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Thread: Using Stock Analog Light Board With Wired DCC Decoder?

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    Default Using Stock Analog Light Board With Wired DCC Decoder?

    For my Labor Day Weekend project, I'm planning to do my first real wired decoder install (I installed a wired decoder into a Tomix Thomas the Tank Engine last year, but it was too easy to be considered a *real* wired install ). The subject is a Digitrax DZ126 into Life-Like 2nd Generation GP38-2, released in the mid-2000s. It's actually a good DC runner and even looks great for a Life-Like, despite it not being DCC-ready. I tried selling it in the past but got no takers. I figured I'd hold onto it since it was the last thing I bought from a beloved LHS right before they closed for good, so there's some sentimental value in it for me. The decoder is small enough to fit under the existing light board without any frame modification.

    Anyway, I understand the basics of installing a wired decoder -- make sure the motor is totally isolated from the frame, most of all. I have Kapton tape and have been taping off the inner barrel where the motor sits. The rest is somewhat straightforward as far as where to solder.

    Thing is, it has an analog light board and from running it DC, I like the brightness and the LED glow (nice golden color, not the ugly cold white from other LEDs). Plus, it has the LEDs in the correct position for the front and rear lenses, and if I did remove the analog light board, then I'd have to manually wire in some SMD LEDs + resistors.

    Here's what the frame looks like (Image from the Spookshow.net entry on this loco):


    So, is there a way to install this wired Digitrax decoder and use the existing light board? If so, how would I wire in the yellow/white/blue wires? And would I also have to isolate the light board from the frame? Or is it best to remove the light board and use my SMDs/resistors?

    This is what the decoder looks like:


    Metro Red Ln (Metro Red Line)
    Under the streets of Los Angeles

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    You might be able to tuck the decoder in the space between the light board and the frame, on the left in the photo. You'd have some wire routing to do.

    If you cut traces and completely isolate the light board from the frame, you possibly could retain the light board. You would have to ensure the current-limiting resistors for each LED were still in series with their respective LED. Then determine which leads of the LED are negative and positive. These LEDs might have a flat spot immediately adjacent to a lead -- that's the cathode or negative lead.

    Yellow or white wire goes to the negative lead, depending on whether it's the front or rear headlight. Blue is common positive. I'd be looking to solder the yellow/white wires onto traces that led to the resistors. You could make the soldering easier by drilling a hole into the trace that's slightly larger than the wire gauge -- it's 26 or 28 AWG, I think.
    Paul Schmidt

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    If you can't get a "fitting" PCB replacement decoder for the loco and you have space for the wired decoder, it's a good plan to keep the light board. On my FEF3, I also soldered a sound decoder to the light board.

    Find out how the traces go, cut (with a hobby knife) so both the LEDs with their resistors and the motor contacts are disconnected from the frame, remove all ESD components (capacitors, inductors... basically anything but the LED resistors) and solder all the wires to the appropriate traces. If you take large pictures from both sides of the light board, I can hazard a guess at where to cut and which wire to solder where.

    HTH,
    Heiko

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    Does anyone know how to properly remove electronic components from a lighting board? I'm supposed to remove a couple resistors and re-install them in a different location on the board.

    Metro Red Ln (Metro Red Line)
    Under the streets of Los Angeles

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    Quote Originally Posted by MetroRedLn View Post
    Does anyone know how to properly remove electronic components from a lighting board? I'm supposed to remove a couple resistors and re-install them in a different location on the board.
    You basically just heat the solder and move it away from the component. Use of a solder wick to pull the solder away from the pad and components highly recommend.
    For decoder installation and JMRI services, please visit http://www.bentraildigital.com
    For n-scale intermodal information, please visit http://nscaleintermodal.com

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    Quote Originally Posted by pbender View Post
    You basically just heat the solder and move it away from the component. Use of a solder wick to pull the solder away from the pad and components highly recommend.
    Doesn't seem to work. And I have a variable temp solder that's pretty high up.

    Metro Red Ln (Metro Red Line)
    Under the streets of Los Angeles

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    With SMD, it's a little bit tricky. With a solder wick, you may not be able to get all the solder underneath the device and the pads. The best way I found in removing SMDs is to have two soldering irons. You don't need much heat so even a 30 watt iron would work. Just heat two ends of the device simultaneously with the two irons and pick it off the board. Sort of like using chop sticks. There are no plate through holes so there should be nothing physically holding the device back.

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    Sort of like soldering tweezers? The Hakko conversion kit for my station is $200, so I've not yet jumped on that boat. I haven't had much luck with soldering wicks so I ended up purchasing a solder sucker. My advice regarding those is don't buy the cheap plastic one, you'll end up going back and purchasing a quality one later.

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    Has long has there is not a real close other componet close, I use a heat gun (shrink gun) I put on a bit of flux on the solder pads and heat it up until,I can remove with tweezers

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    Quote Originally Posted by samusi01 View Post
    Sort of like soldering tweezers?
    Basically, yes. And if you don't have two irons or hot air, get one with a large(r) tip and place it in the middle of the part to heat up both pads at the same time, lift off the part with the iron, then clean the pads with some solder wick.

    Also, if it's feasible in any way, get new resistors and trash the old ones. They are in the 1Ct-range price-wise, which is a small price to pay if it helps you get the job done and keep the PCB intact.

    HTH,
    Heiko

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