Trolley operation and DCC

[scotiatram]

The programming track on my trolley layout is set up using the overhead as one current feed and the two common rails as the other.
I have just purchased a magnificent Peter Witt trolley that functions well on DCC and overhead with the micro-switch set to "trolley", but I cannot access the decoder to program it.
My Digitrax unit gives the "nd" error when I try to access the streetcar's decoder even though all other units can be accessed.
Question(s): do I have to modify my programming procedure for this Bachmann unit to a two-rail system, and / or do I have to access the decoder with the micro-switch set to "track"?

[Jim Banner]

A common problem with Digitrax Zephyr and Bachmann decoders is insufficient current for the Zephyr to detect the decoder.  Adding a 1k (1000 ohm) resistor across the rails while programming is the usual work around.

Jim

p.s. it helps to give all the details when asking.  I am only guessing that you have a Zephyr and not one of the other Digitrax systems.  If you do not have a Zephyr, by all means ask again but let us know witch Digitrax system you do have.

[JerryB]

Since you are ". . . using the overhead as one current feed and the two common rails as the other . . ." the 'programming' resistor Jim wrote about must go between the rail(s) and the overhead.

Happy RRing,

Jerry

[jward]

actually, if you are using the zephyr, you can put the resistor across the programming leads anywhere. i'd put the resistor right at the terminals of the zephyr's programming output. it would be much easier than wiring a resistor between the overhead and the rails.

[scotiatram]

I have a DIGITRAX DCS 50 and the programming circuit has the resistor that came with the unit.
The trolley has a micro-switch underneath the chassis which permits 2-rail or overhead operation.
Last night I wired the trolley's wheels directly to the programming circuit and positioned the micro-switch to 'track' but received the same "nd" error. I made sure the truck's electrical sliders were making proper contact - to no avail.
I tested the hook-up cables and they were good. Then I positioned the micro-switch to 'trolley' with similar "nd" result.

Any help on this?
thanks
scotiatram

[Jim Banner]

I have a DIGITRAX DCS 50 and the programming circuit has the resistor that came with the unit.

The 120 ohm resistor shown on page 14 of your Mobile Decoder Manual is to be connected in series with the programming track.  This is not the same as a 1000 ohm resistor connected in parallel with (i.e. "across") the programming track.  Without the 1000 ohm resistor across the programming track (NOT in series with it,) the decoder does not draw enough current to be detected by your Zephyr.  That is why you are getting a dnd (Did Not Detect) error.  And when your Zephyr does not detect a decoder, it will not try to program it.  As you have already figured out, you must switch your trolley to run off track power in order to program on your programming track.

If you cannot obtain a 1000 ohm resistor, you can alternately use blast mode programming mentioned in the DCS51 manual, available online at the Digitrax website.  This feature is also included in your DCS50 even though it was not documented in your manual.  If you use this method, be sure to observe all the appropriate precautions.

Incidentally, there is no such thing as a "nd" error.  I am assuming you are getting a dnd error  (see page 22 of your Zephyr manual.)

Jim