How-to de-touch a touch-screen.

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ICMF
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How-to de-touch a touch-screen.

Post by ICMF » Tue Apr 04, 2017 11:36 pm

A lot of larger LCDs come with touchscreens. If yours did, and if you don't want a touch screen, here's a simple, image-heavy guide to ripping it off! :D

(standard disclaimers: not responsible for damage; your screen may vary, etc. etc. It's not a difficult operation, but I think everyone recognizes all this stuff is done at your own risk.)

My screen is a Waveshare 5" HDMI (B) - it's an HDMI screen (not composite) with USB power/touch interface (not GPIO), but most screens in this class seem to have a fairly similar construction. Details may vary a bit, but the general process should be about the same. It's a pretty straightforward operation. The touch interface is a piece of glass that's attached to the LCD with double-sided tape. Just peel it off, remove the LCD from the PCB, then de-solder the touch panel's ribbon cable.

What we're working with.Show
Screen has decent resolution, but the glass touch panel has a matte finish which gives the image a weird, blotchy look
Image
Touch calibration sucks.Show
The touch interface is garbage, though. Accuracy gets worse the closer you get to the edges, until you hit the dead spots at the edge of the screen. The square should be centred under the stylus here, BTW.
Image
Disconnect ribbon cableShow
Step one, disconnect the ribbon cable on the back of the PCB.
Image
Like that.Show
It would be nice if the ribbon was slightly shorter, so it would lay flatter across the board. Is it possible to trim a bit off the end to shorten it?
Image
Peel off the touchscreen.Show
To remove the touchscreen, slide a sharp X-Acto blade between the metal LCD frame and the glass touchscreen panel. Slice around all four sides, and the screen will come free. If you keep the blade over the metal frame, there is zero risk of scratching the LCD. (the strips of tape are only about 1mm wide)
Image
Careful not to tear the ribbon.Show
Screen peeled off. Still connected by the ribbon cable, though.
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Remove PCB from LCD.Show
Next we have to remove the LCD from the PCB. There's a section of ribbon cable with circuitry tucked between the LCD and PCB, so we need to remove the screen to access it. As an added benefit, losing the foam shaves a couple mm off the thickness. Slice through it with an X-Acto.
Image
Screen removed.Show
After slicing through the foam on one side, the LCD can be carefully peeled away from the other side. Peeling left a cleaner surface. And you can now see the ribbon circuit, attached to the LCDImage
Remove adhesive.Show
Foam tape peeled off. The adhesive residue can be removed with lighter fluid, goo gone, or any other adhesive remover.Image
Focusing on the touch attachment.Show
The PCB can be set aside, as we focus on the touchscreen's solder connection.
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Remove Kapton tape.Show
You can see the solder points under the Kapton tape. Carefully peeling the tape back lets you save and re-use it - we'll be exposing the solder points, so they'll need to be covered to prevent shorting.
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De-solder touchscreen.Show
I didn't photograph the de-soldering process, but it's pretty simple. Sweep your iron back and forth across the four contacts, while gently pulling back the touchscreen's ribbon cable. You don't need to pull, just keep the solder melted and let gravity do it's thing.
Image
Smooth the back of the PCB.Show
The last modification is to (carefully!) grind down the legs of the HDMI connector. They stick out a fraction of a mm and would interfere with the screen. A very delicate touch with a dremel will remove most of the metal; they were then smoothed out with a fine jeweller's file
Image
Test.Show
The screen gets plugged back in to the PCB, then it's connected to a HDMI source for a test. Hooray! It isn't broken! Oh, and note that the black, ribbon circuit is behind the PCB now. Because we ditched the foam, there isn't room for it between the LCD and PCB any more; also because we ditched the foam, there IS enough room to wrap it behind the PCB (rather than through it).
Image
Before and after.Show
Out of the box, the screen was about 8.5mm thick. By losing the touchscreen and foam, we're down to about 5mm thick. Nice.
Image
Image
Bare screen left; touch screen right.Show
More important is the picture. It's *really* hard to photograph, but hopefully this gives an impression, at least. On the left is the bare LED (no touchscreen). Nice and sharp and bright. The left side has the touchscreen laid on top. It's softer, duller, and a little blurry. It almost looks like it's had a shader applied.Image

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Re: How-to de-touch a touch-screen.

Post by abrugsch » Wed Apr 05, 2017 2:14 am

nice tut! I have one of these waveshare screens and have no intention of using the touch aspect so this perfect

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Re: How-to de-touch a touch-screen.

Post by kendon » Thu Apr 06, 2017 4:36 am

This looks like it works exactly the same way on the Kedei screen.

What I am wondering: why not just cut the touchscreen cable? Any reason not to do it?

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Re: How-to de-touch a touch-screen.

Post by ICMF » Thu Apr 06, 2017 8:37 am

I can replace the touchscreen at a later date if I want to by resoldering the cable.

Also, I didn't want to butcher it. Cutting the cable is quick and easy, but desoldering is the 'correct' method, so I went that route. Just a personal preference.

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Re: How-to de-touch a touch-screen.

Post by kendon » Thu Apr 06, 2017 3:13 pm

Figured that ;) and cut it, since I have no intentions to ever use it as a touch screen. Even if I wanted to, at that price I would just buy another one. Gotta say, for the price it is quite good (I have a Pd035vx2 here, but haven't got around to actually use it yet), there is definitly no problem with screen tearing as I hace read on the forums (talking about the Kedei). Played a few rounds of GB Tetris, GB Super Mario Land, SNES Donkey Kong and MAME Metal Slug, they are all totally fine. Viewing angle could be better, but is absolutely OK for the price and a handheld one-player device, which I intend to use it for. HDMI set to 480x320, sound is output at the 3,5mm jack of the display board. I'll see where I will grab the sound for the final GBZ once the cases and the AiO board arrive, but it seems viable to just use the output of the display board.

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Re: How-to de-touch a touch-screen.

Post by Awesomenatious » Wed May 03, 2017 3:02 am

I have the Kedei screens too, I was thinking about using the sound direct from the screen. If you do it that way can you post some pics so I can basically copy you. 😉

Thanks in advance.

Also, using the Kedei screen, is there anyway to get HDMI output to the TV since we are already using it for the 3.5 display? (Like a throughput I guess?)

Using the same HDMI output twice? I dunno, that's why I'm asking.

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Re: How-to de-touch a touch-screen.

Post by inches » Sat May 13, 2017 11:14 am

Touch screens are pretty expensive for the larger ones. I spent about $50 on Ali for a 14in touch overlay. Try to keep them in tact if you want to take it off!
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Re: How-to de-touch a touch-screen.

Post by salami738 » Wed Nov 15, 2017 1:55 am

Hi, this tutorial helped me prepare my 3.5 inch hdmi screen for my GBZ build. Thanks!

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Re: How-to de-touch a touch-screen.

Post by BadBert » Wed Nov 15, 2017 5:58 am

thanks for the tut!!!!
My first GBZ build -=HERE=- -> Became a gift to my little brother!
My 2nd GBZ build -=WIP HERE=- -> going with HDMI!

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