Sometimes we get customers who report that their decoder is broken. We don’t doubt that they were handling their decoders with care, but we like to show you the process we are going through to make sure we deliver a top and working product to you.
We test all decoders automatically, with a test bench and a dedicated software made by us (see image at the right). This software was improved over the years, and it is used to validate each decoders hardware before it gets the latest firmware and is shipped. All the decoders have to pass this test and as a result they are validated. Later, before delivery, if it is the case, the decoders are updated with the latest released firmware. At that time, the basic functionality is tested again.
The decoders hardware contains circuit elements to receive external stimuli and signal (DCC, ABC braking, etc.), to detect malfunctioning (short or over-current protection), and drive the adequate outputs (motor, AUX). During the test, all this components are tested, by their functions. The protection of the outputs is handled in 2 separate ways: after each power on, before applying electrical signals to the outputs, the decoder is testing if the respective outputs does not present a short circuit. If yes, it will be omitted from handling and the error condition is flagged in CV30 (the error CV), and/or is signaled with the light flashing. Only after all are parsed, the driving of the respective outputs begun. On the other hand, there is a continuous monitoring of the outputs during the operation of the decoder. If an error situation appears (overcurrent, short circuit), this is detected, flagged, stored in CV30, etc.
While the decoders are tested, we are applying with purpose all possible error stimuli (we are shorting the outputs, overloading/shorting the motor outputs, and the decoder is tested if it is handling these error conditions.
After the decoder is tested it is 100% functional. No decoder is delivered without passing this test, Because of this, we are completely confident that the decoders are leaving the factory in good working conditions.
Despite all of this, we can't say, that over the years we have not received any complain from the customers. But from our experiences, these happened in 99% of the cases with wire connection type decoders. Where the user installed the decoders soldering the wires in to different locations of the locomotive printed circuit board. All points at that in these cases they made a mistake, which has happened to all of us, but do not always realise they’ve done so. With the wire type decoders it is very easy to make something erroneously. And the fact that the decoders are not protected by the heat shrinkable tube, also exposed them to short-circuits. It is easy to touch touch the decoder printed circuit board to some conductive part of the locomotive, and a short is produced. This can't be excluded, and it would be almost impossible to handed by our "protection circuitry". It would require a protection circuit for each of the circuit.
What we also found frequently (especially with model trains manufactured in China, so it means almost every :-) ), that the locomotives present from factory a potential cause for malfunctioning. It is because of the poorly designed mechanics, electronics, etc. Cheap products made in China, high potential for defects. We have seen for example a model where one of the motor wires accidentally was in short with the chassis (from the factory). This still not causing a problem, but when the track contact (current pickup) of the boogie touches the chassis (and unfortunately this happened too often), a nasty short appeared between the bridge rectifier inside the decoder and track. Unfortunately this can't be handled (it is equivalent with a short-circuit of the electronic board with some metal surfaces. A few decoders died, before we realised what is going on. Anyway, we would like to see which decoder would survive to such a short.
To keep a long explanation shorter: normally a short-circuit on the decoder outputs can't cause permanent damage. But if a short appeared, it is flagged in CV30. You can read out CV30, if the value differs from zero, something happened. BUT!!!!! As long as CV30 is not zero, the decoder will not handle the respective outputs (AUX or motor, whatever they are). So in such cases, CV30 should be reset, writing it with zero value.
If you have any question, write us here and we will be happy to answer them.