Command 2000 Modifications





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An easy modification of your MRC Command 2000 Walkaround throttles will allow them to be used in pairs without interfering with one another

According to the designer at MRC, the Command 2000 system properly supports only one Walkaround 2000 unit at a time.  Using two of them  results in one interfering with the other, particularly when one is unplugged to move it to the next jack station.  This occurs even if the rules concerning keeping the unused throttles turned all the way up is followed.  With the modified Walkaround 2000's, there is no interference between units, not even in panic situations where an engineer forgets the rules and slams both throttles off.  With this modification, three (or maybe four) persons can simultaneously and independently operate trains with two of them using modified Walkaround 2000 units.

If this sounds too good to be true, then it must be hard to do, right?  Wrong!  In its simplest form, it is the easiest electronic modification you will ever make.  Open the case.  Cut one wire.  Close the case.  The hardest  part is removing the three Phillips slot screw that hold the back on the case.  This modification will give you a Walkaround 2000 unit with only one operational throttle.  The other throttle will be dead at all times, so it cannot interfere with the other Walkaround 2000 unit.  Just make sure you disconnect the left hand throttle in one unit and the right hand throttle in the other unit!  The wires to cut are as follows (referring to the picture below):

Cut the wire connected to rheostat (slide control) terminal B in the unit where you want the left hand throttle to work and the right hand throttle to be dead.

Cut the wire connected to rheostat (slide control) terminal F in the unit where you want the right hand throttle to work  and the left hand throttle to be dead.

For modellers with an interest in electronics, there is a schematic of the MRC walkaround near the bottom of this page.

The down side of this simplest possible modification is that you can no longer use one Walkaround 2000 unit to operate two trains.  Maybe you will never want to.  Or maybe you can afford a third, unmodified Walkaround 2000.  Occasionally I do want to run two trains with one Walkaround 2000 but I do not want to go out and buy a third one.  So I did a little bit more complicated modification on mine.

Cutting one wire off the rheostat opens the circuit and renders the throttle dead.  But it is possible to install a switch to allow you to optionally close the circuit up again, bringing the throttle back to life.  In the photo at left, A is the wire I disconnected from terminal B of the rheostat.  I attached wire A to a miniature toggle switch C.  Then I connected the other terminal of the toggle switch back to terminal B using a small wire D.  This took care of the right hand throttle.  Next I disconnected wire E from terminal F and connected it to toggle switch G.  Then I connected the other terminal of switch G back to terminal F with wire H.

Having done one Walkaround 2000 unit, I then did the other one exactly the same.  It has since been pointed out to me that all I really needed to do was add one switch to each Walkaround 2000 unit, to the left hand throttle of one unit and to the right hand throttle of the other unit (the remaining throttle on each unit would remain untouched.)  That would indeed work and cost less too, but the extra switches ensure that the rheostats are used about equally, lengthening the lives of all of them.

Radio Shack sells some miniature Single Pole Single Throw (SPST) toggle switches that mount in 1/4" holes.  These have two terminals on a small body and are suitable for this application.  Sharp eyed readers may have noticed that the switches I used have three terminals.  That is because they are Single Pole Double Throw (SPDT) switches that I had on hand.  If you use SPDT or DPDT switches, just connect to the centre and bottom terminals, leaving the top terminals disconnected.

I mounted my switches (arrows, lower photograph) by drilling holes in the case and pushing them through from the inside.  The centres of the holes fall on the white trim line and exactly line up with the tops of the slide control slots.  I started with a 1/16" drill, then worked up to 1/4" in three or four steps to avoid damaging the aluminum label.

Usually these switches come with nuts, which should be added to the outside of the case. My switches are unthreaded printed circuit board switches that fit snugly between the case and the rheostat, but threaded ones with nuts would be better.

By turning on only the left hand switch on one Walkaround 2000 and turning on only the right hand switch on the other Walkaround 2000, I can now use them independently with no interference between them.  By turning on both switches on one Walkaround 2000 and making sure the other Walkaround 2000 is disconnected from the system, I can use one Walkaround 2000 to control two trains when I am operating alone or running show loops for visitors.  This arrangement has been fully satisfactory.

For reference, a circuit diagram of the unmodified Walkaround is shown at left.


Modifying the Command Station   Some simple changes to the command station allow you to use two additional walkaround throttles.

Building Tethered Walkarounds   Use two of these with your modified command station to move throttles two and three elsewhere on your layout.  Optional extended low speed control is ideal for switching.

Building Memory Walkarounds  Use two of these with your command station, modified or not, to replace the memory walkarounds supplied by MRC.

Cords and Cables  Some guidance on extension cords and installing throttle stations. 

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this page created 7 April 2000,  last updated 28 February 2001