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LL GP-20 w/LE103XF & Speed Table Mod.
by Phil Hartung, used with permission
Last night I installed my first LE103XF into my
new P2K GP20.
The GP20 has so much extra weight that contrary
to conventional wisdom, I had to shorten the decoder wires significantly.
It was easier to connect it all up with long wires, then de-solder
the wire from the decoder, shorten, strip, and resolder to the decoder.
I replaced the entire P2K lamp board, and wired
in new 12v, 50ma GOW bulbs with 47 ohm, 1/8w resistors in series.
Everything worked great, but the throttle response
seemed a little sluggish. (wouldn't get up a hill unless at least
on step 10 of 28).
Then I read the documentation (I'm a male engineer,
why would I read instructions????).
The preprogramed speed curve is very shallow. The
following table shows the speed step, preprogramed value (of 255),
% of full scale, and % of full voltage:
Spd Step Value % of Full Scale % of Full Voltage
1 1 3.6% 0.4%
2 6 7.1% 2.4%
3 12 10.7% 4.7%
4 16 14.3% 6.3%
5 20 17.9% 7.8%
6 24 21.4% 9.4%
7 28 25.0% 11.0%
8 32 28.6% 12.5%
9 36 32.1% 14.1%
10 42 35.7% 16.5%
11 48 39.3% 18.8%
12 54 42.9% 21.2%
13 60 46.4% 23.5%
14 69 50.0% 27.1%
15 78 53.6% 30.6%
16 85 57.1% 33.3%
17 92 60.7% 36.1%
18 105 64.3% 41.2%
19 118 67.9% 46.3%
20 127 71.4% 49.8%
21 136 75.0% 53.3%
22 152 78.6% 59.6%
23 168 82.1% 65.9%
24 188 85.7% 73.7%
25 208 89.3% 81.6%
26 219 92.9% 85.9%
27 240 96.4% 94.1%
28 255 100.0% 100.0%
As you can see, 11% voltage (about 1.4 volts)
at 1/4 scale and 27% (3.4 volts) at 1/2 scale is pretty shallow. I
run more mainline trains than industrial switching, so this curve
was a little frustrating. (Didn't try to MU with any other locos -
all my other decoders are NCE D102/DA102)
Here is a linear speed table that I programmed in
(by hand - not too hard on a NCE PH-Pro) to give a more "normal"
response
Linear Speed Table
Speed Step Value % of full scale and full voltage
1 9 3.6%
2 18 7.1%
3 27 10.7%
4 36 14.3%
5 45 17.9%
6 54 21.4%
7 63 25.0%
8 72 28.6%
9 81 32.1%
10 91 35.7%
11 100 39.3%
12 109 42.9%
13 118 46.4%
14 127 50.0%
15 136 53.6%
16 145 57.1%
17 154 60.7%
18 163 64.3%
19 173 67.9%
20 182 71.4%
21 191 75.0%
22 200 78.6%
23 209 82.1%
24 218 85.7%
25 227 89.3%
26 236 92.9%
27 245 96.4%
28 255 100.0%
Hope this helps if anyone else gets this excellent
yet inexpensive decoders.
(I thought I did pretty good considering my first
try at speed tables - and manually at that!)
We welcome comments or suggestions
from readers; please write
or call.
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