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DCC Decoder shows short circuit


Neal Ball

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Hi there. Any suggestions would be appreciated.

 

I have just bought a brand new loco, which runs fine on DC in both directions.

 

At the same time, I bought a Howes Sound Decoder and put it into the tender of the loco. (Hornby GWR Caerphilly Castle). When turning the power back on, it makes a sound like a short circuit (although does not cut off my circuit breakers which sounds odd)

 

I have checked the obvious connections and can not see that solder is touching the next pin etc.

 

I then took the new decoder and tried it in a different loco and it works fine....

 

Any suggestions?

 

Thanks, Neal.

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Your evidence points to a wiring fault in the Hornby Castle loco.   It requires testing.  Most likely from your evidence is that a pickup and motor pin are connected, with this the loco would be fine on DC, but would be short-circuiting the decoder on DCC.   I've seen such faults on several locos from different makers. 

 

 

The standard advice is that a fresh installation is tested by putting the loco on a Programming Track and trying some Programming instructions.   With those, the current to the decoder is limited to a very short burst of power at low current, so will show a faulty installation, but won't damage the decoder.   Testing on the main line should only happen after passing tests on the Programming Track. 

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Thanks for that Nigel.

 

Having stripped the tender down...

1. Decoder socket was poorly soldered, with a short over red & black. Having re-soldered, makes no difference.

2. Check wiring through the tender and it seems ok.

3. Checked the connection from tender to loco

3. Swapped this tender for another Hornby one - inconclusive

 

Overall, it would seem the fault lies in the loco, which I am not prepared to strip down for fear of not being able to rebuild it. ( the rear sand pipes have already broken.

 

I think the tender wiring leaves a lot to be desired, a definite Friday afternoon job in the Chinese factory, with poor quality soldering.

 

I will call Howes tomorrow to arrange a return....

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  • 4 weeks later...
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The loco has now returned from Hornby and is running very well.

 

The next issue was how much of the tender needed to be taken out to fit the sound decoder and speaker! - Small price to pay

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