KB880: Installing Digitrax Wired Decoder in Kato N-scale AC4400CW

This article was last updated on Oct. 28, 2010, 6:55 p.m. | Print Article | Leave Feedback

This article courtesy of Ken Bessler, concerning installation of a decoder into earlier Kato C4400W's.  Current produiction of these locomotives use DN163K1C or similar board replacement decoder.

I wanted to convert my 2 new Kato AC4400CW's to DCC but there were several problems:

1) The recommended PnP decoder, DN163K1a has a chip right where a shell component is. Using this decoder requires shaving off the plastic retainer clip under the exhaust stack. IMHO this is not good as it leaves too little support for the stack.

2) My dealer was out of stock of the PnP decoders.

3) A quick look inside the loco shows there is PLENTY of room for a DZ123 and they cost half what the PnP decoder's do!

So, I decided to use a modified form of the OEM control board with a DZ123.

First off, the OEM board was NOT designed with DCC in mind - it was designed for an environment where short circuits don't blow components. So, the traces on the board are not enameled and some run close to the frame or each other.

Start by trimming off all unneeded traces. Trim all off *except* the following:

Traces holding components

The last part of a trace leading up to a component - need something to solder to!

Leave the trace from the LED resistor (above the motor, marked "795") to the '+' side of the rear LED. Leave 2-3mm of trace from the front right frame pad.

Wires:

Black - solder this to the frame clip under the decoder
Grey - solder this to the top of the left side motor clip
Blue - solder this to the front edge of the chip resistor
White - solder this to the left side of the chip capacitor up front
Yellow - solder this to the engineer's side of the rear LED
Red - solder this to the trace leading to the right front frame pad
Orange - solder this to the right motor clip
Jumper - run an extra wire from the rear of the LED chip resistor to
              the right side of the chip capacitor

Wire routing:

We need to make a cut in the pc board to make room for 4 wires. Look at the board - near the rear you'll see the Kato name, logo and a part number. To the rear of this are the solder pads for the rear LED. In front of this the trace from the LED zig zags across the board. Using a marker, draw a box with the left and right lines along the edge of the board, the front line where the trace zig zags and the rear line at the LED pads. This makes a box around the lettering. ANY wires in this box will hit the shell!

Draw a line down the centerline of the loco in this box. Shade out the engineer's side of the box, leaving only the part number showing. Using a saw, cut off the shaded area, making sure to leave a little bit for the right rear frame clip.

Black - easy, run under the decoder to the frame clip
Grey - easy run from the decoder along the left edge of the board to the
motor clip
Blue - run through the board cut out closest to the middle
White - run through the board cut out closest to the right side, to the
right of the LED resistor, up to the left side of the chip capacitor
Yellow - easy, run around the decoder to the LED lead
Red - run through the board cut out next to the blue wire but to the right
of the LED resistor and chip capacitor
Orange - run through the frame cut out between the red and white wires
Jumper - run from the rear of the LED resistor, left of the red wire to the
right side of the chip capacitor

A note on soldering near the motor clips - use a clamp or tape to hold the clips in while you solder or they will swing out. The next time you try to remove the shell, they will hang on the shell edge.

Check your installation by running the loco on a DC system with a ammeter in place - if the loco draws more than 120 ma - check your work  again before exposing it to DCC system power!

That's it - all done!

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