Well I finally sat down last night and commenced to modify the 73 Class ready for the installation on DCC sound. As we all know the 73 class is not DCC friendly due to the light boards and there are 2 options to convert it to DCC.
1) Install a decoder and only wire track pick-up and motor connections and forget about the lights. Approx. 15 mins work.
2) Modify the light circuit boards to make them DCC compliant then continue with the usual installation. Possibly 2-3 hours with sound. This requires above average soldering skills to alter SMD components.
Now option 1 is quick and easy but with the quality of our RTR model these days I feel why have a new release loco with the functions of a loco of 30+ years old, so I went with option 2.
Let me warn you.... this is not something that should be done unless your are confident with your soldering skills. I personally have not done something at this level before but I took my time and have successfully completed stage 1 of this conversion to DCC.
Stage 1: To modify the light circuit board. Thanks to Ben O'Malley for his hard work discover the problems and to produce an article in the current issue of AMRM will help describe how to do it.
I have used his guide but have made some changes.
Due to DCC function restrictions only 6 available unless a separate function decoder is added and I don't think there is room for 2 decoders, I have linked the number boards and headlights together to be directional with travel, now only 4 functions left for markers. In the article it appears the way it is wired that the number boards remain on at all times having a permanent GND wired to them. I guess this means the number boards will be on all the time the loco is on the track. Not what I wanted when it might be sitting in a yard.
I will be separating the 4 markers to 4 functions in order to have front and rear red markers on when shunting. This has its own problem as I'm using the ESU 21 pin decoder which only has 4 outputs and 2 logical. An adapter board is available but with space inside the 73 Class limited, it may not fit. However, once again thanks to Ben, he has a solution to this and requires more modifications.
For now I can say that stage 1 is completed and both light boards work the way I need for DCC.
Hints: Mark the (+) end on the SMD LED with a marker before removing as they are so small it helps when re-soldering them back on the board.
Place a container under your work to catch the SMD LEDs. Remember you need to put them back and finding on your work bench could be hard.
Don't use the soldering iron too hot. I had it set around 280-300 which was perfect to remove the SMD LEDs quickly with no damage.
When testing the board on completion the markers have resistors on the light board but the headlights and number boards will need an external resistor on (-) function wire.
Stage 2: To modify the 21 pin adapter board ESU # 51967 for full 6 functions.
I'm working on that at the moment, waiting for parts.
Stage 3: Installation of adapter board, decoder and speaker.
Here some pics so far:[img]http://i1055.photobucket.com/albums/s501/captain_underpants1/Auscision%2073%20Class%20DCC%20Sound%20Installation/73ClassModifiedLEDLightBoardcopy_zpsdb397010.jpg[/img][img]http://i1055.photobucket.com/albums/s501/captain_underpants1/Auscision%2073%20Class%20DCC%20Sound%20Installation/73ClassModifiedLightBoard_zps206e9cfd.jpg[/img][img]http://i1055.photobucket.com/albums/s501/captain_underpants1/Auscision%2073%20Class%20DCC%20Sound%20Installation/73ClassWhiteMarkers_zps51a36535.jpg[/img][img]http://i1055.photobucket.com/albums/s501/captain_underpants1/Auscision%2073%20Class%20DCC%20Sound%20Installation/73ClassRedMarkers_zpsa22ffc16.jpg[/img]
More to follow....