KB1011: Troubleshooting Guide for Digitrax Sound Decoders

Digitrax SoundFX Decoder Troubleshooting Guide

This troubleshooting guide assumes that you are working with an operating Digitrax system that is able to run trains and that the locomotive you are troubleshooting is operational and has a Digitrax sound decoder and speaker installed correctly. 

If there is no sound, first make sure the decoder is not muted:

• Press the Function 8 (F8) key, and make sure F8 is OFF.  Function 8 is used to toggle between sound active (F8 OFF) and mute (F8 ON).

If there is no sound and the locomotive won’t move when the address is selected on your throttle:

• If the locomotive has lights, turn on the lights using F0 to see if you are using the correct address for the locomotive and it is selected on your throttle.  If you do not know the address of the locomotive, you can read it back or reprogram it to a known address.
• Verify the 2-digit (AD1) or 4-digit (CV17, 18) address and CV29 are programed properly.  (See CV29 calculator under the Support/CV Information and Tools Tab on digitrax.com or use the Digitrax Tool Box App on your smart phone to calculate the appropriate values for CV29).
• Reset decoder to factory default CV settings by programming CV08 to a value of 08 on a programming track.  This will reset the decoder to address 03.

If there is still no sound output after trying above suggestions:

• If you have downloaded a sound file into the sound decoder, check CV60. Digitrax decoders can have two sound projects loaded into them and CV60 controls which sound project is used by the decoder.  Some downloads only have a single sound project.
  1. Set CV60 to 00 to use the first sound project.
  2. Set CV60 to 01 to use the second sound project. (if there is not a second sound project installed there will be no sound)
  3. If no sound is heard, try changing the value of CV60 from 00 to 01 and vice versa.
• Read back CV126 on a programming track and be sure it has a value of 07, which indicates that all the information required for a sound project has been properly loaded via a PR3.
• Try downloading the sound file to your decoder again or try a different sound file.

“Scratchy” or distorted sounds:

• This may be caused by metallic debris that is attracted by the magnet of the speaker. This debris will get stuck to the cone of the speaker. If you see debris, clean it off the speaker cone.
• Lightly press the speaker’s cone with your finger.  If you get better sound while pressing the speaker’s cone, consider replacing the speaker.

Speed decreases when you blow the horn, ring the bell, etc.:

• Use a speaker with the correct impedance (8 or 32ohms) specified for the decoder you have installed.
  1. We strongly recommend using speakers correctly rated for the decoder you are using.
  2. If you do choose to use an 8 ohm speaker with a decoder that is rated for a 32 ohm speaker, you will need to add a resistor rated at 8-22 ohms in series with the replacement speaker.
• CV57 (speed stabilization/back EMF) should be set to a value of 00.  In no case should CV57 be set to a value greater than 01.

Low sound volume:

• Enclose the speaker in an airtight baffle (speaker enclosure). This will force the sound waves to exit the speaker in one direction and prevent them from interfering with each other and making the volume low.
• Use the largest possible speaker in a baffle that will fit in the locomotive or rolling stock.

Problems programming sound only decoders:

• When programming a sound only decoder such as the SFX004 Soundbug, it is best to program it by itself and then add it to the mobile decoder.

Sound drops out while locomotive is in motion:

• This is most likely due to dirty track or wheel contacts.  Cleaning the track is a good place to start with this issue.
• We highly recommend the use of an external power storage capacitor with all sound decoder installations for best operation, especially in a dirty track environment.  Depending on your environment, sound decoders may not run satisfactorily without a capacitor.
• Digitrax decoders come with capacitors.  Some are already wired to the decoders and others are provided in the packaging. 
• You may substitute capacitors with similar ratings if they will fit better in your installation. Be sure to observe correct lead polarity when installing the external capacitors.