I suspect this is normal. I have a DCC equipped loco (DZ123). When I use it at a friend's house who only has analog (via buzz pack), I get very little throttle control. Slow speed is non-existent. It almost functions like a switch. You're either stopped or after about 15% of throttle movement on the buzz pack, you're at warp speed. Is this normal?
FYI for those encountering the same problems in the future. The culprit is the buzz pack. With a multimeter hooked up to it, I saw that it was initially 0 volts for a brief moment and then it shot up to 16.5V immediately with no in between. The spot where it did this is the same spot that I noticed the loco either standing still or going to warp speed. This explains why it behaved so whacky through the Jump Port. The port is only interpreting the voltage of the buzz pack. Thus 0 and 16.5V will give you the on/off effect instead of smooth throttle transition. I'm no EE (only Mech. Eng.) but I think the circuit in the buzz pack has to rely on a load by the loco to drop the voltage down so that the throttle can have a range. Through a Jump Port there is no load so it's either 0V or the full 16.5V.
The reason for this is that most power packs do not vary the voltage but instead vary the amount of amperage available to the track. Power packs typically contain a transformer and a rheostat. The rheostate is just a winding of wire with a wiper that moves when you turn the knob. When the wiper is just slightly past the zero position, power must go through the complete length of the wire winding to get to the wiper. The effect is to depisapate some of the power by converting it to heat. The voltage is not affected. When you turn the knob to the maximum position, the power only goes through a very small amount of the wire winding and very little power is disapated. Another thing, the decoder will have a dead band to start with. It has to have enough power to before its processor will know that it is on a DC layout and act accordingly. The solution, get your friend to change to DCC. Hasn't he heard that DC is dead. LOL David
A Rheostat is just a variable resistor in series with the loco. The amount of voltage you see at the output will depend on 1) the applied (input) voltage, and 2) the amount of current drawn. If you are just using a voltmeter, very little current will be drawn through the rheostat, resulting in very little voltage drop. Under a larger load (say, a locomotoive) the drop will be more and the measured votage consequently will be lower.
