any idea with this please

[bulleidboy]

Hi dtb - the TCS DP2X-UK decoder will fit into the Hornby M7 without having to remove anything. This is a direct fit decoder with no plug or harness.

The picture shows the TCS DP2X-UK fitted to a Hornby H Class. BB

IMG_0620 by Barry Clayton, on Flickr

[Brian]

No decoder fitted will result in an error message of some sorts.

If the rail volts remained constant the loco is defective and needs to be returned for repair or replacement!

[dtb]

It almost sounds as if it has a DCC decoder onboard already...

Strange!

Spot on MG reading 55 on the prog track and a very smooth runner as well.
It wasn't listed as DCC fitted on the retailers site so the money I paid makes it an absolute bargain.

Thanks for all the input, I've certainly learned a bit more from you all.

BB, I'll grab one of those decoders as I have a H Class on my 'want' list. Cheers

[Mountain Goat]

It almost sounds as if it has a DCC decoder onboard already...

Strange!

Spot on MG reading 55 on the prog track and a very smooth runner as well.
It wasn't listed as DCC fitted on the retailers site so the money I paid makes it an absolute bargain.

Thanks for all the input, I've certainly learned a bit more from you all.

It was the bit you said about the direction that made me think that the loco can only act like that if it has a decoder. Ordinary DC can't really give the same symptoms in the way you described it, and yet it is a well known character of DCC at times when it may be assuming that there is a DCC signal present from your DC controller and start doing unusual things.. I am wondering if the Gaugemaster controllers may have something that makes it think it is picking up a DCC signal? It is well known for feedback controllers to do this as feedback controllers work differently to ordinary DC controllers which supply anything between 0 volts and 12 volts as a constant voltage of whatever speed one wants the loco to go (E.g. just for a theoretical idea 6 volt would be half speed in the 0 to 12v DC range. In reality it is more like 8 or 9 volts is half speed as it takes a few volts before the wheels start to move).
Feedback controllers send pulses of 12v DC where the faster one wants the loco to more the more pulses within a certain time it sends (Frequency?) This makes locos more responsive at slow speeds and helps them climb hills etc, but it does make motors buzz. (If you have ever ran a loco or a 12v motor directly from batteries one will realize the difference as it will run quietly as the supply is pure with no pulses or anything like that. Excuse me in trying to explain with my limited knowledge).
Now DCC decoders are looking for DCC signals so if they sense a waveform or pulses etc they will assume they are being told an instruction and act according to what they think the instruction is and keep responding to the next percieved instruction etc. Hence why the decoder in your loco was missreading some sort of pulse or waveform on your DC controller and thinking it is a DCC signal.... So at each time it updates it assumes it has been told to run the other direction...