DSX Buffer Circuit
by Don Fiehmann

Do you have a problem of the DSX sound system restarting while running at a steady speed? This is caused by short interruptions in power due to wheel/rail loss of contact. Wheel and rail cleaning will help. Adding a capacitor will also help. Soundtraxx will add a capacitor to you DSX if it was a recent purchase. Check with them to see if your unit is eligible. If not this circuit will help if not completely solve the problem. This circuit is installed between the rails and the Soundtraxx DSX unit. This circuit is designed to provide power from the capacitor during short periods of power loss due to rail/wheel contact problems. This will keep the DSX circuit running until power returns or the capacitor is discharged.

The circuit passes the negative part of the DCC signal through the 2N3904 on the left and the diode on the right. This transistor detects the negative signal with the 2K resistor. This transistor is needed to prevent feed back to the decoder when power is lost.

The positive signal is used to charge the capacitor and feed the transistor on the right. The loss of the negative signal causes the left transistor to turn off. The voltage on the capacitor then turns on the right transistor. When power fails the right transistor continues to supply voltage to the DSX unit until the signal returns. Capacitor can be extended with a long pair of wires if it makes installation easier.

We welcome comments or suggestions from readers; please write or call.