3rd rail Bigboy backup light

I'd add a resistor or the constant current chip.  Diodes alone won't yield a satisfactory solution I would imagine.  The motor voltage can get fairly high under load, and having diodes to drop that will result in no light at lower speeds.

A diode, the CL2, and an LED will solve this problem from the motor drive.

Dale, it's not having 3V that's the issue, if you have unlimited (in LED terms) of current available, when the motor voltage goes past the 3V required by the LED and the .6-.7 dropped by the diode, the LED current will hit the ceiling and the LED is toast.  You need current limiting for the LED in this scenario.

What is it that you want to check?  Are you asking if the board is still available and where, or if there's a way to perform a component-level repair (replace a part), or ???

Dale, I mistook how you were connecting them, you're connecting the diode in parallel with the diode string, that's different!  I agree, that will work, however there is an issue.  You drop three volts across the diode string, that may adversely affect running.

thanks for all the help. I've heard from 3rd rail and it looks like they still have the correct NOS reversing board for this loco.  If so I'll have no problem wiring it in.  This is the best way for me.  thanks to all.

Ogauger