Massoth 10-amp DCC decoder

A 10-amp XXL2 decoder
RELATED TOPICS: CONTROL AND ELECTRICAL
massothxxl
Kevin Strong
10-amp DCC decoder
Massoth Elektronik GmbH
Frankensteiner Str. 28
64342 Seeheim-Malchen
Germany
See dealer for price and availability
Website: www.massoth.com

10-amp DCC decoder (# XXL2) for motor, light, and functions; no sound

Pros: High current handling capacity suitable for multiple-motor locomotives; 12 function capacity with servo and pulsed smoke drivers
Cons: Jump from stop to step one may be abrupt; manual lacks details on programming many aspects of the decoder
There are an increasing number of DCC decoders for large scale on the market, but most top out at around 3 to 5 amps. There are times that more is necessary. Maybe you want to run a set of double-headed diesels off of one decoder. Maybe you’re running a loco that draws an exceptional amount of current. It’s times like these when you want to bring out the big guns.

Massoth’s XXL 2 decoder is designed to be in this group of decoders. It’s a heavy-duty decoder rated at 10 amps peak and 6 amps continuous for the motor. This is an updated version of their original XXL decoder, which we reviewed in the February 2010 issue.

This new decoder includes more functions (12 independent lighting or smoke functions), two servo-control outputs, a broader level of customizing function-output mapping (which function buttons control which functions) and also, for the track-powered DCC folks, the ability to plug in a “keep alive” bank of super capacitors to keep power going to the decoder in case the track is dirty. The board allows you to hook up a magnetic reed switch to trigger some automatic operations, like station stops, though the manual is decidedly thin on how this can be programmed.

I do not have anything on my roster that would draw anything near 10 amps, so I didn’t attempt to test this decoder to the point of tripping its over-current protection. I have run diesels with four motors that draw fewer than 5 amps, so I’m not particularly worried about that rating. I tried to stall out the motor on the locomotive I used to test it (stall current of 3 amps).

The board itself is on par with other large-scale DCC decoders, at 25/8" x 11/4". It has screw terminals on either end of the board, making wiring pretty simple. The PC board has labels for each terminal, so you know by looking what goes where. The labels are abbreviations for the German terms, though, so keep track of the instructions for reference.

Two books are supplied: an installation manual, showing how to wire your decoder into your locomotive, and a programming manual that explains the various CVs and what they do. As mentioned above, there are areas where the manual leaves a lot to the imagination and experimentation. (Fortunately, it does outline how to reset the decoder to factory specs.)

I installed the XXL2 decoder in the tender of one of my locos. This engine has historically been something of a problem child in terms of performance, so I figured the BEMF control of the decoder might help keep things on an even keel. This motor control is designed to keep the locomotive moving at a constant speed regardless of the load on the motor. The train could be going up a hill, around a tight curve, or running free on flat track, and the decoder will keep the locomotive moving at exactly the same speed for a given throttle setting. This engine’s motor tends to bog down easily, making the loco difficult to control under the best of circumstances. I specifically wanted to see if BEMF control could make it more controllable. (Some would argue that such a rigid BEMF control takes the fun out of operating a train as it encounters grades and curves. There’s some degree of truth to that, and you can disable the BEMF control on this decoder if you prefer.)

Installation was straightforward, since the locomotive was wired fairly simply already, with only the motor and headlight connections to make. The XXL2 decoder has

12 extra functions that it can control, so there’s plenty of opportunity to really go crazy with regard to lights, smoke, and even automatic couplers via the two servo controls if you wanted to. Various lighting effects are outlined in the programming guide, including flashing lights (rotary beacons), ditch lights, Mars lights, firebox flicker, even a random glow as you would get from a TV, as well as a camera flash. The smoke control is pulsed, which can be used in conjunction with a chuff trigger for a fan-driven smoke unit synched with the drivers.

With everything hooked up, I turned on the power and did some basic preliminary programming. The decoder comes set to 14 speed steps by default, to be compatible with LGB’s early MTS control system. I changed this to the more common 28-step compatibility, as that gives the operator smoother control over the speed.

With that set, I notched the throttle to step 1 (out of 28) and the locomotive sprang to life. By “sprang,” I mean it lurched forward and began crawling at around a scale two miles per hour. This was the BEMF motor control kicking in. No matter how much of a load I put on the locomotive, it started moving at this speed. I could put my hand on the coupler to introduce drag, and feel the BEMF kick in to make the locomotive pull harder. The lurch from stationary to two scale miles per hour is a bit jarring on the eyes when you bump the throttle from stop to step 1 but it becomes a little less noticeable if you dial some momentum into the throttle and let it slowly ramp up to step 6 or 7 when you first start out. Still, I wish there was a way to adjust the BEMF control to smooth out that initial jump.

I turned off the BEMF control to see if that made a difference in how the engine started and, as I expected, it did start out much more smoothly. The trade-off is that when I grabbed the coupler to introduce some drag as before, the loco just bogged down and sat there. Motor control without BEMF is far less precise.

With BEMF turned back on, I set out to run the loco around the railroad, making a point to start and stop here and there, as I would doing my normal prototypical operations. The loco proved quite controllable and responded well to changes in the throttle. Every now and then, it would get slowed by a twig or branch and I’d see the BEMF kick in to increase the motor’s speed to compensate for the added drag, then quickly re-adjust once the loco broke free of whatever was slowing it. Sometimes a surge of speed was noticeable as it broke free and recovered; other times it was more even. Regardless, what had been a somewhat unpredictable locomotive in terms of performance calmed down nicely.

Overall, I found the control on the decoder to be good. The “lurching” to speed-step 1 is somewhat dependent on the motor it’s controlling, so it may not be as noticeable on other locos with different motors. I didn’t notice it during normal operations on the railroad. Because this is a motor/function-only decoder, you have to pair it with a sound board if you want sound. I have a Phoenix board installed in this loco and it worked well in parallel with the sound board.

Again, this decoder is overkill for running a single-motor Mogul pulling six or seven cars. It’s not the decoder I’d ordinarily use in such an installation. It does work well and, for those installations where you need brute strength and/or extra function outputs, it’s a good option.

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