replacing proto 2 with proto 2

Are you using a PS2 3V board to do what you want?  

Yes, just replacing the defective board from the original engine set up.  Most of the connectors and wires are the same color code and connectors, except for the smoke unit which had both heat and fan come into the same plug.  I've always been told not to reuse bulbs from proto 1 to proto 2 but I can't find any references for proto 2 9 volt to proto 2 3 volt.

It won't work.  Those harness plugged into the board in the engine.  Since the board goes into the tender now, you need to use the PS-2 3V harness. 

 

The tach and bulbs are all the same, but how they are connected to the board is the issue.

 

I assume this is the RK version from the freight set?  If you can mount the board in the engine around where the 5V board was, then you just need to swap the connectors from the 5V board (black), onto the 3V board (white).  Than all you need to do is plug the original harness into the new 3V board. 

 

You do have to change the speaker to 4 ohm and change the battery and harness to the 2.4V battery.

 

Or get a Steam upgrade kit and upgrade with those harness and parts.   G

Like George says, the easiest install will be to gently pull the connector shells off the pins of the 3V board and bad 5V board and slide the black 5V shells on the 3V board connectors.  Then the speaker and battery harness gets replaced.

 

If you go that route, a little heat will help take the connector bodies off without damaging the boards.

 

I am using the steam upgrade kit so if I understand correctly I can use existing lights and tach board just make sure wires match up (all are the same color or really close)

Thanks for the help!  When I get home on Thursday I'll connect the wires and let you all know how I make out!