# Digitrax sound decoder install question



## Bwells (Mar 30, 2014)

I have on order a Digitrax sound decoder SDXH166H 16 bit. I have not received it yet but I have downloaded and printed the manual and I am currently trying to get my ducks in a row before it shows. This will be my first decoder install. I will be installing this in an Athearn F7A-A set where one is a dummy. The controller I will be using is an NCE Power Cab and this is HO scale.The Athearn is not the Genesis nor the blue box but is called ready to roll. It has flywheels and hopefully a can motor. The dummy trucks are the same as the powered ones but without the gears. The track pickups are in place, just no wires. This is where the decoder and speaker will go.I'm trying to figure out a connector between the two locos with the minimum number of pins. If I use the dummy trucks for track pickup, that leaves me with 4 conductors between locos, 2 for motor and 2 for light.

First question I have is about functions. I assume that function 0 = F0 = 0 on the keypad etc up to function 12 = F12. As seen in the pic below, all functions are spoken for.








Next question is in regards to this pic.








It shows on the left a blue wire, pin 6, as being common+. I was under the assumption that common is always - in DC circuits. Not a big deal though as I can figure that one out by trial and error. Next is pin 1 and pin 9. Pin 1 says F2 and Pin 9 says F1, great, however these two functions are already spoken for and why is there a wire to do these? Where exactly would these connect?

My next question will be about gyra/mars lights as the F7 has two locations and I would love to do a solid light on top and a gyra/mars below. I need to do a little thinking on that as I'm not sure the decoder will do that. I need a break and my two fingures are worn out!


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## wvgca (Jan 21, 2013)

the blue wire is common power , the function connections are actually grounds ... white / yellow for forward / rear lights ...and others for additional light effects..


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## Bwells (Mar 30, 2014)

Which others are for light effects? There is not a lot of choices. If I can find a constant 12 VDC somewhere, I think I can do the gyro thing as well as a constant headlight.


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## JerryH (Nov 18, 2012)

White and yellow F0 is used for the front and rear lights. Use green F1 or violet F2 for the other lights. Ditch, mars, gyro, etc.


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## Bwells (Mar 30, 2014)

Okay, thanks for the info. I think a little more research and reading on my part is in order.


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## JerryH (Nov 18, 2012)

Digitrax instructions and manuals are quite confusing. In this case the decoder F functions are not the same as the throttle Functions. You have 2 F0 and F1, F2, F3, F4 light feeds with that decoder for a total of 6 controllable light hookups. There is some flexibility in how you map the decoder functions to the throttle functions.


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## Cycleops (Dec 6, 2014)

I think you may be confusing function (F) numbers on your controller with output (F) numbers on the decoder, as JerryH says, the two are not in any way connected. Its the fault of the confusing instructions.

It looks like the purple and green are used for the extra light functions, the blue is common. You will have to read to see if gyra/mars light are supported on the decoder. You may want to change the bulbs for LEDs in which case you will need resistors which usually come with the pack.


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## DonR (Oct 18, 2012)

You would have a thick cable of wires to the 'A' unit if you
mounted the decoder in the 'B' unit.

You may find that mounting the decoder in the loco itself,
and running only a pair of wires for the speaker
to the 'B' unit would be easier.

Small plugs and jacks suitable for this are available
at Radio Shack.

Don


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## Bwells (Mar 30, 2014)

Thanks for your help! I was way out in right field here as I had no idea there were two different functions, controller and decoder. I still need to do a little more research though. Once again, thank you.


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## tkruger (Jan 18, 2009)

I have done a few RTR conversions and several BB conversions. Both models are vary similar. YouTube has some good videos on converting Blue Box locos.


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