This installation of TCS MC2 Decoder is for HO Scale Rivarossi 0-6-0 Saddle Tank and was performed by Claude Quesnelle of Candiac Quebec, Canada.
Photos and text by Claude Quesnelle of Candiac Quebec, Canada.
Decoder Installation in HO Rivarossi 0-6-0 Saddle Tank Engine: Item #1286 Reliance Rock Co. #1
I recently was faced with the installation of a decoder in a HO Rivarossi 0-6-0 saddle tank engine (Reliance Rock Co. #1). According to the supplied literature, and as confirmed by measurement, this loco drew 0.35A when running (@ 12V), and went up to ~0.7A when stalled. With the limited space available, and this reasonable current requirement, I decided on the MC2 decoder. There is sufficient space in the boiler for this decoder, sitting atop the weight.
The installation was very straightforward. Once the body was removed (as outlined in the included information sheet), it was clear that the motor was already isolated, with two wires coming from the driver electrical pickups to the motor brushes (located on the top of the motor). The original front headlight was also attached at that point.
The first step was to remove the headlight and unsolder the pickup leads from the motor brushes. Once this was accomplished, the decoder (which was originally tested to be ok) was temporarily attached in it's final spot with double sided tape but with the wiring harness plug temporarily removed from the decoder), and as seen I decided to orient the decoder with the wiring harness pointed towards the front so that the black and red decoder wires were on the correct side of the loco. With the decoder in place, the black decoder lead was trimmed to minimize the amount of loose wire and soldered to the left side pickup wire, and was covered with heat shrink tubing. The same was done with the red decoder lead, this time attaching to the right side pickup wire. Then the orange and brown decoder wires were trimmed, fitter through the slot that originally was used to pass the wires from the track pickups, then soldered to their respective motor brushes (orange to what originally was the right side pickup, brown to the left). I placed the loco on the programming track at this point and CVs were read back and programmed without any problem, so far so good. Also, secured the loose white, yellow and blue wires then made the first test run — worked great.
Now for the installation of the lights. Instead of the front light bulb that was originally there, I decided on 3mm golden white LEDs for both the front, and the rear lights (more on this later). For the front headlight, the LED was to be placed just in front of the decoder, facing forwards (obviously!!) and was to be secured to the boiler weight. The front headlight is actually a light pipe, and the light illuminates inside the boiler and this light is transmitted through the light pipe out. For the installation, the white decoder lead was trimmed enough to allow it to fold back past the decoder, then fold back again and connect to the resistor (470 Ohm) that will lay beside the weight, alongside the decoder. The other resistor lead was attached to the LED cathode (originally the long lead, also identified by the flat spot on the LED assembly). Both these connections were insulated with white shrink wrap. The LED anode was attached to the decoder blue lead (also reasonably trimmed), and another piece of blue wire was attached (resulting in three wires coming together) that will be used for the rear light. This connection was covered with blue shrink wrap.
The rear backup light was something new for this model. Luckly, there was a backup light fixture molded into the body just above the coal bunker. This was measured to be 12 scale inches, so a MV Products Lens (#L136, dia.=0.136�/3.5mm) was used. Also, I decided to house the LED in the boiler and direct the light to this lens via a fiber optic (0.040�) enrobed in shrinkwrap (I chose black to be less conspicuous in the cab). The lens and LED were drilled to accept the ends of the fiber optic. With this done, the LED needed to be attached to the decoder. I wanted the LED to be firmly held inside the boiler, so that the LED � fiber optic � lens was one piece and not to be disturbed. Consequently, a bit more wire was needed between the LED and decoder to allow for the removal of the body from the frame. I also put in some home made connectors so that the body could be completely separated from the frame should the need arise. To accomplish this, I used a trick explained to me by Dan Kirlin to fashion homemade connectors. For this, I used inexpensive IC pin clips (I paid 10 cents each) which were fastened / soldered to the appropriately shortened blue and yellow decoder leads, and these covered with blue and yellow shrink wrap, respectively. With the female ends as the electrically live end of the wires, I could run the loco with the body removed and not worry about any shorting. For the male part, the blue wire from the LED anode was soldered to an IC socket pin (as purchased as a length of 40 or so in a row, and one was separated/snapped off) and also covered with blue shrink wrap. The LED cathode was attached to a short length of yellow wire (covered with yellow shrink wrap) then to the resistor (470 Ohm), also covered with yellow shrink wrap. The other resistor lead was trimmed so that it fits inside the female socket discussed above. Consequently, the resistor lead acts like the other IC socket pin. For assembly, one just connects the appropriately colored lead with the matching female counterpart.
To complete the rear headlight assembly, some modification to the loco body was required. First a hole was drilled in the backup light housing to allow the fiber optic to pass. Also, a V-shaped section of a baffle inside the boiler was removed so that the fiber optic can reach the LED when this was stuck to the inside of the boiler. The fiber optic was inserted in the hole in the back of the lens, then inserted in the circular housing and secured with a small dab of matt medium. Once dried, the fiber optic was trimmed to the correct length, then a length of black shrink wrap was fitted over it. The other end was inserted in the hole in the LED resulting in a snug fit, so no glue was required. This was enrobed in black electrical tape, then secured to the top inside the boiler.
Final assembly was just to connect the yellow and blue LED leads to their counterparts from the decoder, reassemble the body onto the frame.
Important Soldering Tip
Please do not use any flux either liquid or paste on the mother board. Over time, the acidic properties of liquid or paste flux will begin eating away at the fiberglass PCB and will damage it. Use only Rosin-core solder or no-clean flux approved for electronics use.
TCS recommends the use of Kester "44" Sn63 Pb37, .015" diameter Rosin-core solder. Kester part number 24-6337-0007.
You can order this solder from the following retailers:
Digikey - PN:KE1110-ND
Techni-Tool - PN:488SO6775
Other solder tips
When stripping wire, only strip a tiny little bit of the insulation. Strip no more then a 1/64 of an inch. When the wire gets tinned with solder, the insulation will shrink back more. Try to not expose any more wire then half the length of the solder pad at most. In no case should solder or exposed wire wire ever be outside the boundary of the the solder pad you are attaching a wire to.
Click here for important information on properly Stripping and Tinning wire