GRJ....I usually don't post on one example and do not post unless I have personal experience with a topic,but I've been working with this conversion (F3A powered and sound in dummy F3 A ) for a month or so and once alive the LCRU 2 LED has always worked first try. BTW the RS 3 sound system works and sounds good even has road name and engine number correct NYC 2344. All parts were available This past November.
Off topic, I have the boards and parts in for your smart mother board. I plan to try my hand at surface mount soldering soon, Those three caps next to the R2LC look like a good place to start.