If the speaker is turned down my 540c chime does not sound. If it was just a dead display that was not dragging down the rest of the machine you should hear one heck of a lot of disk seeks as the rest of the machine boots up independent of the display. Once the machine is fully up you can turn it off without a working display just by hitting the on/off power button once and then hitting return to select the default. You are lucky to have another similar machine to do swaps, the processor/memory swap is an easy one to try. Just be sure to take the usual static electricity precautions and touch metal on both machine grounds before removing and moving parts from one machine to another, and if you have to set parts down somewhere grounded foil or conductive foam is best. In swapping displays go gently on the plastic trim parts, it is easy to break off the various little tabs that hold everything together. If you do break off pieces save them, they can be reattached by a welding or adhesive process later. If just the backlight is faulty or is turned off, I can see the screen displaying the desktop of my 540c (just barely) if I hold a 60W desklamp 45 degrees to the side and also place my eye near the lampshade and look at light reflected back towards the lamp.