Saturday, February 25, 2017

N-scale convertion to dcc: sd-35, kato F3-B, kato F3-A

1- sd-35
2- Kato F3-B
3- in progress

1- SD-35-atlas N-scale

-TCS amd4 dcc board clips in easily.

-Ditch lights - The edges of the metal cast frame were drilled with a dremel to accomodate Led lights. SMD Leds (no resistor as already on TCS board.) are engulfed into a shrinking plastic case and glued on the frame depressions with epoxy resin.

-2x 220 uF smd capacitor added with discharge resistor of 4.7k ohm. Tight fit.

-Why a 440 uF cacapitor? to help with bad connections passing switches and limiting the high voltage peaks originating in the solenoids in the motor from power cuts/dirty track.

-Why a resistor in parallel with the capacitor ? I observed a funny bug with the TCS board with the capacitor only connected: if power is cut for 3-4 sec, the board is unresponsive. The capacitor maintined the board under ~0.5V - 0.2V for a long time. adding the discharge resistor of 4.7k ohm makes the TCS board able to resume from the issue after 10 sec only.

- Since the big capacitors hide the led on the board from the case light holes, i added 3 short 0.8mm optic fibers to let the light get on the other side of the obstruction.

- The plastic case was painted inside at the level of the super bright LEDs

Capacitor side with the 3 optic fibers taped on capacitors passing enough light...

Ditch lights in action, cabin side


2- Kato F3-B

- I wanted to add capacitors to the dcc decoder, a TCS M1, so that the run is smoother. Despite the fact that it could only have a limited impact on performance passing switches (capacitor size is limited in N-scale...), it could help get the rails and wheels dirty less quick by limiting motor peak currents.
The decoder does not offer a wire for the negative polarity. I found it opposite to the smd capacitor connected to the blue (+ accessories) wire. Soldering a black wire on the tiny capacitor (-) is tricky. If solder is applied on the top of the capacitor, it will break and pull out like it did with me at first. i had to resolder on the side of the capacitor for it to hold (contact with the PCB board more likely to be brute force resistant).
So the new black (-) and blue wires can be connected directly to the homemade smd 2x 220 uF capacitor board. Since the + pole is available on the board, i also added the contacts for the smd yellow Led light.

picture shows how i checked the correct polarity on the M1 board with a multimeter and without altering the insulator protection.

Opposite to the pseudocabin in the frame, a cavity must be dremelled to accomodate the opposite direction smd led. it is a smd led with 1k ohm resistor engulfed in a thermoplastic sleeve.

the fit is tight but works

The smd light and a 1k ohm smd resistor on the capacitor board, docked into the carved space of the frame.

the light in rule 17 mode (dimmable)

The F3-B diesel locomotive craws even slower than the sd-35...

The carved frame with the motor already hooked to the TCS M4 decoder
-front (left): space for the ditch lights
-rear (right): cuvette for the decoder, then deeper carved edge for the capacitors

front view with the board hole

The homemade ditch lights board, basically, resistors and Leds.
and a closed view to the space on the frame carved for the 2 x 220uF capacitors. As for TCS M1 DCC decoder, an additionnal wire needs to be soldered on the board to collect the ground for the additionnal capacitors.

The final results :) (+/- 16 h work later) with ditch lights as small bits of optic fiber glued on the body. PS: the inside of the body was painted in black matte to avoid reflections all over the place.