Keep alives—priming the pump
In the February 2016 DCC Corner column I mentioned the use of keep alive or stay alive units to keep your locomotives from stalling and having their sound interrupted on dead frogs and dirty track. Since that article came out I’ve had requests for more information on how these work and how to install them. First, let’s talk a little more about how they work.
These units consist of several high capacity capacitors which store electricity and feed it out to your decoder when it needs it. In order to do that they have a charging circuit and a discharge circuit. Some are regulated and some are not. That simply means that a regulated unit will discharge at a set voltage then die whereas the unregulated will have something of a die away voltage curve. There are some that work at 13.5 volts and others that use 15 volts. However you won’t get 15 volts if your track is set to 14.
On decoders designed for the use of stay alives there may be a socket or at least a couple solder pads where they can be easily added on. However, decoders made before the adoption of these units and those not designed to be used with one, probably won’t have easily distinguishable contact points. Basically, the blue wire on the stay alive needs to be connected to the blue common wire or a positive solder pad on the decoder and the other wire goes to a negative contact. On new decoders there may be a black and white wire for the negative connection. However on older decoders you will have to find a place to connect to, and therein lies the problem.
Finding a place to connect to on older boards probably will require contacting the manufacturer tech support team for that information. Fortunately there also are several sources for that kind of information on some decoders. Soundtraxx has a good document on their website showing how to connect their Current Keepers to various older Tsunami boards. NCE also has a document on their website providing suggestions for adding their No Halt unit to decoders. There is an excellent website (http://www.members.optusnet.com.au/mainnorth/alive.htm) with clear photos showing installations on several decoders. Finally Mark Gurries website (https://sites.google.com/site/markgurries/home/decoders/keep-alive-compatibility) has a very technical discussion about how stay alives work and compatibility. Hopefully one of these resources will get you going in the right direction.
Now for the disclaimers and warnings. Be aware that soldering these units to a decoder will be a very delicate operation that will require removing the plastic covering from the decoder. This may void your warranty as will actually soldering anything to the decoder board unless the manufacturer has specifically provided contacts for that purpose. So first, make sure you have a small enough soldering iron and the requisite skills to do the job. And remember that a bad connection will show itself in a puff of smoke when the decoder is powered up. In the long run, for some older first and second generation decoders, it may be time to replace them instead of trying to upgrade them. Sell it on eBay and use the money towards a new decoder that is designed for a stay alive unit. Look forward to more in the March 2018 DCC Corner column! That’s all I can say right now.