Thinkpads Forum

Hi everyone !

I have a T420 (and I like it) with a trackpoint failure ; a SMD component has been pulled off the board as you can see on the pictures below :





The problem is that I can't identify this component so I can't replace it. I searched for a similar component on used motherboards or any kind of equipment with SMD on it... no success...
Is anyone has an idea of what it is so I can try to fix it ?

Note : I can live without the trackpoint working then I won't buy a complete keyboard just for replacing this little...thing.

Hi

In fact you do not want to know

First you need to find out the name of the microcontroller - see image :
https://geekhack.org/index.php?action=d ... 3229;image

If this name is TPM754A, see page 9 :
http://pdf.datasheetcatalog.com/datashe ... PM754A.pdf

Maybe you will smile fortune, and it will be just a resistor

Good luck

Measure the SMD length and width and this will be your dimensions in 4 digits in mm, also they look right to be all same also I can tell they are resistors. Measure ohm with your meter on on both ends of each and see if all other 3 are same and get like ohmage one from any junker parts.

Cheers, thinkpadcollection

Go to e.g. Wizz-Itech in Quimper and check with their repair/parts department if they have a spare keyboard from a T410/T420/T510/T520/X220/W510/W520, they are all usable.
Look at the color of the small "cups" under the individual keys: manufacturer NMB=red, ALPS=white, Chicony=grey

PS: as for your signature: holy cow!

RealBlackStuff wrote:PS: as for your signature: holy cow!

Nice reference! I had that scene from the movie as my desktop background on a T23 many years ago.

Here are the infos I gathered from your advices :

1 - The micro-controller is a PTPM754DR.
I tried to get some infos from the TPM754A datasheet, but I'm not good at understanding it. I'll give it an another try.

2 - SMDs are 1x2mm sized.
From left to right I measured : [the_missing_one] - [809 ohms] - [825 ohms] - [875 ohms]
Not exactly what I expected...but they seem close anyway.

3 - Keyboard "cups" are transparent white. I keep searching for spare parts...

I'm now going to cross the bridge of Death. If I see something, I'll tell you guys.

sample



I think- the resistance should be the same
To know exactly, it is necessary to cut the conductive paths.