Hi Rog,
I think you've got a defective potentiometer in the Mod Wheel and having looked around all the available settings, I cannot find a means of actually permanently disabling the Mod Wheel. However,I would think that in your case, the Modulation only affects the Right1 and Right2 sounds. It does affect the other sounds in Parts 1 through 16 if they are used in say Technicord. I expect that when you use Technicord, you would generally use either Conductor or perhaps Right2, to provide the Harmony part?
If this is the case - Try this.....
Press Program Menus > Sound > Part Setting and Scroll to Page 5. On the right of the screen, you will see two settings MSB and LSB. These parameters set the range of the Modulation Wheel - the larger the value - the greater the effect when you move the wheel. These parameters are normally set : MSB=0 and LSB=64, by default.
At the top left of the screen, Select Right1 sound and set LSB to '0'. Select Right2 sound and set LSB to '0'. That should ensure that there is no Modulation effect on Right1 and Right2, when moving the Mod Wheel.
If you do use say Part 4 as the Harmony voice for Technicord, then you will also need to set that part's LSB to '0'
However, if you change any set-up using Panel memories, or by loading a new file from SD Card or Disk, these values will be reset to the Default values of '0' and '64' and I can see no way of avoiding this
So, you will have to either change these settings every time you switch on, or, load each of your files from SD Card/Disk, change the LSB setting to '0' and then re-save.......
Using this option, will mean that every time you load one of the 'modified' files, the new value for MSB and LSB will be ='0'.
I have seen some earlier references to spraying some switch contact cleaner into the area, but I think this would be a bit of a hit-and-miss effort, since it is not possible to effectively target the actual potentiometer resistive track and wiper, because they are normally enclosed in the metal body of the potentiometer.
Hope this helps Rog............