Chrissaf Posted October 10, 2020 Share Posted October 10, 2020 Has anyone powered a Wrenn locomotive with a hornby sound decoder? Do they have the current requirement for the heavier older die cast metal engine? (The heavier loco and motors may well be outside the sound decoder specifications) Just wondered as someone may have. Link to comment Share on other sites More sharing options...
Chrissaf Posted October 10, 2020 Share Posted October 10, 2020 Hornby sound decoders, assuming you mean TTS, are only motor rated at 500 mA Link to comment Share on other sites More sharing options...
ColinB Posted October 10, 2020 Share Posted October 10, 2020 I looked at this a while ago, if you don't know you need to isolate the brush holder that has no isulation, which involves making the brush mounting hole bigger and inserting a sleeve. When I looked, Shapeways did a suitable insulator, which requires fitting. As for decoder you probably need nearer to a 2 amp decoder, Zimo do one, which is about £35.00. When I was talking to YouChoos I think they had converted a Wrenn. I know one of my converted Ringfields has the 2 amp version as I was unsure what the maximum current was, so I fitted the one with the biggest current. In the end I didn't want to devalue my Wrenns by messing with them so I gave up on the idea of conversion.As for sound, you need to look at the more expensive suppliers, again Zimo, I don't know about the others, people use them for O gauge so they must exist.Forget TTS for this, as Chrissaf says they are only any good for 500 mA. Link to comment Share on other sites More sharing options...
37lover Posted October 10, 2020 Share Posted October 10, 2020 Given the respective low cost of a TTS would it be possible to fit two decoders; a heavy duty to drive the motor and a TTS just for the sound. Would you need to have some arrangement to fool the TTS re motor load, etc? Link to comment Share on other sites More sharing options...
Chrissaf Posted October 10, 2020 Share Posted October 10, 2020 The issue with that, is that sound decoders generally monitor the load on the actual driving motor to invoke different engine running sounds. Chuff rates for example, or notching and coasting on a Diesel. A dummy motor load is unlikely to be feeding back the appropriate conditions to invoke those special sound sequences. Link to comment Share on other sites More sharing options...
ColinB Posted October 10, 2020 Share Posted October 10, 2020 Sorry, that will not work. The issue is the current to the motor is limited to 500 mA, then generally the device burns out. The Wrenn motor at a rough estimate takes at least 600 mA which has to be sourced by the decoder, so unless you can split the feed to motor from two TTS, which you cannot it is never going to work. The TTS is marginal at the best of times, I don't even fit them to my ringfield motored Limas or Hornbys as I am concerned about the current drain.although the specification says 500 mA that is a bit on the optomistic side, assuming decent cooling, which is why you will see posts on this site where they have blown up on a hot day. Anyway if we look at it from a logical point of view two TTS will cost about £80, a decent sound decoder that does exactly what you want will cost you a £100. I know it is £20 difference, but you are getting a decoder that meet your requirements exactly. Link to comment Share on other sites More sharing options...
37lover Posted October 10, 2020 Share Posted October 10, 2020 Colin,I wasn't suggesting two TTS; I was thinking of the Zimo @ £35 plus TTS @ £40+ with the Zimo driving the motor, no load sharing. Chrisaff confirmed why it wouldn't work Link to comment Share on other sites More sharing options...
ColinB Posted October 10, 2020 Share Posted October 10, 2020 Sorry 37lover, I didn't realise that is what you were thinking of doing. It is not such a bad idea, the back emf is the issue, I don't know if you fed the motor feed from Zimo to the TTS via two 1 kilo ohm resistors whether it might work. Trouble is, all the voltage references would be wrong and the TTS is not the most robust piece of electronics, so you could end up blowing both of them up. I would still go with the proper decoder, I know it is expensive. I know the problem, I have a TTS on my Duchess of Gloucester that keeps losing sound, I have checked literally everything and have come to the conclusion there is some weird reaction between TTS and motor, it even does it on my spare TTS decoders I tried. I think I know what it is, but it is something I cannot fix. Anyway, I am rapidly coming to the conclusion I will replace it with a Zimo, I am just fed up with it, but again it takes a lot to justify the extra £70. Link to comment Share on other sites More sharing options...
Howbi Posted October 10, 2020 Share Posted October 10, 2020 I use the Soundtraxx Econami sound decoders rated at 1 Amp, cost £75 plus a speaker.......slightly larger than the TTS but with enhanced features such as an adjustable chuff rate, 6 functions, function mapping........HB Link to comment Share on other sites More sharing options...
ColinB Posted October 10, 2020 Share Posted October 10, 2020 Thanks howbinman, I didn't even know they existed. Link to comment Share on other sites More sharing options...
fac Posted October 24, 2020 Share Posted October 24, 2020 Thank you all for contributions, most helpful will be looking into the soundtrax range. Link to comment Share on other sites More sharing options...
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