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HP 320LX - very dim screen

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wmundstock Page Icon Posted 2023-01-19 1:29 PM
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Factorite (Junior)

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Hi.
I took it apart this morning and here is what it looks like. I cleaned the flat cable contact and maybe its me but seems like it got just slightly better. Maybe its just the lightning that is better.

Regarding a resistor I could not find any trim pot or something alike. I did find a 30 ohm resistor very near that flat cable.



Schematics of the board would be awesome... I could not find it though.

Thank you!
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Citgo Page Icon Posted 2023-01-19 2:01 PM
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Factorite (Elite)

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I'm still not sure if it is not normal with you screen. On your videos it looks like my 300LX screen.
So not the best contrast but I dont think you can expect a better contrast.
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wmundstock Page Icon Posted 2023-01-19 3:09 PM
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Factorite (Junior)

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Maybe that is the best contrast I will get, but I find it hard to believe that the contrast would be so bad.
Really, I have to make a strong effort to read anything on that display.

I have to set contrast to almost minimum so that the small characters show better and look very closely to be able to read a word.
It feels like this screen is "too green" then it mixes up with the dark LCD bits turned on.

It is like the images have pass through with a semi translucent green curtain. In addition darkness results in a lot of reflex, making it even harder to see.

The screen is turned off on this picture, but you can clearly see how much reflex it has.
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dl1av Page Icon Posted 2023-01-19 3:14 PM
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Factorite (Elite)

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Thanks for sharing the picture.

I don't see any trimmer, too and without a circuit scheme it is hard to tell where to look.

But I don't think it's the polarizer. My actual 320 looks like yours and as I remember it they didn't look different back in the days (but it is 25 years since then). Today you compare it (even if only subconcious) with your experiences with modern devices (or with the color-Jornadas) but back in the days there was no such competition and we were ok with it.

Stefan
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Citgo Page Icon Posted 2023-01-19 3:29 PM
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Factorite (Elite)

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It's the same with my 300LX.
The screen is very reflective and the contrast is a bit muddy.
I don't think that you can change this.
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dl1av Page Icon Posted 2023-01-19 3:37 PM
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Factorite (Elite)

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This is mine with and without backlight. The reflections are unavoidable, I just used available light.

These transflective displays need every photon they can get to look good. In bright sunshine or in a lab with shiny neon lights.

They are perfect for outdoor use in the sun when you don't see anything anymore on your colorful glare display.

I once had a slate with half-transflective color display. The more sun the better it gets. The colors seem a little washed out compared to modern displays and there was a mouse-trail to see (not the software-induced one ) . When there was no available light you had to turn on the display light (but only in that case). Just as with the b/w-Jornadas.

I wonder why noone makes transflective displays anymore. Even the famous Nokia 7650 had one.

Stefan

Edited by dl1av 2023-01-19 3:50 PM




(hp1a.png)



(hp2a.png)



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wmundstock Page Icon Posted 2023-01-19 4:52 PM
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Factorite (Junior)

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OK, now I can clearly see the difference.


It is like there was a layer of "something" in front of the display. It make is really GREEN and Dark.
When I look at the display with it turned off, it has a very dark green color. It looks like a grass field, maybe even darker.

Mine


Vs yours...
It is grayish and even though the contrast itself isn't greatest, I still can clearly see everything.


In this one I can clearly see everything.

I understand that the contrast isnt all that good. But in order to use the device I have to move it around, open the lid, close the lid, twist, until I can find an angle that I can read. Then I have to get very close to be able to differentiate the letters.

Note: Yes, I use glasses, but its not all that much hehehe

Here is another picture comparing 3 different displays. By any chance, do you have a 48G to compare?



I have a strong feeling that something got darker inside, in one of the layers. Maybe it got exposed to sunlight.. maybe temperature through the years... not sure.
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Citgo Page Icon Posted 2023-01-19 5:07 PM
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Factorite (Elite)

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Don't forget that the HP got some more layers for the touchscreen in contrast to the other devices.
You talked about the "bubbles" on one photo.
Maybe there is really a problem with that layers on the screen.
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dl1av Page Icon Posted 2023-01-19 5:21 PM
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Factorite (Elite)

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OK, now we are getting to it.

Do you see the two white spots on my display. The one right to the Word icon and the one in the Tasks icon?

I suppose this came from some mishandling by some pre-owner. Some liquid used to polish the screen was too aggressive or it was an accidental drop of some liquid.
Fortunately there are only some of these spots at the upper edge of the display.

This is some chemical degradation inside the top level of the display. In the transparent plastics that was treated wrong.
Not in the touchscreen matrix (works fine even in that area) and obviosly not in the polarizer that rests below the touchscreen matrix one level down.

Maybe one of your pre-owners tried WD40 to clean the display?
Your display definitely looks like mine in the spots.

You could try to disassemble the display. Try to remove the touchscreen matrix from the LCD and see if the display itself is ok.

I don't have my 48 by hand but it has a very clear and contrasty display like yours.

Stefan

Edited by dl1av 2023-01-19 5:24 PM




(hp3a.png)



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wmundstock Page Icon Posted 2023-01-19 5:28 PM
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Factorite (Junior)

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This is getting interesting...

It was probably a stupid decision, but I took the screen apart.
Turns out that the polarizer filter is not glued to the LCD screen. It just stays between the LCD and touch sensor.
This explains the "air bubbles" I saw earlier.

Honestly I am thinking some dirty technician messed up with this before me.
I found a small crack in the lid and wait for it....
... The polarized filter is cut in a non-rectangular shape. I doubt it would come from HP like that. One side is about 4mm larger than the other.

What I think is that someone used a polarized film to replace the original and used a too dark one.



Now we are talking! This looks like a more normal screen to me. See how clear it is when I have my camera's polarizer over it?

So what I need is to find a polarizer that isn't as dark as this one and it will be as good as new.

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Citgo Page Icon Posted 2023-01-19 5:37 PM
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Factorite (Elite)

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As I said before...

Thats interesting with your polarizer. Maybe some replaced it with a bad one.
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dl1av Page Icon Posted 2023-01-19 5:41 PM
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Factorite (Elite)

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Looks good

So your touch matrix is clear and transparent?

As you are in the task of disassembling: Is the outer plastic layer (the one you scratch on with the pointer) removable from the touch matrix? Or is that the top layer of the matrix, sealed to it?

Stefan
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wmundstock Page Icon Posted 2023-01-19 5:46 PM
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Factorite (Junior)

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dl1av - 2023-01-19 5:41 PM
So your touch matrix is clear and transparent?


Yes, it was clear. I cleaned it with some isoprolyl alcool to be sure.

Quote
dl1av - 2023-01-19 5:41 PM

As you are in the task of disassembling: Is the outer plastic layer (the one you scratch on with the pointer) removable from the touch matrix? Or is that the top layer of the matrix, sealed to it?


I did not pay much attention to that and I already put the LCD back.

That said, I think its not easily removable. So when I disassembled there were 3 pieces:
1. The LCD panel.
2. The Filter (i think it should be glued to the LCD
3. The Touch panel.

Perhaps there is an adhesive layer in front of everything.



Edited by wmundstock 2023-01-19 5:47 PM
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dl1av Page Icon Posted 2023-01-19 5:58 PM
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Factorite (Elite)

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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.

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

Stefan
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Citgo Page Icon Posted 2023-01-19 6:05 PM
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Factorite (Elite)

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Try to get a new polarizer with the right dimensions and try it
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