Hornby Class 40 Railroad version

[garrytheskate]

Brand new loco - Runs perfectly on dc
Fitted decoder - Runs intermittently from very slow to immediately very fast. Sometimes runs well in one direction.
Checked decoder in another loco - works fine
Any ideas as to whats wrong?
Garry

[2e0dtoeric]

It might seem obvious - but check you have the chip plugged in the right way round - orange wire to pin one! (marked by an arrow, a dot of paint, or with the loco facing with the socket to your left, the chip plug wires point to you).

[garrytheskate]

Definitely in the right way. In fact it shouldn't matter using a decoder for just power, just means it goes the other way

[ace10086]

I would check for and remove any capacitors on the motor. Other than that, and assuming there is nothing wrong with the loco, I could really only suggest using a more advanced (and expensive) decoder, one that allows adjustment of motor control (which

unfortunately rules out the Hornby decoders). You would also need a controller capable of adjusting CV values (e.g. an Elite rather than a Select)

[Rog RJ]

What decoder are you using?

[garrytheskate]

R8249 Also bearing in mind that it ran perfectly on DC but intermittently on DCC if I hold off the driving wheels from the track it works perfectly on DCC.
Dont make sense does it!!

What decoder are you using?[/reply]

[ace10086]

garrytheskate said:

R8249 Also bearing in mind that it ran perfectly on DC but intermittently on DCC if I hold off the driving wheels from the track it works perfectly on DCC.
Dont make sense does it!!

What decoder are you using?

[/reply]

It

makes sense in that it seems to be related to Back EMF, where the decoder is trying to compensate for load but either the default settings don't match the type of motor being used or the BEMF signal is being distorted by interference capacitors across the

motor.

Most of my locos have Hornby decoders however when I require good motor control I use Lenz decoders or ESU for sound.

One thing you could try is disabling DC support, setting the decoder to DCC only.

[garrytheskate]

Thanks for that How do I disable the DC support
Regards

[Flashbang]

Hi
Before you start tweaking CV settings, I would have a good close look at the wheels and the wheel pick-up wipers. The wipers need to remain in continual contact with the rear of the wheel when the wheel moves across the loco side to side. If the

wheel treads and the insides of the wheels and their wiper faces are dirty, then clean them. Best to use is ideally a fibre brush and follow up with some IPA (Isopropyl Alcohol) applied via a lint free cloth or a cotton bud, but ensure no cotton fibres are

left by the cotton buds use.

I doubt is disabling dc operating will overcome the problem! Normally dc enabled can cause run aways on DCC rather than poor running. But if you wish to do it then its via CV29. Read what the current CV 29 value is and deduct

4 from whatever value is read and enter that revised value.
This sitres CV29 calculator is a hand tool to keep in the Favourites/Bookmarks area. http://www.2mm.org.uk/articles/cv29%20calculator.htm
Of course CV adjustments cannot be done if your a Hornby

Select user.

[Flashbang]

To correct and to add..
The above next to last paragraph should read.. This web sites CV29 calculator is a handy tool to keep in the Favourites/Bookmarks area. etc....

If you can adjust CVs, I would also consider setting CV10 to a very low value.

A value of 1 or 2 etc. This is the Bemf setting CV and a low number all but turns off the Bemf. Its normally set to maximum value of 128. See how the loco runs at a very low value, then increase the value by unit values of say 20, and see how it runs after

each adjustment setting, until your happy.

[garrytheskate]

I must apologise bacause the decoder is in fact a Bachmann 36-553 which if I read the write-ups correctly is not suitable for hornby locos!!! Have replaced it with a Hornby decoder and hey presto works a treat.
Again my apologies
Regards
Garry