WARNING! Rapido GMD-1 ditch lights
The brand new HO Rapido GMD-1 with stripes and ditch lights uses none standard configuration for the ditch lights.
They are connected via AUX 5 and AUX 6 of the brand new Loksound decoder (Product ID 86 or better). Those lines are not specified in the Loksound 4.0 documentation and use none documented pins in the 21 plugs.
That was a harsh surprise for me. I ordered the DC version to be used with a Tsunami 2 sound decoder. Everything was great just the ditch lights can not be switched on.

I am forced to use a humming ESU decoder if I want to have operational ditch lights. That makes me really upset.
Hello Reinhard,

you run just into one of this little purgatories which Mr. Lindner has prepared for not so devotional members of the Esuitic Ordre.
In ironic terms: "I (ESU) am your Lord and Master and you should not have other DCC components than mine!"

In earnest, your problems are outgrowths of marketing politics by ESU to which i have very mixed feelings about. Sadly enough ESU left the fully compatibility to NMRA Standards.
And the MTC21 connector has it's own pitfalls. That is caused in the history of this connector. MTC means Märklin Trix Connector and was developed initially for the Märklin BLDC motors. For this there are some certain connector pins reserved. When you use a standard DC motor these pins are obsolete and may be used (not conform to standards?) for other purposes.
May be this helps to identify the connctor pins: <!-- m --><a class="postlink" href="http://morop.eu/downloads/nem/de/nem660_d.pdf">http://morop.eu/downloads/nem/de/nem660_d.pdf</a><!-- m -->

And fortunately for those who do not want ESU, the the Soundtraxx Econami (SX-883004) and the Tsunami2 (SX-885013) are available in PNP form to avoid hassle with the motherboard which also is manufactured by ESU.

My 2 €ents
Cheers Lutz
Hi Lutz,
I did not know the meaning of MTC ..... but that explains everything to me. ESU is grown up with the fenced market of proprietary Maerklin design.

I try to avoid ESU decoders where ever possible and the Tsunami PNP decoders fit perfect in most other engines. e.g. the Intermountain U18B and GP10 are perfectly glad to receive a Tsunami. I am positive the current Atlas-ESU disease can be cured with a PNP decoder very well too :-)

The GMD-1 has a very different design that makes is at least to me almost impossible to install a PNP decoder without massive milling. The light units are very integrated and the cables are terrible short. May be I will give it a try some time later.


Anyhow the great Rapido company got a top position on my black list just next to ESU.
I could not rest until the basic problem of an ESU dominated GMD-1 is solved.

Step 1
Strip the drive down, put a Tsunami 2 EMD PNP with double side sticky tape on the motor aligned to the end of the rear flywheel and solder the rail and motor wires in place. This vehicle should run perfectly.

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Step 2
Rewire the ditch lights. + and - minus are printed on the small PCB

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Step 3
Understand the front and rear light units. From left to right: Number board, Marker lights, Head light and right side is common Plus

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Step 4
Rewire the light units. I wired front light and number boards together. Not fully correct but on a small switching layout a simple solution. The marker lights are not used.

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Step 5
Assemble the light units with a drop of CA glue in the area of the former screws and isolate the bottom side

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Step 6
Mount the light units with capton tape. It looks awfully but it works great. It is my preferred method to mount light things in the shell.

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Step 7
Solder the wires to the Tsunami but do not forget to protect all four wires (front, rear and two ditch lights) with 1k5 resistors! I use FX3 and 4 for the front and rear ditch lights. May be I will rewire it to use FX 3 and 4 for the front and FX 5 and 6 for the rear ditch lights. Anyhow I wanted to keep the first test simple. The wires should shortened to when you know everything works.

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Step 8
Put on "ESU-free GMD-1" on the rails. Absolut no humming at lowest speed Big Grin

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The ditch lights are rewired to be individual controlled by X3, 4, 5 and 6. That permits alternate ditch lights and grade cross logic (solid on of F key, alternate for n seconds after horn is operated). Just two more 1k5 resistors and two more wires.
Very helpful tutorial Reinhard...thank you.
You know that Jason and his staff at Rapido are always looking for helpful and friendly feedback from customers. If you and Lutz and others that you know were to email Jason at Rapido about the issues with the ESU decoders and the MT C plugs and were to explain to them how and why for the humming, you might be pleasantly surprised by their reaction. Just a thought.
Great work but I would have sent the loco back to where I bought it and told them to fix it or give me my money back. Thank goodness they didn't have working ditch lights on the Murphy branch in 1965 or I would have to give up the hobby and take up golf! Icon_lol

Sent from my pocket calculator using two tin cans and a string
Reinhard you did it! Thumbsup

With my Atlas Diesel ordered in DC it was a much more simple task to digitalize them. Even in to 2 CN wide cabs the ditchlights are working immediately as they should after simply plugging the MTC21 decoder in and programming it by Decoder Pro: <!-- m --><a class="postlink" href="https://www.youtube.com/watch?v=NMkIiV-Ws_g&feature=youtu.be">https://www.youtube.com/watch?v=NMkIiV- ... e=youtu.be</a><!-- m -->

But there is an other bug bear with the ESU made motherboards. The noise supression chokes and capacitors for analog DC running should be placed onto the dummy plug and not onto the motherboard as ESU did.
These noise supression devices are very useful for DC, but DCC decoders (ESU not?) have integrated these elements on their own PCB. So a double implementation is obsolete and may cause trouble with BEMF working properly. In doubt when BEMF is not working proper, remove the chokes and bridge the gaps, remove the capacitor also.
Cheers Lutz
ESU offers a small adapter for use of the 21 pin MTC decoders with home made wiring. It's part number is 51967. I got two of them (for reuse of my 21 pin Tsunami 2 decoders) from eBay and they look good to me.
So you would solder your Tsunami2 wires to the pads on the adapter and plug the adapter into the existing ESU motherboard that came with the loco?
Genetk44 Wrote:So you would solder your Tsunami2 wires to the pads on the adapter and plug the adapter into the existing ESU motherboard that came with the loco?
That is not the plan. I intend to plug the Tsunami 2 21 pin sound decoder in the adapter and wire it via the solder pads directly into any locomotive with sufficient space. Candidates are my BN SW1500, CR GP15-1 etc.
The point is that a spare 21 pin decoder is not limited to 21 PCB equipped locomotive (e.g. GMD-1, IM GP10 etc.) but can be wired into any locomotive with the required space.
The GMD-1 motherboard is already completely replaced with a Tsunami 2 PNP decoder. I do not know if he GMD-1 PCB/motherboard is made by ESU or Rapido.

The 21 pin decoder, the adapter and the decoder plug on to the adapter. The adapter has solder pads on both sides of the PCB.

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ps. Read the booklet that comes with the adapter. The 21 pins are "NOT" 1:1 connected to the solder pads. Most are but some are connected to other pads than you may expect!
The day to use the 21 pin adapters came sooner than expected. I am in need for EMD Tsunami 2 for my four Athearn GP15-1 and Germany is sold out. I got two in the US. They are in transit between US and Europe. The other two could be found in UK. Tough luck, Royal Mail misrouted them from Heathrow to Edinburg where they are stuck since three days... That is the moment to get the EMD Tsunami 2 with 21 pins and the ESU 21 pin adapters.

I made two custom boards with the size of standard Athearn/Atlas/Tsunami dimensions. The ESU 21 pin adapter got jumper wires for the standard signals (2 * wheels, 2 * motor, blue and front/rear light).

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The jumpers got wired to the custom board. I have my own "in house" standard of this often used boards. Outside is pickup followed by motor and the center is blue and one lead is cut to form white (front) and yellow (rear).

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The "standard" board is easy mounted on the GP15 drive with double sided sticky tape. the small 2 pin connectors are my standard to connect the LEDs mounted in the shell to the drive.

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LEDs and resistors added
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Back in revenue service
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