Soldering Iron Issues

I recently received an email from a reader who wanted to share with me a problem he has had with installing decoders. He was primarily having issues with blown sound circuits in Soundtraxx decoders especially the Tsunami2. To make a long story short an EE checked out his soldering iron and it turned out his 18 year-old WLC-100 was leaking 32 volts through the tip which was the likely cause of his blown decoders. Since replacing the unit with another grounded and certified soldering station he has had no further problems. So what was going on?

First his 18 year old WLC-100 was produced at a time when they were not grounded–there was no ground prong on the plug. Also his was not ESD (electro static discharge) certified for use with electronic components such as those used in decoders. The current WLC-100 is grounded but there is still no mention on their website of it having ESD certification. Another factor was that he was only blowing the audio amplifier on the decoder when he soldered the speaker connections. I have been installing decoders since 1994 using ungrounded and later, grounded soldering irons (the WLC-100) and I have never had a failure like this so I consider it an unusual occurrence. It is most likely that he had a soldering iron that went bad after 15 years, especially since he only started blowing decoders a couple years ago.

I talked with the folks at Soundtraxx and they were well aware of this case but had never seen a similar one. I also asked several manufacturers whether this issue was a concern for them and whether they see these kinds of decoder failures often. The answer I got was that decoders generally are not all that susceptible to this kind of damage. All test their decoders at the factory before shipping them so they know they are good before they go out the door. The most common issues for returned decoders seem to be over current draw from old motors, making the wrong connections, and the use of acidic fluxes or conductive plumbing fluxes (remember only use rosin fluxes with model railroading work).

So, what is the best way to avoid damaging decoders if your iron goes bad and starts leaking electrons without your knowledge? What I suggest is to unplug the decoder from the wiring harness or motherboard and install just those components and speakers first. Once these are installed plug in the decoder and head for the programming track. This approach will guarantee that any voltage leakage through the soldering iron tip will not damage the decoder.

For most decoders it is fairly easy to remove them from their harness or motherboard–this is not the case with Soundtraxx Econami ECO-100 and Tsunami2 TSU-1100 decoders. These have 4 and 8-pin micro connectors instead of the usual JST connectors. I asked their customer support about this and they could not recommend an easy method for customers since they have to use a special tool themselves. I came up with a way to do it that will not violate the warranty and will post a video soon.

When it comes to LokSound micro decoders, which have the wires  soldered directly to the board there is no work around. I guess if you install one and it still works afterwards then it is probably safe to assume your iron is OK. But if you cook one decoder stop and evaluate the situation before doing any more. Most of these companies have a no questions asked warranty but if you do blow several I am sure they will want to ask you a few questions!


  • So, is there any way to test an iron to see if it is leaking? I don’t have any that are the old two prong, but still, I’d like to be on the safe side.

    • I knew someone would ask that and I am working on a followup post on the subject. So give it a couple days and you’ll have the answer.

  • A “leaky” soldering iron (one not grounded properly) also can damage a decoder and still work for a while, then one day the problem occurs. This is called the ‘Walking Wounded’.