A Peculiar DCC Problem

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Bluegoldfish
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A Peculiar DCC Problem

Postby Bluegoldfish » Tue May 11, 2010 10:22 am

I have a peculiar problem with a new "DCC ready" loco (a Hornby Clan).

The engine runs normally under DC but when I fit a DCC chip (ESU LokSound) it sets off at full speed on speed step 1 but stops dead a couple of speed steps further on.

If I fit the new DCC chip in another loco it works normally and if I connect a known working chip to the new loco it exhibits the the same faulty performance described above.

Does anyone know of any particular fault that could cause this problem to occur (short to the chassis?) or should I just pack it up and send it back to Hornby?

Thanks in advance.

Chris

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sishades
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Re: A Peculiar DCC Problem

Postby sishades » Tue May 11, 2010 12:02 pm

It could be dirty pickups. DCC is fussy about cleanliness. Also check your track. One speck of glue can cause chaos.
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Roger (RJ)
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Re: A Peculiar DCC Problem

Postby Roger (RJ) » Tue May 11, 2010 12:09 pm

Could be capacitors on the motor ?

Does it do it with a Hornby decoder?

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Flashbang
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Re: A Peculiar DCC Problem

Postby Flashbang » Tue May 11, 2010 4:12 pm

Hi
Same question is being asked here too!....Link to web site
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Broken? It was working correctly when I left it.

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Bluegoldfish
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Re: A Peculiar DCC Problem

Postby Bluegoldfish » Tue May 11, 2010 5:15 pm

It is true. I posted the question here and in the ModelRailways.co.uk forum. I hope this didn't cause a problem or offend anyone :( . That was not the intention. I only wanted to get a quick answer.

Chris

Dad-1
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Re: A Peculiar DCC Problem

Postby Dad-1 » Tue May 11, 2010 5:35 pm

Hi Bluegoldfish,

I would suggest you own substitution test proves there's nothing wrong with the chip. So if two decoders that work well in other locomotives won't run in this one it must be the locomotive. Possibly a loose wire somewhere, but sending to Hornby can be iffy although what other option have you ??

Geoff T.
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viewtopic.php?f=22&t=32187 and Another on viewtopic.php?f=22&t=28436&start=60&st=0&sk=t&sd=a

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hobby boy
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Re: A Peculiar DCC Problem

Postby hobby boy » Tue May 11, 2010 5:38 pm

could it be a faulty decoder?

Andrew
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Flashbang
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Re: A Peculiar DCC Problem

Postby Flashbang » Tue May 11, 2010 6:45 pm

Not a problem Bluegoldfish :D :D
But you do end up with twice as many similar/same answers and often from the same people!

Hobby Boy
The decoder has been fitted into another loco and works correctly.
So IMO it unlikely to be faulty.
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Broken? It was working correctly when I left it.

Bigmet
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Re: A Peculiar DCC Problem

Postby Bigmet » Wed May 12, 2010 10:21 am

Return the loco to the retailer for exchange, it must still be in guarantee, and your testing has demonstrated it is unfit for purpose: it is sold as DCC ready, but fails to perform correctly when proven good decoders are installed.

What is most likely wrong with it? Most likely guess, one of the pick ups has a direct connection to a motor terminal, probably a wiring fault or damage, (pair of wires crushed together, blobby solder joint, are possibilities). So when the decoder is set to speed step 1, there is a circuit made through the decoder's rectifier, and the motor gets a half cycle of full track voltage, which will make it go pretty fast. The decoder's protection cuts in as it detects the heating from a large current, the loco stops quickly. Whatever the fault is, since it doesn't affect DC operation, the direct connection from pick up to motor terminal must be the right one. Going out on a limb here, the most likely place for this to happen is in the four pin plug or socket that connect the loco and tender electrically. Wherever the problem proves to be, this particular fault will not be detected in a test at the factory...

You can check for yourself if it is a direct connection between one of the pick up sides and one of the motor terminals by taking the loco body off, and with the loco and tender connected, and the decoder socket blanking plug removed, testing whether there is a connection between one of the pick ups and one of the motor terminals: with the blanking plug removed there should be no connection if the loco wiring is OK. Don't try any more decoders in it BTW, you may get unlucky and blow one if my guess at the problem is correct.


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