N scale GMD-1 Locomotive Support Page (2014 Release)

N scale GMD-1 Locomotive Support Page (2014 Release)


Important DC Advisory

Do NOT use MRC 1300-series DC controllers with any of your Rapido locomotives. The RailPower 1300 is notorious for voltage spikes and it WILL destroy your locomotive. There is no “if” about it. We will try to help you if we have the parts, but we are not responsible for locomotive damage due to voltage spikes in your power supply. As well, we will not repair any locomotive damaged by an MRC 1300-series controller (or any other "train set" DC controller) unless you have retired the controller. Otherwise the damage will soon reoccur. “Train set” DC controllers should not be used with any modern model locomotives.

General Problems and Inquiries

If your model arrives with damage or there is any other issue, the best thing to do is to call our support team. They take care of all of our warranty repairs and they are all swell guys. The toll-free number is 1-855-LRC-6917 (1-855-572-6917) (outside North America, + 1 905-474-3314 or 905-474-3324).

Click Here for Special Notes Regarding Our N GMD-1

To view the files, you will need Adobe Reader. Click below to get it. Adobe Reader

GMD-1 Non-sound Decoder Manual

Special Notes Regarding Our N GMD-1

As many of you are aware, our first N scale locomotive, the GMD-1, has some issues which are preventing some of you from getting the most out of these engines.

There are three main issues with the N scale GMD-1, and here are our proposed solutions to them.

1) Backwards Operation:

The silent NAR and CN 1600-series GMD-1A locomotives run backwards in DC. If you have one of these engines and you are using DC control, this must be extremely frustrating! Despite having the same wiring in our sound-equipped NAR/CN 1600 models and in our HO NAR models, this is the first time we've encountered the backwards running in DC.

We had intended to produce replacement chassis for the N scale NAR and the CN 1600-series locomotives. This was tied to our production order for the 1400-series GMD-1 locomotives. Unfortunately, sales of the 1400s are not yet high enough to begin production.

Rather than leave the chassis on an indefinite production timeline, we have decided to allow people to send their locomotives to our Markham office so that we can rewire them for correct operation in DC.

Because of the specific nature of this issue, we are handling the repair process a little differently from normal. Please contact us to request a repair number and for instructions on how to return your locomotive.

We apologize again for the inconvenience this has caused.

2) DC Headlight Operation

Again for the silent locomotives, the headlights do not go on in DC unless you first turn them on using a DCC system. After that they will work fine in DC. The easy fix is to place the loco on a DCC layout, turn the headlights on, then place the loco back on your DC layout. The headlights will work fine now.

If you can not get to a DCC system and you would like to remove the decoder so the headlights always work properly in DC, we will offer Digitrax dummy plugs at no charge for anyone who requires them. Again, we need you to send us your end labels and we will send you a dummy plug.

To do the fix, just unplug the decoder and plug in the dummy plug. These will be available next month.

3) Tight Wheel Gauge

3. Finally, the gauge of the drive wheels are a fraction of a millimetre too tight on many units, which causes the GMD-1 to derail or jump on some turnouts. The drive wheels can be spread out manually, but if you go a fraction of a millimetre too wide, they bind in the trucks.

So we are making replacement drive wheels available to anyone who has a GMD-1 and is having these issues. You just need to to send us by e-mail. and let us know how many you need. We will upload a YouTube video showing how to do the driver swap. Please put "GMD-1 WHEELS" in the subject heading.

Did you Read the manual?

We have had some reports of the sound models stuttering at slow speeds. To solve this, there is an awesome automatic fine-tuning mechanism in the ESU decoders under CV 54. A number of people have emailed us this solution which they "discovered" after spending days scouring the internet and talking to experts in search of a solution.

But in fact, that solution was always recommended in our full GMD-1 instruction manual (page 12) which was uploaded to our web site when the locomotives were released. We urge everyone to please download our N scale GMD-1 manual and read it, especially if you have limited or no experience with ESU Select sound decoders.

Overall, reports we've had from most of our customers have been overwhelmingly positive, and the criticism we've received has been, for the most part, polite and constructive. We thank you for that and hope that the above solutions to the major issues with the GMD-1 will help us get closer to our customer satisfaction target of 100%.

Function Issues on Digitrax Systems

If you operate with a Digitrax DCC system and your DCC loco does not seem to be responding as it should, please try the fix described below before contacting us. It may save you some time and aggravation!

Apparently, some Digitrax systems store the address of every single loco that they've ever used on them, and regardless of whether the loco was dispatched or not. Once this memory fills up, any new locos that attempt to be used by that system exhibit very unusual behavior including non-working functions and odd responses.

The solution to this is easy. All you need to do is clear the memory in your system. This is done by clearing slot #36, see the instructions below. Once you've done this, you'll likely find that your loco operates exactly as you expected it should.

General Instructions for Closing Command Station Option Switches (for specific instructions for your command station and throttle, see the instruction manual for your equipment):

  • On the command station, set the MODE toggle switch to the OP (center) position.
  • Using your throttle go into Switch Mode
  • Enter the Option Switch number you wish to change (in this case 36).
  • Press the “c” key on the throttle.
  • You will hear a beep.
  • On the command station move the MODE toggle down to SLEEP then back up to RUN.
  • Using your throttle, turn Track Status back on.

For more information, see this page from Digitrax’s web site.

Shell Removal

Removing the shell of your GMD-1 is quite easy. There are no screws to undo, no hidden buttons to press, no secret lampholders to pull. Start at the long-hood end, and press in on the radiator screen on the end while pulling up. The locking tab at the end will come free, and the shell will start to come off. With a jewellers slot screwdriver, carefully wedge the shell upwards along the length of shell towards the short-hood end on both sides of the unit. As a last step, you'll have to pull the handrail pins out of the cab, but that's it! Your shell is free!

Gauging the Wheels

If you find that your models wheels are out of gauge they can be adjusted. Accessing the wheels is a bit more tricky on your GMD-1 than it is on other locomotives. In an effort to make the wiring as durable and bomb-proof as possible, we hard wired the power pick-up wipers to the decoder. This means, however, that it may be necessary to remove the shell of your loco to be able to get enough slack in the pick-up wires to be able to remove the gearbox cover and sideframes.

Copyright © 2023 Rapido Train, Inc. All rights reserved.