TTS Decoder Smoking

[Cwagler8]

Hello folks, 

I wonder if you could offer me some solutions here. I bought a 2000s Duchess from Hattons and have been trying to wire in a TTS Decoder. I've smoked out two decoders so far. Any ideas what I'm going wrong? I basically just put the decoder straight onto the positive and negative from the pickups. Do I need what I think is the resistor somewhere? Let me know if you have any helpful wiring diagrams for manually installing a TTS decoder.

Also, I'm wanting to install a keep-alive capacitor. What in the decoder would I wire this to?

Thanks in advance for your help! 

Caleb 

[Chrissaf]

I basically just put the decoder straight onto the positive and negative from the pickups.

 

You don't wire the decoder over the top of the pickup wiring, which your phrase infers you are doing. You disconnect the wires from the pickups. The red and black decoder wires then wire to the pickups replacing the factory pickup wires. The orange and grey decoder wires go to the motor.

 

If you wire the decoder to the pickups without disconnecting the existing wires [which your question text infers you are doing], you are creating a short circuit between the DCC track power and the motor output of the decoder which will instantly fry the decoder [which sounds like what you have done].

 

Do I need what I think is the resistor somewhere?

 

No ... no further components are needed when installing a decoder .... especially not a resistor.

 

Let me know if you have any helpful wiring diagrams for manually installing a TTS decoder.

 

The schematic below is for a Diesel with LED lights. For a 'Steam Loco' just ignore the LED wiring part of the schematic on the white, yellow, green and blue wires. Pre-wired 8 pin sockets can be purchased on eBay to make installation easier.

 

/media/tinymce_upload/56baa7cc32314eadb2bf7143df590f66.jpg

 

Also, I'm wanting to install a keep-alive capacitor. What in the decoder would I wire this to?

 

Common question that has been asked before. Click the link below for a previous answer.

https://www.hornby.com/uk-en/forum/stay-alive-install-for-tts-decoder/?p=1

 

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[ColinB]

The best way to do any DCC conversion is to wire in a socket, it makes life so much easier. I am pretty sure there is room inside a Duchess to do this, if not do what Hornby now do with their newer models, mount it in the tender. Once you have wired in the socket you can check none of the motor or function wires are connected to the pickups, that is what normally smokes the decoder. Then put a DC header in the socket to check it still runs on DC, then when you are happy fit the decoder into the socket. I do this with all my conversions, it is so easy to short the motor to pickup without realising, even Hornby have been know to do this on some models. Using the socket makes it so much easier to check.

[Cwagler8]

Thank you for your assistance! Contrary to what I implied, I didn't wire the decoder on top of the pickup wires (not on purpose anyway). I did wire the pickups to the red/black, then the gray/orange to the motor. Perhaps my leaving the resistor in the circuit did it in. Also I'm sure it'd be easier to install a socket. I've found a supplier for a Bachman 8-pin, would this work? 

Thank you! 

Caleb 

[jane1707819582]

Is your duchess tender driven ? . If so you must ensure the motor is electrically isolated from the chassis.

The resistor you refer to is probably a rf interference capacitor .the socket you refer to should be OK .

With the number of pick up points on a large pacific a stay alive cap could be unnecessary.

[96RAF]

If your Duchess is the loco driven one shown in Service Sheet 223 then that is the most standard and simple DCC conversion going.

Compare with service sheet 336 which is the DCC Ready version. You can dump all that capacitor gubbins, although it is shown on the DCC Ready version it is not needed and only fitted by the manufacturer to cater for the DC running scenario. A decoder has its own RF suppression.

In essence you remove the wires from the motor brushes and these go to the decoder red and black. The decoder orange and grey connect onto the motor brushes.

If your Duchess is indeed a tender driven loco with a ringfield motor then it needs special treament as Jane says to isolate the brushed from the wheels and is not such a straightforward conversion, but it is not difficult.

[Going Spare]

For clarity, service sheet 223 covers a tender driven Duchess.  For some strange reason, Hornby kept the same service sheet number across the change and sheets 223C onwards do cover the loco drive models.

[Chrissaf]

If you have a Ringfield.

 

Ringfield motors, as others have said, need special electrical isolation. Click the link below and scroll down to the Ringfield section and then use it to identify what Ringfield type you have and what needs to be done to isolate it.

 

Not isolating the Ringfield correctly is definitely one cause of blowing decoders.

 

https://www.brian-lambert.co.uk/DCC-Page-1.html#decoderinstalation

 

There are no resistors, only inductors and capacitors. An inductor may look like a resistor.

 

I've found a supplier for a Bachman 8-pin, would this work?

 

Select one from this link instead, assuming you mean sockets and not decoders.

 

[ColinB]

Yes an 8 pin Bachmann socket will work, I think that they are better made than the Hornby ones anyway. I am assuming it is not a ringfield motor. Anyway once you have the socket wired in, check between pins, they should be open circuit except between pins 1 and 5, which should measure motor impedance/resistance. Check pins 4 and 8 are not connected to any other pins. Where did you get the Bachmann 8 pin, I am always on the lookout for decent 8 pin sockets.

[Cwagler8]

I do not have a ringfield, mine is loco driven. So I gather I shouldn't have issues. Also, I don't recall where in my wiring I left the capacitor, but I also gather that could've done in the chip. I plan to buy a Bachmann 8 pin socket and blanking plug (ColinB I'm in Canada so I imagine my supplier isn't near you) to get the loco up and running with its socket and will likely wire it into the tender. Once I'm satisfied I'll buy my new TTS decoder. Sound like a good course of action?

[Howbi]

@Cwagler8...........this is the capacitor and wire clamp that need removing prior to wiring in the 8 pin socket......HB

/media/tinymce_upload/6a53a2b8058180dfc8c3641879a6c3e3.jpg

[96RAF]

In the slot car world they call the capacitor gubbins - Ferrite Man

https://images.app.goo.gl/z7knpy6w3vskX8oW7

 

Oddly they leave him in on digital cars, presumably because the cars spark more than locos.

[Cwagler8]

Excellent howbiman! I will be sure to remove that. Since there's nothing I really need other than wire, am I able to just solder my connection right onto the motor poles after removing the old ones?Also my using a Digitrax controller wouldn't have smoked it out, right? It would have been the capacitor and wire clamp?

[jane1707819582]

If the capacitor is a short cct then yes otherwise no. Your controller should not blow a decoder .you need to ensure the chassis of your loco is isolated from the motor connections when you have verified this then connect the power.

[rpjallan]

The best way to do any DCC conversion is to wire in a socket, it makes life so much easier.

I disagree with this. I think that adding a socket to a loco that doesn't already have one is just over-complicating matters. In fact, I am sometimes inclined to remove sockets from locos. I have had a number that had a built in short ciruit.