[help] 7866 How to repair red Leds and Flashing unit

[Bloodwave]

Hi everyone,

I have encountered some issues with my 7866 Level Crossing.

First, the flashing unit does not work anymore. I managed to open it (here is a pic from Mark Bellis's brickshelf for illustration http://www.brickshelf.com/gallery/mbellis/Trains/Electronics/set_7866_12v_flash_unit_2.jpg) but as I don't know anything in electronics, I can not see what's going on. I believe that one of the condensators/transistors/résistors/whateverstors is dead but how to be sure and is it repairable ?

Second problem : my son let the level crossing gates down all night long and one of the to red lights have burst. I wanted to try to open the brick in order to replace the light inside but with no success (except that now the brick has serious scratches due to my tries). Is there any secret move to open a light brick ?

Thank you

regards

[Heppeng]

I also had issues with my flasher unit, pretty much in the same boat and Andromeda helped me greatly, without his help I might not have succeeded in fixing it. You might find this thread useful:

http://www.eurobricks.com/forum/index.php?showtopic=85647

For the second part this may help:

http://www.eurobricks.com/forum/index.php?showtopic=78641&hl=%2Blight+%2Bbrick

However you will want to do a like for like replacement for the bulb rather than a diode since the flasher unit relies on its exact resistance to regulate the flashing rate. It might be worth getting a standard white 12V brick and swapping the bulb.

[Bloodwave]

I also had issues with my flasher unit, pretty much in the same boat and Andromeda helped me greatly, without his help I might not have succeeded in fixing it. You might find this thread useful:

http://www.eurobrick...showtopic=85647

Thanks a lot , I swear I use the search command, but obviously with the wrong key words. My bad.

Andromeda's post is very interresting, but very technically "high level". It's almost like reading chinese for me , and I have no DVM or tester. May be one of my friend who is an engineer will be able to help me.

For the second part this may help:

http://www.eurobrick...l=+light +brick

However you will want to do a like for like replacement for the bulb rather than a diode since the flasher unit relies on its exact resistance to regulate the flashing rate. It might be worth getting a standard white 12V brick and swapping the bulb.

Thanks to your link, I was able to open the light brick (and it's indeed pretty easy when you know the trick , see photo )

I think your idea is good, as it seems pretty hard to find a diode with the correct resistance.

Thank you very much for you kind help

Edited November 13, 2015 by Bloodwave

[Heppeng]

Thanks a lot , I swear I use the search command, but obviously with the wrong key words. My bad.

Andromeda's post is very interresting, but very technically "high level". It's almost like reading chinese for me , and I have no DVM or tester. May be one of my friend who is an engineer will be able to help me.

Don't worry, it took me a while to find it and it was even a topic I started! The fact that at no point in it was '7866' written did not help...

I don't think I had a DVM or tester handy either. The replacement components are dirt cheap, so I figured if I replaced both transistors which are the components most likely to have gone pop, as well as a diode I thought was suspect I might get lucky, and I did, although in retrospect I think the original diode was OK. So there is a good chance that if you replace both transistors it will work, and if it does not you have not lost much. If you are really determined you could replace every component on the board, and providing your soldering skills are OK it really should work after that!

Edited November 13, 2015 by Heppeng

[Bloodwave]

Well, in my case, the lights just do not light at all, and according to Andromeda, the guilty part seems to be the 12/15/18R resistor if I have not misunderstood his post. As the issue you described concerning your unit was lights constantly on, I understand the Mpsa13 is just here to command the flashing, right ? Anyway I'm gonna try to find a seller for both parts ans see what happens.

For the red bricklight, I followed your advice and swapped the diode from a white one, of course it works now :). To replace the diode I've extracted from the white brick, I've found a seller near my home who sells 12v 3mm wide lamp, although the lamps he sells are 60mA, not 40 like it seems to be in lego bricks. Hope it will work.

Thanks again for your help in these issues ;)

[Heppeng]

They are all bulbs, or filament lamps, not diodes. The difference is both significant and important. If the original bulb is 40mA and if you replace it with 60mA you will alter the flash rate, as well as the brick running brighter and hotter which might not be good for the plastic.

[Bloodwave]

They are all bulbs, or filament lamps, not diodes. The difference is both significant and important. If the original bulb is 40mA and if you replace it with 60mA you will alter the flash rate, as well as the brick running brighter and hotter which might not be good for the plastic.

Right, diode was not the proper term, my bad.

For the intensity difference, as told before and following your advice, I will keep the original Lego lamps exclusively for the level crossing lights in order to have the right intensity and resistance, that way the flashing unit might do its job properly.

I will try a 60mA lamp as locomotive light plugged in the 12v motor, I hope that as the locomotive lights are never "full powered", the temperature will not be a problem.