N Scale Kato F7
This page is currently under construction.
The Kato F7 is an example of a great looking
and running N scale locomotive that is not
"DCC ready" out of the box. This
is due mainly to that fact that the frame
completely fills the shell, leaving no room
for the decoder. The good news is that the
F7 is one of over 40 N scale locomotives that Aztec Manufacturing supports
with their Track Master frame machining service.
If you want to learn more about Aztec and
their products, click here.
Recently we had a pair of these locos in
the shop for DCC conversion using the new
Lenz LE0511W decoder. I stripped down the
frames and had them machined by Aztec. As
I was sizing up the install after receiving
the frames back from Aztec, I noticed that
the shell had two headlight lenses while
the frame only accomodated a single LED behind
the upper headlight. The LED mounts on a
small circuit board that fits between the
frames halves, and the clear plastic headlight
lenses are actually a single piece with a
light pipe connecting them. While this arrangement
does manage to get some light down to the
lower headlight, it wasn't nearly as bright
as the upper light. Besides I wanted to employ
the lighting special effects available on
the LE0511W to simulate a Gyralight on the
upper headlight, and that required that the
upper and lower lights operate independently.
I contacted John Claudino of Aztec, and asked
if he'd consider supporting the lower headlight
in his program for the Kato F7. I explained
how I would like to use a surface mount LED
to directly illuminate the lower headlight
lens, and emailed him a sketch of the required
change and an outline drawing of the LED.
John was very enthusiastic about the change,
and asked me to return the two frames so
he could work out the changes to the program.
When the frames came back from John they
were perfect, as you can see below. The LED
fit right in behind the lower headlight lens
with plenty of room for the wiring.
Next I got to work on modifications to the
light board to allow it to support the second
LED circuit, as well as to supply track power
to the decoder. The first step is to remove
the resistor and yellow LED with a soldering
iron, being careful not to lift the copper
traces from the board. After the components
are removed, the board should look like this.
The sketch shows the circuit side (bottom)
of the light board. The three main copper
traces on the board are shown as light areas
on the sketch, while the dark areas are bare
board between the traces.
The next step is to remove several areas
of copper from the board. This is easy to
do but does require some care as the board
is thin and small. Simply cut through the
traces on the edges of the areas marked in
red on the sketch, using a sharp blade and
your favorite hobby knife. It is better to
press lightly and make several passes with
the blade to cut the trace. If you press
too hard you could possibly cut through the
board or have the knife slip and cut a trace
you didn't want cut. After cutting the traces
as shown, use the tip of the blade to lift
the copper parts marked in red from the board.
I installed two surface mount resistors (620
Ohm 1/8 Watt 1206 size -- Digi-Key part number 311-620ECT-ND) as shown by the green rectangles in the
sketch. A good pair of tweezers, a soldering
iron with a fine tip and a steady hand are
needed to do this successfully. It is helpful
to tin the ends of the resistors before soldering
them to the board.
Next I installed the upper white LED (T-1
size -- Digi-Key part number 67-1606-ND or CMD204UWC-ND) and connect the wires. Too much heat applied
to the small pads may cause them to delaminate
from the board, so be careful when soldering.
Add the lower white LED (3.2mm x 2.8mm surface
mount -- Digi-Key part number 67-1608-1-ND or CMD67-21UWCCT-ND) stuff.
Put it together and test it. Program the
CVs so that it works like a gyrolight. Have
fun.
Follow the link for images of the install and operating headlights.
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Copyright 2003 by Robert M. Luzenski, all
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