Quote from: r.cprmier on March 09, 2007, 06:20:02 AMThe Bachmann decoder operates at a frequency heard by people with normal hearing as a hum.
BTW, would those two yellow caps on the board have anything to do with that hum?
The capacitors have nothing to do with the frequency hum. Capacitors across the motor circuit are part of the motor electrical noise suppression so it does not interfere with other electronic devices.
Some decoders have an internal capacitor to do the suppression and the decoder is tuned to work with them. When external capacitors are added they cause de tuning, which results in poor motor speed control.