ThinkPad X230T digitizer and pen not working anymore!

[idoit]

Hello everyone,

I was working on my ThinkPad X230 Tablet and accidentally cut one of the very thin wires (0.2mm thickness). It turns out it was the ground wire (GND) for digitizer. There are 5 thin wires for digitizer and here is the schematic for it:

pin description
23 USBP4+
24 USBP4-
25 STOP
26 VCC3BLEDBD
27 GND

I turned the laptop with wires 23-26 all active and flowing to digitizer board BUT ground wire not connected (cut). Now when I turn the laptop on, neither touch nor pen is working. I tried and soldered wire 27 back together and turned the laptop on. Same, no finger touch or pen. They are not recognized under Windows either. I have attached high quality photos of both finger touch and pen/stylus PCBs.

I was wondering what happened? Have I fried the digitizer pcb? Anyway to identify which component got damaged and fix it? Any pointers are welcome. Thank you!

[mon2]

Re: ThinkPad X230T digitizer and pen not working anymore!

The connector in the pics is silk screened '1..10' and there are 10 solder contacts (not 5).

Can you share clear pics of the mating cable for CN1 ?

Respectively, you should have 10 contact points to review for the pointing widget.

Most likely, the fault is probably a broken connection between the 2 parties.

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

Thanks for your reply @mon2.

I have attached a few photos, close-up from CN1 mating cable as well as the whole cable to give a better idea. (Please let me know if they are not clear enough and I can take better photos)

As you can see in the second photo, there are only 5 thin wires that go into CN1 (digitizer/touch pcbs).

Looking at the whole cable: the big end on the left connects to the laptop motherboard. There are 32 thin wires which are grouped into 4 bundles. Let's call them A, B, C, D:

bundle wire# description
A 1-14 Tablet buttons and front speakers
B 15-22 fingerprint reader
C 23-27 digitizer
D 28-32 microphone

You can see I have cut bundles B and D. Could this be the reason? Even though they go to other areas of the laptop that have nothing to do with digitizer!

Also a few of the cables are loose now, when I had them running in laptop I made sure they are connected. Also using a multimeter, when I connect positive probe to +3.3Va and negative probe on AGND or DGND, I can measure 3.3v flowing into digitizer pcb.

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

I also found it odd that there are only 5 wires for both functionalities of touch and digitizer?! To me, these two are more complex and intuitively, I imagined there would be more wires needed! Especially when you look at connector between two PCBs (photos in my first post), there are 14 pins.

My guess is: some data feed comes from the connector below marked with red arrow, maybe?!

[mon2]

Re: ThinkPad X230T digitizer and pen not working anymore!

The connector with the red arrow is the video display connector.

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

Right. And that doesn't contribute anything to the digitizer issue, correct? (LCD works flawlessly when I turn the laptop on)

I am clueless what might have happened? Did I fry the pcbs by not having a GND wire and just these four wires flowing in? (USBP4+ USBP4- STOP VCC3BLEDBD)

[mon2]

Re: ThinkPad X230T digitizer and pen not working anymore!

Meter in Diode mode setting.

Red meter probe to ground. Note this.

Black meter probe to the usb+. Reading?

Then repeat for the USB- pin. Reading?

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

I looked at my multimeter and unfortunately it doesn't have diode mode. it's an ancient one from a brand called Micronta from 1960s! I will buy a modern multimeter and will report back.

A few questions:
- On these two PCBs, the components are mostly transistors and capacitors, right? With diode mode, can I test all components too?

- Black probe that goes to COM port should go to USB+ and not GND? Oh boy, I've been assuming the other way around all this time! I really need to RTFM some electronics basics and manuals

Thanks!

[mon2]

Re: ThinkPad X230T digitizer and pen not working anymore!

Micronta ? Ah the childhood memories...that one is from Radio Shack. I recall saving up for it and used the life out of it over the years in the 80s. Great product considering it was analog.

You can probably grab an ok meter from Amazon - for long term, Fluke is a nice brand but is very much higher on the $$.

https://www.amazon.ca/AstroAI-Digita...xpY2s9dHJ1ZQ==


Here is one of many good videos on using DIODE mode for testing:

https://www.youtube.com/watch?v=pRpyHF2dfq0

Update - also consider to purchase some nice sharp meter probes:

https://www.amazon.ca/Multimeter-Pro...ps%2C86&sr=8-5

are similar to what we have here but recall that they are < $5 on Aliexpress or similar store.

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

Thank you @mon2. I couldn't find a thank button in this forum.
It might take sometime till my next update, but I will report back. I'm thinking of buying an automatic multimeter as opposed to manual ones.

I hope it can be fixed, as I was so bummed out. I'm normally very careful with my belongings, and for such a small misstep, the whole touch and pen functionality of one of my all favorite time laptops gone!

[mon2]

Re: ThinkPad X230T digitizer and pen not working anymore!

If you are really in a pinch, you can send it in to us. We are in Windsor Ontario. The flex cables may need to be replaced but can check.

Perhaps some store on Aliexpress has a replacement for your cable.

[idoit]

Re: ThinkPad X230T digitizer and pen not working anymore!

If you are really in a pinch, you can send it in to us. We are in Windsor Ontario. The flex cables may need to be replaced but can check.

Perhaps some store on Aliexpress has a replacement for your cable.

Luckily I'm not in a rush as I have other laptops and PC. I am quite confident it's not the flex cable as all the traces match up and it looks good. My suspicion is that turning the laptop without GND thin wire killed one or some of the small components on the pcb. Which I'm not sure if this type of frying pcb is even possible. Thank you @mon2.

It's kind of a good learning experience too and if I can revive the touch and pen functionalities, it'd really make me happy and feel accomplished. That being said, if I can't I can send it to you.