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I'm getting a PRR 2-8-0 which was sold as not working since the seller said, someone removed the electronics from the tender, after looking in the instructions, the board is in the engine so it should be fine. However, in addition to the tender needing a battery (no big deal) I noticed two wires hanging in mid air, they could be to the volume pot? They are grey and green. Any ideas? When I get it, I'll post better pictures as these are just screenshots from the listing.

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Those are NOT the volume pot wires, they're the backup light wires!

The volume pot has three wires, blue, red, and gray.

Ah alright. I don't think this model has a backup light. In that event, would adding a backup light be as simple as running a hot and common to those two wires? Also, since those aren't the pot wires, does it matter that it's not connected or would it fry if the pot isn't wired?

John is absolutely right, I checked my wiring diagram catalog and it has corrected my memory!!  Those are for backup lights but the odd part is that that engine does not have a backup light in the tender.  Those early railking 2-8-0 engines only had a headlight.  Plus that volume POT is bare, you have some work cut out for you here. The electronics on those engines also were located in the engine not the tender.

Make sure the backup light wires aren't shorted or they'll cook the FET on the control board.  You can add a backup light by just supplying a 6V bulb and drilling out the dummy backup light if it exists, or adding the backup light fixture if it doesn't.

With the PCB in the locomotive, the volume pot leads are still brought back to the tender, so you can still control the volume from the tender.

Wire one end of the pot to the wire from the tether pin-3, wire the wiper of the pot to pin-7, and wire the other end of the pot to pin-5.  Obviously, all of these wires should be available at the end of the tether cable.

You need to trace the wires, yes sometimes the green is used.  Look at the pad on the engine.  They did not need all ten wires so there will be spares.  BUT blue, gray and red from the 12 pin on engine side are the volume pot and you need to trace there location on the tether at tender side.

Battery had its own red line, but it was shared with blue via a black wire on the blue of the volume pot on some models, but not this one it seems.

From engine on PCB 1 and 2 are coupler, 9 and 10 (wht/Yel) speaker, Need to check but RED and Black at 7 and 8 are probably battery,  Then Gray and blue at normal positions for volume pot instead of tach.  Leaves the one red at 4 which is probably volume pot center.  That red probably is the green wire (normally smoke fan on tender based board).

Always need to check though, many times these get rearranged to compensate for a bad tether wire, so they use another and change positions on the engine PCB.

To test just put engine on track and see if lights and smoke come on.  You could wire battery direct into plug to test motion conventionally too.  But with DCS it should work with motion too.  G

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