PaperTRW posted:If you can find a RS5 board and chipset (but not Legacy 5.5 or 6) that you like, this could be added to your RS4 loco. There's one small quirk in doing that, as the transistor that powers the tender back-up light on the RS5 board will be destroyed, but the function will still work because of the AD20 in the tender. This really only becomes a problem if you want to put the RS5 board back into an RS5 loco (and is repairable if you needed it to be).
There's nothing connected to pin 7 of the 691-PCB1-038 motherboard to cook the lamp driver, so why would it be damaged? FWIW, I plug RS5 boards into my little test rig with a similar motherboard all the time, and the backup lamp and rear coupler function work when they're placed back into the proper tender.
