Thanks to the guys who replied.  I think I've found the solution that works for me.  After studying the wiring diagram, I saw that the track voltage from each truck and the wires to the headlight are called out and accessible on wires going to the circuit board in the fuel bunker.  So I disconnected the track wires coming from the front truck and connected them directly to the headlight wires, bypassing the circuit board on both of those circuits.  i left the orange and gray wires on J1 disconnected so the motors remained disabled.  I did put a 1K-ohm resister in series with the headlight circuit to limit the current flow there, although the headlight did appear to work OK without the resister.  I think the end result got me where I wanted to be, i.e. the headlight and cab/firebox lights come on full in the 6-12v range (DC), and the motors remain disabled.  So a simple 12VDC power supply to the track should give me what I need for the static display.  Next I plan to put it in a clear case with a narrow row of trees on a hillside behind it.

My layout is HO, but I was intrigued when I ran across a guy on eBay who said he had bought up the last remaining stock of these Shays from Bachmann and was selling them for only $350 or so.  At that price I couldn't resist.  I built a low trestle to display it on.  With the addition of crew figures from RailRoadAvenue, installation of all the Bachmann-supplied details, the noted wiring changes, the trestle, some decals, and a weathering job, I'm happy with the way it's coming out.  Now to find a good place for a 3-foot-long display case....

Carl

I have a 55-ton 3-truck Shay, DC version.  I want to set it up for static display (no motor action needed), but hopefully with the lights on via DC voltage applied to the display track.  In an attempt to disable the motors, so far I have disconnected the orange and gray wires on pins 3 & 4 on connector J1 on the circuit board, and this did indeed result in the motors being cut off.  When I put voltage on the track now, I get the cab light and the firebox light, but no headlights.

Can anybody shed any light (no pun intended!) on how the headlights are powered?  I assume the circuit board has some kind of constant lighting circuit built into it.  Is current flow to the motor circuit required to get the headlights to come on?  Just wondering what my options here might be.  Also wondering if I disconnected the motor wires right at the motors instead (with those pin 3 & 4 wires hooked up again) if that would make any difference.

So, in summary, I'm looking for a way to get the headlights on without turning the motors and without the motor current draw, as I'm using an HO DC cab to power the track and it won't supply enough amperage to drive the motors.

Any suggestions would be appreciated.