Decoder Tester

DCCWiki, a community DCC encyclopedia.
Jump to: navigation, search

Summary: A device used to test a Multifunction Decoder for proper operation prior to installation or for troubleshooting purposes. Some include additional features to test a sound decoder. Configuration and testing can be done on the workbench prior to installation.


Commercial Decoder Testers


ESU 51900 Decoder Test Stand

The ESU Decoder Tester is designed to handle a number of different decoders, both sound and non-sound. It can also test Marklin decoders.

It is meant to work with your command station or a LokProgrammer from ESU. All connection points are labelled.


Five pole motor to correctly load the decoder motor outputs. Many decoders will not work if the motor load is not present.
LED indicators for functions.
Multiple DCC connection points.
Speaker with impedance selection: Off, 100 or 16 Ohms [1].

The ESU Decoder Tester has connections for the following decoder interfaces:

  1. 21 Pin MTC Connector
  2. Terminal Block for wired connections
  3. NEM 651 / NMRA 6 pin DCC
  4. NEM 652 / NMRA 8 pin connector
  5. PluX22 connector (This may be missing from earlier versions)
  6. Next18 (May not be present).

The blue common (postive) wire is not required as the device provides the common connection[2].

Track Power is supplied via the TRACK connections

LED Indicators
  1. Headlight
  2. Taillight
  3. Auxiliary 1 to 4

ESU 53900

May be called the LokTester V2.0

Features the NEM 651/652, 21MTC, PluX22, Next18 and connections for a wired decoder. It also has a coreless motor, LED monitors, with a speaker and an extension port.

  • The 53901 extension module is for the LokSound XL / LokSound L multifunction decoders, with LED monitor and servo connections.

For a tutorial, see: ESU decoder tester (Video)


The ZIMO MXTAP Decoder Test and Connector Boards for use with the MXULFA, MX10, and other ZIMO products. Can be used to update decoder software, download sound projects and testing decoders.

Most features of the ZIMO MXTAP are compatible with older ZIMO and other third-party systems and products.

Decoder Connections

  1. Quick Terminal Block
  2. Next18 (NEM661)
  3. 6 Pin (NEM651)
  4. 8 Pin (NEM652)
  5. PluX (NEM658)
  6. 21MTC (NEM660)

MXTAPS Features:

  1. 15 Function LEDs
  2. 5 pole Motor
  3. 13 x 18mm speaker

The SUSI port available on a MXULFA, MX10 and MXTAP decoder can dramatically increase uploading rates for sound files compared to standard "TRACK" connections. Automatically interfaced to the MXTAP "SUSI" port on decoders equipped with PluX, 21MTC, or Next18 interfaces, and ZIMO large scale decoders.

The "SUSI" connection for the boards are configured in parallel by using the two "SUSI" plugs to create a daisy chain allowing a user to simultaneously load sound files on multiple decoders. Each decoder must be connected to its own Decoder Test and Connector Board (MXTAP).

Manufacturer's Site: MXTAPS and MXTAPV

Digitrax LT1

Main article: LT1

The LT1 is included with all Digitrax Starter Sets. It consists of a harness with 6 conductor Telco type wire and a male plug, a tester with a female 6 conductor jack and a protection resistor. The LT1 can be used to test LocoNet cables, as well as multifunction decoders. While it is basic, it can indicate the motor control is working, as well as functions.



The Decoder Test Kit from NCE.

The DTK works with any decoder. It tests them with track power, allowing programming of a decoder before installation.

  • Indicator lights for
    • Motor FWD and REW
      • An optional motor can be added for load testing
    • F0, F0r, F1 and F2
  • Accessory decoders can be tested

This decoder has an 8-pin interface, which limits its usefulness.

Train Control Systems (TCS)

1595 Decoder Tester

The TCS 1595 Decoder Tester looks a lot like the ESU decoder tester, and is fully featured as well. It comes with a Kato 5 pole motor, 28mm speaker and 8 LEDs for testing functions. Power is from the track connections of your booster


  1. 8-Pin NMRA
  2. NEM651
  3. PluX22
  4. Universal 21-Pin
  5. TCS 21-Pin
  6. Screw Terminals

The DT-AUX board adds the following connections:

  • 9-Pin JST
  • 7-Pin JST
  • 6-Pin JST for FL2
  • 7-Pin JST for TCS WAUX (WOWSound Auxiliary Harness)

Other Decoder Testers

These are no longer in production, but can be found used.

Loy's / Urlich Decoder Tester

The Loy's Toys/Urlich Models DT01 Decoder Tester includes clips to quickly connect decoder wires to an NMRA socket to test decoders with an NMRA plug. LEDs are used to indicate speed, direction, and function status. This device is assembled and ready to use - not a kit.

Build a Decoder Tester

Build a Simple Decoder Tester.

An article also appeared the September 2001 issue of Railroad Model Craftsman regarding building a decoder tester. This issue is probably unavailable from the publisher but may be available from used book sellers.

Additional Resources

Further Reading


  1. Some multifunction decoders with sound use high impedance (such as 100Ω) speakers.
  2. Multifunction decoders use an Open Collector to drive functions.