When you say it has an old AB Drive, is it the one with a 16-position Rotary switch on the drive board? If so, position 9 monitors the speed feedback from the tach. 0 to -8 in the down, and 0 to +8 in the up. Also, just a thought, are you getting the same polarity at A1 and A2 on the M switch? And lastly, do the DS fault indicaters on the main control board indicate a fault? the 4 LED'S add binarily.
