I have run the Hornby class 50 on dc for many years, later on converted it to DCC. No Problem. I have recently fitted a Hornby sound decoder. Using a Bachmann controller, the loco set for 14 speed steps. When the speed is set at 1/14 the loco judders, the distance varies from 10 to 25mm. Increasing the speed to 2/14 the control is perfect from then on up to 14/14.
Any ideas please.
Thanks