# DCC Conversion Question



## ccutrer (Nov 11, 2012)

I want to convert a Percy (from Thomas & Friends) engine to DCC, but when I opened it up it already has some resistors in there:









Red and black are the power pickups and orange and brown go to the motor and "moving" eyes. I couldn't get that portion of the loco apart, so I think I'll be fine with not separating moving eyes as a function (yet).

So do I insert the decoder between the trucks and the existing resistors (cutting the black and red wires), between the resistors and the motor (cutting brown and orange), or bypass the resistors completely? If the first option and I later decide to separate the moving eyes out as a separate function, do I need to duplicate the resistors for the function output of the decoder?

The backside of the board with the resistors, for reference:









Are the things at C3 and C4 anything? I can't tell that they're actually connected to anything.


----------



## rrgrassi (May 3, 2012)

I have never taken a "Thomas" type apart. Are the moving eyes electrically controlled or mechanically controlled?


----------



## ccutrer (Nov 11, 2012)

Hmm, good question. I couldn't get the boiler to snap apart easily, and figured I had enough info for my purposes so didn't press the issue. Next time I have him apart I'll try harder and let you know.


----------



## NIMT (Jan 6, 2011)

The eyes are mechanical.
You need to remove that board and replace it with a decoder.
Here is a decoder that fits in the same small space.
http://www.northidahomodeltrains.com/Pages/USA_CDNSN_852001_MC1H102P8.aspx


----------



## ccutrer (Nov 11, 2012)

Thanks. So what do the resistors do when there's not a decoder in there (I'm definitely *not* an Electrical Engineer) - prevent too much current from reaching the motor or something?

And yeah, I'm aware it's a very small space. I'm already looking at the Digitrax DZ123 for another HO locomotive with limited space to put a "normal" HO decoder.


----------



## NIMT (Jan 6, 2011)

Yes they limit amperage and on the back side this has capacitors that eliminate sparking of the motor and wheels too.


----------



## NIMT (Jan 6, 2011)

Here is also another option Soundtraxx 851002.
Similar decoder to the digitrax decoder.


----------

