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Discussion Starter · #1 ·
I'm trying to fit a Hornby decoder into an old Hornby OO DMU.

The DMU is not DCC ready so I'm hard wiring it.
I know that the red and black wires go to the pickups and the orange and grey wires go to the motor brushes.

The DCC documentation describes connecting the the wires to the correct "+" and "-" terminals. But I see that the DCC decoders conatin a rectifier . I assume this is true for the Hornby decoder as well. So my question is does it matter how the wires are connected? As long as the red/black go to the tracks and the ornage/grey go to the motor?

My question is prompted because the DMU, with it's DCC chip is very jerky and stalls a lot. Whereas other DCC locos are very smooth.
 

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Swapping the red and black or orange and grey wires is not a cause of poor running (if it is poor on DC it will probably also be poor on DCC). The main reason to get them right is so that when selecting 'forwards' on the DCC handset the loco actually moves forwards. However if this comes out wrong it can also be corrected by changing the decoder configuration. It is also important if you still run the loco on DC, so that it runs in the same direction as other DC locos, and if you need to use certain advanced DCC features such as the Lenz ABC system.
 

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QUOTE (fabben @ 19 Dec 2007, 18:23) <{POST_SNAPBACK}>I'm trying to fit a Hornby decoder into an old Hornby OO DMU.

The DMU is not DCC ready so I'm hard wiring it.
I know that the red and black wires go to the pickups and the orange and grey wires go to the motor brushes.

The DCC documentation describes connecting the the wires to the correct "+" and "-" terminals. But I see that the DCC decoders conatin a rectifier . I assume this is true for the Hornby decoder as well. So my question is does it matter how the wires are connected? As long as the red/black go to the tracks and the ornage/grey go to the motor?

My question is prompted because the DMU, with it's DCC chip is very jerky and stalls a lot. Whereas other DCC locos are very smooth.

***The jerkiness is either mechanism or chip. The Hornby decoder is not the most sophisticated and another chip may so a better job. The stalling is most likely intermittend power collection - dirty track or pickups needing adjustment/improvement or wheels needing cleaning.

The conventions for wiring are:

red to right rail (right as per the "drivers view)
Black to left rail
Orange to top brush
Gray to bottom brush

However.... top and bottom bruch is a bit subjective as some loco's have left and right :). So... connect as you think and reverse orange and gray if the loco runs backwards compared to your other loco's.

Regards

Richard
DCCconcepts
 

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Discussion Starter · #4 ·
I can't remember how it ran in dc mode so I might take out the decoder and run it on a bit of track under dc and see what happens.

Then I'll put the different decoder back in and see if that helps.

thanks guys,
 

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Discussion Starter · #5 ·
Took of the decoder and ran the DMU from a DC controller. It had running problems. When you touch it it shoots into life, then stops.

I fund that the wires from the pick ups to the motor brushes are connected via those "crimp terminals" which hold the wire and push onto a connector and one of these was loose. the wire could be turned, easily within the connector. So I removed it, cleaned it, then soldered the wire back in.

Now it works much better but it's still not perfect, I notice the pickups are only over one power boggie. I think what I need is to do some major engineering work on the non-powered car, pickup over all wheels and pass this back to the powered car. This is for another day though.

Fabben
 

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QUOTE (Richard Johnson @ 19 Dec 2007, 12:34) <{POST_SNAPBACK}>The conventions for wiring are:

red to right rail (right as per the "drivers view)
Black to left rail
Orange to top brush
Gray to bottom brush

However.... top and bottom bruch is a bit subjective as some loco's have left and right :). So... connect as you think and reverse orange and gray if the loco runs backwards compared to your other loco's.

Regards

Richard
DCCconcepts

A handy reminder is to think
Red - Right
bLack - Left

For the motor, the convention is
Orange to brush that was connected to right rail (thing oRange - Red)
Gray to brush that was connected to left rail

Andrew
 

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A handy reminder is to think
Red - Right
bLack - Left

I'd like to point out that with a DMU it doesn't really matter as you can't tell which way round it is because of it being symmetrical, but with other locos it is more important, however I haven't wired some of mine correctly and really should rewire them, but have never found it a complete frustration!
 

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Normally, as far as D & E goes no.1 end is "forwards".

The other thing to consider when using decoders that plug in is that the lights (if fitted) will not work if the decoder plug is the wrong way round, although the model will run, albeit, the "wrong" way.
 
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