How-To Repair Dead Lego Mindstorm LCD

So, your good old Lego Mindstorm display went dead?  What a drag!  Now what?

Well, I found some info on the net which brought my Lego Mindstrom LCD back to life.  Problem was, the fix didn't last for long.  So, in this instructible I'll discuss the conventional wisdom, plus, my own finding to help you bring back your Lego brick back to life.

For reference, here is the link to the original post: http://blogs.wsd1.org/etr/?p=495  This post has some good info and is worth reading.  However, their "fix" is to simply re-solder the LCD caps inside the brick.  Seemed strange to me that re-soldering ceramic surface mount caps would make a difference.  But, I must say, it did work the first time I tried it.  This fix lasted for about three months.  Then, the LCD started flickering and fading  again.

Since my Mindstorm's display was failing again I decided to perform a better fix by replacing the goofy caps.  This "better" fix only lasted about a week.

There must be something else going on with the display besides those caps.

Upon close inspection, I believe the true cause of the display problems is not the caps at all, but instead is the LCD connector ribbon cable.  I think that fooling / re-soldering  the caps simply flexes the ribbon cable which gets the display working again.  However, overtime, the ribbon cable comes loose again.

Well, anyway, below are a bunch of pictures that should help you get your Mindstorm back up and running again, one way or another.  Oh, and standard disclaimer here - do this repair at your own risk.  You could make matter worst for your brick.

Step 1: Dissaembly

There are just four screws that hold the Mindstorm together.  Remove the four screws inside the battery compartment and pull / pry the white top half away from the bottom base. 

The hardest part of this whole repair process is separating the LCD / PCB from the Mindstorm.  The PCB fits tightly on locator pins and the LCD is stuck down with double face tap.

Don't be shy, that LCD and circuit board gotta come out!  However, don't be too rough either - the LCD ribbon cable is delicate.

Step 2: Repair

I replaced all three surface mount caps in my Mindstorm and still had problems return.  In my judgement, re-soldering / replacing the caps is a fool's errand.  However, I think goofing around with the caps inadvertently flexes the LCD ribbon cable and gets the LCD working again (for a while).

The real fix is to repair the ribbon cable.  The ribbon cable is held to the PCB with glue.  Overtime, the stiff ribbon cable pulls away from the circuit board and bad connections develop. 

The fix involves using your thumb to rub hard over the the ribbon cable to circuit board interface.  Rub hard on both side to reestablish / reactivate the bond between the ribbon cable and circuit board.

I wish there was a better way to permanently attach the ribbon cable to the circuit board.  My fear is that the ribbon cable is simply going to come loose again, overtime.

Step 3: Reassembly

Reassembly is easy.  It all goes back together very easy.

Make sure all finger prints have been removed form the LCD and inside surface of the LCD window.  I used a little glass cleaner on both the plastic window and LCD.  Another suggestion, after using glass cleaner make sure ALL the cleaner has evaporated before reassembly.  You don't want trapped alcohol vapors inside your brick.

I also wiped a small amount of oil around the openings where the buttons protrude through the plastic housing.  My buttons, being a sticky kind of rubber, were starting to stick down after being pressed.  The oil film keeps the rubber buttons from sticking.  Very nice.

MOST IMPORTANT

Don't cross thread the four screws that hold the case together.  Make sure you slowly back turn the screw until the screw falls into the thread before driving the screw down into the case.  These are self-taping screws and it's very easy to cross thread them.  If the display needs more work in the future your going to need those threaded holes to work!  Be careful and take your time.  If correctly done, the screw should NOT take much torque to drive home.  If it does, your cross threading the hole.  Stop, reset, and start again.

Step 4: Hallway Speed Racer

As always, you can get more info at my web site.

ph-elec.com

I plan to post some info about our current Lego project - the Hallway Speed Racer.  It's not easy to race down a very very long hallway in the school.  In fact, without active steering it's really impossible!  Our Lego club is having a race soon and I (no, I mean my son) intents to WIN!

Good luck with your brick repair,
Jim

Step 5: Followup - 11/23/2011

I think I found a replacement LCD at a Chinese manufacture.  Have a look at the follow web link:

http://wandisplay.en.alibaba.com/product/202533550-200851330/productdetail.html

Attached to this step is a drawing of the LCD this I received after a request for more information.

The problem is, there is a minimum order requirement of 3,000 pieces. 

I just lacked the initiative to follow-up with the manufacture to verify this is the correct LCD.  Maybe one of you readers will take on the task.

Comments

[digitalf8]

Yup, the NXT (1.0 or 2.0) has problems with the glue. Especially when it gets hot. The glue on the ribbon cable will creep under the contacts and raise them of the surface over time. Then you go to resolder the caps and it may work because you're melting the glue, maybe making a little better contact, but then creeping off the PCB again with a little vibration or heat.

Thanks for looking up the replacement part. There are a ton of these NXT's on ebay for $20 with screen out. Maybe worth the volume purchase from alibaba to make money back. Let us know if that works.

[kirthik2]

I get internal compiler error while downloading a program,in that program i have used switch case where switch checks the condition and executes the loop.Only one case is executed properly and the rest not.why?

[alaafprojs]

I have a NXT 2.0 and this tutorial is for the NXT 1.0

PS: You still can use it even with a blank screen

[JohnD744]

On my device the issue seemed to be the connection between the ribbon cable and the daughter board (as opposed to the ribbon cable and lcd) I tried heating it with a reflow gun and pressing down but that fix was short lived. What has worked for me so far is squashing some open cell packing foam underneath the lcd (where the ribbon cable joins the lcd) so that it applies pressure on the connection between the ribbon cable and daughter board. Hope this helps somebody.

[iandrewmartin]

I've had to fix two of the NXT bricks now for this issue and the fix is easy if you use a hair dryer, and a teaspoon.

1. Do everything up to the complete disassembly as in the steps above.

2. Set your hairdryer on high heat, low fan speed and heat the ribbon cable on the board top for a couple of second only (it gets hot fast) and you can bend the underlying plastic carrier underneath)

3. Using the end of the spoon rub the tape/ribbon cable down.

4. Let cool to the touch on the back of your hand/fingers

5. Turn over and repeat for the other side of the board .

6. Then reassemble partially to test.

6a. If all is OK then reassemble as above.

6b. If you don't get it to fully work first time through go back to step two and repeat. Don't overheat, repeat several times if needed.

Hope this helps anyone having troubles with their NXT brick LCD panels.

[FabianT15]

this worked really well for me (in contrast to the thumb rubbing). thank iandrewmartin you saved the day for my son and myself!!

[iandrewmartin]

FabianT15 - you're most welcome. There is no permanent fix for this issue except getting the unit replaced by Lego. Problem built in from the factory. Glad I could help.

[jvolk]

Problem is not in the capacitors but in flat cable. Check out:

[jimk3038]

Wow, that looks crazy to me. The odds of that working long term are slim to none. One good hard hit on the case would make the brick NFG again.

Seems the easier answer is just to send the brick back to Lego for a free repair.

Still, thanks for the link - the video was interesting.

Jim

[bobbydee]

and, how does this work exactly?? would love some contact info for the Lego repair.

[bobbydee]

well, I answered my own question...

http://forums.usfirst.org/showthread.php?18087-broken-nxt-brick

[Strawberrymake1]

For the replacement: You may want to look at aliexpress.com, they mostly offer the same things from alibaba in small quantities (1 or so), but they are a bit more expensive

[BS Kustomz]

i rubbed mine with the handle of a plastic X-mods screw driver and it works fine... FOR NOW lol better than it sitting there and beeping

[jimk3038]

Yep,

Mine died again. Crap!

There must be something I can over the old tape to hold it down better. Maybe some epoxy? Maybe a big wad of sticky-tack? Something?

The old tape is just shot.

[mstokes3]

I have just purchased some conductive tape from Digi-Key for an exorbident price. Here's the link:
http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=M970312-ND&x=10&y=15
When I receive it, I'll test it. I'm pretty sure it'll work (based on the spec sheet). I'll let y'all know. I apparently have several to fix here.

[jimk3038]

Will the tape not short the contacts on the board?

The issue, seems to me, is that the existing tape is not holding the mylar ribbon cable down onto the circuit board. Even when the existing tape is reattached it tends to up up again.

I'm thinking of adding a ball of blue-tac right on top of the existing tap. Mushing the case down onto the tac will add pressure onto the existing tape / ribbon cable. The hope it that this will force the combo down onto the circuit board. Only problem is latter opening the case. The blue-tac is going to pull the tape away as the case is opened.

The blue tac is not the best solution - I just can't think of a better one. And yes, my display went dead again too! Gotta find a solution before school starts again.

Tough problem to solve,
Jim

[mstokes3]

Actually, no. The tape is only conductive in the Z dimension. The particles of conduction are spaced far enough apart to allow tracks with a minimum distance of 0.4mm. There are a lot of tracks but they are guaranteed to be separated by this distance. Time will tell. I'll let y'all know.

[phoppel]

Any word yet on the tape? If it works, I could sure use some to repair an NXT brick for the school Lego League team.

Thanks, Pat

[jimk3038]

I'm not have any good luck either.

My Lego Mindstorm LCD seems rather dead.  If I push / pull on the display just right I might get it working for a few seconds.

Turns out the tape is just a protective cover. Messing with the tape is just a way to flex the internal ribbon cable, I'm guessing.

Have a look at the attached pictures.

Rather a poor design, it seems to me. See how the ribbon cable makes a really sharp bend? Not good.

I did find something that might be a drop in replacement. Have a look at this:
http://wandisplay.en.alibaba.com/product/202533550-200851330/productdetail.html

I put in a request for info. However, the rep is in China so communications is difficult. Kinda at my wits ends. Might just end up buying a new unit.

Good Luck,
Jim

[luca_crema]

Hi,
any news about this approach?