The X and Y axis of a retrofitted machine will not home consistently between reboots. If it varies it is exactly 0.100" more, exactly one encoder revolution. We purchased this machine not running so I don't know if it ever homed properly. It is an old Monarch VMC75 that has a 1:2 gear train driving BEI EX116 1000 line quadrature encoders and a tachometer nearby for the analogue amps. We have rotated the encoder in 0.005" axis movement increments, clockwise and counter clockwise, trying to find the best home switching position relative to the marker pulse without improvement. It doesn't seem to make a difference if the home switch closed 0.020" or 0.080" before the marker pulse; sometimes it still goes around again another 0.100" to the next marker pulse. We have changed the homing limit switch that slows the axis for marker pulse reading with no improvement. We have reduced all the axis speeds via parameters that influence the homing routine with no improvement in repeatability. In the static position all voltages to the limit switches and encoders are correct. We were thinking of putting an oscilloscope on the encoder to check for a low voltage marker pulse or noise. Any comments or suggestions as to what else we should be doing or looking for?