Using track voltage bulbs with DCC decoders

The bulbs were connected directly to the track and worked on this loco on DC, why should I not just connect them to the decoder's "track voltage" output?

To get some light out of the bulb at less than full speed, the manufacturers use 12 volt (or sometimes even less) bulbs. When you connect these to the (frequently as high as 15 volt) outputs from your decoder, their life is severly limited.

Bruce recommends LEDs as the primary replacement for bulbs.

If you insist on keeping bulbs in your loco, there are two things that you can do to prolong the life of the bulb and the decoder.

BEWARE that track voltage bulbs and the series resistors get VERY HOT.
They may melt plastic shells or detail parts.

  • Put a 22 ohm resistor in series with the bulb. This does two things! Firstly, it limits the inrush current to the bulb when it is turned on cold, protecting the decoder. Secondly, it SLIGHTLY reduces the voltage on the bulb, prolonging its life. The resistor will get HOT - keep it away from plastic shells!
  • Change the bulb out for a 14 volt bulb and STILL USE the 22 ohm resistor. Being closer to the voltage coming out of the decoder, they will have a much longer life than the original bulbs.
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