4-4-0 running in reverse - power pack problem?

[LarrySmith]

In an earlier post I described how my new 4-4-0 would only run in reverse.  Though I missed it at first, all of my DCC equiped engines will only run in reverse when my power supply, MRC Model 500, is in the "pulse" position.  When the power supply is in the "full" position the engines run in both forward and reverse but at a high rate of speed. 

The MRC Model 500 power supply is from the 1970's and regular DC engines run without any problems.  Can anyone tell me how the DCC circuit works so that a pulse only lets the engine run in reverse?  Is it possible to get speed control when in the "full" position or will the engines always run fast?

Two additional questions while I am here.  (1) Does the 4-4-0 have any space to add weight and give the engine more traction?  (2) My new SP GS4 4-8-4 seems very large compared to 2-10-2 and 4-8-2 engines.  Are these engines built to scale?

Information will be greatly  appreciated.  Thanks, Larry Smith.

[Tim]

Larry

Rule #1: Never run decoder equipped loco's on pulse power.
It fools the decoder into thinking it is on DCC, in your case the decoder
thinks the pulses are telling it to go in reverse.  You were lucky that is all that
happened.  Pulse power can also fry a decoder.

The reason for the high speed is the older power packs had rheostats for speed control
they cannot properly control the newer low current motors.  A Tech II or later will work, as
they have a potentiometer for speed control and are solid state.

Tim Anders
Soudertio, PA

[richG]

Here is a link to the Bachmann Quick Start Guide. Downloaded it to your PC, print it out and keep it at the layout. Also, put the link in your Favorites folder. Page 9 tells you to use filtered DC, no pulse.
http://www.soundtraxx.com/documents/manuals/Bachmann%20Quick%20Start%20Guide.pdf

Rich