A decoder tester is actually a test fixture that allows you to easily connect a decoder to a DCC test track and check the decoder to make sure that all aspects of it are functioning correctly. Why do you need one?
Two keys issues:
As a result of these types of considerations (both time spent installing and warranty considerations), it is strongly recommend that all decoders be tested before starting the installation. From personal experience we can tell you that it is very frustrating to completely install a decoder only to find that the decoder is not working properly!
Decoder testers are also handy when you have a problem with a decoder and would like to test it outside of the locomotive. We've also used them when we want to program a decoder prior to installation.
If you only plan to do one or two decoder installations, then perhaps you can make do without a decoder tester. If you plan to do more than a few installations, we think a decoder tester is a worthwhile investment. You can either build your own decoder tester, or purchase one of the commercial ones currently available on the market.
Building your own tester
Railroad Model Craftsman ran a do-it-yourself article by Jeff Scherb on building a decoder test fixture. The article appeared in the September 2001 issue. If you are considering building your own tester, you may want to get a copy of this article, as it will provide more details on building such a test fixture.
Purchasing a commercial product
At the time this page was last updated, there are three commercial decoder testers on the market.
Loy's Toys produces a Decoder Tester assembled and ready to use. You will find more about it on their web site at Decoder Tester. The Loy's Toys tester is available direct from the manufacturer as well as other DCC dealers.
NCE sells the DTK -- a pre-assembled decoder test kit. You'll find more about it on their web site on the Accessories page. The DTK is available from any DCC dealer carrying NCE products.
Digitrax sells the LT1 Tester for Decoders & LocoNet Cables. More information is available on their web site. It is available from Digitrax dealers, and at this time this page was written, the LT1 is also included with Digitrax starter sets.
Like all things in life, all decoder testers are not created equally. Each of the models above has different features and appears in the market at a different price point. So if you planning to purchase one, be sure to compare their features before making your purchase. Some features you may want consider:
A final thought is that regardless of the tester you select, it is usually possible to extend the commercial tester to make some connections easier. Here are a few extension & upgrade ideas to consider.
NCE Decoder Test Kit
1) The NCE DTK is very compact decoder tester, with significant flexibility. But it leaves packaging to the user. The image at the left shows what you receive in the package (along with a user guide). The image at the right shows just the tester itself. (Click on any thumbnail to see a larger image.) I carry my NCE DTK in my tool bag, and extended my DTK with the following modifications/additions.
Loy's Toys Decoder Tester
Loy's Toys Decoder Tester is the decoder tester I use on my bench. It is a little larger than the other two, but on my bench, storage space is not a large issue. And I've upgraded it to make testing a little easier. Here is a photo of the stock Decoder Tester (on the left), and my upgraded decoder tester (on the right). (Remember that you can click on any of these thumbnails to see a larger photo.) I made the following upgrades to my unit :
In the photo at the left you can see the motor as I mounted it. I drilled three small holes in the end of the tester near the clip leads to the track. One hole (to the left in this photo) is where the wires to the motor are run, and the other two holes are used to pass a cable tie through to hold the motor in place. Like the NCE DTK upgrade, I used a small DC motor that was in my parts box. Remember to leave the wires to the motor somewhat long so that you can have the cover off of the decoder tester to make other changes. I soldered the motor wires directly to the pads for the gray and orange nail clips on the underside of the board. And I put the locking tab of the cable tie inside the box for a neater finish.
In the photo at the right you can see how I mounted the speaker on the opposite end. I used a Miniatronics speaker -- part #60-078-01 -- an 8ohm 7/8" round speaker, 9/16" high, and already in a case. This was an easy install, since I just had to drill two small holes behind the speaker for the speaker connection posts to pass through, and then hot glued the speaker to the end of the box.
On the face of the decoder tester I drilled three small holes (5/64") to add three additional nail clips. You can see them in the photo to the left. I added two violet nail clips, and one brown nail clip. With this size hole, the nail clips fit very tight. I also added some hot glue on the underside to give them more stability. The fit of the nail clips was tight enough that I needed to use my hammer to push them down. Be very careful if you do this, as it is possible to bend the nail clips. If you intend to do much of this, your best bet would be to get the T20 nail clip driver from E-Z Hook which has been designed expressly for this purpose. The reason I added three nail clips instead of two is that I have the two violet nail clips (10 piece pkg, E-Z Hook part #81-1-S VLT, Digi-key part #461-1247-ND) connected to the speaker connection posts. And I have a 16V 47μfd bi-polar capacitor connected on the underside of the board between the brown nail clip (10 piece pkg, E-Z Hook part #81-1-S BRN, Digi-key part #461-1241-ND) and the lower violet nail clip. With this approach if you want to test a older SoundTraxx decoder that needs the capacitor, you can connect one speaker wire from the decoder to the brown nail clip and the other speaker wire from the decoder to the top violet nail clip. If you are testing the newer SoundTraxx Tsunami decoders which have a capacitor already wired in, then you can just connect the two speaker wires directly to the two violet nail clips.
Note: this second upgrade with speaker, additional nail clips, and capacitor is designed specifically to test SoundTraxx decoders. Other sound decoder manufacturers use different ohm speakers and thus I would recommend testing in the standard manner. If you primarily use another manufacturer's sound decoders, you should be able to make similar improvement to the decoder tester to speed testing of that manufacturer's sound decoders.
Copyright © 2002-2006. C. M. Greene. All rights reserved.