Do locos equipped with newer/better DCC decoders run more smoothly than earlier decoders?

Model Railroader Electronics and DCC
1

I’m just dipping my toes in the world of DCC and experimenting with installing DCC decoders in my existing locomotive fleet, including some that were purchased DCC ready (or equipped) and others that were not. Two of them are 3rd version Bachmann GE 44 tonners, which came equipped with DCC decoders. On both, I originally removed the decoders and lighting circuit boards because I installed them into a pair of General Electric steeplecab electric freight motor bodies (a MEW brass body, replacing the original open frame mechanism, and a Shapeways plastic body.) At the time, I only ran DC and removed the decoders and circuit boards to fit the chassis in the body, and because I didn’t need the original lighting circuitry (but I kept the parts, just in case.)

After I switched to DCC, I reinstalled the Bachmann-supplied decoder (which has a very compact body) in one, and a Digitrax DH126 1.5 amp decoder in the other, in both cases wired directly to the motor and track power. The mechanisms of both are otherwise identical, but the motor with the Digitrax decoder ran much more smoothly than the one with the Bachmann-supplied decoder. I later replaced the Bachmann decoder (the one I had reinstalled) with another Digitrax decoder, got better low-speed performance and the motor ran more quietly.

Have DCC controllers changed over time and provide smoother/more power, or are these quality differences of different brands of decoder, or some combination of both? Obviously there are other differences with the decoders (the Bachmann only has 2 functions for forward and reverse lights) but are there other differences in how they provide power to the motor?

Pictured below are some of my DCC converted fleet so far, including a GE 70 tonner (originally a two-motor DC chassis, replaced with a newer 70 ton chassis with DCC equipped), a 2nd generation 44 tonner (originally “DCC ready,” I was able to install the 3rd gen lighting board and decoder in it, it drives the motor but the LED headlight

2

In my experience you identified your whole issue. The plain Bachmann non-sound decoders are poor, IMHO. I even have an old locomotive fitted with a decoder from the old MRC Command 2000 system (anyone remember that?) that runs smoother than a newer Bachmann non-sound decoder. It might be possible to tweak enough settings on the Bachmann decoder to get acceptable performance out of it and maybe someone will chime in with the details. Personally, I would look to replace the decoder with just about any other one at your earliest opportunity.

3

It’s all about the decoder and the mechanism. A mediocre decoder with a good mechanism will run nicely, but the best decoder with a poor mechanism…

If it ran nicely on DC, it should run just as well on DCC. Some decoders have better motor control than others, and some have a lot more options to fine tune the motor control.

The DCC command stations and boosters haven’t changed much, but the decoders have gotten much better in the past 20 years. Some of the OEM installed decoders may not offer the same level of options as a retail, install yourself decoder does.

4

don’t decoders that monitor BEMF which indicates motor speed providing feedback to the decoder perform better?

5

Yes…but only as much as it is capable of improving. As betamax indicated, DCC is NOT going to make a poor mechanism run well. It should run “better” but that doesn’t mean it will run smoothly.

TCS & ESU from their inception have offered decoders with VERY smooth motor-control - right out of the box. Soundtraxx has definitely improved in that regard. Digitrax and NCE are good decoders but not as good TCS & ESU.

The biggest change in decoders - for me - has been lighting options/FX and improved/more sound files.

Tom

6

In general my observation is that newer decoders give better motor control than older decoders can.

I notice this particularly when a decoder equipped locomotive is run on DC power.

As for additional features and functions in modern decoders, including better sound, I don’t find those very interesting, at least so far.

Good motor control is important for a more enjoyable modelling operation. Current decoders are very good in that way.

Some of the improvement has come from improvements to the physical mechanism itself. For example, the twin flywheel arrangement implemented by Athearn in their Blue Box diesel locomotives all those years ago has since been refined and improved by others as well as by Athearn and really is quite excellent. Steam models have single flywheel mechanisms and of course more rotating and reciprocating stuff to drive but current stuff from Rapido for example is also excellent.

7

BEMF can create erratic performance on steamers. Some say it has do to with the flywheel… Anyway, when I install a decoder on a steamer, and it acts funny, the first thing I do is remove the BEMF. In quite a number of cases, it stabilized the performance. Sure, the loco will slow down a bit on slopes, but I suspect the real ones lost a bit of power on hills as well [:)].

And yes, some decoders offer better motor control. But as noted above, a three-pole motor will not perform better at low speeds with a high-end decoder…

Simon

8

New decoders support more speed steps, that can make a huge difference. Remember when a DC engine ran better than a DCC one but that was long ago and was soon fixed.

9

Thanks for the advice, it verifies what I suspected after removing the Bachmann DCC decoder. I started my DCC conversion with my smoothest runners (and easiest upgrades) and those that ran well on DC run better with DCC. I also installed a “Keep Alive” in my interurban combine, and combined with a coreless motor and hefty flywheel, it sails through even my most notorious dead track spots without a hiccup! The new decoders I purchased so far don’t have BEMF but apparently are an upgrade from the older Bachmann decoder.

Is there any potential reuse of the old Bachmann decoders? As ersatz function decoders, or as a “spare tire” to bust out when a better decoder dies and you don’t have a comparable replacement on hand?

10

You could use them as function-only decoders - e.g. lighting inside a passenger car or building…

Tom

11

You know I never thought of that.

12

You would need to make sure that you didn’t exceed the current load max for each function output.

13

Most decoders need a motor connected to the orange and grey wires to program. You may need to install a hefty resistor or a temporary motor to program. I put some old decoders inside buildings for lights and set up a hobo camp fire for a friend’s layout using an old Lenz decoder that had a firebox flicker function. I used a red and amber LED and 2 of the functions for it.

Pete.

14

Also good to know; think I’ll keep the Bachmann decoders for a “donut spare.”

15

That’s a common misconception but it’s actually not true. Many decoders need a load attached to acknowledge the programming (they acknowledge by pulsing the motor outputs to temporarily increase current draw). The acknowledgment comes after the programming to let the command station know the programming was successful. The command station may report an error because it doesn’t see the ackowledgment pulse, but the programming will still have tacken place, unless it failed for some other reason (dirty track, bad connection). Most decoders also pulse the headlight outputs, so you can watch for that for programming confirmation.

The exception to this is when programming extended (“long” or “4-digit”) addresses. It takes three seperate “writes” to program an extended address, two for the address and a third to enable the extended address (if not already enabled). Many command stations will stop after the first write if they don’t see that acknowledgement pulse. You can still program extended addresses in those cases, but you have to calculate the three cv values and program them each seperately.

16

Hello All,

To answer your question…

A definitive- -Yes!

I have two (2) consists in my motive fleet.

One is a four (4) unit consist of Bachmann GP40s.

The second is a three (3) unit consist of GP30s, also Bachmann.

The four (4) GP40s had mismatched motors- -some with flywheels and some without. Three (3) had OEM PCB decoders, while one was “DCC Ready” with the OEM Bachmann decoder installed.

Unfortunately, the OEM Bachmann does not support CVs 5 & 6; which is necessary to properly speed match.

The three (3) GP30s had two (2) “DCC Ready” OEM PCBs and a single OEM PCB decoder (see note above re: unsupported CVs).

I re-motored all of the GP40s with the same motors, and hardwired them with Digitrax 166D series decoders.

With the GP30s I replaced the single OEM PCB decoder with a PCB from Bachmann that was “DCC Ready”.

In all three GP30s I installed Digitrax 126P decoders with an NMRA 8-pin harness. The motors all tested equal, despite two being a horizontal split frame and the thrid being a horizontal spit frame.

With the GP40s, after standardizing the motors and decoders there was no need to speed match through the manipulation of CVs.

I adjusted the V Start, V Mid and V Max CVs to the same values and they run well together.

After standardizing the GP30s with the same decoders, there was a bit of CV manipulation to get them to run as a consist.

As has been posted…

Converting an ill-performing DC unit to DCC won’t solve its problems.

However, upgrading both motors and decoders to current (excuse the pun) standards can make a world of difference.

Hope this helps.

17

Not quite sure I see the virtue of this. Why would you want to take apart a locomotive with a failed “better” decoder and replace it with an “inferior” decoder, only to take it apart again when you get the replacement “better” decoder?

Sounds like extra work to me. And it’s not like your loco is adrift in the middle of the Pacific Ocean and you are in danger of being bombed if you don’t get underway quickly. Surely better to wait a week for the new item and only do the work once.

18

Installing a decoder takes a few minutes, especially if it’s set up with a connector plug. In a couple cases my loco bodies are held in place by nothing but gravity, so it’s just a matter of taking it off the layout, popping off the body, and a wee bit of soldering. It didn’t run horribly with the original decoder, but better enough with the new one that I’m not going to change it back. I know some folks prefer to never touch their locos, but it never bothered me much to do so. Plus, I’m kind of cheap and never throw things out if they might be useful–it sounds like they might potentially have utility as function decoders, the Bachmann OEMs are very compact, and I do have plans to eventually add DCC lighting to a couple of passenger trailers and cabeese, so who knows?

19

Yes they do. Newer decoder use more CVs for more optimized PWM and Back EMF which can be adjusted to different motors. Always go for the newest technologies.