NXT Brick problems. How to fix them?

[m2fel]

I had the idea of building something with the good old NXTs. My attempt to get my four NXT bricks up and running ended in disappointment.

Two of my NXT four bricks are completely broken, and the display on the other two no longer works :( One of them had the “click of death,” but I was able to fix the problem by updating the software on the brick (I had to dig out an old laptop that still ran Win XP to do this).

I did some research on the internet and finally decided to open the brick. The displays on the two bricks that still work flicker or even work perfectly when you apply the right amount of pressure to the display connector, but I couldn't get the display to work when I reassembled the brick. There was nothing obviously broken on the circuit boards of the two defective bricks. No damaged capacitors or oxidation on the top. I didn't desolder the circuit boards from the case to see if there were any visible problems on the other side of the board.

Is there any advice on what to look for or how to repair them?

[chip1e]

Hi I fixed the display on mine. A quick flash over the back of the conector cable with a soldering iron, it re-melts the conductive glue that is used to conect the cable to the board. I held the iron on just enough to curl up the protective tape. Lots of other methods have been used on the forum do a search for fixing display problems. I do hope you can fix them.

[1963maniac]

I don't know if this will help your problem since it uses a PC.

[m2fel]

Hello and thank you for your feedback. Heating the connector cable did not work. When I apply pressure to the connector cable in weird angles, the screen sometimes flickers, and once it worked perfectly fine for about 5 seconds :/ I will try the screen cloning tool, but I am quite disappointed that such a simple cable failure can render the NXT almost unusable :(
There are still two NXT bricks that don't work at all. Do you have any suggestions on what I should look for on the circuit board?
I'm going to visit a mobile phone repair shop. Maybe they can help with the connector cable. There's also a Repair Café nearby that opens once a month and they might be able to help me. I'd be happy if the bricks worked again. It's sad that they broke just because of their age and not because of abuse while playing :P

[m2fel]

An update and what I've learned so far :)

After some tinkering, I now have two NXT bricks with working displays :). Tried a lot of heat and melted the cable sheating but it didn't make any difference. What worked was squeezing some cardboard under the circiut board and between the circiut board and the display in different angles and thickness until it worked again. At least for one NXT Brick, the other kept flickerig or only worked for sevreral second. Then I had the idea that maybe a display of one of the dead NXTs still works. And one of the two displays only needed some cardboard squeezed in and was back alive. In the process I had to solder and unsolder speaker a few times due to clumsiness :/ Now one brick has sound and the other not... Yeah, I can live with that. Let's see how long the surgery will last.

In the meantime I got my hands on the converter cable NXT to old 9V and this is magic. I figured out that a NXT motor can be run at a PF batterie box but a PF extension cable is needed as the 9V plug does not work with PF directly. Then I discovered that it is possible to connect a NXT motor to a PF IR receiver and use it with the normal or train remote. With the train remote it is even possible to control the speed of the NXT motor. I will  get some PF plugs from Ali Express  and replace the 9V ones at the NXT converter cable to avoid having to use extension cables.

I still did not give up on the two dead NXT Bricks. Seaching the internet for information I stumbled across a PDF for the Lego Mindstorms NXT Hardware Development Kit which includes all wiring diagrams of the NXT Brick. Therefore, not all is lost yet.

Next, I'll get started on building, as I had an idea as to why I dug out the NXTs in the first place.

But I'm still angry at Lego as they sold really poor electronics, and while testing, I even found a defective PF M motor that hadn't been used for some time 

Edited September 16, 2025 by m2fel

[1963maniac]

Could you please show what you did that worked. Pictures need to be posted elsewhere and link to it here.

[m2fel]

Some pictures of the tinkering. It's hard to explain and trial and error. I tried cardboard in different thicknesses and widths. It's all about pressing the right spot with the right force. I tried using a brick seperator to narrow down the required position. I even used a small screwdriver to poke on the cable. Overall, I wasn't particularly careful. I removed a battery to break the circuit when removing the display assembly, and only put it back in once the display pins were reconnected. Else I wasn't grounded and even used metal tools like the screwdriver. You have to make sure that the rubbery button cover fits back in place. Nothing more frustrating than the display works but you can't get the buttons in place and after fixing the cardboard the display is down again 

The pictures are just examples with one of the displays that is still defective. To get the cardboard under the circuit board, I took it out, and the cardboard between the circuit board and the display was pushed in there while installed and powerd.