DCC concepts loco lamps

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THE CHIEF
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DCC concepts loco lamps

Postby THE CHIEF » Mon Jan 02, 2017 5:50 pm

I'm pulling my hair out here... I'm fitting a red DCC concepts lamp to a guard's van. And I cant get the bloody thing to work. I've fitted a few yellow lamps without issue but for some reason I'm having trouble with a pack of reds I picked up on ebay.

The circuit is as follows using a basic Hornby decoder in a van.

red and black to the track, obviously :)
orange and grey have a 510 ohm resistor wired across to aid programming.
white and yellow are unused as I don't need a directional function.
green to lamp negative ( short wire )
blue to lamp positive ( long wire ) with supplied 50k resistor fitted in between lamp and decoder.
purple unused.

I just don't get it. The decoder should be sound as I "borrowed" it from an installation already using the lamps.

If anyone has any ideas... Thanks :)

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Flashbang
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Re: DCC concepts loco lamps

Postby Flashbang » Mon Jan 02, 2017 6:32 pm

Hi
50K series resistor seems rather high unless the LED is hardly lit?

Anyway... I would remove the existing LED and it's resistor from the decoder wires and then try any standard LED with a 1K0 series resistor. Wire Blue to resistor and resistors other end to LED longer Anode lead. Green wire to LED shorter wire.
F1 on the key pad will normally turn On/Off the green wire function. But check with decoder leaflet.
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Broken? It was working correctly when I left it.

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THE CHIEF
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Re: DCC concepts loco lamps

Postby THE CHIEF » Mon Jan 02, 2017 7:36 pm

The 50k resistor is a supplied item and helps the lamp effect. With a lesser value resistor it looks like a laser sight! I've tested the lamp on 12v DC and it works well. I'll try a basic LED and see it it works. Perhaps the resistor is too strong for the decoder?

Cheers FB ;)

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THE CHIEF
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Re: DCC concepts loco lamps

Postby THE CHIEF » Mon Jan 02, 2017 9:26 pm

Cracked it! After proving the circuit with an LED I still couldn't get it to work... So I tried it the other way having nothing to loose. And blow me the long leg is negative! For some reason all the red lamps are backwards. Perhaps because they are for the rear? Doesn't make electrical sense but that's the answer :roll:

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pete12345
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Re: DCC concepts loco lamps

Postby pete12345 » Fri Jan 06, 2017 4:31 pm

As a possible extension, you could add another tail lamp to the other end of the van, so it can be used in both directions. I'd have these wired to the white/yellow function wires- you can then use the forward/reverse control to determine which is on. This frees up the green wire to be used as an interior light function for the guard or something else.
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