sorry beforehand if this post is in the wrong place, don't know exactly where it should be.
i got a laser3d about a year and a half ago, and it has never been flown mainly due to college and lack of funds/work. I was recently able to finish the plane but still cant fly it due to problems with the electrics. the problem is with the elevator where the servos constantly jitter, sort of like when you have power to receiver and servos but havent turned the transmitter on only worse. I have tested the servos on a servo tester which drew a blank, tried different receivers, crystals and tried a higher voltage battery pack but still get the same problem.
What could be wrong.

The electrics are all JR with JR extension cables/y-leads.

Thanks in advance.