The sequence is:
1) Checking the mechanical part (linkage) from steering-gear to RT-2. The linkage often consists of two parts connected. Make sure the linkage is firmly tightened in both ends and there isn't anything loose in between.
2) Check/adjust the RT-2. See guide attached.
3. Make sure the amplifier (TDG-210DG) is providing the right output. When the RT-2 is adjusted measure the voltage coming out from the TDG is correct - see measuring values on last page in guide.