Model Railway Forum

This evening I fitted a Hornby TTS Sound Decoder to a Vitrains Class 37 that I had lying relatively unused in my BR Blue Fleet. After messing about for a while to find the best speaker for a sound v fit compromise, I was quite happy when the loco set off for a test run around my layout....... however a few seconds later the system had a short circuit and my immediately panic that I had wired something wrong and blown the decoder was calmed when I noticed that my Class 31 ( now also TTS fitted) had moved by itself and fouled points which were set against it.

Once the short was cleared, the class 37 set off again, only to encounter another short, this time due to my Class 20 ( also TTS fitted) fouling the points...... no other loco turned a wheel and thus It would appear to be TTS related.

I have had multiple TTS loco’s on the layout before and this has never happened, so something introduced with this new decoder....... any suggestions welcomed before I trouble shoot this some more in the coming days.

Thanks Richard

Hi Richard, I had the same issue a few weeks ago. I had already fitted ‘snubbers’ to each end of by bus which should have cancelled out any interference so I was at a loss as to why I was getting runaways.
In the end the problem disappeared once I had cleaned the track and the wheels of the loco I was running at the time.
It also pays to disable DC running on the decoder, or so I’m told, but I’ve not got round to actually doing it yet.
Does the the 31 sound as good (imho) as it looks?

Hi Steve,

Thanks for the feedback......I have doing a bit of research since my earlier post and have drawn two initial conclusions based on many reports of similar problems:-

A) I need to have DC disabled as you suggest - CV29 I believe.

B) the new decoder is as yet still set at the datum address of “0003”...... I have seen reports that because all Decoder come with this address, that despite being changed to new addresses, TTS decoder inparticular still seem to have a tendency to want to react to a “0003” code ....... I will re-address the new decoder and see what happens.

Yes - “Cerberus” sounds as great as it looks......I managed to fit an small iPhone speaker that is wedged behind the cab bulkhead and projecting all of its output up thru the rooftop fan grill....... one of my tasks during the holidays is to finally make a video of the layout in action, and for sure the Class 31 will have centre stage.

And did you notice that the fan is now ‘dirty’?

I forgot to answer the question - DC is disabled via CV29, you may find this calculator useful.

http://www.2mm.org.uk/articles/cv29%20calculator.htm

I have also seen the problem. Some took off, others just flashed lights or set sound running. I put it down to DC running enabled and also my flaky ‘bus’ wiring being inadequate. Layout since demolished so cannot replicate.

From memory at the time I was programming using Elite controller and can only think there was some cross talk on the wires.

I changed the address of my Class 37 this morning from the default “0003” to a loco specific address of “3731” and everything seemed to operate fine thereafter, with no movement from another TTS fitted loco

I decided however to go the extra mile and adjust the CV29 reading to remove DC enablement, and also overcame some slow running jerkiness by adjusting CV150 to 0, CV151 to 255 and CV152 to 1......The performance is now considerably better at slow speed.

Thanks for all the inputs which pointed me in the right direction.