# D808 install in USAT GP7 Question



## Jim Agnew (Jan 2, 2008)

After installing the Decoder by simply inserting it between the track pickups and the motor input plugs, I have no power to the cab or number board lights, with DCC as the track power. If I switch to straight DC, I have power to the cab and number board lights. The headlights and rear lights are wired separately to F1 & F2. What do I need to do to get power to the lights under DCC?


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## Greg Elmassian (Jan 3, 2008)

Jim, you say you installed the decoder by inserting it between the track pickups and motor... cool, that is the "quick and dirty"... 

But then you say you wired the front and rear headlights. 

How? Specifically what wiring changes did you make? I'll need details on at least 3 wires from the decoder. 

Greg


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## Jim Agnew (Jan 2, 2008)

Greg, I replaced the headlights and rear lights with LEDs. Headlight wires are in Output #1 & common, Rear light wires are in Output #2 & common. I'm wondering if I have a problem with the decoder, because the D808 normally doesn't like DC, but this one acts like a Digitrax Decoder.


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## krs (Feb 29, 2008)

I assume you have the polarity of the LEDs correct and have a current limiting resistor in series which each one. 

Knut


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## Jim Agnew (Jan 2, 2008)

Posted By krs on 02 Aug 2012 06:30 PM 
I assume you have the polarity of the LEDs correct and have a current limiting resistor in series which each one. 

Knut 
Yes.


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## krs (Feb 29, 2008)

OK, next I would check if the problem is with the decoder or the wiring of the LED. 
Easiest way to check this is to disconnect the wire going to the function output, say F1, then connect a resistor of anywhere between 500 ohms and 10K, doesn't matter much what value, whatever you have, between F1 and the common of the decoder, and then check to see if the voltage on F1 changes as you press the F1 function button. 
F1 would normally go the ground, the common is normally the DCC voltage less the diode bridge drop. 

Or if you have an 18 or 24 volt bulb, you can connect that between F1 and common and check if it lights when you push F1.

Edit - Sorry, I think I read your first post too quickly

I have no power to the cab or number board lights, with DCC as the track power. If I switch to straight DC, I have power to the cab and number board lights. The headlights and rear lights are wired separately to F1 & F2. What do I need to do to get power to the lights under DCC? 
.....Are headlights and rear lights connected to F1 and F2 working OK and the problems are the cab light and number board lights that don't come on under DCC?


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## Greg Elmassian (Jan 3, 2008)

He did not rewire the cab or number boards from what I read. Since USAT locos are wired for negative common, and DCC decoders work with positive common, I was not surprised at this statement, but did not comment to allow focus on the headlights. 

One simple thing, if you really did hook the front headlight to output1, and the rear headlight to output2, then I need more information.

By default headlights work from F0, so what CV settings did you use to CHANGE the decoder from stock to allow F1 and F2 to control the headlights as opposed to the STOCK programming for F0? Please give the specific CV's and values. 

(if you did not reprogram the decoder, then to turn on headlights is F0.... it controls both the front and rear headlight)... F1 is normally reserved for bell, and F2 is normally reserved for horn/whistle. 

Greg


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## Jim Agnew (Jan 2, 2008)

Greg and Knut, sorry for the confusion regarding the headlight & rear light connections. I should have said they're on outputs number 1 & 2, not F1 & F2. F0 is functioning correctly. What I cannot get powered are the number board lights and the cab light. I'm trying to use the existing PC board to power these lights. If I connect the decoder to DC, the lights come on. Thanks for your help.


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## krs (Feb 29, 2008)

Posted By Jim Agnew on 03 Aug 2012 12:50 PM 
Greg and Knut, sorry for the confusion regarding the headlight & rear light connections. I should have said they're on outputs number 1 & 2, not F1 & F2. F0 is functioning correctly. What I cannot get powered are the number board lights and the cab light. I'm trying to use the existing PC board to power these lights. If I connect the decoder to DC, the lights come on. Thanks for your help.





















Jim,
Have you looked at George Schreyer's web page on this?

http://www.girr.org/girr/tips/tips5/gp9_tips.html

That should give you all the information you need.

If the cab light and number board lights were changed to LEDs you can either wire them up to a function output of the decoder so you can turn them on and off remotely or if you keep the existing wiring, ie power them from the track directly, you need a bridge rectifier between the track and the LEDs.

Knut

PS: Maybe I'm missing something subtle in the wiring of the USA Trains loco that creates a problem, I don't own one so perhaps Greg can chime in.


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## Jim Agnew (Jan 2, 2008)

Knut, thanks for the link to George's website. I wired the cab light to output 5 and added the resistor, now controlling it with F3. Changed the number board bulbs from 5 volt to 18 volt and wired them to the track pickups. Thanks for your help.


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## Greg Elmassian (Jan 3, 2008)

I have on various times, reversed the leds, rewired the lamps, replaced with leds, etc. As I mentioned, those boards are negative ground, DCC is basically "positive ground" .... 

It takes a bit of work, but you can rewire the boards. 

I did a GP9 recently with a D408 and changed the class lights from the red/green ones to red/white ones... used up all the function outputs and mappings for sure. 

Read down to the bottom where I detail the changes in leds and the D408 programming. 

*http://www.elmassian.com/trains/mot...-power/gp7* 

Greg


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