dcc problem

[jbustle742]

 Hello all of you brains, i have a question for you. I am installing new decorders in 2 new N scale ER Sharks using oem circuit boards, here is the problem on the test track the engine will operate correctly using address #3(default) but put engine on the main tracks and it will not operate at all on DCC but will operate on dc if you short rails together but can not control it as it runs full speed,put back on test track and it works fine. All other engines operate correctly on all adresses including #3. Test track is running a Digatrak Zepher and the main tracks are running a Digatrak DCS150 with a DT400. The decorders are MRC AD330 purchaced new. Any help would be apprecated.  Joe

[Jim Banner]

I think I understand what you are trying to say, except the part about shorting the rails together (which rails??).  Based on what I think I understand, you probably have a bad decoder, particularly as it runs only at full speed on dc.

[taz-of-boyds]

I am ignorant and curious.  How are you testing the loco in DC mode?

Thanks,
Charles

[jbustle742]

Taz-of-boyds, sorry i meant to say operating on address of 00 on the main track but still uncontrolable.

Jim Banner,i was talking about the main rails on the main tracks but if the decoder is bad why would it operate at address of #3 on the test track which is controled by the Zepher which is totally seperate from the main layout when all other engines run correctly on it?This doesn`t make any sense!  Thanks again to you both.  Joe

[Jim Banner]

What I am guessing is that the errant decoder cannot deal with the minor differences between your two command stations.  The outputs of command stations can be anywhere within a range of voltages and within a range of timing of the pulses.  A good decoder can deal with any signals that are anywhere  within these voltage and timing ranges, and even a little outside of them.  A decoder that can deal with only part of those ranges may work with one command station but not another.  But if it cannot work over all the ranges, it is not up to specifications.  In other words, it is bad.

There are other possibilities.  For example, the bus or buses that feed your rails may be too long or of too small a wire gauge.  I ran into this problem with one Digitrax decoder which would act like it was possessed on one part of my layout.  That was after switching my H0 layout to DCC but before rewiring it to DCC standards.  Since upgrading the wiring, that decoder has performed just as well as the rest of them.  I don't know about your specific MRC decoders but the group I model with has had problems with them on our portable large scale indoor layout.  Mostly, this has been a problem with them reprogramming themselves to another address, but occasionally we have had them burn up for no apparent reason.

In any event, trying a different decoder may well solve your problem.

[jbustle742]

 Jim thank you for the info. Ithink i will put in a dz123 as i have had good luck with them.  Thanks   Joe