DCC light problem

[billyboy]

Hi Lads,

 

I've wired up my loco for front & rear lights (LEDS) , the front led lights up just fine and I can program it for the various modes . The rear light stays on constantly unless I drop the power to the BUS and then off it goes. I've check the polarity on the LED, the common blue wire and the yellow reverse wire is as it should be

 

 

I'm using a Digitrax DH126D. I've factory reset the chip and still the same.

 

Any ideas?

 

Bill

[irishthump]

Hi Lads,

 

I've wired up my loco for front & rear lights (LEDS) , the front led lights up just fine and I can program it for the various modes . The rear light stays on constantly unless I drop the power to the BUS and then off it goes. I've check the polarity on the LED, the common blue wire and the yellow reverse wire is as it should be

 

 

I'm using a Digitrax DH126D. I've factory reset the chip and still the same.

 

Any ideas?

 

Bill

 

That's a weird one...

How did you connect the blue wire to the front and back leds? Did you wire them with a resistor on each one? (BTW if you get the polarity wrong on the led it won't light at all.)

[BosKonay]

Do you have the front and rears on function 1? Any chance of a quick circuit ?

[billyboy]

Very weird, I've double checked everything. Wiring is:

 

Blue common from the chip to both LEDs on the positive.

 

Yellow to the rear light negative.

 

White to the front light negative.

 

For good or bad I've the 2k resistor on the positive common on both LEDs. I'll change that and put the resistor on the negative.

 

I'm pretty sure I've both lights on Function one but still learning and working my way through manual.

 

Bill

[irishthump]

Very weird, I've double checked everything. Wiring is:

 

Blue common from the chip to both LEDs on the positive.

 

Yellow to the rear light negative.

 

White to the front light negative.

 

For good or bad I've the 2k resistor on the positive common on both LEDs. I'll change that and put the resistor on the negative.

 

I'm pretty sure I've both lights on Function one but still learning and working my way through manual.

 

Bill

 

The wiring certainly sounds right. and it should'nt make any difference if the resistor is on the positive or the negative. 2K sounds a little high, I would use a 1K for most LEDs but it should'nt cause a problem. The most important thing is that they are wired in parallel with a resistor on each.

I have read that the older Digitrax decoders don't work well with LEDs for lighting but I though that was fixed with the later ones like the DH126D. Might be an idea to try some incandescent bulbs if you have any just to see if they work.

 

By the way, what DCC system are you using?

[billyboy]

The Digitrak DCS51 , I've a BR Class 37 thats DCC ready with a chip and I can program away on that with both front & rear lights.

 

I'll strip it down again tomorrow night or Stephen's day and have a look.

[irishthump]

The Digitrak DCS51 , I've a BR Class 37 thats DCC ready with a chip and I can program away on that with both front & rear lights.

 

I'll strip it down again tomorrow night or Stephen's day and have a look.

 

You could have a stray wire or piece of solder which is allowing current to get to the LED. It might be worth stripping the heat shrink off the decoder.

[irishthump]

The Digitrak DCS51

 

The reason I ask is that with my old Hornby Select some decoder's lights would stay on whether the function button was on or not! Something to do with the Select's output signal being very rough.

[billyboy]

Well I fried the chip it seems, while checking the wiring to the front LED it touched the chassis and shorted.If I run a loco with the chip it shorts the controller and kills power to the track. I suspect it may of been slightly iffy anyway as the rear light was a cause for concern.

 

After it was fried I took the blue insulating cover off the chip and no scorch marks or burnt electronic smell. I took the motor off the chassis and ran it purely chip and motor only and it shorted .

 

Lesson learned there.....

 

I'll fire a mail to Digitrax as they as a no quibble warranty on decoders and see if they'll replace it.

 

Thanks guys.

 

Bill

Edited December 27, 2014 by billyboy

[billyboy]

Hi guys,

 

just an update, I went through the Digitrax warrenty, sent the chip back explaining what happened and they told me to bag it up and send it back to them, three to four weeks later a new decoder lands back at my house. I fitted it and now the front and rear leds work depending on direction of travel of the loco , so I'm thinking it was the previous decoder was a bit iffy.

 

I then had over-voltage shutdowns on the loco after running it on a few circuits and also when it met another local on the second parallel track head on and it was also jumping and shorting on a set of points.

 

So I reset the decoder , took the loco part , re-wired it and resoldered to the trucks in what I found on a hunch to be a far simpler and easier setup, my previous soldering job was a nightmare to do. Put it back together again and touch wood four days later it running extremely well, leds working no issues on points.

 

I had a look at the internals of my next two candidates for conversion IE 201 and a GWR Pannier and hopefully with lessons learned above it should be easy enough.

 

Bill

[irishthump]

When you say "over voltage shutdown" do you mean the decoder or the DCC controller was shutting down?

[billyboy]

The controller and both locos powered down , sometimes it was momentary they'd halt and then start on their way again, once or twice full shutdown and power off.

[irishthump]

The controller and both locos powered down , sometimes it was momentary they'd halt and then start on their way again, once or twice full shutdown and power off.

 

Forgive me asking all the questions, but I'm curious about this one! What exactly would happen? What do you mean by the loco meeting another local on the main? Did you say the loco was an Athearn?

[billyboy]

I've two tracks that run parallel , main up & down. Prior to the rewiring if I ran the Athearn SD40 on down line and it met in parallel the Class 37 coming towards it on the up line they would both halt and stop momentarily and move on or trip the power on the controller triggering a shutdown. This didn't happen with the previous chip in the SD40 .

 

Except for one glitch I noticed late last night when the SD40 crosses over a Peco point to the main up its running just fine.

 

The shutdown may of been down to my wiring , since I re-wired it running a lot smoother as well.