Well, this one took some thought and feedback from others.
My original plan was to install a 73100 narrow board in this loco but in the end decided to go with the standard 73800 Loksound select micro due to a number of factors but mostly locating the speaker with an enclosure of reasonable depth and that measurements taken would suggest the 73100 board would be too tall to fit under the shell just aft of the motor and in way of the exhaust stack. Speaker mounting could go aft of the 73100 but to get a reasonable speaker enclosure in you would have to remove the radiator and cut out the shell under it and maybe mess with the radiator mounting/securing arrangement too.
One thing I did not want to do was remove or mess with the motor cradle mounting, ( I avoid this at all costs) so these areas are untouched.
Another thing I did not want to do was to remove the frame slots for the board at the front so these could be used for electrical pick up with a small piece of pcb material. As it happens I made a small light board and frame pick up pcb and fitted that at the rear and used that instead. The frame halves are drilled and tapped and the pcb board screwed down with 00-90 screws.
You could easily fit a 16x9mm speaker where I have the 8x12mm speaker by just removing more or all of the frame uprights ahead of the speaker, but you would loose the frame slots for electrical pick up then. I don’t have any 16x9mm speakers left right now anyway but this is an option for the future. It sounds good to me with the 8x12mm speaker so this is not on my immediate to do list but a bigger speaker/enclosure set up would no doubt make the sound better, I believe.
Frame was modified by filing a step at rear of motor ( to clear that exhaust stack that protrudes into the shell right there), immediately over the motor and between the motor cradle clips and just in front of the motor where the speaker sits. Also the nubs at the rear of the frame were removed to get a flat surface for the rear pcb light and pickup board.
I also sanded out the shell a very small bit in way of the decoder by a fraction of a mm on each side so the frame comes off and goes on easily. I use one of those nail file boards and just keep cutting it back as it wears out. Shell sanding took about 10 minutes altogether.
The front light and resistor fit just ahead of the speaker on another home made pcb.
You do need to be carful routing the wires as free height within the shell is very limited on this big loco. I placed mine mostly under the four 100uF x 20v caps along the motor cradle upper longitudinal as I have a slight recess there between the frame halves.
Anyhow here are the photos and a video.
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