Digitrax and NX18

[Timothy-350163]

Having a short circuit problem with all Hornby TT:120 locos.

All four of the NX18 socketed locos run perfectly with a DC power pack/controller.

Remove the DC power pack and connect the Digitrak Zephyr and all locos are seen as a short circuit on the Digitrax unit. The track status light blinks and the message Local Booster track Fault appears in the display. A short circuit.

Removing the NX18 blank plug from the socket in the tender, with the loco on the tracks and the Zephyr does not see a short.

Is the Zephyr available current too low for NX18?

Has anyone had a similar issue?

Does this same issue happen using an Elite controller?

Appreciate anyone's insight to DCC operation.

[Rallymatt]

This would probably be better put in the DCC section where more fellow Digitrax users might have some valuable input

[ntpntpntp]

Er... have the locos actually got decoders fitted? You mention "NX18 blank plug"? If it's just a DC blanking plate then you shouldn't be placing them on a DCC layout or hooking up a DCC system to the trackwork they are sitting on, you'll fry the motor of an "unchipped" loco quite rapidly.

[Timothy-350163]

It seems to me all TT:120 locos that are DCC ready are NX18 socket equipped, so believe this is the right place for the discussion.

Hornby NX18 locos either come with a blank plug or a decoder. The socket is in the tender and if the loco is simply a DC loco, there is a blank plug in the socket. That blank plug is a circuit board needed for conventional DC operation.

A NX18 decoder fits in the same socket and Hornby makes their version which operates with the HM 7000 Blu-tooth system.

The Digitrax Zephyr should operate these conventional TT:120 locos, but it does not. The Digitrax unit sees these locos as a dead short. Possibly through the components on the blank board plugged into the socket.

[ntpntpntp]

@Timothy - you haven't answered my question: have your locos actually got DCC decoders fitted or just DC blanking plates? If decoders are fitted, which ones?

If they are decoder fitted it seems very odd/unlikely that they'd all suffer the same problem. Have you tried swapping decoders between locos, or just testing with one decoder and trying it in each loco?

The Zephyr can apparently operate one unchipped loco by "zero-stretching" the DCC signal, but as I mentioned before I would strongly advise against it with small scale motors (TT or N for example, nor is it good for 00 either). It's an old part of DCC capabilities which fell out of favour many years ago. An unchipped loco will buzz on a DCC track whilst frying the motor.

[Fishmanoz]

Timothy, looking at your original post and the exchange between you and Nick, my interpretation of your problem/questions is this - Can my DCC controller run DCC Ready locos with their blanking plugs fitted? And to give you all some more detail, my controller is a Zephyr and the locos are all TT:120 with Next18 sockets.

If this is in fact your question, then Nick has given you the comprehensive answer. If I have it wrong, let us know how and we can revise the answer to suit.

PS. Yes, this can be seen as both a TT:120 and a DCC question. However, if I’ve got it correctly, it is more properly DCC than TT:120.

[Timothy-350163]

The locos are all fitted with the blanking plate for DC operation. They all perform perfectly with a straight DC controller.

When these locos are placed on a track controlled by the Digitrax Zephyr, that unit gets addressed as 00 and the loco should operate but instead the Zephyr sees it as a short circuit. If the blanking plug is pulled out the short goes away.

For a test, the Zephyr was connected to a piece of HO gauge track and I ran a Hornby Sentinel on it with no problem. again used the OO address.

My guess is this a Digitrax problem but they were contacted and I was told there was a problem with the Hornby socket. I don’t believe that but have no other recourse at the moment.

Thank you all for your input.

[96RAF]

With the blanking plug removed the loco becomes totally non-operational as you have removed the link between the wheel pickups and the motor.

Whilst it is possible to run a DC loco on a DCC powered track it is not advisable as the motor effectively sees the full 15v DCC as AC when static and this is not good for it.

At present your question is still a DC question until you get some decoders fitted, but given your problem I would not fit them until you have bottomed out on this. Time to get the multimeter out and do some basic fault finding checks.

My guess would be your Digitrax controller is seeing a short due to its trip sensitivity.

[ntpntpntp]

@Timothy wrote:

The locos are all fitted with the blanking plate for DC operation. They all perform perfectly with a straight DC controller.

When these locos are placed on a track controlled by the Digitrax Zephyr, that unit gets addressed as 00 and the loco should operate but instead the Zephyr sees it as a short circuit.

 

 

As RAF and I have both advised, DON'T use the "address 00" facility which is really bad for small motors. It doesn't produce a true DC output, rather it "bends" the DCC signal to give it a DC bias and you still have DCC power running through the motor even when stationary. Large scale motors can handle the heat build up better than the tiny motors used in small scales, but even then it's still a bad idea.

I think most recent DCC systems no longer include this option (I use NCE systems which stopped supporting it well over 20 years ago). Other brands eg. Bachmann specifically say in the instructions for their DCC systems NOT to use this analogue mode with N gauge locos (and I would consider TT:120 more akin to N than 00 in this respect).

If you want to run the loco on either power source then fit a decoder which will then work on both DC and DCC without risk of damage.

It does seem odd that the Zephyr actually trips out.

[Rallymatt]

Adding to Nick’s comments about Bachman, the Dynamis, which is really an ESU system rebadged, specifically warns NOT to use any locos without a DCC decoder or it will result in motor damage. Controllers that support address 0 were not designed to work with many of the modern motors. Hopefully the Zephyr cutting out has actually saved your motors from serious damage.