DCC Decoder problem

[james_nelmes]

I picked up a Hornby GWR Railcar at a swap-meet yesterday, fitted with a compact 8 pin DCC chip of unknown make except the main chip says 'ATMEL Mega 168'? on it. When I accelerate very slowly, the motor stops after turning the controller anywhere between 1/3 - 1/2 way. Bringing it back to zero and starting again the motor turns. If I turn the control to full in one go, it accelerates up to full speed and runs fine. I'm using a Hornby Select.

Any ideas would be really appreciated.

Thanks

James

[Brew Man]

Is it just that loco that you have the problem with? If so try changing the decoder. I have two of those rail cars and both run absolutely fine.

[james_nelmes]

It’s just this decoder. I wondered if there is a CV needs changing. Next move is to change the decoder.

Thanks

James

[ColinB]

If you haven't already reset the decoder, sometimes that fixes issues.

[96RAF]

Try a reset of the decoder, which will set factory defaults of all CVs and put the address to 3. Write value 8 to CV8 as this works for most decoders. If it responds then to address 3 you know the reset worked.

If anyone has fiddled with the settings this should give you a baseline to start fresh diagnostics from.

[james_nelmes]

Thanks - I’ll give it a go.

[james_nelmes]

Tried that and no difference. I’m going to assume it’s a faulty decoder. It’s unbranded so I’m not thinking it’s a great decoder.

[Hipwell]

Have you got an analogue controller and a blanking plug to try it with? If it doesn't work properly on analogue then no point getting a new decoder

[Flashbang]

Whatever you do DO NOT CONNECT A DC supply to the rails with the Select still connected to the same rails. You run the high risk of blowing the Selects internal components! Ensure the Select's 'Track' connection wires are removed from the Select or the rails.

With the Selects 'Track' pair of wires disconnected from the rails and all other DCC accessories also disconnected, you can then test with a 12 volt DC controller or if you don't own one use a new PP3 9 Volt battery directly across the rails. Of course the battery will only provide full power, but they are good for testing. Swap the battery around on the rails to make the loco move in the opposite direction. Most DCC loco decoders are set to work on DC (Except TTS) or unless the previous owner has turned Off DC operation. But removing the decoder and fitting the DC blanking plate is the ideal testing option when on DC. grinning

[96RAF]

Just to explain why decoder equipped locos don’t work very well on DC.

DC is variable from 0-12v depending upon the controller speed knob position.

A DCC decoder requires a certain voltage to boot up, then it has to decide (if such instruction has been programmed in) that it is on DC and not DCC and that it should switch over to DC control. Put the controller to zero (the decoder drops out) and back up again and the boot process repeats.

Summary - DC is OK if you want to set a fair fixed voltage to run in a DCC loco but not OK if you hope to run a DCC equipped loco on variable potential DC under any sort of reliable control.

[james_nelmes]

I tried the decoder in a HobbyTrax decoder tester and the behaviour was replicated. I am confident the model is working well with some limited DC testing

[Brew Man]

Sounds like a new decoder is required then.

[BADWOLF525]

now i have my elink working i am on the next set of problems lol hear go's the pic shows the loco am trying to add to RM i have installed the 77150 decoder into it dubel checking the pins are the right way and think i have set it up right its on a program track but there is no life to it do i have it set correcley in the pic?? or do i need to edit the pannel on the left that has notting init thanks in advance

[96RAF]

The programming track is a low potential and is only powered during the actual programming burst. There is not enough power to run a loco, so once you have clicked the green tick in the RH frame it now has to go on the main track and should respond to address 3.

As the 4-pin decoder does not support either sound or function outputs the right hand frame should all be not used.

In the centre frame you do not need a detection ID as Hornby has not yet released loco detection.

The LH frame will only populate when the loco is on the Programming track and you click that green tick. It will then attempt to read all the decoder CVs it can but may report read errors which you just click through.

[BADWOLF525]

am glad to say that the first dcc train is now up and runing

[96RAF]

What you need to do now is bring up that LH frame again with the loco on the programming track and enter a new address (say 10) in CV1. If you then press the pencil icon (bottom left corner) RM will write that address to the decoder, then you free up the default address 3 ready for your next loco.

[P-Henny]

If you do edit the value of CV1 to change the address, you will also need to edit the middle frame to change the 003 in the Loco ID pull down box to the new decoder address as well.

As an alternative to directly editing the value of CV1 in the left frame, you can achieve the same task by clicking the 'steam loco icon' at the bottom of the middle frame. Using the 'steam loco icon' will also give you the opportunity to configure a long address [an address higher than 127], whereas directly editing CV1 limits you to using addresses between 001 and 127. Using the 'steam loco icon' to change the address, still requires you to edit the 'Locomotive DCC ID' pull down box from 003 to the new address to match. As this is not done automatically by railmaster.

[BADWOLF525]

thanks al bear that in mind but there is only going to be 2 locos on the track for now the second one i have to buy yet and the decoder this part is where it gets tricky am not

good with nubers lol

CV 1 = primary address 1 = loco 0003

so the reprogram would look like this

CV1 = primary address 1 = loco 0001 yes?

the loco icon is not on as you can see in the pic dose this only come on when you programing the loco?

[Fishmanoz]

Only if you want to change the address to 1. To change it to 10, then 0010.

It is good practice to test new locos on 03 then change while still on the programming track to something else. That way 03 is always clear for any new loco whenever it turns up.

[96RAF]

You may only have two loops and think you can only have two locos but the beauty of DCC is you can run multiple locos on the same track - in different directions if you want to. My guess is you will end up with more locos, so you should plan ahead with your addresses.

[BADWOLF525]

yeah sounds good to me thanks. i can't run loco's in different directions becuse there is only one track looped unless i work out how to do that. its in the living room see pic, yes i know you can run more then one loco thats why i went with dcc. most of the turnings are 1st radius so i can only run loco's that run on that

Am having to redo two of the bottom RH turnings because the coach’s wont go around them