TUTORIAL Replace bulb on 12v light brick

[bricks n bolts]

I had a whole stack of broken 12v light bricks where the bulb had gone. In particular they don't last that long when set in lamp posts.

Sick of buying more so needed a way of replacing the bulb with a longer lasting LED.

The first difficultly was finding the right LED with a built in resistor so they can run straight off the 12v power supply.

I hadn't found 3mm white/clear LEDs before, just coloured ones, but found a supplier here for what I needed. These should also work fine for 9v.

Then the other tricky bit was to open up the light brick without breaking it. This wasn't as difficult as I first thought, so here is the guide - no soldering and no glue!

The tools used (almost common household items!) excluding the light brick and LED are :

1. A micro-screwdriver.

2. A bent curtain hook.

3. Some sharp nail scissors.

Step 1.

Using the screwdriver scrape off the plastic tab that helps hold into place the inner part of the light brick :

Step 2.

Using the holes for the plug as an anchor lever out the inner part of the light brick with the sharp end of the bent curtain hook until you can get under it :

Step 3.

If the inner part is still not loose rotate the other end of the curtain hook in the space made at the bottom :

Step 4.

Take out the inner part :

Step 5.

Use the micro srewdriver to remove the old bulb and contacts until the inner part is clear :

Step 6.

Throw away the old bulb and wiring and Insert the LED :

Step 7.

Bend the LED wires around the light brick making sure the LED is centred :

Step 8.

With the screwdriver continue to bend the LED wires into the plug contact holes :

Step 9.

Re-insert the metal contacts. This may take some force, but it will be this additional friction which means the removal of the plastic tab earlier doesn't matter :

Step 10.

Trim off the excess LED wires with the scissors :

Step 11.

Re-join the central part of the light brick with the cover (remember which way is up!) :

Complete!

Remember as it's an LED it won't work plugged in either way to the power supply, but that doesn't bother me in the slightest as you just turn the plug around / swap the pins if it doesn't work

For train lights where the power will be reversed when you reverse the train I can recommend Janco's light bricks which are superb

[JopieK]

you should also include a resistor shouldn't you?! 12V 20mA and an LED voltage of ±3V so 11 / 20mA so 9V left, 9V / 20mA = 450 Ω and a good value (E12) will then be 470Ω.

[bricks n bolts]

you should also include a resistor shouldn't you?! 12V 20mA and an LED voltage of ±3V so 11 / 20mA so 9V left, 9V / 20mA = 450 Ω and a good value (E12) will then be 470Ω.

Nope, the LED chosen has a built in resistor. http://www.goodwillsales.com/white-12v-flat-top-3mm-leds-no-resistors-required-prod-2114.html

Good brightness too, I have several of these running now in my lamp posts.

[alainneke]

Thanks for the clear pictures! If you still want to use bulbs instead of LEDs, you can also try these:

- http://www.conrad.com/ce/en/product/727091/?insert=62&insertNoDeeplink&productname=Micro-filament-lamp-Clear

- http://uk.rs-online.com/web/p/filament-indicator-lamps/6559198/

(source: http://www.heinerberg.homepage.t-online.de/tips.htm)

[bricks n bolts]

Thanks for the clear pictures! If you still want to use bulbs instead of LEDs, you can also try these:

- http://www.conrad.co...ment-lamp-Clear

- http://uk.rs-online....-lamps/6559198/

(source: http://www.heinerber...ine.de/tips.htm)

Thanks for the links! I missed those micro-filament bulbs on Conrad. I wonder how they compare with the original Lego ones for brightness and longevity.

Also lots of interesting things on http://www.heinerberg.homepage.t-online.de

[kieran]

Nice work and write up, much better with LEDS

[LEGO Train 12 Volts]

Fantastic topic!!! :thumbup:

We can also try with the more expensive red light bricks!

Thanks for sharing!

[bricks n bolts]

Thanks guys!

I did do one in red whilst waiting for clear LEDs to arrive :-)

[zzap64]

Great tutorial.

I love this forum, it really brings out the old scientist in me :)

[Andromeda]

Nice job! My next project after the 12v point motor was going to be the very same...!

I like the idea of LED's because of the low mA draw, but I like to run my lights on the 13V A.C. output to maximise what can be plugged into the transformer .

I found the same filament bulbs on RS as Alainneke and have them on order.

There's life left in the old 12v ogeL yet!

[bricks n bolts]

Nice job! My next project after the 12v point motor was going to be the very same...!

I like the idea of LED's because of the low mA draw, but I like to run my lights on the 13V A.C. output to maximise what can be plugged into the transformer .

Thanks, I'm running mine off the transformer D.C at the end plug where all the switches go, don't notice any drop off from there.

There's life left in the old 12v ogeL yet!

Sure is, dont forget to check out my post on how to use PF motors on 12v http://www.eurobricks.com/forum/index.php?showtopic=63535&hl=

[Andromeda]

Thanks, I'm running mine off the transformer D.C at the end plug where all the switches go, don't notice any drop off from there.

Kudos where it is deserved !

I run lights from both the switch 'end' connection and the above mentioned a.c.; you can run 800mA from each...

Sure is, dont forget to check out my post on how to use PF motors on 12v http://www.eurobrick...topic=63535&hl=

Already have! Now I know why I have so much competition on 3bay for the old ogeL 12v track !

[Luke_likes_Lego]

Sweet mod b n b....thanks for sharing.

LLL

[Rick]

Sweet mod b n b....thanks for sharing.

LLL

It's really nice of you that you want to thank someone for starting a topic, but please also consider our policy on topic bumping (linked in the Site Guidelines). Thanks.

[Evans]

Sorry to bump this topic, but pictures are no longer there. Is it possible to reupload them?

I have two yellow 4,5V light bricks that are not working anymore, and I don't want to ruin these. I even think about upgrading these to 12V.

Is there any difference in manipulmation between the clear lens and the diffuser lens?

[bricks n bolts]

Hi Evans,

Sorry, this is totally my fault, I'm hosting the pictures myself and in the middle of a house move, so server has been offline since Thursday until I can get my line restored.

[bricks n bolts]

Pictures are back now!

[Arrow]

Thanks!

[Evans]

Thanks for putting back pictures!

Aren't the LEDs too bright compared to the original bulb? I've recently bought PF LEDs, and I find the light way too bright compared to my 12V and 9V lights.

Anyway, I will try to find such light bulbs to revive and upgrade my broken 4,5V light bricks!

 

[bricks n bolts]

Yes, they are brighter, the diffuser in the brick helps a bit to spread the light though.

The link to the original LEDs I got died, so not sure the best place to get LEDs currently, but the bulb replacement suggested by Alain is still there if you want to try with bulbs -  https://www.conrad.com/p/barthelme-21101240-micro-filament-lamp-727091

[Ncore]

Apologies for reviving an old topic...

...but I am trying to do the same thing. Replacing 12V light brick interiors with leds, that is.
Originally I thought I won't bother, but after rest of my family unintentionally left the lights on for the night and in the morning both of my station lights were out, I started to realize a more long term solution is needed... leds.

An additional benefit I discovered when testing this by connecting the leds and a resistor to 13V AC lego wire:
You can chain the leds using only one wire (of course you need to make every led in the chain is the right way), on to the next, and onward... until circling back from the last led.
(This requires the leds themselves have no resistor, but that you have one resistor of the right value in the chain.)

But when trying to take apart the light brick I ran into problems.

Eventually I managed to get the brick open nicely, only broke one. Then I struck a wall at the above instruction step 5:
 

Quote

Use the micro srewdriver to remove the old bulb and contacts until the inner part is clear

How do you get the metal contacts neatly removed? They are so tightly squeezed in the plastic brick and impossible to get a hold on that the only way I managed to get them off was using some round metal of a similar size and hammering them right through (after nothing else had worked). Well I got them off alright, but there is no way they'll fit back in, let alone hold the led wire tightly in place between the metal ring and the plastic.

Or does anyone come up with a better solution during the past years?

Edited January 10, 2023 by Ncore

[bricks n bolts]

Am still here

Wonder if you have an older style light brick? But you can see that my contacts were hollow tubes, so the micro screwdriver could reach all the way to the bottom of the contacts and they just fell out.

They were loose at that point, only the friction against the LED wire made them tight again.

[Ncore]

Nope, can't see anything. The pictures aren't there...

Looks like in my bricks (the two I have opened) the contacts are just hollow tubes, but they won't come out. Even getting the bulb contacts out between the plastic and the contacts seems impossible - but could of course be that they are the thing that is hold the contacts in place...

[Ncore]

Apparently they are not entirely hollow tubes, there is some sort of... roundness to the form.

https://imgur.com/a/3hCou0I

 

[Ncore]

So.

My light bricks are apparently the old kind, where you simply can not get the metal contacts off.

As you can't get them off the brick, you can't replace the bulbs with leds and attach them the same way - ie. sqeeze the contacts between the metal contact rings and the plastic.
As the metal contacts are attached to the plastic brick, you can't solder anything onto the contacts either - it would melt the brick (tried that).

So I was left with one option.
Solder the led directly to the wire, put it inside the light brick with the wires sticking out of the contact holes, and hot glue the whole thing so that the solder isn't exposed to whatever movement happens on the wires, and keeping the led fixed in its place. Then add a one-pronged connector to the end of both wires.

As I had a led without a resistor and a separate resistor, I also made an invention:

Use 13 V AC power, direct one wire through a resistor (attached as the led above), then on to the led (through one wire, again), on to the next led (again, through one wire), etc. You can daisy-chain these leds as many as you want (tested on three so far though), and the benefit is that you only need one wire to connect them. Then eventually circle back to the power source.
Of course all of the leds need to be connected in the right direction.

Edited January 14, 2023 by Ncore