Touch Screen Issue - Cable or LCD?

[EVA3863]

Hi everyone, 

 

I recently pulled out my old Sony Vaio handheld PC VGN-UX180P from storage and decided to finally replace the cracked screen I broke back in high school (it was kicked on the ground...) and rendered the touch screen unusable.

 

Its a pretty unique little computer, very ahead of its time in terms of features. It runs Windows XP (some later ones came with Vista), has two cameras, a slide up keyboard reminiscent of the old flip phones back then, supports SD cards and a SIM slot and a USB2.0 port. A cool gadget that I'd eventually like to find some use for...

 

So I replaced my screen with a new one from EBAY, but there was an issue with the touch screen - touching anywhere on the screen would peg the mouse pointer to the top of the display, however, I can still move it left or right. I can't move the pointer up and down at all. Note that this only occurs when I touch the screen, I can still use the built in mouse stick to control the pointer while not touching it. 

 

Does this seem like an issue with the new display or a bad ribbon cable? I want to know if I should request a refund/replacement for it while I still can. I already tried re seating the ribbon cables and cleaning the contacts with IPA. I also noticed a single dead pixel in this new display, so I'm leaning towards it being a problem with the LCD. 

 

Thanks!

[Kilrah]

Sounds like it would be the connection to the vertical axis. 

If you have a multimeter you should be able to set it to resistance mode, and with the touch flex disconnected measure across the X and Y pairs and see if they both correctly change with touch. If it does then the touch layer is OK.

[EVA3863]

On 10/6/2023 at 12:18 AM, Kilrah said:

Sounds like it would be the connection to the vertical axis. 

If you have a multimeter you should be able to set it to resistance mode, and with the touch flex disconnected measure across the X and Y pairs and see if they both correctly change with touch. If it does then the touch layer is OK.

I figured it was a problem with some connection with the X and Y axis, just not sure which contacts those would be. This is my old screen - The connector labeled CN2 is the large ribbon cable to the motherboard. CN1 is a small ribbon cable used for the indicator LEDs (HDD, Bluetooth, Wi Fi, etc) CN4 wraps around to the front of the screen and connects to this thin film on top of glass. The gray rectangle around the screen where the ribbon cable makes contact appears to be a pressure sensor (to register touches and clicks). I also noticed an array of "dots" on this thin film, so this might actually have something to do with the touchscreen position tracking. I am not sure what CN3 is for, it is a 4 wire ribbon cable that goes underneath the LCD from the side (maybe for backlight?) Then there are two large ribbon cables that go underneath the LCD from the bottom. 

 

I appreciate the help, still learning how this screen works...

 

[Kilrah]

15 minutes ago, EVA3863 said:

I figured it was a problem with some connection with the X and Y axis, just not sure which contacts those would be.

CN4. Yep the front plate is the digitizer and the 4 conneections to it are the X and Y resistance measurement points.

[EVA3863]

On 10/7/2023 at 1:19 PM, Kilrah said:

CN4. Yep the front plate is the digitizer and the 4 conneections to it are the X and Y resistance measurement points.

Aha! It was a loose ribbon cable at CN4. Looks like it might have been damaged. Reseated the cable and its working! Thank you for the help