I'm purchasing either a Proto 2000 FA1 or a Genesis F3A, each of which has a Mars light. A friend told me that I'll need the Digitrax DH163 decoder to operate the Mars light but he isn't always totally accurate so I'm wondering if that is true. Also I'm wondering if the 163 is my only Digitrax option for operating the Mars light.
I have been running with only DH 121 (now DH123) and know mothing about the other decoders so I would appreciate any advice.
In my opinion, the Digitrax Mars light is the best I have seen to date. I have DH 163 decoders in a number of my locomotives and am satisfied with the performance. There are decoders in the DZ and DN series as well that will do Mars light function. The DN-142 comes to mind as well as the DZ-143. DZ and DN series decoders are 1 amp continuous rating whereas the DH series are 2 amp or more. All of them will work as long as you don't overload them. I have plenty of DN series decoders in HO scale locomotives. They fit much better most of the time. My HO scale S-1 and S-2 switchers have DZ-121 and DZ-123 decoders. No problem- and....they fit !
I just finished installing decoders into five Genesis F-units- an ABA set and an AA set. For the A units, I used the DH163A0, and the B unit got a DH121 I had on hand. I chose the DH163A0 for the A units because the DH163A0 is designed to snap neatly in place of the existing circuit board in the Genesis F unit.
I wanted a Gyralight in the A units as well as dimmable ("Rule 17") headlights. Both the 163-series and the 123-series Digitrax decoders offer that combination of features. Since the B unit I was modeling has no lights at all, any decoder would do.
The Genesis A units come with 1.5 volt bulbs. You can keep them in place, but to make them work without burning out takes a few more parts.
For the light that won't have special effects wired to it (the red warning light that only comes on in reverse), I used a 1000 Ohm resistor (1/2 watt) in series with the existing light bulb.
For the bulbs which will need to be dimmed (the gyralight in the upper housing and the headlights in the lower housing), I used a method that Stuart Sabatini suggested on one of the DCC-related YahooGroups- I installed a 330 Ohm 1/2-watt resistor between the bulb and the lighting output, with a pair of diodes in series across the bulb's leads, with the anode end connected to the bulb wire that goes back to the function common output (the blue wire on wired decoders). This allows the 1.5 volt bulbs to be full-on bright or visibly dim when the function requires it. Each bulb that will use special functions uses its own resistor and diodes. If you use just a 330 Ohm resistor without using the diodes, you'll burn out the bulb almost instantly.
And believe it or not, these diodes and resistors are still available at Radio Shack. This method would also work with the comparable TCS and NCE decoders.
For a Genesis A unit with a red bulb and a clear bulb in the upper housing and two clear ones in the lower housing, I use one 1000 Ohm resistor for the red bulb (connected to the Reverse light function) and three 330 Ohm resistors, and six diodes (1N4004) to supply the three clear bulbs. The two bulbs in the lower housing are wired (with their resistors and diodes) to the Forward light function, and the clear light in the upper housing (with its resistor and diodes) is wired to Function output 1 to run the Gyralight.
Believe it or not, there IS room inside the shell for all those components. It's more difficult to explain than it is to do. And the resulting effects are very nice.
Since the P2K loco uses 3 volt bulbs, the DH163L0 would be your best choice electrically, though I don't have an FA1 so I don't know how well it would fit. The Forward and Reverse light output on this decoder are current-limited for the P2K bulbs and need no resistors. Since an A unit has no reverse light normally, you might consider connecting the upper bulb (for the Mars light) to the Reverse light output, then reprogramming the decoder to treat it as a Gyralight controlled by the Function 1 button on the throttle. The DH163 and DH123 decoders will let you do that.
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