Having programming problems?

Although I have periodically written about various kinds of programming equipment I still all too often get questions from folks asking why they can’t program decoder X using command station or programmer Y. So hopefully this will answer most of those questions. So what’s causing these complaints? First, there are timing issues involved. The NMRA standards specify how long a decoder may take when responding to a command and if it takes longer than the command station expects then programming fails. Some programmers attempt to get around this by keeping power on longer for individual programming commands which probably explains why they take longer to read and write CVs.

There also are problems with some programmers that cannot program CVs above the old NMRA standard of 255–this is particularly common with indexed CVs. DecoderPro can deal with some of these situations when programming decoders that have developed work arounds for programming these extended CVs. LokSound and WOWSound have provided work arounds. The LokSound manual explains how to use their free software to calculate the required CV values and then write them individually using a throttle. TCS has an online calculator that will spit out the required CVs for programming WOWSound features.

Second are programming track power issues. Keep in mind that this issue first arose about 16 years ago when Soundtraxx released the Tsunami decoders. The capacitors in these decoders sucked up enough power to interfere with programming so the company also came out with the PTB-100 programming track booster to compensate. Now we have a combination of indexed CVs and keep alive circuits with multiple super capacitors to deal with making the job more difficult.

Decoders also require a minimum amount of power on the track to program successfully. LokSound decoders for example require at least 13 volts so their LokProgrammer puts 15 volts on the track. The Soundaxx PTB-100 puts out a regulated 12 volts so shouldn’t work reliably with LokSound decoders but usually does. I recently tried using a higher input voltage of 17VDC with a Digitrax PR3 based on a recommendation from a dealer who told me he regularly uses 18VDC instead of the 15 volt maximum the manual recommends. I got very reliable results programming most LokSound and recent WOWSound decoders with it. There also can be significant differences among decoders of the same brand and batch. I have two first generation WOWOSound diesel decoders one of which I can program easily and another that doesn’t respond at all.

When testing decoders I have found that they usually respond well to individual programming commands on a programming track using a throttle. However that same decoder may not respond at all using DecoderPro with the same command station, especially when programming indexed CVs. Finally, when all else fails programming on the main usually will work. After all you do get full track power when using that mode.

A lot of the problems I was seeing a year or two ago have now been worked out in DecoderPro and with the decoders themselves. Some came down to timing issues whereas others depend on how power is fed to the decoder during programming.

OK, now for the bottom line, what works:

  1. My best success has come using Sprog and Power Cab programmers. This is particularly true when using DecoderPro.

  2. If you are using a Digitrax PR3 consider trying a power supply of about 17VDC. I have been told by the designer that the PR3 hardware can easily handle that voltage. Most decoders are rated to take up to 20 volts but check your spec sheets and don’t exceed what they can take. A PR3 puts out about what it gets from its power supply.

  3. If you can’t program your decoder using DecoderPro then try programming it using individual commands with a throttle on the service mode track.

  4. If you have problems using service mode programming then consider using a programming track booster.

  5. If it won’t work with service mode then switch to programming on the main. You may even get good results that way with DecoderPro, and if not then try using individual throttle progamming commands. You won’t be able to read what’s in the decoder but you may be able to program it successfully.

  6. If your LokSound decoder can’t be programmed reliably then consider investing in the LokProgrammer. It is designed specifically for programming their decodes and works very well.

  7. If your WOWSound decoder doesn’t program reliably using these methods then use the Audio Assist feature, it is very reliable with those CVs it is designed to program.

  8. Don’t overlook probelms caused by having a stay alive device installed. These can interfere with programming, mainly on the service mode track. One trick is to allow the loco to sit a minute or two on a powered track so the stay alive can recharge before programming. You may even have to disconnect the stay alive when programming. This should not be a problem when programming on the main.

  9. If none of these work it is time to contact tech support and/or arrange for a trip back to the factory.

A final tip–always install and test a decoder long before the warranty period expires. Modelers have a habit of buying things and leaving them sit until they get time, which never seems to come, and manufacturers don’t consider that in their warranty coverage.


  • I have a PR3 and now I have 2 questions! Exactly how did you wire the 17V supply? What about amps? The PS14 is rated 14V/300mA.

    • I have a Digitrax PS514. It has several switch settings that allow you to set voltages from 12-24 volts. It also has a set of barrel plugs that makes it possible to use it with devices having a range of sockets. At the 16.8 volt setting (I rounded to 17 volts) it puts out 3.5 amps. The amperage rating of a device like the PR3 just tells you how much it requires to operate. If you supply more it will just not use it. For example your decoders are usually rated at 1 amp continuous and 2 amps for short bursts, but you typically supply 5 amps.

      Warning—read your decoder manual. Some decoders such as Digitrax, specifically state that the programming track voltage must not exceed 16 volts. So don’t use more than a 16 volt power supply with these decoders.

  • Nice article, but I gave up on using any of those devises. Kept have sporadic read and write issues.

    Now I only use a home brew DCC++ Command station. I now get almost 100% reads and writes on any decoder, especially Digitrax and sound decoders.

    You might want to look to do and article on it.

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