Application Notes : Bachman Spectrum Series Steam Engines

Application Notes : Bachmann Spectrum Series Steam Engines
Con Cor and others

There is a capacitor across the motor circuit that drastically Affects the speed curve when using a Quiet Drive decoder. It causes an over-speed problem. It must be removed from the circuit. Do this by simply cutting one lead of the capacitor and bending it out of the way. The capacitor is typically yellow and has a marking of 105.


Shows circuit board in tender of 3-truck Shay steam engine. Capacitor is cut on one side. View is from fireman's side.	Shows circuit board in tender of 2-8-0 Consolidation Steam Engine. Capacitor is cut on one side and moved out of the way.

Technical explanation. The capacitors are placed in the circuit by Bachmann for the purpose of reducing the possibility that electrical noise generated by the motor when running would interfere with a TV or radio or cell phone or possibly some other electronic device. All TCS decoders have this capacitor built into the decoder and there for external capacitors are not needed. The TCS decoder is tuned to work with its own internal capacitor in operation. With external capacitors applied in the circuit the result is a de tuning which results in poor speed control. That is why the Bachmann applied capacitors need to be removed. The internal decoder capacitor reduces the possibility of electrical interference so there is no harm in removing the external capacitors.

More than one capacitor?

Question: On the new Bachmann Climax there appears to be two yellow capacitors on the board. One on the fireman's side right next to the plug and the other one is on the engineer's side about midway on the board. Which one do I cut or do I cut both them.

Answer: Cut both capacitors.

Also view this application note for more information. Bachmann Steam engine Speed Control Problem