Last post, a week or so ago, I posted pics of some new models of SBB trains I had acquired second-hand from Ellis Clark Trains. Two of the three locomotives were either DCC-ready (Roco Ae 6/6) or already equipped with a DCC decoder (Lima Re 6/6). The third was an older Roco model, also an Ae 6/6 but was not DCC ready.
I contemplated the circuit board for some time before working out how to convert the latter to DCC. This involved cutting a few tracks to separate the light circuits, and bypassing the track feeds altogether to go straight into the decoder (red and black wires), with the brush wires (orange and grey) also going directly to the brushes. I removed various redundant components, like the capacitor between the brushes, two chokes leading to the brushes, and the two diodes feeding the light bulbs. The light bulbs were replaced with cool white LEDs (I should have used warm white, but they are easily swapped later).
I also soldered the changeover contact solid so it could not be accidentally switched to overhead pickup from the pantographs.
I soldered the LEDs and resistors to the remaining appropriate pcb tracks, with the continuous one being connected to the blue positive wire, with the new resistors in circuit to the positive legs (shortened) on the LEDs, and the remaining negative legs (also shortened) soldered separately to the yellow and white wires.
I used a 9-pin JST harness so I could try it all out with a cheap Gaugemaster decoder, before swapping it for something better. Unfortunately, I found the Gaugemaster OPTI to be on the large side for the available space and I cannot quite clip the body back on properly, yet. The main thing is, it proved my wiring and modifications were good, and it all worked as it should. More by luck than anything else, I got the lights working th correct way for the direction of travel (that would have been easy to correct if necessary, either with some CV tweaks to reverse them, or simply swapping the white and yellow wires).
I may have to desolder the JST harness and sodler a much smaller (and better quality) decoder in, but having worked it all out properly to start with, that should be a relatively quick and easy job.
The first photo shows the chassis with all the mods and rather messy wiring. The decoder is tucked on its side down the side of one bogie (restricting the swing, but allowing me to get the body on sufficiently to take the remaining photos.
This is Ae 6/6 Co-Co locomotive 11494,
Schlieren, now available for service. Bear in mind that the body is not quite fully seated, so there is some light bleed at the side from the LED.
Anyway, that has been my evening's work with the soldering iron, knife, and drill.
P_20200303_234049_vHDR_On by
Jeffrey Lynn, on Flickr
P_20200303_233952_vHDR_On by
Jeffrey Lynn, on Flickr
P_20200303_233940_vHDR_On by
Jeffrey Lynn, on Flickr