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Loco Works on Layout but Unreadable through SPROG


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Not a massive problem, but one I would prefer to solve if I can.


I have a Hornby HST (new shape Swallow) with Legomannbiffo sounds on board.


It works on the layout fine but when coming to read it through the SPROG, it reports there's no loco detectable.


The SPROG reads everything else fine, including a Class 68 with Legomanbiffo sounds, which makes me think it's just this loco.  I'd rather not open it as the speaker I've used is squeezed in the back.  I thought originally perhaps I'd snapped a wire off the decoder but when I tested it on the track again, it's fine.


The only thing I can think of is whether the chips are linked somehow (bearing in mind they are with the sound as one power car starts after the other by design)?

I only put the motor car on the SPROG track as it's only the motor information I'd like to store really.


Any pointers I can look into?


FYI: Tried cleaning the track, and tested other locos which are all fine.

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Do you have two decoders here, or just one ?  

There is no method for reading two decoders simultaneously, other than getting some hybrid garbage back.  (It might work, but its pure luck!). 


Does the decoder (one at a time, singular) have a motor connected to it ?

Without an adequate load on the motor or lighting outputs, you won't read any decoder.  The load is necessary to generate the response pulse back to the programming device.   For temporary use, you can substitute a resistor for a motor, but don't leave it there for running as it can overheat and melt the model. 



- Nigel

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I have one of Biff's chips in my HST. It is boxed up right now but I am sure I could read CVs with my PowerPro. I'll dig it out later & give it a try.

There is a warning on DC Kits' website that there is an issue with the PCB of Hornby's HST, which is why they recommend either keeping the 125 address or placing it in a different loco or on a decoder tester in order to change it.

I wonder if this is causing your issue?


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Yeah, just the motor loco and one chip.

The address is set to 125, which is the same as when I bought it (not from a shop though).


This INTERCITY loco (with the problem) will read back using my Prodigy Advance 2... just to throw another mystery into the mix.  I'm sure I was able to read back anyway.  I'll do some testing later.


My other HST (MML livery) is set to 1252 and reads fine.  However this doesn't have sound.

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Note that '125' is in the best-avoided-range if you are ever likely to run your loco on layouts using differing makes of controller..

eg Lenz and Roco [until recently??] 1-99 = short 100+ = long,   ZTC (also expressnet) 1-127 short, 128+ long  

Some others: 125 = short, 0125=long

What make of controller programmed it to 125 ?  What make are you using - do they treat 100-127 the same way ??


The best thing to do is simply reset the decoder, and program again - even if to the 125 value ... it will then be the way that is recognised by your controller.

Edited by Phil S
tryping erers
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If you don't now that the default setting for the Legoman biffo sound project are firmly set as default values ( best to ask or download the instruction sheet if available ) - then simply write the new address  and new value to CV29  - depending on whether you are creating a short or long address ..... simplest method is to write CV1 as 3, and CV29 as 6 (not 38)  ... this also allows running on analogue dc with a battery to test it - which should work whatever the loco number is (as long as dc has not been disabled)

If you want, as some do, disable dc analogue running - then change CV29 again after testing it okay with the  battery.


Reminder: You do not need to know the existing loco number to reprogram it, and the process if faster without 'readback' [ the motor pulse is still produced on programming]  - and CV29 needs to be written for a short or long address as appropriate.    When buying locos second hand at shows - take a 9V battery with you (with a cap over the terminals if just left in your pocket to avoid a cshort circuit !!! )  Running on dc analogue (with battery or smooth dc controller does not worry about loco number)

Not using the 'reset' option 'runs the risk' that another value such as 'consisting' or bad back-emf-value remains from previous use- that's all.


'Testing' with pre-historic H&M controllers and the like which only rectified, but did not smooth the dc output, should be avoided because the 100Hz full-wave rectified sinewave  produced will cause the decoder to reset 100x a second, and also be fed with upto 28V peak (off load, measured values from an H&M DC 60)

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  • 4 weeks later...

Just to bring this to a conclusion...


After looking inside the loco, I found the orange wire was broken.

So I soldered an extension, popped it back on the track and it worked fine.


Put it on the SPROG track and now it reads fine too!


Don't understand how it could have worked before if the orange wire was broken, unless it broke somewhere between the layout to the SPROG track, although I'm sure I tested it after the SPROG track anyway!


But all working fine is what I'm trying to say.

Edited by Sir TophamHatt
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