Reply to "Help needed please. Factory new RMT Beep Diesel."

Well, there's nothing wrong with a BEEP with an "old" board. Here she is at ~3V pushing 3 cars at 14 scale mph:

Now, at ~7V at 40 scale mph:

Finally, at ~9V at 45 scale mph, which is likely as fast as a small switcher like this would go IRL:

So, thanks Darrell you were right! Oh, and here she is at ~11V pulling 8 cars at 31 scale mph:

I also ran like this with the shell removed to check for motor and/or diode overheating. While both motors, the bridge rectifier and the 4 "big" diodes got warm to the touch after 10 min under this relatively heavy loading, nothing got hot. So, overall, I'm really happy with my first BEEP. Next will be a DGLE one like Bob has!