Design Jet T120 paper set-up and missing tray part

[ACBerryhill]

I took a chance on an estate sale T120.  I figured for $150 I couldn't go wrong.  I've got new ink and cleaned the print head and have at least that end working ok (the yellow is still plugged).  But I'm vexed by paper loading issues.  I believe I'm missing part of the paper tray assembly.  I've got the lower part that locks in place, but the upper section that contains the sliders to adjust for paper size is missing.  It was my hope that I could just print from the roll.  I can do diagnostic printing to the roll of paper, but when I try to print something from AutoCad, I think it is sensing something amiss with the missing paper tray.  I can see the printer on my computer via USB just fine and select it as my desired device.  But it doesn't allow me to choose print from the roll (I do have print from roll selected on the printer itself), only choose in the computer's print winder different sizes of paper that would be fed from the  tray.  I'd hoped to find a contact switch for the missing tray that could be taped over to fool the machine to thinking the tray was present, but no luck finding that.  Aside from trying to track down a replacement tray from who knows where, does anyone have any idea what is going on and what an easy fix could be?  Thanks, Andrew