About decoders...?

[Jacktal]

When I read about DCC,I got to believe that the choice of decoders would be dictated by size,power handling capacity and number of optional accessories to be controlled.Now,by reading different posts and replies,it seems like there is a different decoder for every make/scale/model combination of locomotive.Is this true?

May be it is but that doesn't seem logical to me as most locomotives of a given scale,assuming they are of quite similar technology,should have close current draw requirements,carry similar options,etc.Or is it that decoder selection is merely dictated by their physical shape,other parameters being similar?

As an example,I own a Bachmann DD40AX which is powered by two motors(a fine running engine),does this mean that I will need two decoders to convert it to DCC?Even more,this loco has a printed circuit that activates a cabtop flasher(prototypical...?),what will happen to it with DCC?

The final question ,is there a "rule of thumb" for determining the proper decoder for an engine or if we have to rely on every maker's catalog to select the right one.Can a decoder be extracted from an ill fated loco to be installed in another one,assuming power requirements are similar?Is there an expert around?

[nfmisso]

Jack;

There are many suitable decoders for each application. They can be re-used if not damaged.

I am not familiar with how your DD40AX is wired, but it will not be too hard to convert it to DCC. As far as the flasher goes; you have several choices. You could connect it to an accessory output on the decoder, and control it. You could connect it to one of the motors, and it would operate it as it does now, or you could connect it directly to the track - which might cause it to fail.

I would use an acc output on the DCC decoder. I would use a Digitrax DH163D decoder, and wire the motors in series; to reduce the current draw, and slow down the locomotive.

[cacole]

While it's true that there are some decoders made specifically to fit a particular type of locomotive, such as North Coast Engineering's DASR decoder that is an exact replacement for the constant lighting circuit board that is in a Kato, Atlas, or Athearn Genesis locomotive, any generic decoder with at least 1 Amp stall current output can be put into these locomotives by soldering the various wires; the DASR just makes the job a lot easier and costs more. If you know how to solder and can read simple schematics, you can purchase Train Control Systems, Lenz, Digitrax, or any other 1 Amp decoder in bulk packs for around $15 each and save money, since nearly any of these decoders will work OK in any locomotive. As far as the Bachmann DD40X with dual motors is concerned, no, you do not need two separate decoders. The only thing special you will need is a decoder that has a strobe output for one of the functions. I put a 1.5 Amp decoder wired in parallel into an Athearn DD40X with dual motors, which draws a lot more current than the Bachmann motors, and have had no problems with it. All you have to determine in order to select the proper decoder is the "Stall Current" of a motor; i.e., how much current does it draw at full throttle when you hold the locomotive still and push down until the wheels stop spinning. Nearly all newer locomotives with can motors draw less than 1 Amp stall current. That's the standard that is used to measure decoder current requirements; however, if you stop and think about how unlikely it is that you're ever going to hold a locomotive still and push down until the wheels stop spinning, this seems like a silly way to judge a motor. I guess you could say that the stall current measurement is the most idiot proof of all ways to determine what decoder you may need to use, and was no doubt dreamed up by the early decoder manufacturers to make sure people didn't burn them out and then claim that they were faulty. I have installed nearly 100 decoders and smoked only one because it could not handle the current draw of the motor (the motor had a shorted winding).

[BR60103]

Jacktal:
I think you'll find that there are some special decoders for those locos that have fancy printed circuit boards that handle lighting and things. Although most of these should have some sort of socket for the decoder built in.
Buying a designed decoder will probably save you time and may be more compact than using a generic decoder. For some people, it may mean that the loco works after conversion. (I mean me, not you!) Some of them also come with a bunch of lights pre-wired.

[Anonymous]

I would like to see a sound decoder to fit in a MDC 2-6-0 old timer tender.
William