it negative and the other positive. On the positive side, on 0 degree angle it get a green color tone, if you turn it up to 40-45 degree it becomes a bit more to the yellow tone.

I tried tweaking the angle closer to the 45 degree and it gets just slightly more readable, but still not good enough. Still have to make a big effort to read anything on screen.

According to this post from HPCFactor, the display used on the device is FSTN. I saw this interesting instructional video about LCD display types, and noticed it mentions that the F on FSTN means that a "special optical film is added in front of the LCD which makes me believe the film is NOT the same as for regular backlit LCD screens like laptops, mobile phones, etc.

With that information at hand, I found this product on aliexpress which is the only reference I found to a FSTN polarizer. The description says 45 degree - which is different from the 0 or 90 degree films that I see around. In addition it says 570nm, which is the wavelength. It also have a picture of a NON BACKLIT Gameboy! It is not cheap, but given the difficulties, so I think I'll go for it.

If that fails I may try another, more invasive approach, which would be to replace the display illumination LEDs with more modern, high brightness, LEDs. To be honest I did not look with enough detail on that circuit yet, but I think it should be doable depending on how many volts and amps the device throws out there. I hope it doesn't come to that.

For the ones curious with how this ends: It will probably be a couple of weeks until I get my hands on the films and try it out.

In the meanwhile, I wanted to take the time to thank all of you that are contributing to resolve my issue. It is really nice to see such active community on such specific topic.

Thanks.
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