If the motor's not moving then your problem isn't in the
feedback system. If the head isn't tilting there's nothing to trip the sensor.
Since you've got a motor that's not working when connected properly, but you get it to work by swapping cables around, keep working towards the motherboard from the
PCB you're talking about. Pretty much everything on a
Mac works on a
home run from the motherboard and all of the other
PCB's in the head and
yoke just
relay that information from one cable to another. So you just have to work back. If you have a few extra known good cables lying around you can use them to run from
PCB to
PCB to see if the old cable had a short. The cables in Macs are such a small
gauge that they short for all kinds of silly reasons and are the most common issue I've found in teching Macs.
If you're reasonably sure that all the
PCB's and cables are good then you can open the
base of the
unit and make you're own
home run from the mother board. Just unplug the Pan motors so that the head doesn't spin on you (They are usually labeled PAN but could also be labeled 33) then you can run whatever cable you can find that's long enough straight out of the motorboard to the tilt motor. Just like with pan usually the cables for the tilt motors are labeled TILT but they could also be labeled 32. Pay attention to the order of the color scheme of the motor cables because the left motor cable is backwards from the right one.
If you come to find out that the problem is that the motherboard try flashing the software on it. If that doesn't work you probably need to
call Light Parts or your favorite other repair
house......