Introduction: 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.
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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.
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.
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,
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:
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.